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Bill S. #54222 07/27/15 11:59 PM
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Lets take the easy one kinetic energy of a non-rotating object moving at velocity

In classic physics you know it by a simple equation

Kinetic Energy = 1/2 Mass * Velocity * Velocity

Lets change the velocity terms into a different form for you

Velocity = DISTANCE / TIME

So Kinetic Energy = 1/2 Mass * DISTANCE / TIME * DISTANCE / TIME

You still think you can randomly change distance(space) and/or time?

Kinetic energy of a moving object going near your version of spacetime distortion is going to be fun isn't it smile

You might need to be careful changing DISTANCE and TIME or you break all energy equations smile

KE under Bill.S theory:
The Kinetic energy of an object can be anything as it is dependent on the metric of the space it's in and the time factor of that piece of space. For this reason we have dispensed with Kinetic Energy as a concept as it is utterly useless. All discussion now will be about Bill Curvature of spacetime although it isn't clear how Bill Curvature relates to everyday physics.

It's not even clear to me how I can calculate a velocity I have to ask Bill what the curvature and time is at any given point of space so I can calculate my velocity.

Is the problem clear now?

At the moment you have done a Marosz and broken everything and it's not terribly useful smile

So can we be serious now and either discuss how GR does it, or you need to start addressing issues.

Last edited by Orac; 07/28/15 02:00 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
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Orac #54223 07/28/15 02:17 AM
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Originally Posted By: Bill S
Could you identify the "answer" to which you refer?


Apparently not.

I’m trying to learn and understand.

Entertaining as your circumlocutory derision may be, your comments are of little value unless you attach them to the “answer” you are criticising.

A plethora of deprecatory comments, and a surfeit of seemingly sneering emoticons is probably not the most productive way forward.

Let's either get back on track, or stop wasting our time.


There never was nothing.
Bill S. #54224 07/28/15 02:28 AM
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You posted this

Originally Posted By: Bill.S

1. Gravity has energy.
2. Gravity distorts spacetime.
3. Gravity creates more gravity.

In achieving 2 & 3, is the energy of gravity diminished, dissipated or exchanged in any way?

THE ANSWER IS YES ENERGY IS EXCHANGE IT HAS TO BE!!!!!!

Why ... well it's dam obvious ... Energy is what connects the curvature to the normal everyday physics as we know it, after all the curvature is supposed to be what produces the effect we measure isn't it or vice versa for that matter.

The only thing you can measure is energy, name something you measure that has no energy. That is the funny part of time if you have no energy you can't measure and time is meaningless and where you have gone. I think that area has a name usually covered by religion/philosophy as I can't test anything and I have to believe whatever you say.

If the energy isn't connected, you have Bill Curvature which is random but involves time and Energy which involves time but it isn't connected to the curvature ... say what. One may ask is Bill curvature of spacetime and normal physics time even the same thing if they aren't connected.

So at least in physics if you have time you have energy exchange. If we can measure something different then you have a difference in energy. So gravity produces an effect we can measure so it is exchanging energy. So if Bill curvature is caused by physics or is creating physics it can only do so by exchanging energy.

Now this has got totally stupid and gone Marosz can we get back to reality, we need energy exchange to define time at least in physics. I really didn't think I would have to explain that to you.

Now if you really really want to push the envelope and not have energy I at least need some observable I can test so this isn't a religion/philosophy thing.

Assuming you don't want to push the envelope Bill curvature is either caused by something in physics or something in physics causes Bill curvature it matters not which way. I supposedly can measure a cause and effect so therefore energy is being exchanged.

If you can't do either of above we are back to a Bill's law and I don't really care about Bill Curvature it rates about the same as invisible martians push things down as an explaination of gravity ..... AKA Newton gravity ... AKA you aren't offering any solution so why discuss it as there are plenty of religion/philosophy forums.

Lets see if I want to continue this .. here goes

So am I going to be able to measure something or some effect from Bill Curvature AKA are we exchanging energy?

Last edited by Orac; 07/28/15 07:22 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Orac #54226 07/28/15 05:26 AM
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Leap of faith we aren't doing philosophy or religion we are exchanging energy smile

I am going to stretch your thinking back from classic physics towards GR. Many of the concepts in GR does not require curved spacetime at all
https://en.wikipedia.org/wiki/Equivalence_principle

Quote:
Einstein combined (postulated) the equivalence principle with special relativity to predict that clocks run at different rates in a gravitational potential, and light rays bend in a gravitational field, even before he developed the concept of curved spacetime.

So what is the reason you need a curvature of spacetime, well to turn GR into a force that you see in classical physics.

Quote:
In general relativity, objects in free-fall follow geodesics of spacetime, and what we perceive as the force of gravity is instead a result of our being unable to follow those geodesics of spacetime, because the mechanical resistance of matter prevents us from doing so.

See the simplicity here there is nothing special about matter here it just can't be moved out of the way. So Einstein defined an equivalence of energy replacing your force with spacetime curve. That equivalence links the curvature to energy in a very precise way or to be exact what Einstein says is that the curvature of space-time and Newtonian stress-energy are the same thing.

You are trying to not talk about classic forces, energy and avoid stress energy in your Bill Curvature statements and I am going like what the hell sort of theory is this!!!!!!!

Now it does get more challenging when we can't simplify to a nice reference frame like above but SR provides most of the answers which GR adopts.

To me you are sort of coming at this backwards you are trying to curve spacetime without first working out why you want to do that and specifically trying to avoid incorporating classic physics.

Last edited by Orac; 07/28/15 08:50 AM.

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Orac #54227 07/28/15 10:38 AM
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Thanks Orac. A few years ago I was trying (in my low-tech, hitch-hiker way) to argue that causing and maintaining spacetime curvature must involve energy exchange. I was being shot down from all angles. It seems that a more devious approach can elicit quite different results. To be fair, I don’t remember if you were among the shooters, but I have my suspicions. smile

I just need to find a bit of time to digest your last couple of posts; I’ll be back.

BTW. A silly thought:

Gravity: that which keeps everyone down.
Grabity: that which lets the few rise above the masses.


There never was nothing.
Bill S. #54228 07/28/15 11:34 AM
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Originally Posted By: Bill S.
Thanks Orac. A few years ago I was trying (in my low-tech, hitch-hiker way) to argue that causing and maintaining spacetime curvature must involve energy exchange. I was being shot down from all angles. It seems that a more devious approach can elicit quite different results. To be fair, I don’t remember if you were among the shooters, but I have my suspicions. smile

I can say I hope it would have not been me unless I really didn't understand what you were saying or had a bad hang over. If it was me I was wrong and I apologize because I could not have been more wrong, Einstein says you were right and I accept it smile

You may officially give me a hard time if I got it wrong and tell me to go fix up the rest of physics I just broke laugh

Here is what you were asking a more technical way
http://physics.stackexchange.com/questions/70993/how-energy-curves-spacetime
Lubos's answer is the most technically correct and he even tacks in the local feedback but I agree the most voted answer is the best layman answer, and best layman formula ever that says basically says what you did in the statement above.

You were right at least until I or someone else can disprove GR anyhow smile

I am hopeful you get the bit about why the tensor can't be measured directly as anything but zero but it will be very obvious in your surface gravity of a black hole at the event horizon you were doing. Bill G I don't think gets that by his answer to that problem and as I warned you the answer to that problem is actually funny.

Last edited by Orac; 07/28/15 12:18 PM.

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Orac #54230 07/29/15 04:20 PM
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Originally Posted By: Orac
You have a curvature in spacetime in the presence of energy/matter but something has to invert time back to what it was originally. You can make it whatever you like space is elastic, there is a back pressure, the green alien inverts it back but something has to as you have spacetime as passive currently.


This makes little sense to me, unless you mean that as a gravitating body moves through spacetime it distorts spacetime; then something else must act on spacetime in order to restore it to its original, non-distorted, state. Is that what you are saying?


There never was nothing.
Bill S. #54234 07/30/15 04:17 AM
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Originally Posted By: Bill S.
This makes little sense to me, unless you mean that as a gravitating body moves through spacetime it distorts spacetime; then something else must act on spacetime in order to restore it to its original, non-distorted, state. Is that what you are saying?

Correct you must force it back or if space is passive have a radiation effect.

Lets take any random point in our solar system it's gravitional distortion is based on the effect it feels from every point in the universe. Lets deal with that not from the really really distant ones but the close ones but the lets say from earth to sun like distances.

You know the calculation the sun is 8 minutes away at the speed of light from earth which is the speed of gravity theoretically. So lets take a point right angles either side of the suns position right now and 8 minutes at the speed of light away. The deformation is some value x. Now roll forward one second. The sun has moved as we were initially right angles (the shortest distance) the distance to us must have increased slightly and so the gravity must drop by a small amount delta so we have x - delta. The key point here that point must not only distort it must undistort somehow.

We are back to the exact same situation as electric charge there are exactly three options here

1. The object is radiating gravity and space is passive. So the gravity at any point in space is the sum of the gravitational radiation of all objects. That is how classic physics taught electromagnetism so you end up with gravity looking like that radiating from everything. You can even end up drawing pretty radiation field lines like you did in classic electromagnetics. Big objects radiate the attractive force more than little objects because they are bigger and we have our theory.

2. The object is passive and space has an energy that can be deformed in the presence of mass/energy but will return back to normal when it moves. We saw this with Quantum Field Theory that particles become viewed as just a disturbance in the field and so gravity would be just some disturbance in some field. Underpinning this idea however is the the distortion of the field is unnatural and the field is fighting to return it to uniformity as the distortion carries energy. Hence a little mass distorts a little way a big mass further, you get your proportionality. In QFT we even had resonant points that could persist for long periods because the resonant point stopped that force being seen and we called them "real particles" and "virtual particles" were decayed by that force. In Electromagnetics we call it back EMF or counter-EMF, the opposition to deform the field. You can't have a field of this type without a back pressure, think about why.

3. Some mix of the above two schemes. We didn't really discuss this with QFT but there could be some sort of mix of both effects. The whole idea called heralding, it's sort of like phone ahead or notify in advance. In QM there are quite a few things that can be setup to be heralded so you know they are going to happen but as you can imagine this would make gravity really complex. This is like hidden variables explaining QM.

So number one would be how Newtonian physics would work with things radiating attractive force. GR fits into two and Einstein realized he needed a pressure to push spacetime back so he introduced the cosmological constant AKA dark energy.

The story is well covered in
https://en.wikipedia.org/wiki/Cosmological_constant

Einstein did it as the article says to "hold back gravity" and achieve a static universe.

Last edited by Orac; 07/30/15 06:58 AM.

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Orac #54235 07/30/15 04:22 AM
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My personal views, isolated because it is my view

From reading Einsteins work I get the impression he thought of energy as a "quantity" and the universe as a bath full of it because of the laws of conservation. As he viewed it that way he arrived at modelling the pressure as a perfect fluid. I think his logic was energy had some property internally that makes it want to spread evenly like a something dissolved in liquid solution. As energy clump together it created an a pressure which in a normal liquid solution you would call osmotic pressure ( https://en.wikipedia.org/wiki/Osmotic_pressure)

The reason Einstein made the stress tensor always zero is because he made it like a surface tension of zero in a fluid. No such fluid exists by the way so why do it you ask.

Well surface tension is not a property of materials but of interfaces between two (or more) materials. It is implicit in its definition that the interface separates two kinds of materials that behave differently (otherwise the interface would be just some imaginary surface inside the one material with no physical meaning). In real liquids that surface is indeed subject to blurring because of forces which is why no zero surface tension fluids exist.

Worth a quick look it's short
https://en.wikipedia.org/wiki/Perfect_fluid

I think Einstein wanted a clean division between the energy and its internal pressure and our physical world. It gets messy if you start modelling interface tension in GR and the maths blows up but some people have tried it. So Einstein wanted a clean divide between the energy domain and our physical world, I think the motivation was E=mc2 it's either one or other with c as a constant.

Do you understand now why you are never going to be able to measure the tensor directly as anything other than zero if Einstein is right?

However I also scratch my head if Einstein believed that of energy why did he have so much trouble with QM.

Anyhow there you have it why something called "Dark Energy" is actually needed in any non radiative version of gravity. GR is a non radiative version and has that back pressure inbuilt into it. If you make a field version of GR you must in build the back pressure of deforming the field. Finally the tensor is always zero in GR because of the clean symmetrical interface it defines.

Bonus now if anyone doing electronics asks you what the back-electromotive force or Lenz's law exists you can explain it smile

You know how I love cosmologists and consensus well apparently I am right to a science confidence of 99.996% smile
http://www.port.ac.uk/uopnews/2012/09/12/dark-energy-is-real-say-astronomers/

GR isn't my area and I can't go much deeper than this but I do know the basics but I could always be wrong !!!!!

If you understand all that you actually have got generalized field theory understood ... what a field is in physicality that is a whole other story smile

The other lesson is the one Bill G failed at... look at what is being said, not who said it. For example I always read Lubos Motl on GR even though he is a string theorist because he knows GR very very well, I have seen that on a number of physics forums. Don't take him as gospel but do read what he says very carefully.

Last edited by Orac; 07/30/15 07:36 AM.

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Orac #54239 07/30/15 09:47 PM
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Originally Posted By: Orac
You know the calculation the sun is 8 minutes away at the speed of light from earth which is the speed of gravity theoretically. So lets take a point right angles either side of the suns position right now and 8 minutes at the speed of light away. The deformation is some value x. Now roll forward one second. The sun has moved as we were initially right angles (the shortest distance) the distance to us must have increased slightly and so the gravity must drop by a small amount delta so we have x - delta. The key point here that point must not only distort it must undistort somehow.


Surely this apparent movement is due to the rotation of the Earth. The angle between sun and Earth does not change significantly. Obviously the fact that the Earth's orbit around the sun is not circular changes the angle through the year, but your 1 sec interval is not going to mark a significant difference to that.


There never was nothing.
Orac #54240 07/30/15 09:56 PM
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Originally Posted By: Orac
The problem is obvious if time wasn't restored back there would be this big time curvature tracks carved across space where planets/suns moved thru. It would be like a boat moving thru water and the water not levelling the wake left behind it.


Water pressure smoothes out the wake; why would vacuum pressure not smooth out the spacetime distortions?


There never was nothing.
Orac #54241 07/30/15 10:46 PM
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Originally Posted By: Orac
.....there are exactly three options here.


Could there be a 4th?

The Universe is a gravitational field, particles of matter are distortions in that field. Energy is a distortion in the gravitational field. All other fields and particles are subsidiary to this.

Just a thought.


There never was nothing.
Bill S. #54242 07/31/15 01:24 AM
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Originally Posted By: Bill S.
Surely this apparent movement is due to the rotation of the Earth. The angle between sun and Earth does not change significantly. Obviously the fact that the Earth's orbit around the sun is not circular changes the angle through the year, but your 1 sec interval is not going to mark a significant difference to that.

I didn't introduce Earth there it was a blank empty piece of space? If you want something there lets put a neutron particle there as it will provide almost no other interactions. Sorry I only used earth/sun as a distance because I know you knew the time of flight of light. Sorry my for my bad English again, I concentrate on the translation so much I lost what I meant.

So the point is a blank empty piece of space yet the gravity field must reflect every gravity attraction from every point in the universe and it must go up and down.

Last edited by Orac; 07/31/15 06:29 AM.

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Bill S. #54243 07/31/15 01:31 AM
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Originally Posted By: Bill S.
Water pressure smoothes out the wake; why would vacuum pressure not smooth out the spacetime distortions?

Well two things

1.) You haven't introduced a vacuum pressure so far? Space has vacuum but no-one has ever measured a pressure because of next point.
2.) Vacuum pressure requires a positive pressure to already exist and you remove something in layman terms.

For the record the measured vacuum pressure in space near earth is 3x10E-9 Pascals and that is positive caused by the few stray particles and it is the wrong way it's going to keep spacetime curved.

You need a negative pressure so any ideas?

In meantime a hint: casimir force.
https://en.wikipedia.org/wiki/Casimir_effect

Quote:
The Casimir effect can be understood by the idea that the presence of conducting metals and dielectrics alters the vacuum expectation value of the energy of the second quantized electromagnetic field.Since the value of this energy depends on the shapes and positions of the conductors and dielectrics, the Casimir effect manifests itself as a force between such objects.

Casimir is again the idea that deforming a field involves energy and creates a force within the field. We know electomagnetic fields do it we can measure it and it's fully resolved with quantum electrodynamics.

Sorry had to bring QM in Bill G will be on me whistle

Last edited by Orac; 07/31/15 06:38 AM.

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Bill S. #54244 07/31/15 02:13 AM
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Originally Posted By: Bill S.
Could there be a 4th?

The Universe is a gravitational field, particles of matter are distortions in that field. Energy is a distortion in the gravitational field. All other fields and particles are subsidiary to this.

Just a thought.

That is actually the same as 2 ... and now you have converted a classic gravity field theory to a quantum gravity theory.

Remember we did that in QFT.


I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Orac #54247 07/31/15 07:36 PM
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Originally Posted By: Orac
That is actually the same as 2


I thought this went beyond 2.

In 2: "gravity would be just some disturbance in some field."

In 4: matter and energy are distortions in the gravitational field. Everything else arises as excitations of the gravitational field, which is fundamental. What initiates these excitations? Quantum uncertainty, of course. smile

Quote:
and now you have converted a classic gravity field theory to a quantum gravity theory.


Bill S cracks quantum gravity! or not! Might have to wait a bit for the Nobel.


There never was nothing.
Orac #54248 07/31/15 07:58 PM
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Originally Posted By: Orac
Originally Posted By: Bill S
OK. Let’s look at three things I think we have said about gravity.

1. Gravity has energy.
2. Gravity distorts spacetime.
3. Gravity creates more gravity.

In achieving 2 & 3, is the energy of gravity diminished, dissipated or exchanged in any way?
Yes absolutely it is


This brings us back to questions I was asking a few years ago about where gravity’s seemingly inexhaustible supply of energy comes 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. Among the responses I received then were things like: “No energy is expended”.

We now seem to have reached a point where we are saying that gravity does work, therefore it expends energy.


There never was nothing.
Bill S. #54249 08/01/15 02:44 AM
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Originally Posted By: Bill S.
Bill S cracks quantum gravity! or not! Might have to wait a bit for the Nobel.

I think your just behind Marosz in line for the Nobel smile


I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Bill S. #54250 08/01/15 03:06 AM
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Originally Posted By: Bill S.
This brings us back to questions I was asking a few years ago about where gravity’s seemingly inexhaustible supply of energy comes 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. Among the responses I received then were things like: “No energy is expended”.

We now seem to have reached a point where we are saying that gravity does work, therefore it expends energy.

Ok Gravity most certainly does expend energy as we can show it does work and exchanges energy.

The problem comes back to the tensor being zero, Bill G's little friend.

I usually don't like Sean Carroll but on this subject he has written the most honest evaluation
http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/

So you can either build a whole massive amount of energy into the gravity field which you are never going to be able to measure OR just say energy is not conserved.

LM gives it a similar treatment in more technical language
http://motls.blogspot.com.au/2010/08/why-and-how-energy-is-not-conserved-in.html

Quote:
The main lesson here is that general relativity is not a theory that requires physical objects or fields to propagate in a pre-existing translationally invariant spacetime. That's why the corresponding energy conservation law justified by Noether's argument either fails, or becomes approximate, or becomes vacuous, or survives exclusively in spacetimes that preserve their "special relativistic" structure at infinity. At any rate, the status of energy conservation changes when you switch from special relativity to general relativity.


In simple terms Energy conservation does not hold in general relativity (GR) because it is replaced by Energy stress tensor which we set to zero and therefore does not include gravitational potential energy. Now you know the dirty little secret I was trying to get Bill G to understand.

Last edited by Orac; 08/01/15 03:07 AM.

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Orac #54253 08/01/15 10:47 PM
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Originally Posted By: Orac
I usually don't like Sean Carroll


For me, one of Carroll's strong points is that he usually seems to be able to explain things in a way that I stand a good chance of understanding. I know that doesn't make him right (or wrong), but if I can understand it, I can form a judgement.

At a brief glance, this article seems to be saying that in physics you can say that energy is conserved, or it is not conserved, and be right whichever you say.

Hopefully I shall have time to read it properly tonight.


There never was nothing.
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