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#54706 11/11/15 03:57 AM
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I'm not going to make any argument one way or the other. I think it does, but what do I know? Anyway, just for Bill S., here is a link to Sabine Hossenfelder's latest.

Dear Dr. B: What do physicists mean when they say time doesn’t exist?

Bill Gill


C is not the speed of light in a vacuum.
C is the universal speed limit.
.
Bill #54707 11/11/15 05:52 AM
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That is actually a good link for Bill S, thank you Bill. It is actually covering part of the issue we were discussing elsewhere. I hadn't considered coming that way into the problem but it will get him there. I am sort of regretting going into this with him at the moment I think it would have been easier to say I agree with him AKA lie.

You are a classical man Bill, time is always real for you. Stick with that and it won't get into any trouble and most times you will get the right answer. This stuff only becomes problematic when you try to take a zero frame to the universe and you open Pandora's box.

Sabine's answer is reasonable, however I have to nit pick over the reversal problem she said quote "you would have to arrange the molecules in the dough so precisely that it’s impossible to do". Actually uncertainty principle says it is completely and utterly impossible you can not determine the exact position of a single molecule much less all the ones in the mixture. Idea was correct execution left open some idea that it might be insanely hard but possible. Then she went and did it, said it might be possible to unmix a small patch of dough based on an experiment which has a different thrust, and why she does my head in at times. It's clear she doesn't get the experiment she linked to is about energy at small scales and the mixed dough is about positional accuracy these sort of details are important. So again I am left in the situation with Sabine that she gets enough right to read her articles but I can never implicitly trust her articles.

With the energy experiment she highlights what surprised me was anyone needed to actually do it or that it was newsworthy. At times you wonder at what point will some just accept that classical physics isn't coming back and almost all it's laws require some handwaving.

Last edited by Orac; 11/11/15 06:32 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Bill #54714 11/11/15 02:01 PM
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Thanks for the link, Bill. No time to read it at the moment, but I'm printing it so I can take it with me.


There never was nothing.
Orac #54723 11/13/15 04:52 PM
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Bill #54724 11/13/15 05:59 PM
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Originally Posted By: Orac
I have to nit pick over the reversal problem she said quote "you would have to arrange the molecules in the dough so precisely that it’s impossible to do". Actually uncertainty principle says it is completely and utterly impossible


It's soap-box time!! I have to nit pick the nit pick, and ask:

What's the difference between "impossible" and "completely and utterly impossible"?


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Bill #54725 11/13/15 06:05 PM
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Originally Posted By: Sabine
Having a time reversal-invariant law means that the equations remain the same when the direction of time is reversed. This doesn’t mean the processes remain the same.


From the experts' point of view, that might be self evident, but for the benefit of hitch-hikers every expert who writes on this subject should include this. I would even forgive them for writing it in upper case. smile


There never was nothing.
Bill S. #54730 11/15/15 06:13 AM
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Originally Posted By: Bill S.
What's the difference between "impossible" and "completely and utterly impossible"?

Well lets see Sabine said it's impossible then she goes on

Quote:
It is worth noting that all of this is true only in very large systems, with a large number of constituents. This is always the case for daily life experience. But if a system is small enough, it is indeed possible for entropy to decrease every once in a while just by chance. So you can ‘unmix’ very small patches of dough.

So perhaps you need to take the issue up with HER. The impossible part is a correct statement the adjustment after is complete garbage and so I guess I have to put "completely and utterly" because obviously impossible is not absolute with her.

As I said she does my head in she gets some very complicate things correct but then completely botches basic things any undergrad would get right. It's like she read or got told the impossible bit but it never sunk in they really really mean it. The garbage after is all her you won't find it in anywhere else.

Last edited by Orac; 11/15/15 06:28 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Bill S. #54731 11/15/15 06:27 AM
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Originally Posted By: Bill S.
From the experts' point of view, that might be self evident, but for the benefit of hitch-hikers every expert who writes on this subject should include this. I would even forgive them for writing it in upper case. smile

If you are asking me what she meant with that I have no idea it looks like some sort of idea out of chemistry that is completely butchered.

Again for QM interactions many things are simply not directly reversible not even conceptually they are only reversible via a different mechanism (Antiunitary and antilinear transformations).


I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Bill #54733 11/15/15 01:52 PM
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Quote:
But if a system is small enough, it is indeed possible for entropy to decrease every once in a while just by chance.


I don't like her example with the dough, it's too easily misinterpreted, but consider the box of gas example. The box is divided by a partition with a small hole through which molecules can (and do) pass. If there are just two molecules in the box, the equilibrium state would be one molecule in each side. Would it not be possible, occasionally, to find both molecules in one side?

Let’s go further into your field. Our divided box (no need for a hole, now) has one quon in each side. Doesn’t uncertainty say we could find both in one side in any particular observation?


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Bill S. #54734 11/15/15 04:46 PM
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In both situations there is a probability that you will find them both sides and so entropy is unchanged it just becomes probability based on size of hole versus size of particle etc. This problem was realized in the 1870's see the difference between Classical thermodynamics and Statistical mechanics (https://en.wikipedia.org/wiki/Entropy).

Quote:
For a given set of macroscopic variables, the entropy measures the degree to which the probability of the system is spread out over different possible microstates. In contrast to the macrostate, which characterizes plainly observable average quantities, a microstate specifies all molecular details about the system including the position and velocity of every molecule.

So using Statistical mechanics in your example the entropy has not changed. So another one of those examples where you need to throw the classical description out.

You are however going along the right lines now what you do is introduce a little demon who controls the gap. The problem is called Maxwell's Demon (https://en.wikipedia.org/wiki/Maxwell's_demon) and it was argued it theoretically breaks the 2nd law.

When attempts to do the experiment with QM the problem became apparent. It costs you energy to measure where the particle is and to effect the control of the gap and that energy is always more than the energy of the entropy change.

This was the result with a single electron maxwell demon
http://arstechnica.com/science/2014/09/researchers-create-a-maxwells-demon-with-a-single-electron/

You may be curious to see Sabine had to learn the same lesson the hard way:
http://backreaction.blogspot.com.au/2014/12/the-remote-maxwell-demon.html
Give her half marks she did first worked out she needed to change to statistical mechanics but minus half the marks for not working out fully why her machine fails correctly.

In 2012 another group of Japanese physicists claimed they could do a maxwell's demon using entanglement
link: http://www.technologyreview.com/view/428...say-physicists/
It will fail for the same reasons as all the others and is no better than Sabine's.

Strangely the first correct argument of the impossibility of Maxwell's Demon was first made in 1961 by IBM founder Rolf Landauer in Landauer's principle (https://en.wikipedia.org/wiki/Landauer's_principle). You will note in the discussion it was widely accepted in QM and then experimentally verified.

It costs a small amount of energy to encode QM information and as no gain mechanism is known QM can not create Maxwell's demon.

You see with the stupid papers above why it is important that you learn the QM foundations. Those who do not bother find they may end up looking like idiots.

Last edited by Orac; 11/15/15 04:49 PM.

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Bill #54737 11/15/15 10:23 PM
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Originally Posted By: Orac
In both situations there is a probability that you will find them both sides and so entropy is unchanged


Isn't the entropy lower if the gas molecules are both on one side, than if they are one on each side?


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Bill #54738 11/15/15 10:42 PM
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Originally Posted By: Sabine
However, a system in equilibrium always has fluctuations. The atoms have some probability to be in an excited state, a state in which they could be stimulated to emit light. If you just knew which atoms were in the excited state, then you could target them specifically, and end up with twice the energy that you sent in.


If the targeted atom loses more energy than is put in; wouldn’t the system continually lose energy, and increase its entropy?


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Bill S. #54742 11/16/15 03:39 PM
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Originally Posted By: Bill S.
Isn't the entropy lower if the gas molecules are both on one side, than if they are one on each side?

Only in classical physics you haven't confined the particles so under statistically mechanics nothing has changed .. did you read the entropy link at all?

Lets turn this to an electron orbital around an atom. Classical physics would likewise say the entropy and energy changes depending where the electron in it's shell relative to the nucleus and so with the probability function of QM both must change right? Only problem is experimentally that isn't what you measure you measure just one exact value which I imagine you know.

This is that problem again that the universe seems to have at it's core probability. If you use the statistical probability you will derive the correct entropy value and any calculation using an implicit time or position of the system will be wrong which is what classical physics and you did.

It gets far worse and far deeper when you consider transmitted messages in your above example you have a physical system but what if I implemented it by transmitting messages. You may care to read the section on information theory under entropy.

You live in a Quantum Universe and the correct description goes, EVERYTHING NOT FORBIDDEN IS MANDATORY. It is called the totalitarian principle (https://en.wikipedia.org/wiki/Totalitarian_principle).

A particle moving from A to B takes every possible path from A to B simultaneously. Two particles A and B in your container are actually simultaneously everywhere in your container with a probability density and distribution to find them, that is why the entropy doesn't change.

There is also a small non zero probability you will find them outside the containers, yeah that problem again smile

Until you close the gap between the sides the particle probabilities are unchanged regardless of where you might measure them.

The moment you made the two particles classical and tried to calculate an entropy of a single position you were doomed to get the wrong answer. Again the warning be very careful with classical physics. The easy way to stop making the error is stop making particles real.

Last edited by Orac; 11/16/15 03:57 PM.

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Bill S. #54743 11/16/15 04:15 PM
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Originally Posted By: Bill S.
If the targeted atom loses more energy than is put in; wouldn’t the system continually lose energy, and increase its entropy?

Again this is Sabine I struggle to know what she is thinking at times as she seems to confuse herself.

I get the impression she thinks you wait for a random QM fluctuation to excite an atom (which cost you nothing) and then hit that excited atom getting twice the energy. I think she then views the atom drops back to repeat the process so it's not losing energy like you suggest but stealing it from QM or the universe ... she has a perpetual machine extracting energy with no change in the universe system save the temporary excite state.

Unfortunately she keeps ignoring the "if you knew" bit would require a measurement and that costs more energy and increases entropy more than the energy she would get back.

Last edited by Orac; 11/16/15 04:18 PM.

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Bill #54746 11/17/15 01:28 AM
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Orac, this just won't do. We seem to be on the same side.

DO SOMETHING! smile


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Bill #54759 11/17/15 05:53 PM
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The original question was: “Does time exist”.

Taking considerations from other threads, I find myself wondering if the answer might be:

Yes, it exists in the same way that “Pi”, “i” and “e” exist. It’s there, as long as there is something to measure with it.


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Bill S. #54764 11/18/15 03:04 AM
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Originally Posted By: Bill S.
Yes, it exists in the same way that “Pi”, “i” and “e” exist. It’s there, as long as there is something to measure with it.

Now you have got very close to what QM says but it extends it a tiny bit, that time exist as long as a field exists. It is after all a field that you are measuring and you need a field to do any measurement. So the interesting question it poses is does time exist in a place with no fields and the answer is you will never know because you can't measure. That is why in the big bang assumes time begins there, at least for us as Quantum beings, because we have the appearance of the first quantum field.

Last edited by Orac; 11/18/15 03:07 AM.

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Bill #54767 11/18/15 02:02 PM
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Originally Posted By: Orac
That is why in the big bang assumes time begins there, at least for us as Quantum beings, because we have the appearance of the first quantum field.


I have no problem with that, and if that is as far as you need to go, that's fine.


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Bill #54772 11/18/15 09:14 PM
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Kurt Godel had some interesting (weird?) thoughts about time which seem relevant to this thread. The following is an extract from John L. Bell, "Time and Causation in Gödel’s Universe".

In 1949 the great logician Kurt Gödel constructed the first mathematical models of the universe in which travel into the past is, in theory at least, possible. Within the framework of Einstein’s general theory of relativity Gödel produced cosmological solutions to Einstein’s field equations which contain closed time-like curves, that is, curves in spacetime which, despite being closed, still represent possible paths of bodies. An object moving along such a path would travel back into its own past, to the very moment at which it “began” the journey. More generally, Gödel showed that, in his “universe”, for any two points P and Q on a body’s track through spacetime (its world line), such that P temporally precedes Q, there is a timelike curve linking P and Q on which Q temporally precedes P. This means that, in principle at least, one could board a “time machine” and travel to any point of the past. Gödel inferred, in consonance (as he observes) with the views of Parmenides, Kant and the modern idealists, that under these circumstances there could be no such thing as an objective lapse of time, that time or, more generally, change, is an illusion arising from our special mode of perception. For consider an observer initially at point P (with time coordinate t seconds as indicated by his own clock). At point Q (with time coordinate t';) he boards a time machine and travels back to point P, taking time t'' to do so. In that case, according to his own clock, t'– t + t'' > 0 seconds have elapsed, and yet an identical clock left at
P would show that 0 seconds have elapsed. In short, there has been no “objective” lapse of time at all. Gödel remarks that in his universe this situation is typical: for every possible definition of an “objective” time one could travel into regions which are past according to that definition. He continues:
“This again shows that to assume an objective lapse of time would lose every justification in these worlds. For, in whatever way one may assume time to be lapsing, there will always exist possible observers to whose experienced lapse of time no objective lapse corresponds... But if the experience of the lapse of time can exist without an objective lapse of time, no reason can be given why an objective lapse of time should be assumed at all.”

Some comments on this could make interesting reading.

Last edited by Bill S.; 11/18/15 09:18 PM.

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Bill S. #54775 11/19/15 07:57 AM
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To be honest this is well covered in wikipedia and Tim did really well on that section

Godel Metric

Key points I would highlight for you

- It isn't a viable model for the universe but it is an exact solution to Einsteins equations, so this universe in theory could exist

- It highlights the problem of observers disagreeing and finding a good reference frame in the model is challenging.

- If you follow Hawking's logic the model shows you what a rotating universe would look like and we can rule out our universe is rotating.


I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
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The impression I had from reading Bell’s article, and from wading through Yourgrau’s disappointing book, was that Godel was saying that relativity permitted past directed time travel, via CTCs, but in a universe with CTCs time could not exist.

This struck me as being a bit unsatisfactory, and I wondered if others shared the same impression.

Last edited by Bill S.; 11/19/15 02:19 PM.

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Bill S. #54778 11/19/15 04:21 PM
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Remember Godel was trying to prove Relativity/Einstein wrong that was the whole point of his work

What he showed was that Einsteins equation allowed CTC's .. we agree even today.
That the presence of CTC's basically renders relativity unworkable ... we agree even today.
Godel noted his model wasn't a model of our universe ... we agree even today

What you are forgetting is we have more than relativity, we have QM ... and CTC's are completely incompatible with QM.

Ok I am going to have work up a complete proof for you this one isn't easily covered in layman media.

Wikipedia bluntly sucks and is out of date: https://en.wikipedia.org/wiki/Closed_timelike_curve

They sort of agree CTC's and QM don't mix but not forcefully.

The most recent semi-believable paper I know of on the subject is
http://phys.org/news/2013-02-spacetime-violate-heisenberg-uncertainty-principle.html

You will note they discuss all the background on how CTC's are incompatible with QM and how they were playing with special versions called OTC's to reignite the debate.

Quote:
Despite such paradoxes, CTCs in general are compatible with general relativity; however, they are not compatible with quantum mechanics.

Science media actually accurately got current status correct .. someone did there homework.

I ignored the paper because what they don't discuss is you would need to rewrite half of QM for all that to be true. In the article they describe it as extending QM smile

I mean it only violates HUP, the no cloning principle and then even better they have things called "dispersion-free states" in which all observables vanish but that state can't even be described in QM. Hey this is a really good theory so far I was just waiting for the pink unicorn's to dance on in.

Last edited by Orac; 11/19/15 04:31 PM.

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Thanks Orac. the Phys.org article is something I must make time to read. So far I've read the first two paragraphs, and have found the answer to the next question I was going to ask you.

You say is semi-believable, so I guess I'll be looking for guidance as to which bits to "believe".


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Bill #54781 11/19/15 09:27 PM
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Let’s start with the illustration. To my untutored eye the difference between CTCs and OTCs is that someone has arbitrarily decided one should involve interaction with a past self, and the other shouldn’t. I’m sure there must be more to it than that. Have I missed it, or is it not demonstrated?


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Nope you got it correct if you travel backwards in time for like to interact with yourself, you enter a different universe. So implicit in the OTC is a multiverse like Everett form. That is the sense it is open and discrete from a CTC where you come back to this universe.

I think all you missed is OTC's require a multiverse.

I was wondering why I didn't pick that up but they said "Deutsch model's" so I knew straight away what they were doing.

Ok that took some finding strangely it isn't under his name entry in wikipedia but it is here
https://en.wikipedia.org/wiki/Quantum_mechanics_of_time_travel

Read the section "Deutsch's prescription"

Strange place to put it and I left a note with wiki.

Last edited by Orac; 11/20/15 05:28 AM.

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Originally Posted By: Orac
So implicit in the OTC is a multiverse like Everett form.


It surprises me that so many people seem to assume that skipping into into another universe solves problems like the "grandfather paradox". The more you think about it, the less likely a solution becomes; unless you can put people into a superposition of states. smile


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Originally Posted By: Bill S.
The more you think about it, the less likely a solution becomes; unless you can put people into a superposition of states. smile

I have no issue with people being put into superposition state that will likely be tested and shown to be true in the far future. As I commented a bacteria will be the first "living organism" to have it done to them and there are groups lining up to try just send money.

http://phys.org/news/2015-09-pair-superposition-state.html

The problem with MWI is it just fails badly and all MWI proponents do is lots of handwaving. The problems are listed and discussed here under common objections
https://en.wikipedia.org/wiki/Many-worlds_interpretation

Unless MWI can give answers to the problems it is little better than witchcraft and certainly isn't science.

Last edited by Orac; 11/22/15 02:56 PM.

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http://phys.org/news/2015-09-pair-superposition-state.html#jCp


Quote:
Superposition, is of course, a principle of quantum theory that describes a concept where two objects can exist in more than one physical location at the same exact moment.


Should one distinguish between quantum states and physical locations?


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http://phys.org/news/2015-09-pair-superposition-state.html#jCp


Quote:
Superposition, is of course, a principle of quantum theory that describes a concept where two objects can exist in more than one physical location at the same exact moment.


Should one distinguish between quantum states and physical locations?

I’m having a job to get my head round what is going to happen here. At the moment it seems like they are going to conduct an experiment on an organism frozen to close to 0K, which may, or may not, survive. After which they will assure everyone that at some point in the experiment, which no one can observe, the unfortunate creature was both dead and alive (or was that in two physical locations?) at the same time.


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Bill S. #54809 11/23/15 09:49 AM
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Originally Posted By: Bill S.
I’m having a job to get my head round what is going to happen here. At the moment it seems like they are going to conduct an experiment on an organism frozen to close to 0K, which may, or may not, survive.

We would do it with you if we could but your cells definitely won't survive smile

They only need to do the experiment at near 0K to get rid of the noise so they can get a defined QM measurement, it plays no other roll in the test. Wheeler's delayed choice experiment itself can be done at any temperature but it's hard to measure QM statistics on a macro object without control of temperature.

Originally Posted By: Bill S.
After which they will assure everyone that at some point in the experiment, which no one can observe, the unfortunate creature was both dead and alive (or was that in two physical locations?) at the same time.

You sort of miss the point play terrorist with the lifeform stick a bomb on it detonated by radio control. If a self interference pattern exists the lifeform lives, if not it gets blown up.

Now look at the quantum eraser and work out when your lifeform lives or dies and when his fate was decided smile

refresher: https://www.youtube.com/watch?v=SzAQ36b9dzs

I have given you a physical meaning cats who go thru both slits live, cats who go thru a single slit die. Any experimental implication can have a real world physical implication.

The reason the lifeform is important is not for any of this but a thought experiment called Wigner's friend (https://en.wikipedia.org/wiki/Wigner's_friend).

Specifically what it is probing is the role of a conscious observer if any.

Last edited by Orac; 11/23/15 02:10 PM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Bill #54814 11/23/15 07:01 PM
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https://www.youtube.com/watch?v=SzAQ36b9dzs

Thanks, that was a great link. It' has already improved my understanding of quantum erasers, and I'm going to have to see it again, before commenting.


There never was nothing.
Bill S. #54821 11/24/15 05:25 AM
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Remember the point is not what you "see", you can never see the cat thru both slits it is that time elapses after the slits and many things can happen in that time. Then some time later you can do something that dictates which slot the cat went thru and that time can be billions of years.

The best layman version I know of is
http://www.bottomlayer.com/bottom/basic_delayed_choice.htm

The problem is zone 3 which could be any event and 13 billion years old and increasing smile

Last edited by Orac; 11/24/15 05:25 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Bill #54835 11/24/15 11:51 PM
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http://www.bottomlayer.com/bottom/basic_delayed_choice.htm

Interesting link.

You are well aware of my crackpot thoughts about infinity/eternity, and you may well recall my suggesting that QM gives us a “window” into infinity.

Let’s take the crackpottery a step further, and "test it experimentally".

The cosmos is infinite, there is no change or time, nor is it possible to differentiate in terms of location. To say that everything is here and now is probably as close as we can get with our terminology.

Our Universe, which is a shadow of the cosmos, is characterised by space, time and progression, otherwise it would not be possible for us to maintain intelligent existence.

In the reality of the cosmos our double slit experiment exists in a static state in which (what we perceive as) a photon, or other particle, exists timelessly in every part of the set-up (and everywhere else).

Because, in our Universe, the experiment is carried out in linear time we are unable to see the complete picture, so we interpret different aspects of the experiment as demonstrating different outcomes.

In the same way that multiverse theories maintain that conflicting outcomes are all realised in different universes; an infinite cosmos theory, if there were such a thing, might suggest that what we perceive as different outcomes are all realised, eternally and changelessly, in the cosmos. Classical physical experiments cannot display the underlying reality, but QM can, and does.


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Bill S. #54837 11/25/15 02:41 AM
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Can I come back to this one you have a lot of different themes running and I would like to see your answer on others first.

I have some problems with this idea but I and science in general don't have an answer either so don't get concerned. You are in good company smile

All I am really doing is connecting your answers up in a first principles method and see what problems fallout in your idea.

Last edited by Orac; 11/25/15 02:42 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
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