When I first met the idea that light from an object that was moving away from us at superluminal speed would never reach us, it seemed quite reasonable. However, I seem to have developed a problem arising from the fact that light must always be observed as travelling at c, irrespective of any relative movement between emitter and receiver. It goes something like this.

A distant object is moving away, relative to Earth, at superluminal speed. At a given point (say 15 billion l y away, which we will call “point A”) it emits a photon. This photon should reach Earth 15 billion years later.

Assume the emitting object is receding (relative to Earth) at 1.5c. One year later it is at point B, which is 16.5 l y from Earth. There it emits another photon, which should reach Earth after 16.5 years; ie, 1.5 years after the arrival of the photon emitted at point A.

Whatever the speed of recession of the emitting object, any light emitted must, from the viewpoint of Earth, be approaching Earth at c, so it must eventually arrive.

I accept that there must be something wrong with this reasoning, but at the moment I can’t see what it is.

The reason we don't receive light from the edge of the observable universe is simple. The Doppler Effect causes the light to be red shifted to a frequency of zero. Well, that is what we say. I better qualify that a little bit. The stretching of space due to the continued expansion of space causes the wavelength to be so long that it is undetectable.

Bill Gill

Thanks Bill.
I had progressed as far as considering the expansion of space. In fact I had made a distinction between the Doppler Effect caused by moving vehicles and that caused by the expansion of space. I was stuck on the idea of the observed speed of light being constant, and overlooked the fact that it would have red shifted away to nothing by the time it reached Earth.

Bill S.

I must say; You have a knack for posing some interesting questions (problems).

BTW; they say that the acceleration rate of gravity within the event horizon of a black hole is super luminal and that no light of any wavelength escapes.

That's right. No light escapes from a black hole horizon because the gravitational red shift stretches the wave length so that it can't get out. Of course the other way to look at it is that time for the wave, in the reference frame of the light wave, is slowed down to 0, in comparison with clocks in our reference frame. The original conception of the black hole was that the escape velocity for a black hole is greater than the speed of light. So there are several ways of thinking of it, depending on what way you want to look at it.

Bill Gill

Is it me, or is nothing straight forward? Let’s take your points one at a time.

“No light escapes from a black hole horizon because the gravitational red shift stretches the wave length so that it can't get out.”
Does this imply that the wavelength would have to be infinite in order to escape? If so, could it not escape when it became "effectively infinite"?

“…that time for the wave, in the reference frame of the light wave, is slowed down to 0, in comparison with clocks in our reference frame.”
Elsewhere, we met the argument that light could not be said to have a frame of reference. How could one re-phrase your statement in order to avoid ascribing a F of R to light?

“The original conception of the black hole was that the escape velocity for a black hole is greater than the speed of light”
Initially, this interpretation seemed to present no problems, but, light must always be measured as travelling at c, so it must be seen (or presumed, if there is no-one to see it) to be approaching the event horizon, from the inside, at c. What stops it from going through?

I told you to stop trying to make me think!

Ok, let's take your points 1 at a time.

re: Red Shift - I am trying to avoid the use of the word infinite, because no body seems to be able to come up with a good working use for it. But yes, the wavelength becomes infinite, and the frequency drops to zero. Keep in mind that an infinite wavelength means that the wave is smeared over the whole universe. Actually I believe that some work has been done which suggests that the light quanta are smeared over the surface of the horizon. I think, but am not sure, that I kind of got that idea from "The Black Hole War" by Leonard Susskind.

re: time slowed to zero - The idea of a rest frame for light is problematic, so let's say that time in a reference frame located at the horizon would apparently be slowed to zero as compared to our clocks. Keep in mind that in the frame at the horizon time would appear to move normally. If you were to fall into a sufficiently large black hole you would be able to fall all the way into it without the tidal effects pulling you apart, because the center of mass would be far enough away that they would be minimal. So as you fell through the horizon you would not notice any special effects. But from a distant observer you would appear to be torn apart and swallowed up. Hey, you thought just QM was crazy?

re: escape velocity - That is one of the poorer ways of describing the black hole horizon. However, it was what the first discussion of a sort of black hole was based on. Escape velocity is the velocity a mass has to have to escape from the gravitational attraction of another mass. If you throw a rock into the air it will slow for some period of time, then come back down and hit you on the head. If you throw it harder it will go up farther and take longer to hit you on the head. At some velocity it will reach a velocity that it will never come back down. That is escape velocity. Well, somebody started looking at that and imagining larger and larger planets, and figuring the escape velocity. This was a purely Newtonian calculation, done long before Einstein. He reached the conclusion that a sufficiently large star could have an escape velocity greater than the speed of light. He was pretty much ignored, but the idea was still kind of floating around. Then when Einstein invented GR Chandrasekhar used to conclude that they were theoretically possible. But escape velocity is still one of the relatively simple ways to explain it. Now after that digression, back to your problem. When a photon, traveling at light speed, reaches the horizon, it has used all the energy it has, and falls back into the interior. Of course since it now has zero energy, it also has a zero frequency, so we are back to the red shift. In fact just about all the ways of looking at how a black hole works are just different ways of saying pretty much the same thing.

Now I hope that is confusing enough.

Bill Gill

Would it not have to stop in order to do that; like that rock that kept hitting me on the head.

Well, it would have to stop moving away from the center, but that doesn't mean it would stop moving. If it was moving at an angle it would just change direction.

Bill Gill

This is a derogatory classification of what you later more suitably describe as being one of the relatively simple ways to explain it.

I happen to agree with Einstein that we should keep things as simple as possible...unfortunately many people have the habit of latching onto new concepts such as 'black holes' and adding their own usually much more extreme aspects (such as worm tunnels) in attempts to have their name associated with such phenomena.

I believe that the person who "...reached the conclusion that a sufficiently large star could have an escape velocity greater than the speed of light." was the British astronomer the Rev. John Michell who, in the 1700's, reasoned that if a star had a strong enough gravity it would choke off its own light but I don't see this as suggesting that having been emitted by the star that light would then be pulled back into same but that the light would not escape in the first place.

In 'Einstein's Universe' Nigel Calder wrote (62, BBC, 1979):- "Light travels faster...toward the centre of gravity than away from it."

The stronger the object's gravitational field the greater that variation and on that basis - as a star collapses the rate of departure of a beam of light traveling away from that (fixed location) source gradually reduces to zero in some cases.

This is, of course, from the point of view of a far distant observer whereas a local observer (located alongside the light source) would determine c for both beams however this is solely due to the fact that his measuring rods and clocks are physically distorted by that field.

Let me get this straight. Are we saying that light does not always travel at c; it only seems like that to an observer?

(Thinking aloud, here): A change of direction = a change in velocity; light changes velocity without reducing speed, so it (sort of) goes into orbit inside the event horizon. (?)

Well, that is obviously wrong. The speed of light, measured in any reference frame, is always the same, approximately 300 million meters per second. What happens as light travels away from the star is that it is red shifted until the frequency gets to zero. Since energy is equal to Planck's constant multiplied by the frequency (e = Hf) then at that point it has effectively zero energy. The energy it had before has been transferred to the gravitational energy of the star. Possibly the source you are quoting misunderstood the way it works.

Bill Gill

Well, I guess that is one way of looking at it. Another way is that it is that, since it's wavelength has become infinite, it is smeared all over the surface of the event horizon. The fact is that this is one more of those things that just really don't have any kind of a real analog in the world we can see around us. I doubt if even physicists that work with GR really have a good feel for what is going on, but they do know the math and can understand what is happening.

Bill Gill

I think you said that on purpose, because you knew I would ask how you fit an infinite wave in a finite space, inside an event horizon.

Anyway; how did we get from talking about distant galaxies to black holes?

They call it thread drift. If you have ever looked at some of the things discussed in the news groups on USEnet you would have seen some really drastic thread drifts.

Bill Gill

The speed of light is always measured as being c due to the fact that the devices employed - clocks and rods - can be physically affected either by relative motion (SR) or respective locations in a gravitational field (GR).

In his book 'Albert Einstein' Banesh Hoffmann (Paladin, 1975) makes no less than six references to Einstein's 'heretical' discovery of the variable speed of light and in 'Relativity, the special and general theory' Einstein wrote that the results of special theory are invalidated by gravity (76, Crown, 1916).

In the introduction to general theory Einstein wrote that the special theory law of the constancy of the speed of light required modification (Annalen der Physik 773, 49 1916).

Imagine that you are looking at a light source located in your reference frame and some distance away from you. The source emits beams of light in opposite directions which, in a certain period of time as determined by your clock, travel identical distances away from that source:-

<----------•---------->

The source now starts accelerating across your line of vision and again emits beams of light in opposite directions which, in a certain period of time as determined by your clock, travel different distances away from their source:-

<---------------•----->

From your point of view, as a distant observer, the beams are moving at different speeds relative to you due to the fact that their source is accelerating.

The light source is now (hypothetically) located at a fixed distance from a black hole. On the basis of the principle of equivalence the respective beams will similarly travel at different speeds away from their source:-

• <---------------•----->

From your (distant observer) point of view the beam that is traveling radially toward the centre of gravity is moving faster away from its source (and relatively to you) than the beam that is headed in the opposite direction (you cannot, of course, actually see those beams).

"Light travels faster...toward the centre of gravity than away from it." (Nigel Calder, 'Einsteins Universe')


In the above detailed event relative to a black hole... the speed of light is only determined to be constant by a local observer whose rules and clocks are physically affected by the gravitational field.

The speed of the respective beams of light is not the same as far as the distant observer is concerned.

Because of the principle of equivalence - the fact that light emitted by an accelerating source is analogous to light emitted by a source located in a gravitational field.

Bill 6, You pick up on the equivalence principle, but you ignore one of the basics on which Einstein based both SR and GR. The measured speed of light is the same in ANY reference frame. It doesn't matter where the light is coming from or what motion the source may have with respect to the reference frame of the observer it still travels at the same speed. Since the speed is constant the only variable left is the frequency. So it is red shifted if it moving away from you, or is coming out of a gravity well.

Remember that one of the problems that Einstein addressed with SR was the failure to detect a change in the speed of light depending on the direction of motion. The Michelson-Morley experiment was expected to find the difference based on the direction of movement of the earth. It failed, and created a significant problem for Newtonian physics. SR, based on the fact that the speed of light is constant for all observers took care of the problem.

Bill Gill

The term 'pick up' implies a surreptitious application. I 'pick up' on the equivalence principle on the basis of its validity and relevance!


I previously pointed out that an observer located alongside the black hole adjacent light source (due to the fact that his measuring rods and clocks are physically affected by the gravitational field) will determine constancy for both beams however the far-distant observer will not!

Are you of the opinion that the relevant beams in my diagram (depicting an accelerating light source, ref below) will not travel different distances away from their source in a given period of time as determined by your clock?

<------------•---->


It is still measured as traveling at the same speed by the local observer but only due to the fact that his measuring rods and clocks are physically affected by their locations in a gravitational field.

Refusing to respond to this point does not invalidate it.

GR tells us, and the Wallops Island experiment confirmed, that clocks which are located at various altitudes will tick over at different rates and, obviously, the same thing applies to clocks that are at different fixed distances from a black hole.

Depending on their point of attachment - radially orientated measuring rods will either be stretched or compressed in length.

A local observer who conveniently chooses to ignore those facts will determine constancy for the respective beams of light.

If you agree that the respective beams will travel different distances away from their accelerating source in a given period of your time as per the above diagram - are you of the opinion that the principle of equivalence does not apply in the situation I depicted; that the respective beams will not travel different distances away from their source in a given period of time as determined by your (far distant observer) clock?

• <---------------•----->

I make every effort to directly respond to all salient points introduced by others and would appreciate reciprocality.

You wrote that I "...ignore one of the basics on which Einstein based both SR and GR. The measured speed of light is the same in ANY reference frame." yet you seemingly choose to ignore the fact that Einstein stated in the introduction to GR:-

"...daß das Prinzip von der Konstanz der Vakuum-Lichtgeschwindigkeit eine Modifikation erfahren Muß."

(...that the principle of the constancy of the vacuum speed of light must be modified.)

There are two ways of modifying that principle - 1) The speed of light is not always constant and 2) the speed of light is not constant and, as Einstein points out in his book 'Relativity', the presence of a gravitational field invalidates special theory.

To the best of extant scientific knowledge - there is no place in the entire universe that is not permeated to some degree by gravity.

The MMX bears no relationship whatsoever to a discussion pertaining to the variable speed of light in a gravitational field ergo reference to same is nothing more than a red herring.

I am of the opinion that when Einstein said that light always travels at the same speed he meant just that. You say that the measuring tools are distorted. I say that they are perfectly correct under any conditions. When I measure a length in a reference frame that is moving or in a different gravitational field with respect to the one I am in I am getting correct measurements, even though they are different from the measurements somebody in that reference frame would get. We are both correct in our measurements, it is just that we are looking at them differently. There is no distortion in any of them. You have to accept that things in a GR world are just not what we intuitively think they are because we live in a world that is very little affected by GR.

Bill Gill

I am of the opinion that when Einstein said, in 1905, that light always travels at the same speed he meant just that and when, TEN YEARS LATER, he said it doesn't he also meant just that.

I have provided you with reference material to that effect yet you choose to deliberately ignore same.


I am obviously wasting my time asking you to respond to my comments or questions as you evidently lack the common courtesy to do so. I have already described the distortion incurred by measuring rods and clocks in a gravitational field but by refusing to respond to my comments you are of the opinion that they never occurred.

Turning your back on a legitimate question is a personal insult indicative of an unworthy opponent.


According to SR - if I change my location to that of another, previously synchronous, clock I will find that my clock then lags behind that clock due to the fact that my clock has, whilst I was moving, ticked over at a slower rate than the other clock.

Whilst I am fully entitled to insist, whilst I am moving, that my clock is ticking over at its 'correct' or 'normal' rate I would be contradicting special theory if I were to insist, whilst I am moving, that my clock's rate of operation has not changed from what it was before I started moving.

Oxford dictionary - 'Distorted': changed.

Assuming that they have read and accepted SR - somebody in that clock's reference frame will get the same measurements as I do with respect to my clock's rate of operation not different measurements as you state above.

It appears that 'what I have to accept' is that you will continue to rudely ignore my questions in your authoritarian ad hominem fashion.

Well, I figure you just need a little education. The fact is that nothing changes in any of the scenarios you suggest, except your perception. Your demonstrations assumes that you are working in space. But in spacetime you have to include the time dimension. When you do that you are actually viewing the projection of the object which is moving partly in the time dimension. This means it is tilted with respect to your view and is thus shortened, as you view it. Just as something that you view at a sharp angle to its length is shortened in your view. Think of an arrow which you look at from almost in front. The view you have makes it look very short. The difference in relativity is that the apparent shortening due to the timelike part of its travels is retained when it returns to a more spacelike frame of reference. And if I really understood what relativity means I would write it up and get me a Nobel Prize. Our minds just aren't really built to correctly visualize the effects of relativity.

And of course there are those who will jump on the "it's your fault for not agreeing with me" bandwagon.

Bill Gill

You are obviously incapable of providing same.


Arrant nonsense indicative of gross ignorance.

The scenario I suggested where one clock (A) is made to move to another clock's location (B) whereby clock A will be found to have ticked over at a slower rate than clock B was ratified by the Hafele Keating experiment.

In that experiment the rate of operation of clock A (the set of atomic clocks aboard the aircraft) physically changed whilst the clock was in motion compared to when it was at rest ergo your claim that nothing changes is egregious.

In particle acceleration experiments it is claimed that the particle's lifetime physically changes as does that of a muon accelerating toward the planet.

In the Wallops Island experiment the rates of operation of the clocks aboard the rocket physically changed during the flight ergo your claim that nothing changes is farcical.


Asinine and irrelevant nonsense! A blatantly deliberate attempt to obfuscate the discussion.

My depictions have not been in relation to views of an object that is moving through space but specifically to observations of beams of light!

I would normally be prepared to discuss the Terrell rotation concept however you have proven to be incapable of carrying out a meaningful conversation.


It seems to me that on the basis of your lack of understanding of what relativity means where it refers to one clock moving relatively to another clock that you have extremely minimal understanding of what relativity means.

Einstein really understood what relativity means and wrote it up in a book called 'Relativity, the Special and General Theory' yet he received no Noble Prize for same but you obviously believe that you would be entitled to do so.


On the basis of your obvious inability to comprehend the concept of physical time dilation as presented in STR it seems that your mind may not be capable of correctly visualizing even a simple effect of relativity however this does not give you the right to assume that nobody is capable of exhibiting this ability.


Well at least I can exclude myself from that group as my criticisms have not been as to whether or not you have agreed with me but to the fact that you rudely refuse to respond to my questions and presentations other than via the application of diversionary, deceitful tactics.

Well, I will give one more reply. You suggested that light travels at different speeds, using a diagram to show it. Your diagram doesn't show anything of the sort. It is the same thing that Michelson-Morley experiment tested for and it was found that it didn't happen. If you measure the speed of light in the frame of reference of the source it will be found to be C. If you measure the speed of light from that source in any other reference frame it will be found to be C. The frequency of the light will be different, but there will be no change in speed. This applies whether the two frames are moving with respect to each other or if they are in locations where the spacetime is warped differently (that is they are in places where the gravitational field is different). Since they are in different reference frames their clocks and other measuring tools will give different results, because of the effects of relativity. The tools will still be completely accurate in their own reference frame, it is just that in comparing them between different reference frames they will appear to be different.

The predictions of relativity, both SR and GR, have been tested to very high accuracy and they have so far been found to be correct. And in none of the tests has there been found any indication that C changes under any conditions. If you can't believe that I suggest that you get a good book on relativity and study up on it.

Bill Gill

Fortunately the OP takes no responsibility for the way in which a thread develops. I'm sorry to see the way this is going, though, and without any of the forum's regular "snipers".

However, to take a positive from it; it's going to make me take another look at the whole idea of relativity. Just when I thought I was getting the hang of it.

This is either a blatant lie, as I suspect it to be, or is indicative of gross ignorance regarding the Michelson-Morley experiment.

In my diagram the light source is ACCELERATING relatively to the observer!

In the MMX the light source is NOT accelerating relatively to the observer!

Are you incapable of seeing the difference between those statements?

The MMX was NOT intended to test the speed of light relatively to an accelerating source but relatively to an assumed aether!

In the MMX all of the equipment including the light source, the mirrors, the interferometer and (assuming that they didn't fidget) any observers were all contained in the same reference frame!



I have already pointed out that "If you measure the speed of light in the frame of reference of the source it will be found to be C."

However in my diagram I showed that after a certain period of time as determined by the distant observer the tip of the left hand beam (A) is a greater distance from the source (S) than is the tip of the right hand beam (B).

A...............S.....B
<---------------•----->

Are you totally incapable of seeing that, from the point of view of the distant observer, the left hand beam has, in perhaps one second of his time, traveled the distance AS away from the source and in that same period of time the right hand beam has only traveled the shorter distance SB away from the source?

Are you truly incapable of seeing that, from the point of view of the distant observer, the distance AS is greater than the distance SB?

Are you truly incapable of realising that if beam B travels a certain distance in a given period of time whilst beam A travel three times that distance in the same period of time from the point of view of the distant observer that beam A has traveled faster than beam B (from the point of view of the distant observer)?

It should NOT be necessary for me to have to point out that the above diagram IS TOTALLY HYPOTHETICAL! It is nothing more than a thought experiment!


(My underline) That's PRECISELY what I've been saying!!In my accelerating-light-source-diagram the distant observer and the light source ARE IN DIFFERENT REFERENCE FRAMES!!!

In my light-source-adjacent-to-a-black-hole-depiction the far distant observer IS IN A DIFFERENT REFERENCE FRAME THAN THE LOCAL OBSERVER!!!

Ergo (in your words) "Since they are in different reference frames their clocks and other measuring tools will give different results."

As I pointed out in a previous post...the local observer, being located in a different reference frame to the far distant observer, will, as you suggest, determine different results; that's what I SAID!!!


It provides you with considerable solace to be able to repeat my arguments without having the decency to acknowledge that they are mine.


They do not merely appear to be different; they are different as determined by the results of the Hafele-Keating and Wallops Island experiments.


One of the 'predictions' of GR was Einstein's comment that the law of the constancy of the speed of light required modification. Has this prediction been found to be correct?

One of Einstein's predictions in 'Relativity' was that the SR law of the constancy pf the velocity of light was not valid when gravitational fields were involved. Has that prediction been found to be correct?

Of course I'm wasting my time asking such questions as you have absolutely no intention whatsoever of answering same.

It is a principle tenet of physics that whilst a theory may appear to have been ratified by numerous experiments it only takes one (repeatable) experiment to invalidate any theory.

If somebody were to design an experiment that determined a variable speed of light in a gravitational field they would be classified as a crackpot as 'everyone knows' that the speed of light is constant in the same way that 'everybody knew' that steel-hulled ships would sink and controlled manned flight was impossible.


I have, during 28 years of research into relativity, accrued some 50 books on relativity and have read perhaps another 20 at libraries.

This, of course, does not include the many articles I have read in peer-reviewed journals and on the internet.

It was the contradictory arguments presented by the similarly academically qualified authors of such work that sparked my interest in the subject.

I have already informed you that according to Professor Banesh Hoffmann as well as Albert Einstein (both of them authors of good books on relativity) the speed of light is affected by gravity yet you have not had the decency to respond to those references.

Hoffmann wrote (117, 'Albert Einstein', Paladin):-

"Where should [Einstein] look next? At gravitation affecting the speed of light, since this already transcended the special theory of relativity in which the speed of light was constant and the same for all observers...Why not let the variable speed of light play the relativistic role...?"

You suggest that I should get a good book on relativity but are apparently of the opinion that Albert Einstein's book 'Relativity, the Special and general Theory' is not suitable reading material.

But of course - the fact that you refused to acknowledge my reference to that book means that as far as you are concerned his opinion does not exist or matter.

My diagram, depicting the varying speed of beams of light relative to a black hole, fully complies with Einstein's comment that a curvature of rays of light can only take place when the speed of light varies depending on its location in a gravitational field (76, 'Relativity', Crown, 1916).

Perhaps, like me, the forum's regular snipers feel that it's only worthwhile contributing if we've got something to contribute.


Relativity's 'law' of the constancy and maximum attainable speed of light is a barrier against scientific progress in general and the conquest of space in particular.

Whilst SR 'allows' long distance travel based on its time dilation factor neither industrialists nor politicians are keen to approve the expenditure of trillions of dollars on projects that might take millions of years to generate profits.

We need to take another look at the whole idea of relativity and if my feeble efforts prompt others to do so then I'll be happy.

A major objection to the concept of a variable speed of light in a gravitational field is the fact that it presents a challenge to the basis of the 'big bang' theory - the redshift of distant galaxies.

There we go - another quantum thread shift.

Ok, I see. You have unilaterally decided that Einstein is wrong, because you want him to be wrong. Therefore all the research that has shown he is right is also wrong. Since you don't want to be educated I will just stop trying.

Bill Gill

A typical spoiled brat reaction.

I exposed the fact that you were starting to agree with me so you spit the dummy.

I have never suggested that Einstein was wrong!

I happen to agree with Einstein that special theory is invalidated by gravity.

In accordance with the scientific principle that no theory can be proven, only disproven, the research that has purportedly ratified SR does not prove SR however people such as yourself find no problem in ignoring such principles when it suits them to do so.

"By denying scientific principles, one may maintain any paradox." (Galileo)

I did not respond to this thread on the basis that I wanted to be educated but if I had I would certainly not accept the words of a biased, deceitful person like you.

As I said, Einstein's theories have been extremely well tested, and they have always passed. Now you say that gravity is wrong in his theories. How do you explain all the times that it has been tested successfully?


The devil can quote the scriptures for his own ends.

Bill Gill

I made no comment to the effect that 'gravity is wrong' in Einstein's theories.

You previously wrote:-


On the basis that you obviously lack the courage of your convictions as well as continue to post comments that you falsely attribute to me I herewith terminate our discussion.

Only in this thread, I hope.

In any thread wherein a contributor resorts to deception.

Then the circular rotation of the earth and its approximately circular orbit around the sun don't produce an accelerated motion. And the experiments operation in the earth's gravitational field didn't cause any relativistic changes.


Well yes, relativity's law of the constancy and maximum attainable speed of light is indeed a barrier against a lot of things that we wish would happen. Unfortunately, no matter how much we would like to find a way around it so far nobody has found such a way. And wishful thinking doesn't count in science. Unfortunately, we can't just wish away the laws of nature, we have to go ahead and live with them. So buck up and accept the facts, instead of railing against people who point them out to you.

Bill Gill

Bill6, I know you said you were terminating your discussion in this thread, but I need some help getting my head around this, so I'm hoping you are still there.

I have no problem with the above quote up to the last sentence. You say: "...the beams are moving at different speeds relative to you...".

My interpretation of your second diagram would be that the two light beams are moving at the same speed relative to the observer, but appear to the observer to be moving at different speeds relative to the source. I'm quite prepared to believe I'm missing something, but I need to know what it is.

I have terminated a discussion in this thread not all of my discussions.


Special theory's concept of the constancy of the speed of light applies exclusively to inertial reference frames.

In my depiction the light source is accelerating ergo it is not an inertial reference frame thus SR's law of light speed constancy does not apply.

In accordance with the principle of equivalence - that law is, as Einstein pointed out in relation to gravitational fields, invalidated by acceleration/gravity.

Before the inevitable deceptive response is posted - there has never been an experiment which indicates the constancy of light emitted by an accelerating source.

But, thanks to your enquiry, I now realise that I confused the two observers and where I wrote that the beams emitted by the accelerating light source do not travel at the same speeds relative to the distant observer I should have written relative to the local observer; i.e. a person traveling along with the light source.

This does not, however, alter the fact that where the light source is at a fixed location from a black hole the respective beams travel at different speeds relative to the distant observer.

I could be getting there - slowly.

Correct me if I am wrongly interpreting you, but you seem to be saying that an emitting source that is accelerating relative to a beam of light will observe that light as travelling at less than "c".
If that is the case, and the source were able to accelerate to the speed of light, would it not observe the light as stationary?

Another thought confuses the issue, but I think it is relevant to the discussion.

Some time ago, if I remember correctly, when we were discussing the speed of light through water, and other media, we established that light travels at “c” through any medium, and that the apparent slowing results from the absorption and re-emission of the photons by atoms in the medium.

If this is the case, why are astronomers able to see the emission/absorption spectra of distant stars? Why are these spectra not converted into the emission spectra of the atoms in the lenses of their telescopes?

I had intended to refer to the following as a response to your OP but carelessly let the chance go by.

**************************

In their book 'The Matter Myth' Paul Davies and John Gribbin wrote (110, Viking, 1991):-

"As the recession speed of galaxies grows with distance, there comes a point at which this speed is so great that it exceeds the speed of light."

(and, page 111)

"This elasticity of space, a feature of general relativity, allows galaxies to effectively separate from one another faster than the speed of light."

and in his book 'Einstein's Universe' Nigel Calder writes (92, BBC, 1979) "If you are accelerating towards a source of light, its speed [i.e. the speed of the light it emits] seems greater. If you are accelerating away from it, its speed seems diminished."

And, whilst wearing his science hat, Isaac Asimov wrote (104, 'Understanding Physics, Light, Magnetism and Electricity', Mentor, 1966)

“To put it briefly, it is possible to deduce from Einstein’s assumption of the constant measured velocity of light that the velocity of any moving body will always be be measured as less than the velocity of light.”

and, in a footnote -

“This is often expressed as ‘a body cannot move faster than light’ but that is not quite right. It is only the measured velocity that is less than the measured velocity of light. It is quite conceivable that there are objects in the universe that are travelling at velocities (relative to ourselves) that are greater than the velocity of light, but we could not see such bodies or sense them in any way and therefore could not measure their velocities.”

**************************

So, in relation to your question - yes - if a source were able to accelerate to the speed of light it would observe previously emitted light as being stationary then, as the above references suggest, as a result of further acceleration that light would be moving away from it thus would not be observable or detectable.

Ok, I'm not absolutely sure about this. I don't have enough in depth knowledge of QM (quantum mechanics) to be sure, but here are my thoughts on the matter.
Whoops! There, I got myself so tangled up trying to think this through that I had to back up and start over.

I guess I could always say, because, but that isn't a very satisfying answer.



So I copied this quote out of the Wikipedia article on Refractive index. What this says is a bit different from the idea that the atoms actually absorb and re-emit the photon. This seems to be saying that it absorbs some of the energy from the photon and re-emits it with a slight delay, so that the probability wave of the photon is pulled back slightly. That is a bit different from our usual idea of what happens when an atom absorbs a photon and the outer electron jumps up to a higher energy level. For a better understanding you might want to read the whole article.

Bill Gill

I don't believe that it is relevant but it's a subject that intrigues me.


I question the decision that light travels through any medium at c. It is my understanding that it does not.


My argument is that the light from distant stars passes through the medium that is our atmosphere before it even reaches those lenses.

My reason for rejecting that subject's relevance is that the light emitted by OP objects that are moving away from us at superluminal velocities does not arrive here.

Well, that isn't quite the way it is. In fact as the recession speed grows it approaches the speed of light (C). Of course as the galaxies approach C their clocks slow down in accordance with relativity, and the frequency of the light they emit is red shifted so much at its frequency approaches 0. Thus, from our point of view, they disappear. In actuality, again from our point of view, they become so short that they appear as 2 dimensional objects. So anything at the edge of the observable universe appears to be pasted to the sky at that distance. They effectively disappear to us, but they aren't moving faster than C. In fact if you could be magically transported to the edge of the observable universe you would look around and everything would look just the same as it does here. And if you could find our galaxy, it would seem to be disappearing from sight into the edge of the universe.

And as far as your quote from Isaac Asimov is concerned. I greatly admire Dr. Asimov's writing, but keep in mind that his PhD was in biochemistry, not physics. So he didn't always get it just exactly right.

Bill Gill

You are absolutely right, of course, but I defend it on the grounds of "thread drift".

I have found an explanation at http://www.physicsforums.com which even I can understand. This is a small quote from it:

"A solid has a network of ions and electrons fixed in a "lattice". Think of this as a network of balls connected to each other by springs. Because of this, they have what is known as "collective vibrational modes", often called phonons. These are quanta of lattice vibrations, similar to photons being the quanta of EM radiation. It is these vibrational modes that can absorb a photon. So when a photon encounters a solid, and it can interact with an available phonon mode (i.e. something similar to a resonance condition), this photon can be absorbed by the solid and then converted to heat (it is the energy of these vibrations or phonons that we commonly refer to as heat). The solid is then opaque to this particular photon (i.e. at that frequency). Now, unlike the atomic orbitals, the phonon spectrum can be broad and continuous over a large frequency range. That is why all materials have a "bandwidth" of transmission or absorption. The width here depends on how wide the phonon spectrum is."

Getting back to the thread - in your OP you referred to the idea that “...light from an object that was moving away from us at superluminal speed would never reach us.” and “A distant object is moving away, relative to Earth, at superluminal speed...”

You then write “At a given point (say 15 billion l y away....) it emits a photon. This photon should reach Earth 15 billion years later.”

As pointed out by Davies and Gribbin, light emitted by an object that is moving away from us faster than the speed of light never reaches us.

“Clearly we could not observe galaxies that recede faster than light, for their radiation would never reach us.” (111, 'The Matter Myth', Viking, 1991)

It is my understanding that Professors Davies and Gribbin are recognised authors of physics books and articles who would not be prepared to publish something that is not accepted by the scientific community in general ergo I prefer to accept their word as to what takes place.

Absolutely! I have enjoyed, and learned from books by both. In fact it was one of Gribbin's books that sparked my interest 20 years ago.

In asking questions like this I am not so much arguing with the experts, as admitting that I don't understand what they are claiming. I cannot pretend to understand something I don't really understand, so I tend to keep at it until others become too exasperated to respond. Continuing to do that is one of the privileges of growing old.

Bill 6

Ok, I have done some research on the web and find that there are some problems with what I have been saying. For one thing Special Relativity (SR) does not apply to objects at the edge of the observable universe. You have to handle them with General Relativity (GR).

I have spent some time trying to digest the information I got from a paper I found on ARVIX Expanding Confusion: common misconceptio...ineweaver, 2003 .
I'm still not sure I understand it all, but here I go trying to write out what I think it said.

The major point in the paper is that there is no sharp cutoff of what we can see at the Hubble Radius. The Hubble Radius is the point at which galaxies are receding from us at C (light speed). The light emitted by an object that is beyond the Hubble Radius moves away from the source at C. Some of it moves away from us, some of it moves toward us. At the time of emission the object is outside the Hubble Radius, so we cannot receive that light. But the Hubble Radius is expanding with time, so that light that was emitted outside of the Hubble Radius when is was emitted may well come within the Hubble Radius. In fact there seem to be many visible galaxies that have recession velocities greater than C.

The red-shift of light due to the expansion of the universe is not due to the doppler effect caused by the speed of the source. The shift is due to the expansion of the universe. Therefore the light is not red-shifted to a 0 frequency, or at least not at the Hubble Radius.

I am still trying to get my mind wrapped around what the authors had to say in the paper. In part that is because it is a technical paper, with a bunch of differential equations in it. I had 1 semester of differential equations over 30 years ago, and promptly forgot all about it when I got out of college. And I suspect that the math in their world is a bit above what I would have learned in a first course.

Anyway, that is what I have come up with so far. If anybody has something that will supplement what I have there, please feel free to reply.

Bill Gill

This gives me the opportunity to the accuracy of a small extract from my past notes.

"Having used the Doppler Effect, with its resultant red shift, to establish that the Universe is expanding, it has to be said that this cosmological redshift which I used as “proof” is not, strictly, an example of the Doppler effect at all. Although the galaxy groups are separating, they are not moving through space; space itself is expanding and carrying the material of the Universe with it. Therefore the stretching of the waves does not occur only at the source, as is the case with the sound waves from a receding car; it happens over the whole distance because it is spacetime that is expanding while the light waves are passing through it. Waves are stretched throughout their journey – the further they travel the more they are red shifted."

Does that sound right?

That sounds just about right. Having read that paper about fallacies in the expansion of the universe I have realized that the far away galaxies aren't really moving any faster than nearer galaxies. It is just that there is more space between them and us and the amount of space is growing faster.

Bill Gill

Presumably each "unit" of space grows at the same rate, but the overall growth rate is proportional to the number of "units".

This is similar to the comment made by Davies and Gribbin in 'The Matter Myth' however whilst I referred to their agreement with the OP this does not mean that I accept that idea.

For 'space' to be able to transport the material of the universe (be able to push the galaxies apart) it would need to be more than simply a void but would have to possess some form of a physical characteristic.

This not only involves the ex nihilo creation of matter but also the continual creation of an amount of energy that is increasingly greater than the infinity of the universe.

I believe in the tired light explanation for the greater redshift of the more distant galaxies and also agree with Asimov that superluminal (undetectable in some RF's) motion is attainable.

Responses pointing out that the big bang expanding universe as well as SR's light barrier have been ratified will be reminded of the principle of physics that whilst a theory may appear to be supported by numerous experiments it only takes one (repeatable) experiment to invalidate any theory.

This bothered me for some time, but then I thought that if you imagine two objects in space; if space is static, these objects will remain at the same distance apart unless some force acts on them. A force is needed to move them through space, so if space is expanding, the objects must move with it, otherwise they are effectively moving through space; movement being relative, and all that.

But so far there have been a great many experiments that ratify SR, and none that don't. Likewise the expanding universe seems to be readily handled by GR. And of course once again GR has been ratified by a great many experiments, and there have been no experiments that don't ratify it. After a while you have to give up and accept that the probability that they are wrong is extremely low. When that happens it is generally accepted that they meet the requirements to be called natural law.

Bill Gill

Once again we run into the equivocal nature of infinity. Presumably we are dealing with a mathematical infinity, or that kind of pseudo infinity for which the surface of a sphere is often used as an illustration. This 2D surface grows as the radius of the higher dimensional sphere increases, so there is only the first part of the problem to deal with: the ex nihilo creation of matter. Solve that, and increasing energy will follow – E=mc^2.

If the infinity is mathematical, there is no problem with the increasing energy being greater than it, because, as Cantor showed, there is an infinite range of “sizes” of infinity.

'We' are not dealing with a mathematical infinity.

I agree with Einstein that as far as mathematical propositions are certain, they do not refer to reality.

An infinite universe has no boundaries - no shape.


And until somebody solves that particular problem it is a work of pure fiction to imply that the universe is expanding as the result of the ex nihilo creation of a greater than infinite force of energy.

On the basis of the claim that the galaxies are all receding from each other and the fact that this would require an increasing, greater than infinite, force of energy...expanding universe proponents are implying that this marvel of creation already exists - has already been solved - ergo the first law of thermodynamics should be scrapped or at least amended.


The infinity to which I refer is not mathematical however the idea that "If the infinity is mathematical, there is no problem with the increasing energy being greater than it." complies with Einstein's comment regarding the questionable veracity of self-consistent ('certain') mathematical propositions.

It is a skillful sleight of hand that allows one of the so-called proofs of a theory to contradict a primary law of physics namely that energy cannot be created or to be able to show that "...there is no problem with the increasing energy being greater than..." an infinite universe.

The very basis of the 'big bang' theory - galactic redshift - as well as the increasing redshift of the more distant galaxies can be much more easily explained (on an Occam's razor basis) in accordance with a universe of infinite time and space as can other of the so-called 'proofs' of that theory but 'simple' explanations do not impress the general public nor do they sell books so Occam's razor as well as Einstein's appeal to keep things as simple as possible are conveniently ignored by physicists.

We certainly agree on this point; and who better to have in our corner than Einstein?

Before we risk getting back into infinite discussions, I would appreciate your comments on my post #48432.

I got the impression that this was merely an agreement with my post #38429 - that the newly created space must have some form of material substance which forces the galaxies apart.

Bill6; perhaps I didn't express it well. What I was saying was that if an object is static in space, and space is static, a force is needed to move that object through space. Therefore, if an object is static in space, and space is moving, the object must move with it, otherwise it is moving through space with no apparent force causing it to move. Relativity tells us that space moving past an object, and an object moving through space must be considered as the same thing.

I still may not have expressed it well, but its 2.15am. and I've done all my thinking for today.

I still don't see any disagreement. If the galaxies are moving apart as a result of an expansion of the intervening space (ergo they are not static in a static space) then that void must have some form of material substance resulting in a physical reaction pushing against thus forcing the galaxies to move away from each other.

I realize that the analogy may be getting a bit strained, but let's go back to the dots on the balloon analogy for the expansion of space. As the balloon inflates the dots move apart from each other. But there is no more balloon between the dots than there was before the balloon was inflated. Space works the same way. There is no reason to postulate the creation of more matter to fill the intervals. In fact that idea was the center of the steady state hypothesis that was overthrown by the discovery of the cosmic background radiation.

Bill Gill

Bill, I'm not sure which viewpoint the balloon analogy supports. No doubt Bill6 will point out that unless the balloon was made of solid material it would not cause the dots to move apart.

Tackling the question as to whether space works the same way is something we probably need to come back to when this particular issue is resolved.

I'm going to give it some thought, and see if I can come up with something devastating.

Bill S, you might want to keep in mind that space is definitely not solid. Remember that it stretches wherever there is mass. Remember black holes? They cause a huge distortion of space. So it has a lot of give to it and can easily be stretched by whatever it is that is causing it to expand. So there is no reason to assume that there is anything being added to cause the expansion of the universe. It is just space stretching, like the balloon in the analogy.

Bill Gill

I couldn’t think of anything devastating, so let’s try it this way.

The location of an object in space has relevance only in relation space. This may seem tautologous, but what I am really saying is that there is no reference point, outside space, relative to which an object can be stationary, or in motion. If an object is in space, and space moves, the object must move with it in order to remain in the same place. It isn’t a question of space needing to be tangible in order to move the object; the object does not move, it remains in the same place in space. The fact that one part of space has moved relative to another is irrelevant, the object is still in the same place.

A reference point relative to which a galaxy can be stationary or in motion is an adjacent galaxy.


Space does not move!


A specific galaxy may be said to retain its location but according to the expanding universe concept all (most of) the other galaxies are moving away from it.

According to Newton's first law of motion - force is required to make an object move and on the basis that 'space' is a total absence of matter it has no physical effect on any object no matter how much it stretches; ten times nothing is still nothing.

In accordance with the expanding universe concept - most of the galaxies are moving away from us and from each other and for any object to be made to move it must be subjected to some form of force however 'expanding space' is not 'a force'.


I, for one, am not talking about one part of space moving relative to another but am referring to other galaxies moving relative to each other.

The fact that 'the object' (a galaxy) may still be in the same place regardless of the 'stretching' of space is not the critical factor which is the then resultant location of other galaxies.

We could perhaps insist that whilst all the other galaxies are moving ours remains in the same place however this contradicts the observed CMBR frequency shifts.

Since the "adjacent galaxy" is also in space, my point still stands.



There are well accepted theories that would not agree with this.

If space is expanding (BB), every part of space is moving relative to every other part.
If space can be distorted (GR), parts of space move relative to other parts.



If a specific galaxy may be said to retain its location, every galaxy may be said to retain its location in space. If space is expanding, every galaxy must move away from every other in order to remain in the same location in space.

It has been determined that the Milky Way is hurtling toward the Virgo galaxy at around 640k-s. The Virgo galaxy is a reference point relative to which the Milky Way's location and rate of travel can be determined.


You may have noticed that I make every effort to directly respond to each and every one of your comments; a reciprocal attitude would be appreciated - space is a total absence of matter. Apart from what some well accepted theories have to say - what are your thoughts in this respect?

Perhaps you could cite one or more of those theories?


I believe that the expression is not that space is expanding but that the universe is expanding.


On that basis - every part of space (more specifically a galaxy that it contains) provides a reference point relative to which another galaxy can be stationary or in motion.


I do not accept that space can be distorted. I am of the opinion that 'a curvature of space time' is nothing more than a fancy name for a gravitational field.

Neither 'space' nor 'time' possess any physical substance thus cannot be bent.

A total absence of matter cannot move relative to any total absence of matter.


The 'specific galaxy' to which I refer is one that is in my reference frame ergo its location remains unchanged whilst that of the other galaxies does not.

Your efforts in this respect are neither unnoticed, nor unappreciated. You are one of a few who do that. I try to do the same, but unfortunately time is often short and frequently I have to divide responses between posts. It was my intention to return to your previous post to address a couple of other points including the "absence of matter".

It is now 2.40am, so I shall postpone further comments until a more civilised hour.

To some extent I am playing “Devil’s Advocate” in an attempt to clarify my own ideas, so please be patient, don’t hesitate to tell me if I slip into semantic nit-picking.

“…'space' is a total absence of matter…”. Agreed. Presumably, this includes an absence of energy?


“…it has no physical effect on any object…”. It would be extremely difficult to argue that a total lack of matter and energy could have a physical effect on anything. However, position in space seems to have some significance, even if only in terms of the argument that a force is required to move an object from one point in space to another.

“…no matter how much it stretches; ten times nothing is still nothing.” Multiplying nothing by any number may be an acceptable concept in mathematics, but in the real world it has no practical application. This leaves us with the idea of stretching nothing: I’m not very happy with that idea, but this brings us to another of your points:



If space is not moving, which must be the case if it is nothing, then as the Universe expands, the galaxies are moving through space, which scientists assure us that they are not doing.

There has to be a lot more to discuss here, but duty calls, so perhaps we can deal with one bit at a time.

Hi gentlemen.

You might like to read through this:

"Wilczek explains properties of space"

at:

http://thedartmouth.com/2010/05/07/news/space

Now if I just understood what Wilczek was talking about. I read the article, but didn't understand half of what it said. That may be because it was written by a reporter. Unfortunately reporters don't have a great record of explaining what scientists had to say. Any way I have no idea what he means by the material grid. Does any body have a link to an explanation of it?

Bill Gill

Thanks Rede, all contributions gratefully received!

My understanding is that what purports to be a description of space is actually a description of what space contains.

If, as the report suggests, all this stuff in space is able to exert pressure that could be what moves the galaxies, but at this point I don't find that very convincing.

Marcus Chown (Afterglow of Creation) says:

"...in Einstein's theory......space is malleable, it can be warped or curved in the presence of matter."

I think I need to know if you are saying that Einstein was wrong, or that the current interpretation of GR is wrong, or whether I have missed your point completely.

Your having sent three posts has complicated the procedure however I feel that I have said all I have to say on the subject of the claimed expansion of the universe preferring instead to accept the Occam's razor/Einstein's simplicity complying concept of the tired light theory which in my opinion, although obviously unacceptable by a vast majority of physicists, has never been disproved.

Space is a void that, however, contains random items of matter resulting in a medium of minimal density thought to average one atom of matter in a matchbox sized area of deep space however there would be a lot of free atoms in a distance of several million light years whereby light from distant galaxies would be absorbed/emitted by that 'medium'.

The greater the distance of those galaxies from us the greater the number of atoms - ergo the greater the redshift.

*********

I made no suggestion that Einstein, having referred to the concept of 'curved spacetime', was wrong.

I believe that the phrase is merely an extravagant description of a gravitational field employed in order to impress us commoners ergo a contradiction of his suggestion that we should keep things as simple as possible.

Thanks, Bill6.

I like the idea that 'curved spacetime' might be an extravagant description of a gravitational field.

I have not given as much attention to the concept of tired light as perhaps I should. I shall leave you in peace while I do that, and mull over the contents of this thread. No doubt I shall be back with more naive questions later.

One of the problems with saying that is that when Einstein developed the idea of curved spacetime he also adapted some very good math that fully described it. GR and the math that describe it have been tested over and over ever since he presented the General theory of Relativity (GR). The theory just keeps passing those tests. Since the math and the tests all depend on curved spacetime I don't think that it is just intended to "impress us commoners", it is a very real description of how the universe works.

As far as light being absorbed and re-emitted by matter in between the source and our instruments. Well, that is a well understood phenomenon, and is used to determine the composition and quantity of matter in the way. However, the red shift of the light from distant galaxies is a completely different thing. The characteristics are much different. Absorption/emission causes discrete shifts in wavelength of light. Red shift causes all wavelengths of light to shift in the same manner. It does not cause different wavelengths to shift in different ways. So absorption/emission does not explain the galactic red shift.

Bill Gill

The one thing that seems to be missing from this description is an explanation of the force that must, surely, be needed to cause and maintain that curvature.

Even the "duality" idea doesn't really solve this, because, in the same way that you cannot observe a quantum object as a particle and a wave at the same time, presumably, you cannot treat gravity as a force and a curvature of spacetime at the same time.

You have one of the major questions that a lot of people have about science. WHY? Unfortunately there is no good answer. A lot of times it is claimed that science is the quest for why things are the way they are. That is not strictly true. Science cannot answer the question "Why is it this way?". What science can do is to describe how the universe works. Let's take a quick example of Newton's law of gravity. His answer to why the planets move the way they do is that gravity directs their motion. But when it came right down to it he couldn't say what gravity was, it is just a force that works according to his law. Then Einstein came along and extended his work with GR. So now gravity is the result of warped spacetime. But we still don't know WHY spacetime is warped.

You are wondering what force caused spacetime to warp. But there is no force causing the warp. The warp just is. When we get right down to it, at the most fundamental level science can only say "That's the way it is just because that's the way it is". You are wondering about what warps spacetime. Well, if you think about the electromagnetic force there is no explanation of why the electric charge exists. Another case where science can understand the interactions between particles, but why the interactions exist is beyond the capabilities of science.

Bill Gill

Bill, it's not so much a question of "why", as a question of "how".
The whys can often resolve themselves into philosophical questions, rather than scientific ones.

I'm going to go through this and a couple of other threads, put the results together with my past notes and see what emerges in the way of silly questions.

I think we may be having a slight semantics problem here. You say that HOW is the big question, while I say that WHY is the big question. Well, to me the how is right in front of us. For example, back to Newton's gravity. How it works is clearly defined. He developed formulas and calculus to be able to say how things worked. So to me how is just the mechanical details of putting the parts together and coming up with a prediction. That is how to me. But why is a whole different story. Why gravity works is pretty much unknowable. We can point to GR and say "see, that is a better way to show how gravity works". But why it works that way is still a big mystery. To me all of science is basically a quest to determine HOW everything works. That is just a description of the way it all goes together and interacts. Why it goes together and interacts that way is a matter of philosophy.

Bill Gill

Bill, you're absolutely right about the semantics.
I see, and agree with your line of reasoning.

A couple of questions and possible answers that illustrate the line I was thinking along.

How did it all start? I don't know, but I'm working on it.

Why did it all start? God wanted it that way.

True, but would I not be right in thinking that the energy exchanges involved in the operation of the electromagnetic force can all be accounted for? Such is not the case with gravity.

You say:"... there is no force causing the warp. The warp just is."

The warp is not there when matter is absent; it is there when matter is present. This is not a "why" question, it is a "how" question. Your own definition of the scope of science makes this a legitimate question to ask. How does matter have this phenomenal effect on spacetime without involving energy?

I have not forgotten this point, Bill6, just had to put thinking about it on hold for a while.

I gotta ask...

These rocks that you throw in the air, do you throw them straight up and wait for them to come back down and hit you in the head, do you throw them away from you some and then go run to where they are going to land or do you mix it up?

Either way I'm thinking you might wanna invest in a helmut.

Marchi, have you considered how history might have differed if Sir Isaac N had been sitting under a coconut palm rather than an apple tree? (<< politically correct icon)

Or a bowling ball tree. Yow.

Well, yes this is a how question. It is answered by


This is Einstein's General Relativity (GR) formula. I copied it from Wiki. But if you can work with the math (I wish you luck) this tells you how space is warped by mass. And I have no idea why you think it doesn't involve energy. There is a great deal of energy involved in warping space.

Bill Gill

It might have something to do with the fact that someone whose opinion I value said:
"...there is no force causing the warp. The warp just is."

Yep, "the force just is". We don't know why, we just know that it is, and that it obeys Einstein's equation. But the equation does answer the "how".

And on further thought, as far as energy is concerned in the warping of space, we need to remember that matter is energy. That then raises a question. Does matter cause the warp in space? Or does the warp in space cause matter? As I understand GR a warpage in spacetime always accompanies matter. But I don't know that there is a way to separate matter and spacetime and say that one is the "real" part or if they are just different ways of looking at the same thing.

Just one more thing to confuse the issue a little bit.

Bill Gill

True, but is, for example, the Earth losing mass by virtue of the fact that it is holding the moon in orbit?



Good question. Raises the possibility that gravity is the essential element in the Universe. Perhaps, without gravity, there would be no matter or energy; perhaps even no space or time.

As threatened, I've done some thinking about gravity. I apologise for any repetition, and look forward to some lively objections.

One of the things Einstein did in the general theory of relativity was to demonstrate that it was not possible, in the absence of external evidence, for an observer to distinguish between the effects of acceleration, on one hand, and of gravity on the other. With a nod in the direction of Preearth, I acknowledge that Einstein was not the first person to think of this, but he took what had previously been just an observation, and revolutionised scientific thinking with it. The equivalence principle highlights the similarity between the effects of gravity and of acceleration.

Not only did Einstein build on the equivalence principle, he also placed upon it an interpretation that was subtly different from that of Newtonian physics. In Einstein's version, the principle asserts that in free-fall the effect of gravity is totally abolished in all possible experiments and general relativity reduces to special relativity, as in the inertial state. What this means is that if you were free-falling in a windowless, soundproofed (so that the sound of rushing through the atmosphere didn’t give the game away) box, you would have no way in which you could tell that gravity was having any influence on your situation. Thus, any experiment you might try, would tell you nothing about gravity, and could be totally accounted for by the precepts of special relativity, which ignores gravity. So you could ignore gravity, at least until your box made contact with the Earth, after which you might well lose all interest in gravity and GR.

Gravity is something we tend to take for granted. Not until Newton did anyone seriously consider gravity as the driving force that kept the planets orbiting the sun, and the moon orbiting the Earth. It was Newton who not only proposed the theory of universal gravitation, but also worked out the mathematics to prove it. There are, however, a couple of things to be kept in mind. The first of these is that although Newton’s equations described the cosmic situation so well that their use has permitted men to land successfully on the moon, and, more importantly, to return safely, as well as facilitating non-manned visits to far flung bodies in our solar system, these truly groundbreaking observations and calculations do not tell us why or how every body in the Universe attracts every other body, nor, indeed, why any lump of matter should attract any other. What is more, they do not offer any explanation for the provenance of this force; which brings us to the second point that must be kept in mind. Where does the seemingly inexhaustible supply of energy come from? Why, for example, after thousands of millions of years of holding the moon in orbit, and keeping vast quantities of loose objects “stuck” to the Earth’s surface, does gravity show no signs of lessening. Does it not seem that nature might have achieved the “impossible dream” of perpetual motion – an endless supply of renewable energy? If this were the case there would have to be some very serious re-thinking done within the hallowed halls of physical academia. Of course, there has to be another explanation.

The apparent violation of the law of conservation of energy, implied in the preceding paragraph, could not be left unexplained. The concept that came to the rescue was the work function. The work function was originally a tool used by engineers to quantify the amount of work done by a specific process or machine. The equation used to express this function was W = F d, where W is the work done, F is the force used and d is the distance over which the work is carried out. Energy can be related to work done, and fuel requirements can be calculated from energy output. Try moving a very heavy object. If the attempt is successful the work function can be applied to it, but suppose you are unable to move the object. The distance then becomes zero, so F in the second half of the work function equation must be multiplied by 0. Obviously, any quantity multiplied by zero must equal nothing, so the equation becomes W = 0. No work has been done; therefore no energy has been expended. In spite of absurd results like this, the work function has been used in this way to explain that objects are held on the Earth’s surface by gravity without expenditure of energy, because there is no movement. No movement means no force, no work and no energy exchange.

To the original W = F d has been added the term cos&#952;. Now the equation is W = F d cos&#952;. Theta can be anything from 0 to 360 degrees. cos converts it into a value between minus one and one. The angle “&#952;” represents the angle between the direction in which the object is pushed and the direction in which it actually moves. If the object moves in the direction in which it is pushed, then the angle “&#952;” is zero degrees and, because cos (0) equals one the equation effectively remains in its original form: W = F d. However, should the object not move straight forward the element cos &#952; will move towards minus one, thus becoming a negative fraction. In the worst case scenario, if the direction of movement lies at 90 degrees to the direction of push, cos&#952; becomes zero, because cos 90° = 0, thus F d must be multiplied by zero. So the amount of work done becomes W = 0. It might be argued that it is unlikely that a consistent push, or pull, in one direction will result in motion in a direction at an angle of 90 degrees; but this is exactly the situation in the case of one body orbiting another, larger body. If we reason that the moon is attempting to travel in a straight line past the Earth, but because of the gravitational attraction between them it is being constrained to orbit the Earth, then it follows that the line of force holding the moon in its orbit lies perpendicular to the direction in which the moon is travelling.

This is where someone will point out that gravity is not a force, and that the moon orbits the Earth, not because it is held in place by a force acting perpendicular to its line of travel, but because it is following the curvature of spacetime caused by the presence of the mass of the Earth. However, the question of how this curvature might be caused and maintained without expenditure of energy becomes significant.

Consider a rock lying on the ground. If you pick up that rock, then let go of it, it will fall back to the ground. Your action in picking it up has involved a transfer of energy: some energy from your muscles has been converted into gravitational potential energy as you raise the rock. If, when you have lifted the rock, you place it on a shelf, and let go of it, it will not fall, but it will still have the energy you transferred to it, still in the form of potential energy. Obviously, if it is pushed off the shelf it will fall back to the ground. The argument here is that the energy you put into the rock as you lift it equals the energy that would be necessary for gravity to bring it back to the Earth’s surface, so there is no net expenditure of energy. Could this explain how gravity seems to work without any apparent energy source? A little thought about this situation must raise some doubts. For example, if the attraction of gravity is directly related to the amount of energy put into the rock you are lifting, why does gravitational attraction not increase with distance, as would be the case if you were stretching a spring? If, having picked up the rock you altered your position so that you were holding your rock over an open well. When you released the rock it would fall to the bottom of the well, in spite of the fact that you transferred to it only enough energy to take it as far as the ground surface. Finally, we would have to wonder why a spacecraft that travelled from Earth to the moon would be attracted by the moon’s gravity. Not only would it not have been lifted from the surface of the moon, but it should have enough potential energy to whisk it straight back to Earth as soon as it stops moving away.

GR postulates that matter "curves" spacetime in its vicinity. Obviously this involves curvature in four dimensions which is difficult for most of us to imagine, so physicists usually suggest we think of spacetime as a rubber sheet stretched out flat. If there are no large masses around, the sheet stays flat, and so any object placed on it and given a push will move around in straight lines. However, a large mass, such as the Earth, makes a dip in the sheet because it actually warps spacetime. Now any other object with smaller mass, like the moon, moving about in spacetime rolls into the dip as it comes past the Earth. It appears to be attracted to the large mass, but is in fact following the most direct route through curved spacetime. This effect of warping spacetime is what gives rise to gravity. It is quite easy to draw a diagram of the two-dimensional sheet depressed by a large mass, but progressing from two dimensions to three dimensions becomes quite complicated, and would involve a quasi-infinite number of depressed two-dimensional sheets, centred on the Earth, facing in every possible direction. We are now faced with the question as to whether or not any work is being done to maintain this situation. The easiest way to think about this is to return to the two-dimensional sheet. If we take the rubber sheet into space and place a massive object on it, it will not depress the sheet. In fact it will work only if the whole experiment is conducted is conducted in a gravitational field. Obviously some force is required in order, not only to distort the sheet, but also to maintain it in its distorted shape. If, having distorted the sheet, we took the whole setup out of the gravitational field the elasticity of the sheet would “lift” even the most massive object so that the sheet could return to its non-distorted shape; and just to prove that there was a transfer of energy involved, the massive object would continue moving in a straight line until acted upon by some other force. Similarly, spacetime that has been distorted by the presence of a massive object will not maintain that distortion if the massive object moves away. It seems that an energy exchange is needed, even in the gravitational model of GR.

Perhaps there is a way round all this that does not deny the work done by gravity, and might even identify an energy source. We will return to the example of the rock, lifted from the ground and thus endowed with potential energy which allows it to return to the ground with no net expenditure of energy. If we accept that the Earth distorts spacetime, and that it is this distortion that holds the rock on the surface and causes it to return if it is moved away, then we have to explain why increased movement away from the Earth does not make movement of the rock increasingly difficult. One way of tackling this is to accept that the distortion of spacetime caused by the Earth is in fact a distortion caused by the combined mass of the Earth and the rock. Of course, the contribution made by the rock is so small in relation to that of the Earth that it would be practically undetectable. However, as the rock is lifted from the surface, a secondary distortion of spacetime (albeit a minute one) is caused. While this secondary distortion remains part of the major distortion the rock “seeks” to return to the surface in order to restore the single, combined distortion. If the rock breaks free of the distortion caused by the Earth it will be free to travel through space, accompanied by its own mini-distortion of spacetime. If it does not break free, the rock will eventually return to Earth, either by the apparently direct route by which it ascended, or by going into orbit around the Earth and gradually spiralling down, perhaps over many years, until friction with the atmosphere ignites its surface and causes it to plunge as a meteor to Earth. This latter route appears to be very much the less direct, but GR tells us that the rock is actually following a geodesic, which is defined as the shortest distance through curved spacetime between two points.
Here the scientifically minded may be constrained to object that the effects of gravity seem to be unbounded in there range, so nothing actually breaks free of the gravity of a massive body. However, acknowledging that gravity decreases as a square of the distance involved, there must come a point where its effects are negligible.


GR is interpreted as saying that there is no force of gravity? David Deutsch (The Fabric of Reality) argues that there is no gravitational force. “In the nineteenth century, few things would have been regarded more confidently as real than the force of gravity. Not only did it figure in Newton’s then-unrivalled system of laws, but everyone could feel it, all the time, even with their eyes shut – or so they thought. Today we understand gravity through Einstein’s theory rather than Newton’s, and we know that no such force exists. We do not feel it! What we feel is the resistance that prevents us from penetrating the solid ground beneath our feet. Nothing is pulling us downwards. The only reason why we fall downwards when unsupported is the fabric of space and time in which we exist is curved.”

GR tells us that matter and energy, simply by their presence in spacetime cause the distortions that give rise to the phenomenon of gravity. Impressive as this assertion is, it leaves some unanswered questions. What GR tells us is that the presence of a massive body, or indeed a body of any proportions, in spacetime causes spacetime to distort. Should it be possible, somehow, to remove this body, spacetime would resume its original shape. So, not only does the presence of mass distort spacetime, it also holds spacetime in that distorted shape, in spite of the fact that spacetime seems to favour returning, like a rubber sheet, to its original shape. Let us return to the sheet with the bowling ball on it. While the ball sits there in its depression, with the whole system in equilibrium, all is still. The sheet is being held in its distorted shape by the “weight” of the ball. The weight of the ball is simply a measure of its mass in relation to the “gravitational attraction” between it and the mass of the Earth. If the bowling ball is removed from the equation, the sheet resumes its original shape; if the Earth could be removed from the equation, it would have the same effect. We know is that if we lift the bowling ball off the sheet and take it up to a height of a few feet above the sheet, thus increasing its gravitational potential energy, then release it, it will fall onto the sheet causing a temporary depression that will be deeper than the depression it caused when it was at rest. The sheet will then push back hard against the ball, possibly throwing it into the air. What does all this tell us? A few things will be immediately obvious. First, when the ball was sitting at rest in its depression, it was being prevented from falling further towards the centre of the Earth because the distorted sheet was pushing it upwards. Newton tells us that for every force, there is an equal and opposite force, and this is something that relativity has not relegated to the shadows. However, we are invited to believe, that that there is no force acting against the force being exerted by the sheet, that somehow the state of equilibrium is being maintained, in contravention of Newton’s law, by the curvature of spacetime, which behaves as though it were a force, but is not.

We should look more closely at the concept of the “equal and opposite force”. When I pick up a stone from the surface of the Earth, then let go of it, it falls back to the surface. Is it the “equal and opposite force” that causes it to fall? It might be tempting to think so, especially in view of the idea that it is the energy I put into the stone by lifting it that caused it to fall back to Earth, but, in fact the answer has to be “no”. When I pick up the stone, my weight increases; in other words my feet press more firmly against the ground. This must be the “equal and opposite force”, but wait, it does not end here. As my feet exert more force against the Earth, the Earth pushes back more firmly than it did before, so where does it end? It seems that it is not the “equal and opposite force” that is involved in gravitational attraction.

One problem with the rubber sheet and bowling ball analogy is that it is simple to visualise it in two dimensions – which, of course, is why it is used as an illustration – but it is much more difficult to visualise the whole thing in three dimensions, and that is without adding the fourth dimension of time. It is, therefore, easy to think in terms of the sun, for example, as sitting in the bottom of a depression in spacetime, with the various objects comprising the solar system circling the sides of the depression at various heights, and lateral distances, just waiting their time to make the final descent. Of course, this is a serious over-simplification, but it is a trap that is easy to fall into, especially when the alternative is trying to come to grips with the idea of a “pit”, the bottom of which is in the centre, and the sides of which slope outward in every direction. It is a lot easier to think of this as a sphere of attractive “force”, at the centre of which is a lump of matter, which is doing the attracting. However, General relativity tells us that we must think in terms of a sphere of spacetime that is distorted in such a way that the shortest distance between any two points is not a straight line, it is a curved line (unless the two points lie on a radial line), and that all these curved lines trend towards the centre of the sphere. Put another way, this is saying that within the sphere the “downward” direction is towards the centre from every point on, or inside, the sphere. Furthermore, it says that, unless any downward path follows a radial line, that path will be curved

Perhaps the use of the word force when writing about gravity is only a sort of “shorthand” which authors employ in order to avoid convoluted, if strictly more correct, terminology. It is also possible that there is a duality associated with gravity, similar to the wave/particle duality of quantum objects. If so, it must mean that that an essentially quantum feature is manifest in the realms of GR.

The apparent force of gravity is the manifestation of the fact that objects move, naturally, through spacetime along the straightest possible paths, but, because of the curvature of spacetime, these straightest paths do not represent Euclidean straight lines. These lines resemble the straightest lines between any pair of points on the two-dimensional surface of a sphere. These curved straightest lines are geodesics, and it appears that we must now add to our laws of nature the law of geodesic motion. Wolfson (Simply Einstein) is emphatic about this. “This law of geodesic motion ultimately covers everything from falling apples to planets and space shuttles and on to the overall behaviour of the Universe as a whole.”

It appears that the degree of curvature of spacetime is directly related to both the mass and density of the body causing the curvature. For example, a body of the mass and density of the sun will cause relatively gentle curvature over a large area. If this mass were compressed to the size of the Earth, the curvature of spacetime around it would be much more severe. Given a situation in which an enormous mass, such as the total mass of the Universe, is compressed into an unthinkably small “speck”, the curvature would be extreme. This approximates to the state of the Universe at the instant of the Big Bang. Therefore, it follows that every particle of matter and energy in the Universe, at the start of its life – or of this cycle of its life – occupied the same point in spacetime. The energy, whatever its source, that caused this infinitesimal, primordial speck to expand, transforming itself into billions of light years of spacetime, would also have caused the curvature of spacetime to expand and to “soften”, but, it would always remain curved, thus it would always tend to return to its original condition, like the rock falling back to Earth once the restraining force has been removed. This would mean that the energy which drives gravitational attraction is the potential energy imparted to every particle in the Universe by the Big Bang. Thus, there is sufficient potential energy within the Universe to bring every particle back to an infinitesimally small speck, unless some external force intervenes. Every particle distorts spacetime around it to a minute degree. As particles clump together, not only are their masses added together, but so is their power to distort spacetime. What is more, without a continued expenditure of energy to prevent this clumping from taking place, it must continue until all the matter and energy in the Universe has returned to its starting point. This would imply that the real mystery is not where the energy of gravity comes from, or why it seems to be inexhaustible, but rather where the energy comes from that is causing the expansion of the Universe not just to continue, but to accelerate, as modern observations assure us that it is.

I hope you don't expect an instant reply to your book, well it almost looks like a book. My quick answer is that I see a few places where you seem to have a slight misconception, but nothing that I can answer just straight up. I will work on it, but you will probably see a bunch of answers, not just one. I will probably take it apart and discuss one topic at a time, then sometime or other I will try to wrap up my discussion in one short piece. Ok, I just copied it off and put it in a Notepad file so I can disassemble it and work on it in little pieces.

Bill Gill

Apart from my previously mentioned objection to the use of the term 'curvature' in relation to space and time as per most of your message it is this final sentence that I find to be relevant to this thread on the basis of its duplication of my comments in #38429 - 05/14/11 10:22 PM -

“For 'space' to be able to transport the material of the universe (be able to push the galaxies apart) it would need to be more than simply a void but would have to possess some form of a physical characteristic.

This not only involves the ex nihilo creation of matter but also the continual creation of an amount of energy that is increasingly greater than the infinity of the universe.”

Recent news reports refer to this force as ‘dark matter’.

I was disappointed that you made no reference to the tired light explanation for galactic redshift.

Imagine a block of glass in outer space. A beam of light is directed through that block as a result of which its temperature (energy content) increases arising from the absorption/emission of that light by the medium’s atoms. The beam departs the object however the increase in the object’s temperature (temporarily) remains.

The departing (emitted) beam has less energy than had the incoming beam, the beam is redshifted indistinguishable from that of a receding object.

The greater a galaxies distance from us the greater the amount of free matter in the intervening space ergo the greater the redshift.

We really have no idea whatsoever as to what lies in the space between us and the distant galaxies so we can only theorise about what is taking place.

Bill; I certainly don't expect an instant reply. I look forward to your taking it to bits. Hopefully it can go back together as something better.

Ok, I'm back with a first try. Keep in mind that this is my first try, I reserve the right to change what I said, or the way I said it.



That is the way it is. I think you are thinking about what happens when you push against something you can't move. In that case it feels a lot like you are doing work. In a way you are, but the work is internal to your body. There is no energy exchange between your body and what you are pushing against, so the work function is equal to zero. Anytime a force is applied to something, but that force does not produce motion in the something then there is no work performed. In physics work only occurs if it causes a change in motion of the object to which a force is applied. Now then you might say that because the moon is in orbit the gravitational force causes the moon out of a straight line, so so work has been done. To answer that I unfortunately had to think some more. The result is the following.

First off, energy and work are basically the same thing. They use the same unit the Joule = 1 Newton Meter.

I will assume that the moon has a circular orbit for simplicity. The amount of energy imparted to the moon to move it out of a straight path in any infinitely small increment in the orbit is f F*D*cos(dtheta). That is dW/d(theta) = Wd*cos(dtheta). If we integrate over theta from 0 to 2pi then the result is that W = 0. So there is no work involved in holding the moon in orbit. And I hope that I got that right. I haven't done any calculus in many uears. I did just run through the calculus list on Khan Academy, but that doesn't make me perfect by a long shot. Maybe somebody on here knows more than I do and will correct any errors. I am pretty sure that the result is correct, but I may have made some error in how I did it.

Bill Gill

Bill6. As I was writing that post I was aware that it was heading towards the subject matter of your comment. I deliberately stopped short of raising that issue, as I thought it would be of value to deal with some peripheral points first.

I made no mention of tired light for two reasons:

1. I didn't really address redshift.
2. I don't yet know enough about it.

I have a section in my notes from a couple of years ago dealing with redshift/Doppler. I'm just looking for some time to swat up on tired light and add it to those notes.

I hope somebody who knows the math looks at this and checks it. I keep having a feeling that I did something wrong in my math. I still think I got the right answer, but I' not at all sure I did it the right way.

Bill Gill

What about Newton's equal and opposite force; does that not mean that the object is "pushing" back.

There is a force pushing back, but as long as there is no movement there is no work being done.

I plan on getting another bit of a reply to your long post in a little bit. I may have it done later this evening.

Bill Gill

So, let's talk about potential energy. The first thing to remember about potential energy is that it is relative. The potential energy that anything contains is relative to the lowest energy level it can move to. So if you pick up the rock from the ground its potential energy is relative to ground level. But if you move it over a well its potential energy is relative to the bottom of the well. The difference is strictly due to the fact that over the well it can fall longer and achieve a greater speed before it hits bottom. The potential energy an object contains is the amount of kinetic energy that it can gain by falling to the ground or other surface below it. The kinetic energy it can gain by falling a few feet to the ground is much less than the kinetic energy it can gain by falling many feet to the bottom of a well.

Now let's talk about how the attraction of gravity falls off with distance.

F = G*M1*m2/r^2

That one should be familiar to you. Newton's law of gravitation. Notice that the force between 2 bodies is inversely proportional to the distance between them. This is known as the inverse square law. That distance is actually the distance between their centers. Let's look at why that is.

I'm not going to find a diagram and insert it here, I will let you make your own. First draw a circle. Now draw a bunch of straight lines through the center of the circle at 15 degree increments. There is nothing magic about the increment size, I just chose 15 degrees because it means the circle will be evenly divided by the lines. Let the ends of the lines all stick out a long way beyond the circle. Now let's pretend that the lines represent the gravitational field from a body. This is a standard representation of field lines around any kind of source. Now draw another circle around the first one, but twice as far out. Notice that the field lines are much more widely separated where they pass through the second circle. If you imagine the circles to be spheres and the field lines drawn at 15 degrees intervals in all 3 dimensions you will see that the area between field lines varies with the square of the radius. Well, gravity works just the same way. Close to the center of a body the gravitational attraction of a body is much greater than it is farther away from the body. That is why gravitational attraction doesn't act like a spring. It works the same way as electromagnetic radiation (light). If you look at a light source up close it is very bright, but as you move away it begins to be dimmer and dimmer. It is also obeying the inverse square law.

Now you may say, but I don't see any difference in gravity between different heights. I better mention that. Let's assume that there is a enormously large planet, say a million km in radius. Never mind that such a planet couldn't exist, this is just a thought experiment. Now if you start drawing your lines through the center of the planet you will find that 15 degree separation means that you can't even see one line when you are standing by another one. So you keep on drawing more lines until you finally get a whole bunch of them in your field of view. Well, the angle between those lines is going to be extremely small. In fact it would take some very fine measurements to find out that there was an angle between them. And the force produced by those almost parallel lines would chage very slowly with altitude. Guess what! The Earth is large enough that the angle between force line is almost undetectable. However, it can be measured, particularly from a space craft. So at great altitudes the force of gravity from the Earth is smaller.

Of course the Moons gravity works the same way, so its gravitational attraction is greater than the Earths gravitational attraction when a spacecraft get closer to it than it is to the Earth. There is a point between the Earth and the Moon (on a line between their centers) where the gravitational attraction is equal from both of them. So before that point a spacecraft would tend to fall to Earth and beyound it would tend to fall to Moon. Of course it doesn't actually "fall". The thing is that spacecraft don't travel in straight lines. They always travel in orbits. The orbits may not be closed orbits, but they are orbits, so that they have enough sideways speed to keep from falling directly to the ground.

Bill Gill

Thanks for the response, Bill.

Let's stick with the potential energy for a moment.


If, instead of picking up the stone, I dig a deep hole beside it, then push it in, can I be said to increase its potential energy when I dig the hole, or when I push it over the edge? On the other hand, perhaps it would be more accurate to say that the stone already had the potential energy to take it to the centre of the Earth, but there was rather a lot of matter in its way. This is really the point I was working towards; that every particle of matter in the Universe has enough potential energy to bring it back into contact with every other particle. All we do when we pick up rocks, or send craft into space, is make a slight local alteration to potential energy that is already there.

It doesn't matter much what you do about potential energy. The fact is that potential energy is just book keeping. It isn't anything special. It is merely a way of looking at something to determine how much energy you can get out of it, in the system that you are looking at. Heck I remember one dumb science fiction story I read one time where the protagonist needed more energy than he had available, so he just redefined the reference point for his system as being on another planet. From that point of view he had an enormous amount of potential energy. Of course the fact is that there is no way to get the energy out of a difference between 2 planets. And no, every particle of matter doesn't have enough energy to bring it back into contact with every other particle. Keep in mind that the universe is expanding, and apparently the expansion rate is increasing. If your hypothesis were true then the universe would be slowing down and/or collapsing.

Bill Gill

My original point was:
"...there is sufficient potential energy within the Universe to bring every particle back to an infinitesimally small speck, unless some external force intervenes."

It seems that the something intervening is dark energy. I believe there is a suggestion that this could be gravity acting as a repulsive force on a grand scale. That could really mess things up.

Well, my point is that potential energy isn't really all that important. What is important is energy period. As far as I am aware potential energy is mostly used to figure out how much energy we can get out of a system. For example in a hydroelectric power station the potential energy of the water at the top of the inlet with respect to the generator is very important. But if we are talking about space flight we are more interested in momentum.

As far as "some external force", dark energy isn't external, it is a part of the universe. What it is is, so far as I know, completely unknown. Any ideas as to what it is are basically just that, ideas. There is a lot of evidence that indicates it is there, but there is no good theoretical way to incorporate it into our view of the universe.

Bill Gill

The potential energy bucket to balance up that you are trying to understand is given in the friedmann equations (http://en.wikipedia.org/wiki/Friedmann_equations)

It is a way of calculating the pressure on spacetime to bring energy into being.

The last line in the article gives you the potential energy formula

Hope this translates properly I struggle with english at times.

Thanks, Orac. The maths in that link caused a major panic attack.
However, I shall return when I have a bit more time, and a lot more courage, to see if I can make any sense of it.

You have no need to worry about your English, some native users do a lot worse.

It's funny my first question I asked was about trying to explain the relevance of the 2nd law of thermodynamics to a group of physicists over the exact some problem.

I couldn't believe they didn't get that GR implies plasticity to spacetime it really makes it a fabric or foam.

They sort of view 2nd law as some sort of probability thing I had to explain no it implies plasticity via mathematics.

If I use the formula F = MA it is hard relationship,

if I say on average F = MA

what I am doing is imparting plasticity the average result is the same but to model it you have to answer a question how much noise about the average do you want. Its like I was pulling via a rubber band or pushing thru a rubber stopper.

If you look at the 2nd law there are two conditions within the law one is time the other is systemic you must have the whole system. If you look at GR for space thats the same parameters space and time .... they really are related.

To me as a modelling physicists GR is a description of the physical world, 2nd law is a description of the energy movements but they are in effect the same law.

When energy like light or radiation is produced on the spacetime fabric it builds up pressure on the spacetime fabric via the friedmann equations and the 2nd law guarantees the energy is resolved off the fabric to release the pressure.

It really is like a very very very large hydrolic system.

That's how we model it anyhow.

Orac, I hope you keep on bringing up good points. We need somebody to keep us going straight. I have been trying, but I don't pretend to know everything that is going on in physics. I will keep throwing out my half baked ideas but I won't object if somebody comes up with a correction to what I have to say.

So far I haven't had a problem with your English. Keep up the good work.

Bill Gill

Bill S. More reply to your long gravity post.


It seems to me that you are getting carried away with the analogy. Remember that the sheet with a weight on it is indeed just an analogy to give us a way to visualize something that we just cannot visualize. Then you try to extend the analogy by assuming the sheet in a no gravity situation. Well, that just doesn't work. No analogy can be extended too far and your idea certainly does that. In fact the energy required to warp spacetime is just the energy encapsulated in the mass that sits at the center of the warp. There is no other energy required to do the warp.

Bill Gill

Hmm my post's because they are moderated are very delayed think my other post will come up between these.

Okay we need to seperate gravity and energy pressure from the fabric of spacetime.

Imagine spacetime as a blowup camp bed putting mass on the blow up bed deforms spacetime (our bed) locally and does put a little pressure on spacetime. However think to make energy we put more pump more pressure in to the bed.

These are really bad analagies but they do show that as a foam or fabric, spacetime can build pressure in two ways.

It is probably somewhat useful because you can also sort of see what pressures would drive universe inflation.

Remember the only thing opposing our pressure we build up is gravity the only attactive force we know.

So in someways visualizing it as a blow up bed or ballon is a good way to view a very very large hyrdrolic like system.

This is the situation I keep coming back to, but each time I arrive there I ask myself: where else in nature can one find a situation in which energy does anything without an exchange that depletes the source?

Where else in nature? How about the Strong Force, mediated by gluons, that binds quarks together, Bill? That is a question rather than answer, I assure you.

Hopefully someone will come up with an answer, but I can confidently predict that I shall not be that one.

How do you distinguish between a force that causes something to happen indefinitely, without expenditure of energy, on the one hand, and perpetual motion, on the other?

I believe you get a mass deficit via good old Einsteins theory .. someone check :-) So I don't really believe this is an energy exchange without depletion even in this case which is what I think Bill is getting at.

I have expressed to you before Bill in some ways GR and the 2nd law of thermodynamics are different views of the same thing.

Given we expect GR to fail at small distances because of QM I would view the most likely places to look is around QM for violations like Red's suggestion ... and my answer is a thought not an answer too sorry :-)

Just checked and yes they are sort of saying what I would have guessed.

Sorry this is beyond my ability at english so I will use a quote



Hmm maybee QM does have another role ... time to ponder that.

Skipping merrily along I have now another comment on Bill S.'s book about gravity

Actually the "equal and opposite force" involved in a rock lifted above the surface of the Earth is the force that causes the Earth to move toward the rock. Let's skip the lifting part and look at the rock as it moves toward the ground, to simplify what we are talking about. The rock falls towards the Earth because gravity causes a force to act on the rock. But at the same time that the rock is falling toward the Earth, the Earth is falling toward the rock. The "equal and opposite force" is the force pulling the rock toward the Earth. The mass of the Earth is a lot larger than the mass of the rock, so the rock moves the farthest and fastest, but both of them are moving.

Bill Gill

Ok Orac Now I have a question about the following quote.



I am trying to get a feel for what you are saying here. My first thought is that F=MA is different if you are looking at it in Quantum way than if you are looking at it in a Classical way. I assume that "On average F=MA" takes into account the uncertainty principle. So that at small scales you do have to use Quantum principles to calculate how a system will act in response to an applied force. Of course at what we might call normal scales the uncertainty averages out so that a Classical system works according to F=MA in the hard sense.

I hope I have that somewhat right.

Bill Gill

I have a feeling your English might have been easier to cope with.

Thank for your latest comment, Bill. It seems to be an answer to the question"...where does it end?". I assume the intermediate stages such as my feet pressing harder on the ground, and the Earth pushing back, are still valid as intermediate stages.

BTW, Bill, I hope that one day you might do a similar dismantling job on "The Divided Universe".

Bill S ... in my words I think what they are saying is that because of uncertainty principle that the quark binding forces can zip in out of being without an energy cost (ie perpetual motion)

That in itself I find both weird and interesting .. I really need to talk through this with some physicists.

I can view it one of two ways

1) The 2nd law doesn't apply to things in the QM uncertainty realm. I would really like to go read and look at what happens with entangled particles because this woudl imply you could use them for lossless transmission across vast distances a fact I find both weird and facinating.

2) That spacetime fabric has "resistance" (sorry best word I could use .. my english is very limited) so like in a electrical circuit transferring energy costs some of the energy. Also a very interesting concept.

Anyone got another view on that?

Ok Bill S. I think this will be my last comment on your book about gravity. And I'm not going to look at any one part of it, just a few general comments.

I think your biggest problem is that you see gravity as a large source of energy and you don't know where that energy is coming from. Well, all I can say is that it is a part of the total energy of the universe. You kind of allude to that in your last paragraph. And you are having a problem with how it can keep up doing things like controlling the motion of all the masses, without losing energy in the process. Well, actually any individual mass will lose some energy. For example the Moon orbiting the Earth will radiate gravitational energy in the form of gravitational waves. The problem with this energy release is that we can't detect it. Gravity is far and away the weakest force in the universe, so detecting gravitational waves requires some extremely sophisticated systems. They are hoping to detect gravitational waves from sources such as neutron star mergers, or black holes in orbit. Here is an article on ScienceDaily Magazine. So then the energy of gravity is used up, or at least transferred from one object to another.

And of course the question of where the energy came from in the first place is still one that is wide open. It is still the question of "why". We just have no idea why the universe exists.

Bill Gill

Orac, I knew you could do it! I get it now! When you have talked it through with some physicists, I hope you will share your findings.

You keep saying how limited your English is , then proving how wrong that is. Give yourself credit, you're good.

Thanks for an interesting link, Bill; and thanks to everyone for your contributions to this thread. I've been trying to find the time to tie all the ends together, but now its a must.

I hope I can tempt someone into "The Divided Universe" thread; even if only to say "rubbish", as long as they say why its rubbish.

Physicists who work with quantum entanglement tend to dismiss the possibility of faster than light (FTL) communication using entanglement, but then Einstein tried to dismiss quantum entanglement completely. I have an interesting book about entanglement, but don't have access to it right now. My daughter has it. I will probably get it back in a couple of weeks, when I go see her. The book is "The Dance of the Photons" by Anton Zeilinger. In it Zeilinger clearly shows why it won't work, assuming that he is right. I figure he is probably right, but then I don't like to lock myself into a position when it comes to advanced scientific ideas. People keep coming up with new ways to bypass the built in limitation.

Bill Gill

Arg ... just when you think you understand stuff someone throws a rock in.

Speaking to some people they pointed this out.

Two views on same work.

http://www.technologyreview.com/blog/arxiv/24759/
http://www.smartplanet.com/blog/smart-ta...s-possible/3967

And that really does defy the second law

It sort of also implies QM isn'g just a wave function or add in to any fundemental theory of everything ... well unless you can explain how you can transfer energy via a probability wave function rather than information as we usually view it.

Yep, it just keeps getting weirder and weirder. Entanglement has already been pushing the envelope in Special Relativity. After all Einstein really didn't like it since it seems to imply some kind of communication at speeds greater than C. But it is real. Now they are pushing the envelope even harder. There is definitely something we do not understand going on in the universe, since there are so many things that one well developed and tested theory says can't happen, and another well developed and tested theory says must happen. There is obviously a lot going on there that is hidden from us right now. I just hope that somebody has their 'aha' moment before long and shows us how to put it all together.

Bill Gil

Could we be moving towards the concepts of the "Zero Point Field"?

Yeah Bill.S we would be heading into those sort of theories if that energy transportation holds up and we probably need time for work to be confirmed. There are obviously quite a few theories this sort of result would favour QCD, variants of string theory (think they allow just about anything to happen ^_^) for example.

It's such a big shift from viewing QM as teleporting information in a classic sense to teleporting energy and able to get involved in energy processes.

Remember we also started out from another fundemental energy/binding force on quarks from the reference from redewener which I hate him for now cause my physics world just blew up :-)

I was backing the higgs boson to be found in a $10 bet ... It's not looking good for me at the moment :-)

I have alot of reading to do around QM but I am guessing theories based more around particles where they tag in QM when symmetry breaks like susy, LQG, spin foam etc with supersymmetry quantum mechanics may be in alot of trouble with this.

This just in yesterday which is sort of heading the same way

http://www.newscientist.com/blogs/shortsharpscience/2011/06/tevatrons-mystery-signal-grows.html

They are saying it's definitely not a higgs boson so those in the QCD like theories are looking stronger.

I love the ending of punzi's presentation
http://blois.in2p3.fr/2011/transparencies/punzi.pdf



And for Bill.S the stand-up physicist has put a spin on it for you (Don't get hung up on the maths) just follow the story.

http://www.science20.com/standup_physicist/why_quantum_mechanics_weird-79513


Not sure I like where this all goes I sort of like my old solid world interpretation but I am guessing the jury will be in sooner rather than later at the rate this is going.

I think we must be close to calling some TOE theories dead now.

http://www.physorg.com/news/2011-06-researchers-create-light-from-almost.html
http://physicsworld.com/cws/article/news/46193
http://www.physorg.com/news/2011-06-quantum-physics-photons-two-slit-interferometer.html

QM is throwing up way to many weird things for them to survive unless they can explain them.

I made http://images.iop.org/objects/phw/news/15/6/4/double1.jpg my new background thats an image that is going to haunt alot of physicists for a long time. You really wonder what Einstein would have said a particle going through both slits.

There are a lot of unanswered questions in both QM and GR. The major thing about both of them is that they work. They are really strange and trying to figure them out is impossible for most of us. But I'm not going to give up, after all, they do describe the world as we see it. It is just that we don't really 'see' it the way they describe it.

And of course Einstein really didn't like a lot of things about QM, even though he did a lot of the work that led up to it.

Bill Gill

For me alot of the answers are there I just don't like them they play with my sensibilities.

I quite liked the idea of light as a probability wave that when I measured solidified to a particle .. see I know waves can go thru 2 slits at once but particles should only go through one.

The idea a single particle can somehow split and pass through both slits but when I measure it's only one particle not two plays with my sensibility.

So I have to accept that everything I perceive is an illusion and now how deep does the hole go ... don't expect me to like this :-)

Individual photons generate their own electrical and magnetic fields that travel along with the photon.

When the photon passes through one of the slits some of the accompanying em radiation passes through the other slit and when it emerges from that slit it interferes with the photon causing it to change direction.

They are measuring the actual spin of the particle via a weak measurement (http://physicsworld.com/cws/article/news/46193) and EM wave simply would not give the results they produce.

The particle has to be there and as the work shows its in both slits at the same time (see the graphs) there is no denying what it is seeing.

That's why this is going to haunt lots of theories like yours above it's dead in the water.

This result is a profound as the original double slit experiment.

I can't explain it, I don't like it but I have to accept it.

That information is either misrepresented or misinterpreted.

The diagram does not present a picture of what actually takes place (i.e. as would a camera) but is a computer generated picture of what is thought to be happening however on the assumption that the diagram depicts what is assumed to take place between the slit card and the target card it shows photons appearing at the back of the slit card at locations where the slits do not exist.

Text books show that a single photon arrives at the target card location as a single pinpoint of light that is located at some position along the curve shown in that diagram but not as an entire curve.

They also show that a series of single photons aimed at the target card will eventually add up to and produce that curve and I believe that this is what that diagram depicts.

No you can not take a picture because you are only allowed to take weak measurements.

What they are doing is reconstructing the trajectories (they know a position and time but not together) and from that they put the partcile in both slits similtaneous, admittedly based on probability.

And thats the point the text books which use Bohr interpretation are wrong.

Edit: The original article has a better image of the single photon tracks emitted by the quantum dot generator
http://www.aip.org.au/Congress2010/Abstr...rajectories.pdf

Edit: I found a more layman breakdown of the experiment which may help

http://arstechnica.com/science/news/2011/06/an-experiment-that-just-keeps-on-giving.ars

I loved the comment.




At every point along the trajectory including going through both slits there was a particle it was never just a wave.

So what we are probably looking at is something like a more modern explaination, I think the doug sweetser (the standup physicist) does a pretty good job here (http://www.science20.com/standup_physicist/why_quantum_mechanics_weird-79513)


At no point do we have light as solely a wave it is always a particle and yes it can go through two slits simultaneous. The wave like behaviour comes from its fundemental quantum nature.

This is a bit like the problem of time in relativity observers can disagree on time because of there frame of reference what doug is showing and mathematically is the reverse of that, observers can disagree on 3d space positions and that is what the experiment shows.

It's not a massive shift you just need to accept that there is always a particle and it can be at two places at once rather than a wave which collapses back to a particle.

When you think about entagled partciles it really is no different and that looks to be where we are heading.

Superposition looks to be a norm for photons and given we can do it to "soild" things is it really that surprising.

There are more and more experiments showing the same thing I am seeing them daily

http://francisworldinsideout.wordpress.c...-the-same-time/

Coming at it from the other way you also do a controlled entanglement of a photon

http://www.physorg.com/news197900557.html
http://www.physorg.com/news/2011-06-chinese-team-entangles-photons.html

There are groups setting up to attempt double slit with entangled photons which should really show us some things.

I should also add this actually may ease the explaination of of the H2 and other particle experiments with double slits

http://www-als.lbl.gov/index.php/science...ysics-meet.html
http://www.physorg.com/news113822439.html

and more recent matter experiments

http://www.physorg.com/news/2011-04-scientists-quantum-breakthrough.html

Light and matter seem to be converging in QM.

Can we definitively say all this to be true at the moment ... no ... but in the same way almost all the old classic "stories" in the text books have shown to be wrong.

I fail to see how any of the material you provide negates the idea that when a single photon passes through one of the slits that its trajectory is then determined by em radiation emerging from the other slit.

The diagram in the first link shows 'Trajectories of a Single Photon' and depicts perhaps 100 separate routes but I believe that it should be headed 'Trajectories of Single Photons' on the basis that a single photon can have only one trajectory not hundreds.

And thats the point its a single photon from a quantum dot (there was a pile of anti-bunching testing done to check it was only one photon) so the photon should have only 1 path not hundreds. Remember those paths are going to be the "light" spot of an interference pattern against itself and it is a partcile on trajectory on each and every path which are meters apart. You can backtrack the trajectory to which slot it came through.

We can't proove to you that it is the same parcticle everywhere beyond that because of QM.

The reality old interpretations are going to have to contrive ways to explain the results like that the particle chooses a different path randomly each time and thats why we see partciles on each of trajectories or its only a wave as it goes through the slit they couldnt get the trajectory up any closer to the slit. But that begs the question why does it change at the slit and how would it even know there was a slit.

I saw a really neat analagy.



No one is ever going to be able hard proove to you beyond this if you believe one of the other options they are equally valid beacuse I will never be able to disproove them QM stops me.

However you are also ignoring alot of the other weirdness thrown up by QM because we have done this with electrons, neutrons, whole atoms, and entire conglomerates of atoms and they all do the same thing but we had the reverse problem we were struggling with where the wave like behaviour came from.

I don't buy either Bohmian or Copenhagen views I am a number 2 man and that means a different yet to be defined interpretation.

That's what I SAID!

A single photon can have only one trajectory at a given instant not hundreds of trajectories.

If a single photon is directed towards one such slit you cannot then have hundreds of identical photons emerging from both slits.


That's what I SAID! The diagrams to which I referred show a number of trajectories applicable to a NUMBER of particles NOT to a SINGLE particle i.e. as you wrote, above - "...the photon should have only 1 path not hundreds."


That's correct - that's what I'VE been saying! We 'see' individual particles on each of the trajectories. We don't see the same photon on each of the trajectories!

Your analogy of weighing a thousand sheets of paper confirms my argument that the experiment to which you refer shows the assumed trajectories of 'hundreds' of photons NOT of a single photon!


You gave the impression that the experiments to which you referred 'proved' that my posting regarding the effect on a particle's trajectory by em radiation passing through the other slit was erroneous - they do NOT!


I object to your unwarranted, belittling criticism. I am NOT ignoring same but am not referring to same on the basis that they have no application to the subject on hand i.e. an explanation for the deflection of photons in the twin slit experiment.

I anticipate no response to this request but perhaps you might suggest which of the other weirdnesses arising from QM provide a solution to the claimed particle/wave duality.

You cannot prove that it is "...the same particle everywhere..." because it is NOT the same particle everywhere and your comments, above, show that you are aware of this fact.

Then you missed the point because it is showing hundreds of photon tracks.

Thats the point of the analagy so if you use copenhagen the particle just divided hundreds of times not quite sure how?

The only other way to contrive an answer is say each time it took different paths but then you wouldnt see lines but a single line because remember 1 photon many many seconds apart??????

They are the only two ways to view the result and neither really works well the second particually because thats not what we see.

Is that clearer .. you may need to read the whole paper the events are quite some time apart they are tracking the diffraction pattern.

It's quite impossible a single photon could produce the interference pattern unless you allow the photon to split in hundreds.

And there in lies the problem.

The single photon became many or the light used its wave nature to interfere through the slits

Both explaination now face problems with different parts of the observation.

The wave explaination has problem in that we can track particles on each and every trajectory. What you are seeing is a classic bohemian tracking

http://plato.stanford.edu/entries/qm-bohm/figure1.gif

Which was not supposed to happen remember this was all supposed to be settled.

The particle explaination has problem with why and how did it split.


Sorry english is not my native language so I may ask Bill or Bill.S to explain if you still don't get it.


There are a few Bohenian nutter's come back out the woodwork with the result I am expecting that but really both explainations are equally flawed.


As I said many on the modern QM groups where not suprised most had already considered Copenhagen dead based on other current work.

I'm afraid I won't be much help in explaining it. I realize that the graph they show is the result of many measurements of many photons, one measurement per photon. I have absolutely no idea why it works the way it does. I do tend to agree with you about which explanation to go with, Number 2, an explanation that hasn't been developed yet.

Bill Gill

In my previous post I specifically asked you to suggest which of the other weirdnesses arising from QM provide a solution to the claimed particle/wave duality.

As anticipated you ignored that request.

I see no reason to continue this condescending monologue.

I in no way meant offence Bill 6, I assure you it is my english language skills not my intent.

I certainly don't have the answer so I am not sure I can be offensive.

I certainly don't wish to stop debates.

You openly accused me of "...ignoring a lot of the other weirdness thrown up by QM..."

It was NOT your English language skills which led you to make that statement. You were seemingly of the opinion that I was ignoring same thus accused me accordingly.

Your intent - i.e. dismissive criticism of my argument - was exhibited by the fact that you made this unwarranted claim NOT the way in which you worded it.

When I accordingly asked you to nominate specific weirdnesses you made no attempt to comply.

This does not indicate a weakness in expressing oneself in the English language but an inability, or unwillingness, to courteously conduct a discussion.

I have no intention of leaving myself open to the possibility of additional unfounded criticism.

Having returned after an enforced absence I find there is a lot in this thread that will need attention. As time is still at a premium, I have had only a quick scan through, so I could be entirely wrong, but I find myself wondering if, to some extent, Bill6 and Orac might be saying the same thing.

They are continuing the work of weak measurement into a fairly powerful tool hopefully giving us some really interesting results

http://www.physorg.com/news/2011-06-canadian-method-quantum-wavefunction.html

I really do appologize Bill 6 ... sorry.

Bill6; I recall saying that I would return to your comment about the convergence of the Milky Way and Andromeda. Trouble is, I can’t remember now what the point of discussion was. Time is too short at present to do a lot of hunting through past threads, so I shall just post a few questions and answers, not necessarily correct answers :), in the hope of getting near the topic. I thought that might be better than just letting the whole thing slip into oblivion.

In an expanding Universe, why are Andromeda and the Milky Way moving closer together?

The expansion of the Universe is causing the galaxy groups to separate. These two galaxies are in the same group, so the major influence comes from gravity, rather than the force of expansion. The expansion of the universe is not enough on the scale of our local galaxy group to overcome the attraction of gravity.

Considering the relativity of motion; is it possible to say if either galaxy is moving towards the other?

At first sight it would seem that the easiest way to tackle this question would be to regard the Local Group as a static frame of reference and decide which galaxy is moving relative to the LG. However, even that is not straightforward. Considering the situation more precisely; if you consider an inertial frame that is stationary relative to the centre of mass of the LG both galaxies will appear to be moving towards each other. There is a school of thought that says that to claim things are moving towards or away from each other is a contradiction in itself, and that instead we should say they are moving towards a state of equilibrium. However, in this instance, that seems not to be very helpful.

Is there any other, larger, thing in the Universe that could be taken as a static F of R?

Possibly, a supercluster can be regarded as a larger static unit, but the only universal thing I can think of is the Cosmic Microwave Background, which seems to approach every point in the Universe, at the same speed, from every angle. Presumably movement relative to the CMB is as near as we could get to “absolute movement”.

Do we know why Andromeda and the Milky Way are moving closer?

Gravitational attraction within the LG has to be the reason. At first glance it might seem that an equilibrium exists between gravity and the force of expansion which keeps the group together, but does not permit it to collapse. However, the collective velocity of the LG is estimated at around 270 kps towards the Virgo cluster (Virgocentric infall rate). It would seem that the LG is collapsing, but Andromeda and the Milky Way must be sufficiently close for their mutual gravity to provide movement in a secondary direction. The trouble seems to be that the closer one tries to look at the situation, the more one finds different movements. For example, both the LG and Virgo Cluster are moving at roughly 600kps (relative to the CMB) towards Hydra Centaurus and converging at the rate 270kps. Where does astronomy end and cosmology begin? Or is it the other way round?

BTW, Bill6, I still plan to investigate the tired light idea when time permits.

Hi, just one question. For our Local Group, would it not be possible to use the CMB (cosmic microwave background) as the F of R?

I am not really expert enough to offer anything more than a humble opinion.

GR explicitly says there is no zero frame because gravity extends infinitely.

QM also explicity expresses the same view through Bell's inequality. It's worth doing the simple Bell test over at science 2.0 (http://www.science20.com/quantum_tantrums/be_be_measured_part_1-79218). Solve the puzzle see the problem :-) If you don't have the maths background he solves it for you in part 2 (http://www.science20.com/quantum_tantrums/be_be_measured_part_2-79615)

So I would say definitely no at a technical level.

Accepting that I can see the argument however that it is probably the nearest you will get to a zero frame the question really then becomes how tainted (not sure this is right word??) your results become.

I think I've already indicated that I do not believe in the big bang/expanding universe theory.


I don't see any difference between saying that it is moving toward us or we are moving toward it or we are moving toward each other.

I don't presently see any way of determining if Andromeda is moving relatively to a fundamental reference frame.


I agree that the CMBR provides a fundamental reference frame however detractors argue that the 'singularity' from which it is claimed the universe developed was moving when it exploded but for this to take place it would have to have been moving relatively to something yet their argument is that nothing existed prior to the 'explosion'.


Agreed.


Isn't the latter an extension of the former?

You are possibly moving around so fast that time is slowing down for you.

BTW, my name is Billspace6 not Bill6

Sorry, Bill 6; I must be having problems with the nature of space.

LOL very good Bill S.

Ulrich mohrhoff over at science 2.0 has put up a really nice current state QM explaination of the revisited double slit.

http://www.science20.com/quantum_tantrums/blog/2slit_experiment_revisited-80111

So basically the current QM view is there is no left or right slit as far as the photon is concerned.


The more I read on QM the more I dislike it :-)

Did alot of asking around and digging and managed to conn some time to talk to a pleb from a QM group.

Alot of the current QM groups believe there is a 3rd partcile besides fermions and bosons called anyons (http://en.wikipedia.org/wiki/Anyon). I had never even heard of these had anyone else?

All the important work is cited in the wiki link.

They sort of predicted the slit doesn't really exist for light based around some works postulated in early 90's. I will link the only one I could find from that era apparently there are more
(http://cdsweb.cern.ch/record/221658/files/cer-000134247.pdf?version=1). Probably why they were the only ones not surprised by the weak measurement results.

Sort of overview of anyon physics (http://sestrilevante08.ge.infn.it/relazioni_su_invito/cappelli.pdf)(http://news.softpedia.com/news/Quantum-Mechanics-Finally-Got-Weirder-16561.shtml)

Now apparently there are proposed tests that would enable the direct observation of the particle .. so stay tuned :-)

Sigh more reading and work to catch up on!

Bill 6. I'm stilltrying to find time to look at tired light. The chances are I shall be slipping in odd questions for some time to come. Here's the first.

I found the following statement: "Since the relation [between observed redshifts] is the same in all directions it cannot be attributed to normal movement with respect to a background which would show an assortment of redshifts and blueshifts."

Why could not "normal movement" produce the observed redshifts?

Presumably because normal movement would generate an assortment (roughly an equal amount) of redshifts and blueshifts not an overwhelming preponderance of redshifts as observed.

Ned Wright has a nice tutorial on it taking you step by step through it.

http://www.astro.ucla.edu/~wright/cosmo_01.htm

Starts as a steady state universe then spherical explosion in a static space to finally an expanding universe.

According to it in chapter 2



So probably start with why that observation ruled them out.

.

I reached this point, then I found myself wondering why spreading might not be considered as "normal movement with respect to a background".

The reverse of that has to be a question for Bill 6.

I don't see the question.

The thought process (if it can be graced with such a title)went some thing like this:

“Models that do not predict this relationship between DA and DL, such as......the tired light model, are ruled out by the properties of the CMB.”

Orac said: “So probably start with why that observation ruled them out.”

Reversed question: Why is the tired light model not ruled out by this line of reasoning about the CMB?

Another question for Bill 6.

How does the tired light model square with results of the Tolman surface brightness test?

Please try not to be too technical

I fail to see how any line of reasoning based on assumptions and personal interpretations can prove or disprove any concept.

OK. Can you be more specific, though, you are dealing with a novice in this area?

does this comment also apply to the question about the Tolman surface brightness test?

Sarcasm is intolerable.

Bill 6.

I was not being sarcastic; it was an honest request for something I could understand. I do not have a background in science, and struggle with some of the things that many of you take in your stride.

I apologise for my reaction.

I, too, am bereft of formal education in the subject of physics however your referral to the following material indicates a superior level of understanding.

According to Wiki - the Tolman test conclusions are based on observations of light emanating from distant galaxies and I fail to see how anyone can insist that said conclusions are indomitable.

From what I can read it seems that his test did not actually disprove the tired light theory but tended to favor the alternative expansion theory.

That was, more or less, my understanding, but I wondered if I had missed anything.

Bill 6: How about doing us a "hitch-hiker's guide" to the tired light model? It should draw a few people in.

I don't understand.

Why “Hitch-hikers’ Guide”? To answer that question it is first necessary to consider what we understand by a hitch-hiker. Obviously, it is, in the strict sense, someone who travels by seeking and accepting “lifts” from other travellers who are going in the same direction. Essentially these hitch-hikers fall into two very broad categories. The first includes people who simply want to get from A to B, but do not have their own transport, and cannot, or choose not to, use public transport. The second category includes those who are travelling for the joy of travelling, and for whom the carefree uncertainty of hitch-hiking adds something to the pleasure of the experience.

The hitch-hikers to whom I refer have much more in common with the latter group than with the former. I refer here to people, like myself, who have no particular expertise or training in science, and are not professionally involved in scientific pursuits. I consider myself to be a hitch-hiker, and suspect that there are lots of others on this forum.

Here I thought you wanted a "HitchHikers Guide to the Galaxy". That of course is already out, written by Douglas Adams.

I personally am not that much up on tired light, except that it has been pretty widely shown to be wrong. Of course Wikipedia has an article on it. Check that out, it isn't too technical. It covers most of the high points, including the fact that current measurements have pretty much ruled the possibility out.

Bill Gill

thanks for the suggestion, Bill. Looks as though you found much the same sort of thing as I did. However, as we have a "tired-lightophile" in our midst it seems a shame not to avail ourselves of the pros as well as the cons, which are more easily found.

I couldn't understand what you meant by 'doing a hitch-hiker's guide' to the tired light model nor why you asked me to do one.

When someone whose oppinion I respect holds a view about which I know little, I find it difficult to resist a little "brain-picking"; or even a lot!

Can anyone cast some light(!) on how Tired Light Theory accounts for the observations that are taken as evidence of accelerating spacetime expansion? Does it explain this second derivative (the acceleration) of the expanding universe in terms of tired light? If so, how?

I'm hoping Bill 6 will do this for us. The references I have found so far seem, generally, dismissive, but with any luck Bill 6 will present the other side of the theory.

You seem to think that I have some sort of expertise in the subject of tired light - I don't - I merely believe that because space is permeated with particles the absorption/emission of photons results in their loss of energy.

If a beam of light is projected through a glass block that object will heat up and remain warm long after the beam has departed.

This accrued energy must come from the photons that passed through the object thus they would emerge from that medium redshifted compared to their frequency upon entry of same.

This is not associated with the scattering challenge aimed at Zwicky's intervening particle suggestion.

So you are an aether believer Bill 6 ... Lorentz or one of the newer variations they seem to be makign a bit of a comeback at the moment?

I have a question however based on you comment above if light is losing energy to the aether in space doesn't that mean there is actually a finite distance you can send it before it ends up losing all it's energy to the space aether?

Hi Bill. Just a quick summary of what I've gleaned on this (this is not out of my head, as I know precious little about it):

There is no known way in which the photons can lose energy (Compton scattering is ruled out by the absence of blurring). Each photon passing through the material is either absorbed or not absorbed. There's no half-measure whereby the photon simply loses energy. The energy does come from the photons - but only from those photons that are removed.

http://www.stolaf.edu/people/jacobel/courses/phys245/Gamma%28photon%29_Absorption.pdf

The Absorption Coefficient:
...Absorbers are inserted between a radioactive source and a gamma sensitive detector. For the latter we shall use a scintillation counter, since it is sensitive to the gamma ray energy. The count rate is determined for several different absorber thicknesses. As one might expect, that rate will decrease exponentially as the thickness increases. The reason for this is that a single interaction completely removes the photon from the beam. (This is unlike the case of a charged particle going through matter. There the charged particle loses energy through many small energy transfers, not a single transfer that removes the particle from the beam.)

Thats a cool explaination redewenur I suspect we could even do better than that these days we could actually use a single photon source and send it in an check we either get a photon at the far end or not at all.

However that does not really completely rule it out in a vacuum it certainly explains the behaviour in other media. If Bill 6 was using it just as a sort of indication not literal we still have not dealt with vacuums.

I still think the bigger issue is consider it is bleeding energy as it goes at some point there is going to be an energy crisis what happens at that point?

I am NOT an aether believer!

My understanding of 'an aether' is that of a medium which transmits light whereas I'm of the opinion that light requires no medium to travel through space.



Several authors (e.g. Davies-Gribbin) write that the light from far-distant galaxies (that are receding at superluminal rates) is moving away from us hence is undetectable.

Alternatively, their distance is so great that their light redshifts to nonvisible frequencies.

That is what I found when I started looking for information on the subject. This is what I posted then.

The idea is that indeed the light from those distant galaxies is "red shifted" down to an undetectable frequency. I used quotes around red shifted because the red shift isn't really a result of velocity, it is because as space has stretched the light has also stretched.

Bill Gill

The operative term being 'no known way'.


We have no way of knowing if the image of a distant galaxy is blurred or not due to the fact that we can obtain no image which does not contain the intervening particles.


My understanding is that ALL of the photons passing through the material are absorbed/emitted by the atoms they encounter which explains why a beam of light takes longer to travel through a medium than to cover the same distance via a vacuum.


Your note refers to absorbers that are inserted between a radioactive source and a detector; it seems obvious to me that said absorbers will ABSORB some of those particles whereas the atoms in a glass block will, according to quantum theory, absorb the original photon then emit their own photon.

You refer to "..those photons that are removed." This obviously relates to the photons that are removed by the absorbers!

There are no purposefully inserted absorbers in a glass block. The atoms absorb then emit.

You further refer to charged particles "...going through matter that loses energy through many small energy transfers." This is what I believe takes place when a group of photons (a beam of light) travel through space encountering free particles along the way. One way to find out if the beam loses energy (redshifts) along the way would be to project one through a medium (e.g. horizontally through a lake).

It has been many years since I referred to the subject but I believe that when light travels radially down into the ocean it redshifts thus red colored objects - fish and coral - stand out more?

True, but if there isn't a known way then you will have to come up with a way that wasn't previously known, and then you will have to provide a solid theoretical basis for your new way.

There is a Wikipedia article about refractive index that explains the lower speed of light through a medium. The photons are not absorbed and re-emitted by the atoms of the medium. Instead they interact with the atoms to drag them off a little and then let them go back where they were. This produces a drag on the photon motion that slows the photon down.

Bill

Are you quite sure of that, Bill? Isn't the resolution of the HST and other modern photon receivers - able to 'see' billions of parsecs - sufficient to rule out scattering as the cause of the measured redshift? Have you taken a look at the Hubble Ultra-Deep Field image?

http://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field

If a beam of light is projected through a glass block it slows down. By the same token, in the tired light model, would light not be measured as travelling at less than "c" after travelling through space?

We had quite a long discussion about the variation in the speed of light in different media in another thread.

The following is an extract from the notes I distilled from that discussion. I would be interested to know if others feel that I "got the right end of the stick".

Manifestly, light slows down when passing through any medium denser than a vacuum, but how does it do that? One explanation goes something like this: Consider a single photon passing through a block of glass; for simplicity, have the glass surrounded by a vacuum. It approaches the glass at “c”. Once it enters the glass, it is absorbed by an atom, then re-emitted. This process is repeated as it continues to pass through the glass. In fact it is not a single photon that travels through the glass; it is a succession of new photons, created at each new emission. Any travelling done by the photon within the glass is at “c”; the apparent slowing results from a succession of minute instants during which the photon does not exist. We have, therefore, to regard it as travelling at “c” whatever medium it is travelling through.

Would that explanations were that simple, but of course they are not. It turns out that if this were what actually happened, then the absorption spectrum would be discrete because atoms have only discrete energy states. Yet, in glass for example, we see almost the whole visible spectrum being transmitted with no discrete disruption in the measured speed. In fact, the refractive index (which reflects the speed of light through that medium) varies continuously, rather than abruptly.

The reason for this is that a solid is composed of a network of ions and electrons fixed in a "lattice". Because of this, they have what is known as "collective vibrational modes", sometimes called phonons. These are quanta of lattice vibrations, and it is these vibrational modes that can absorb a photon. So when a photon enters a solid, and it can interact with these phonons, it can be absorbed by the solid and then converted to heat. The solid then becomes opaque to this particular photon (i.e. at that frequency). Unlike the atomic orbitals which are discrete, the phonon spectrum can be broad and continuous over a large frequency range.

If a photon has an energy beyond the phonon spectrum, the solid cannot sustain this vibration, because the phonon mode is not available. So the lattice does not absorb this photon and it is re-emitted but with a very slight delay. This appears to be the origin of the apparent slowdown of the light speed in that particular medium. The emitted photon may encounter other lattice ions as it makes its way through the material and the resulting reactions accumulate to cause the delay.

You can actually bring the speed of light down to that of sound with a bit of clever physics and prove it absorbs and reemits at each and every atom point in the media
(http://www.physorg.com/news/2011-07-scientists.html)

CSharpner gets the theory right in the comments

When light moves through a medium, each photon is absorbed by an electron in the median, stored for a (very) short while, then it (or a new photon, with identical quantum properties) is then emitted in the same direction. Between electrons, it's moving through empty space and travels at full speed (c). The repetitive stalls while each photon is absorbed by electrons causes more and more of a delay. The light, itself, never slows down. When an electron absorbs a photon, the photon ceases to be "light" and instead is an electron with a higher energy state. Eventually, the electron loses the higher energy state, creating a new photon. While it's a photon, it's always traveling at c.

Photon @ c -> high energy electron state (delay) -> photon @ c, etc...


Prediction and experimental verification I am not sure you can do much better than that unless you want to try and explain the result some other way.

You have two things to consider the light moves at one speed if you dont rotate the glass and this really slow speed if you do ... why if you have a different theory?

Orac, as usual you have come up with something authoritative. I am certainly not equipped to argue with the experts. One question that does seem still to remain is why the absorption/emission spectral lines are not discrete if the absorption and re-emission are due to the quantised absorption and re-emission of electrons.

LOL I am not sure if I am authoritive about anything QM has completely destroyed my world :-)

The questions that are being asked on the forum at the moment are the same ones that are sort of being asked by everyone in physics.

Some of the tests are not that hard to do given equipment today it's thinking okay if that true then if I do this it should do that ... I really liked that experiment because it is simple yet so compelling because the media remains unchanged just spinning.

So now it boils down to a very simple question why would spinning a media slow down the speed of transmission through it.

And speaking of QM get ready for it

http://www.newscientist.com/article/dn20712-how-to-be-in-two-places-at-the-same-time.html

The team is very confident it will go into superposition and then pandora's box is really open.

It was redewenur who suggested that there is no known way - not me.


I do not accept wikipedia as THE ultimate reference.

It is my understanding that scattering has no relationship to redshift but only to sharpness (or blurring).

I assume that it would however to the best of my knowledge no-one has as yet successfully measured a one way speed of light particularly emanating from outer space.

Just for the record, as you probably know, it has been a matter of controversy:

"The Big Bang theory of the universe is wrong because the cosmological red shift is due to the Compton effect rather than the Doppler effect"
- John Kieren:
http://www.angelfire.com/az/BIGBANGisWRONG/index.html

"Kierein's Erroneous Compton Model for the Redshift" (Last modified 4-Feb-1998)
- Edward L.Wright:
http://www.astro.ucla.edu/~wright/kierein.html

E Wright's Home Page:
http://www.astro.ucla.edu/~wright/intro.html

BTW, do you still think we have no way of knowing if the image of a distant galaxy is blurred or not, despite the HUDF images? Surely, if blurring has occurred during the several billion lt yr journey, then it must be of an extremely small order. don't you agree?

Fair comment!
I still think you should give us an account of your understanding of the whole tired light theory, including the origin of the Universe. Picking, as we are, at little bits makes it so easy to be sidetracked.

Those images are just as affected by any free matter in outer space as are those of our personal telescopes.


How can a person possibly know the difference between the amount of blurring affecting a close up photograph and that of a long distance one unless the camera has been located there?

Being of the opinion that there have been no close up photographs of those distant galaxies I have no way of evaluating the extent of any blurring.

You already have my understanding of the whole tired light theory. As light journeys through space it is intercepted by free matter and loses energy.

In my opinion there was no origin of the universe, I believe that it is infinite in time and space.

Well, when I look at a picture of a light in a fog I can easily tell that the picture is blurred by the fog. So when somebody looks at a Hubble picture of a distant galaxy it should be pretty easy to tell if it has been blurred by matter in between.

Bill Gill

You may recall that when the HST was first operated, its images were found to be blurred despite the fact that their definition was superior to images of the same objects taken previously.

"Almost immediately after Hubble went into orbit, it became clear that something was wrong. While the pictures were clearer than those of ground-based telescopes, they weren't the pristine images promised. They were blurry."

http://hubblesite.org/the_telescope/hubble_essentials/

That was rectified by astronauts at a cost of $8m.

In your opinion, should it have been impossible to determine whether the images were blurred or not?

There is a difference between whether blurring takes place or not and the AMOUNT of blurring!

When you look at a picture of a light in a fog you are aware of the fact that there is a fog and that the image of the light is blurred by that fog. You might base the amount of blurring perhaps on other pictures involving less dense fogs or fog free instances however there has never been images of distant galaxies taken without intervening matter ergo the amount of blurring is, at this stage, indeterminable.

An undeniable fact is is that there is matter in outer space between us and distant galaxies and this mustcreate some blurring via scattering.

However I remain of the opinion that the tired light concept relates specifically to the frequency of light not its intensity (I trust I have the terminology correct).

Bill 6: "It is my understanding that scattering has no relationship to redshift but only to sharpness (or blurring)."

So, to recap, while you have no idea what causes the redshift, you're sure that it's not recessional velocity?

I believe that my comment to the effect that when light travels via the random matter in space and creates an increase in that matter's temperature leaving itself slightly energy depleted - i.e. redshifted - IS an expression of my opinion as to what causes the redshift!

I made NO suggestion that the redshift is not due to recessional velocity but pointed out that the energy loss may RESULT in recessional velocity!

In my opinion this part of the discussion has deteriorated into a childish point-scoring competition.

I have pointed out that my argument is in relation to redshifted light NOT blurred light so if you wish to continue in that vein you do so alone as far as I'm concerned!

I have intended my questions to be simple, clear and reasonable, Bill. For all I know, you could be right and the Standard Cosmological Model could be wrong. It's regrettable that you are offended by posts that question your beliefs.

I find no offense in posts that question my beliefs only in the way in which some of them are expressed.

I made no suggestion that your post to which I responded questioned my beliefs hence your comment is unwarranted.

This is the bit that fascinates me. It is also the bit with which I have had lots of problems. I have something akin to a clear picture in my head about it, but it is phenomenally difficult to keep a discussion of the subject in track.

That post and just about all of my posts in this thread question your beliefs on this topic. Be that as it may, I have no desire to annoy you, inadvertently or otherwise, so I'm pleased to let it drop. Actually, I'm inclined to think that you're right regarding time being without beginning and end, although I don't think it rules out the Big Bang.

Oh dear! The dreaded infinite series is making a comeback.

You know I have to take issue with this. Time, without beginning or end, is an infinite series, which is a mathematical concept that can never be demonstrated in physical reality.

Oh, I don't mind at all that it can't be demonstrated. It's the concept of time that sits comfortably in my mind.

Is this not philosophical belief, rather than science?

How do you justify the concept of an infinite series, even as an untestable belief?

Hi Bill S.

It's what I'm "inclined to think", nothing more, nothing less. It's not a matter of science. Not even part of a philosophical or metaphysical system. It's merely something that I lean toward in my personal view. As you'll appreciate, that requires no justification to others. The best I can do, I guess, is to say that I've always had difficulty grasping the idea of a beginning and end to time, whereas infinite time presents no problem to me. That's about it really.

Whilst just about all of your posts question my beliefs you did not have the decency to state that openly but surreptitiously attempted to conceal your criticism.

It was that devious practice which I found objectionable.

This sentence would apply to me if you changed the "no" into "a serious".

I'm not sure if I envy your comfort with the idea of infinite time, or if I just suspect that you have stopped short of thinking it through fully.

Take your pick Bill, I won't hold it against you, he-he.

OK, as long as there are no hard feelings, I'll go for the second option. Obviously, that could lead to lots of questions; some of which may have been asked in other threads, but it would be great to get some resolution on this one.

First question: do you accept that a mathematical infinity is not necessarily the same thing as a physical infinity?

Great to get some resolution, you say? Nice to see an optimist aboard.

First answer:

Lazy eight and the word 'infinity' are symbols that can invoke a concept which may differ between individuals. The concept, a mental representation, is not the physical reality, and may or may not represent physical reality. So yes, I accept that.

It will be interesting to see if anyone else comes in with a yes or no.

2) Is there a real difference between infinity and eternity?

My initial thought was "yes", but I have moved a long way towards "no".

Quick answer: Infinity applies to anything that has no limit. Eternity applies to unlimited duration, something like your wait in the dentists office. So eternity is a specific form of infinity.

Bill Gill

re (2) see Bill Gill's post above.

OK, but your wait in the dentist's is longer if you have toothache, so that must be a Cantor-type infinity.

Seriously, though, it sounds as though you are saying that eternity is "infinite time", and infinity is "infinite everything else". Would that be right?

There's another word, 'sempiternity', that's sometimes used where a particular distinction is called for, as explained in Wiki:

"While in the popular mind, eternity often simply means existence for a limitless amount of time, many have used it to refer to a timeless existence altogether outside time. By contrast, infinite temporal existence is then called sempiternity. Something eternal exists outside time; by contrast, something sempiternal exists throughout an infinite time. Sempiternity is also known as everlastingness."

For our purposes, I'm happy to stick to the popular usage of the word 'eternity'. So, yes, eternity is the label I use for infinite time, i.e. time without beginning and without end. If, for any reason, you prefer to use a different label, that's fine with me, so long as we know what we're referring to.

I would say that "infinity" is more a quality than a thing. Infinity is a concept that changes with what you are talking about. If you are talking about time when you say infinity you mean unending time, if you are talking about space, then you mean unending space, if you are talking mathematics then you mean an unending count of whatever concept you are talking about, such as the infinite number of integers.

Checking my dictionary (Websters' II New Riverside University Dictionary, 1984) I find that infinity is a noun, (1) "The quality or state of being infinite".

Bill Gill

Anyone else find this a bit incongruous?

It seems to make a distinction between eternal and sempeternal, but the reasoning is circular, and we end up with infinite time, in spite of the assertion that "eternal exists outside time".

Consider eternity, space and time. Relativity tells us that space and time are different dimensions of the same thing: spacetime.

Could it be that eternity is a superposition of space and time, such that it is neither until we try to “measure” it; then either the spatial or temporal aspect emerges, depending on what question is asked?

Just a thought.

Apropos the tired light theory; in another ng I happened across a comment in Wikipedia re the Pound-Rebka experiment -

Yes ... keep reading that explaination



That was the original problem if the universe wasn't expanding we would expect to see red shifts, blue shifts and nuetral galaxies which we don't .. we see only red.

We only (predominantly) see redshift because there are vast, free matter permeated, spaces between us and ALL of those galaxies!

We would expect to see red shifts, blue shifts and neutral galaxies in a non-expanding universe ONLY if there were NO random atoms scattered between us and those galaxies.

ALL of the light emitted by ALL of those galaxies has effectively traveled through a medium the atoms of which have absorbed the original photons then emitted their own photons resulting in the aforesaid loss of energy.

I think this goes back the Pound-Rebeka experiment and gives the theory a problem Bill 6



Thats the proposed mechanism by which we lose photons when it goes through a media like your glass you mentioned and it gets hot. In this media we dont see "tired light" we see the same light minus some lost photons.

Might think and look around because I am sure there would be an experiment that could be done with a media to deliberately bleed some energy of the excited atmoic state of the media. Prediction would be you get less light (photons out) when you drain the energy out as opposed to a different frequency light which is what I am thinking tired light theory would predict if I am interpretting properly.

So something like an ant-laser (http://spectrum.ieee.org/semiconductors/optoelectronics/antilaser-invented) but where we are draining energy ... lets see what we can find.

Sigh I am so silly it's essentially what happens with doppler cooling (laser cooling) ... didn't think about it till I started searching.

http://en.wikipedia.org/wiki/Doppler_cooling



I think that covers the basics for tired light.

Good thing we have Bill 6 and Orac to bring us back on track when we start wandering off into infinity. Perhaps we should start an infinite thread.

We already have an infinite thread. Have you looked at the Philosophy of Religions thread in NQS?

Bill Gill

I have. In fact I have made a few contributions. It would be interesting to know how many of the 2.5m hits were Rev.

What do you mean by that comment?

The light from various galaxies encounter atoms that are moving toward and away from the galaxies so presumably the number of photons absorbed will balance out however as I have pointed out on several occasions.. the redshift of the light from distant galaxies is in no way related to the number of photons that reach us!

Challenges to the tired light concept based on the scattering, or otherwise reduction in the number, of photons arriving at our location are either examples of deliberate disinformation or of ignorance.

The problem is we can show that we have never seen an absorbtion an retranmission at anything other than the original frequency ... quantum behaviour of the electron shell behaviour sort of demands it.

If it doesn't retranmit the photon the atom that absorbed it has more energy .. ergo it gets hotter. Ergo space not being a perfect vaccuum is also above absolute zero even in its futherest points due to the above.

Unless you can cite an example where an atom absorbs one frequency and retransmits another based on energy drain while the atom was in the excitation state I am not sure where you are going with this.

I am not trying to disinform or make any assertions here ... I am willing to believe you just at the moment it is not probable unless you can provide an example.

I can't proove that it couldn't occur because you aren't breaking any physics laws but just pointing out you are asking us to belive something we have never seen and should have really if it were so.

Edit: I should say I am not saying I understand light or cosmology any better than you and I certainly have no theory on how it all works. Every theory I have seen so far has problems with it ... I am just asking and probing questions around tired light.

The quote from Wikipedia re the Pound-Rebka article posits an energy loss by the photon that has nothing to do with its original frequency nor that of the absorbing/emitting atom -


Your response intimated that I had taken that quote out of context however the lines that you supplied made no changes to the context of that sentence.


According to the Wiki quote the atom moves when it emits its own photon and I am of the opinion that because it moves it incurs an increase in temperature.

There are no ‘furtherest points’ in the universe. All locations are equivalent.


I have already cited an example with the Wiki quote - above. The retransmitted photon loses energy in accordance with the conservation of momentum concept as the atom progresses from its excitation state.


There have been several claims in this thread that a reduction in the number of photons arriving here due to scattering explains redshift and although I have pointed out that this is a nonsense you continue to make that claim. As far as I am concerned this is an example of disinformation.


We have seen the phenomenon - light from distant galaxies is redshifted. As to why this is so... we have the above explanation from Wiki.

I had hoped that perhaps an experiment (such as the one that I suggested where a beam of light is projected horizontally through a lake) had been carried out but presumably this has never been done and, due to the fact that it could introduce another challenge to the big bang theory, authorities will ensure that it remains untested.

No you are doing it by ommission instead ... because they go on to say and you choose to ignore in that same article and page.






We totally agree and I am saying the same thing a different way.



Lets say a point along way between the nearest sun or galaxy then ... exact position is not important here.




Sorry that same article explicitely told you the frequency would be unchanged ... you choose not to read or accept it.




I am absolutely stumped understanding how a process you described on a physics website leads to a redshift and and simplying asking from clarification but that is somehow disinformation.

I am making absolutely no claims of anything I am asking questions???



As I have said but you choose to leave out part of the explaination.




It will have been done through very many media over vast distances ... I can even tell you I can give you a result better than that, there is a laser project that bounces a beam off a mirror surface left on the moon.

What is it in particular you want to see the original spectrum and the resultant return?




It will have been done and many times. Sorry I like many scientists don't just accept big bang or inflation I am by nature extremely skeptical.

Is your opposition to big bang religious or scientific and I ask only because you seem to be somewhat hard on science in general.

I am trying to ignore any previous knowledge/ideas I might have had about cosmology, and form an opinion based only on the arguments put forward in this specific exchange. So far, I am still on the fence. Don’t stop now!

Ignore what you already know? Some would indeed be gratified. To "form an opinion based only on the arguments put forward in this specific exchange" would be, to put it mildly, unreasonable. So unreasonable, in fact, that I'm sure that's not what you meant. There's a whole universe of research results out there.

You are absolutely right, of course. I was talking only in terms of seeing if either Bill 6 or Orac could present a case that would persuade me either way, if that were the only information I had.

I can't make a case for anything ... they all have holes as far as I can see.

I am pretty much doing the same Bill S because the science is moving so fast.

Did you read the article I posted on space manifolds I actually found it fascinating to think about. We rarely think about the shape of the universe but it may tell us alot and there are some intriguing possibilities.

I mean it doesn't matter what theory you belive from creationism to big bang, inflation or a mirriad of others what shape is the universe.

I will organize a post with some interesting problems I can see for tomorrow.

Edit: I should give you some light reading on what the reporting season from the LHC has seen
http://www.math.columbia.edu/~woit/wordpress/?p=3864
http://www.science20.com/quantum_diaries_survivor/new_susy_fits_post1fb_lhc_data-81223

Thats a whole lot of theories dead and buried including my old string theory one which I was backing :-(

I highlight the big thing



That means we are loooking at a light higgs model or a higgless model and most exotic models are out the window.

To Bill 6:

Been kicking some thoughts on tired light around, I do like its simplicity but still struggling with a mechanism to make if fit all experimental observations.

Saw this article:

http://www.physorg.com/news/2011-08-manipulating-light-at-will.html

Thats details of the study of light through meta material where they can play havoc with the light while in the media.

One of the key findings .. which is the observation that is causing me problems believing tired light.



Now I note they can get a frequency shift by amplifying harmoics



To get a tired light redshift we would need to amplify the lower harmonic essentially halving the frequency.

I am not sure but my guess would be we are going to see too much redshift from a typical sun. Of coarse we really only have our sun to calibrate spectra against so there is some wiggle room here I suspect.

Going to go and look at what happens to spectra lines with harmonic amplification that may kill this line of thought but at least I have found a way to get redshift without defying Quantum mechanics so we have hope.
.

More playing around with tired light theory:

Okay if we take Raman scattering (http://en.wikipedia.org/wiki/Raman_scattering) we essentially have the basics of physics we need for tired light.

Now we need to put Raman on steroids so we don't get approximately 1 in 10 million photons we need almost all do it so it matches our observation.

My initial thought was to argue well the light has come a long way so perhaps it just tells us no photon can get to us without undergoing such a transition because chances are it encounters such a transition on the way.

My problem with this conjecture is we have galaxies which are the same distance away with vastly different redshifts. This leads us to a sticky problem of then trying to make space paths from these galaxies not homogenous.

This is essentially one of the same arguements used to dismiss tired light as quoted by Halton Arp



My next thoughts were in reading on Raman scattering that there is very big differences between Raman scattering and fluorescence. That leads you into a big distinction in that Raman scattering is a coherent process, whereas fluorescence is not. That lead me into Raman Spectroscopy (http://en.wikipedia.org/wiki/Raman_spectroscopy)

This is where I ran into real trouble because the Hubble telescope is very very sensitive. My next problem is the hubble data has been analysed for Raman Spectrum lines as well as doppler redshift.

First jupiter
(http://www.lpl.arizona.edu/~yelle/eprints/Betremieux99a.pdf)
then followed by Venus, Jupiter, Saturn and Uranus.

This shows they can isolate an see the two effects on top of the same data.

Now I really am getting stuck.


Thoughts anyone .... or have I reached the end ???
.

Orac,

I think you have reached an end. When Zwicky developed the hypothesis, right after Hubble observed the red shift for distant galaxies, He himself shot down several possible mechanisms. Since then astronomical measurements have gotten more and more precise. And every one of the possible explanations for how tired light could occur have gotten more and more unlikely. I suppose that there might be some strange effect that hasn't been considered, but there have been a lot of people who have looked into it and they have found no data supporting the hypothesis.

Bill Gill

One thing that seems typical of science in general, and cosmology in particular, is that however good the arguments seem to be for a particular viewpoint, there is always room for an alternative interpretation.

I'm getting a bit out of my depth, so I look forward to a good counter from Bill 6, and hope I can understand it.

To greater and lesser extents, yes, but sometimes perhaps not at all. The natural selection process in evolution is one topical example. But, re the standard model of cosmology, any cosmologist/astrophysicist will agree that there's room for a great deal of modification.

If anyone here hasn't read The Fifth Essence by Lawrence Krauss, I'd recommend it, even though it's 35yrs old and he'd have to make some revisions if he rewrote it. It's broadly about Dark Matter, but the information and explanations re evolution of an expanding cosmos from the Big Bang are very clearly delivered, and continue to be supported as new data comes in.

Disagreeing with it all only because one doesn't like it will leave a scientist unmoved.

http://www.youtube.com/watch?v=iMDTcMD6pOw&feature=player_detailpage

I think I would agree 100% with redewenur I dislike the results science is throwing at me I would like them to be simpler but the results speak for themself and it isn't like that and I just have to accept it.

18 months ago I was confident SUSY would be seen by the LHC and alot of mysteries would be solved. My venturing into QM studies 9 months ago rocked my conviction and here we stand today about to read the last rites to SUSY some have already done so.
(http://www.math.columbia.edu/~woit/wordpress/?p=3864)

I would have liked SUSY to be true it would make understanding easier but you have to face the realities of observations and I simply have run out of wiggle room to explaining them.

I have no more to say in relation to the tired light concept.

The big bang theory is awe-inspiring compared with a ‘mundane’ universe of infinite time and space. It is a basis for more books and articles and is applied in order to ‘justify’ multi-billion dollar research projects thus will continue to remain the preferred theory amongst physicists until disproven.