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#54682 11/07/15 10:20 AM
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Time invariance seems to leave physicists in a bit of a quandary with some suggesting that time could move backwards in a different epoch or inside a spinning black hole etc., but it seems to me to be a simple consequence of Einstein's strong equivalence principle. If all physics is independent of a chosen coordinate system, then it has to hold for changes of the scale of the dimensions used, and therefore a simple change of scale factor for time (from +1 to -1) could not affect the underlying physics. I detail this a little bit more at http://blackholeinside.com/bhi/time-reversal.html
I would love to hear your views on this.

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Dave, even I can follow the maths you link to. smile

One of the problems with time reversal is that it is easy to confuse mathematics with physics. One sometimes hears it said that it must be possible to travel backwards in time, because Feynman said that an antiparticle is just a particle travelling backwards in time. In fact, Feynman did not say that. What he said was that the mathematics governing the evolution of a particle as time moves forwards is the same as the mathematics governing the evolution of an antiparticle as time moves backwards.

This is true, but it certainly does not mean that any physical object is travelling backwards in time. Consider the electron and the positron. We call the electron a particle and the positron an antiparticle; but that is simply convention. We could equally well call the positron a particle and the electron an antiparticle. Which of these would then travel backwards in time?


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Bill S. #54684 11/07/15 02:33 PM
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Congrats Dave and now your ideas have just violated QM as well.

Sorry Schrodinger's equation is not T-symmetric that had been know for 85 years smile

The only way to time-reversing the wave function requires time-reversing its phase, a not to simple process.
Here is a layman reference to it here for you
http://www.soulphysics.org/2009/11/how-to-time-reverse-quantum-system/

In 2012 it was directly observed so now you also have experiments against you as well ... oooopps
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.109.211801

We can also add the fact QM central mechanism is "probability" that violates time-reversal symmetry, your a mathematician try reversing probability laugh

So now you just have to falsify both GR and QM to make your fairytale work in a black hole ... good luck with that.

This is the problem with not actually bothering to listen to those who actually know stuff and tried to set you straight in many exchanges I saw.

Sorry you can't reverse time except in movies and in classical physics which is of little concern given it's is already broken. In the real universe you can't just reverse time it has consequences but no point in even explaining that to you.

Bill S I was very impressed you picked up the layman misrepresentation of Feynmann ... thank you for that.

However on our new liberal forum you are allowed to violate QM and GR so please continue on I am sure someone gives a rats just not me. You have now entered my Marosz book a crackpot to ignore. Please don't bother directing questions to me, I really don't care about your trash and what you understand or think.

Last edited by Orac; 11/07/15 03:09 PM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Bill S. #54687 11/08/15 11:53 AM
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I was not arguing that anything went backwards in time. The notion always seemed preposterous to me. Just wondered if there is anything obviously wrong in my argument.

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Lets take a leap of faith an assume you actually want to know the answer.

Classical physics allows almost anything with time because time isn't really defined in it other than something that exists between two events. Realistically almost nothing is forbidden with time in classical physics besides conservation of energy. It is one of the key problems with classical physics and why it fails to describe the universe correctly and ultimately how it was falsified. Yes we still teach it because it's nice and simple and for most everyday situations it works well enough. It is however wrong so take extreme care if you go outside the mundane problems.

From SR/GR a series of advancements leads to the development of QM and the understanding that time has exactly the same footing and importance as space. One of the key parts of that is that cause and effect events can be encoded in time as well as space. Most layman struggle with the concept but everything from atomic theory, chemistry thru to your black holes relies on it and there is no alternative theory. The predictions that have been shown to be true are so weird most struggle to even think of an alternative.

We have numerous experiments in which we encode multiple events actually on top of each other in the same point in space and you can hold them apart or have them interact depending what you want to do. This stuff has been known for 85 years and yet people still struggle with it even scientists. You may struggle with it but the experiments have been run and with the Higgs discovery as predicted the most extremes of the theory are holding.

I laughed at a recent science media presentation of current status

http://phys.org/news/2015-11-quantum-superposition-events.html

Quote:
"Quantum theory, on the other hand, has shaken our understanding of reality by telling us that physical systems may not have well-defined properties, and may be in a 'superposition' of incompatible states. For example, a poor cat could be both alive and dead at the same time. Now we find that not just physical properties, but also causal relations (or causal orders) themselves can be undefined, and can be put in some kind of superposition—a phenomenon that had not been observed experimentally until very recently."

People struggled enough with our poor dead and alive cat but when we extended experiments to show even trying to determine a time order of QM cause/effect events can be problematic as predicted by theory for 85 years, they go into a tailspin. This is why your flat refusal to give up on the concept of a universal time gets you banned. It is blatantly been falsified by so many experiments that it does our head in that any intelligent person could still believe such a thing, the earth is flat is more believable.

Time is a quantity in QM not something "airy fairy" like in classical physics. It has the exact same quality as space, no more no less. Time becomes something that can be bent, twisted, controlled and exists individually to each observer in the universe.

SR/GR showed things like being just being 1 foot higher than someone else one Earth makes time different for you. QM took that further and shows even standing on the same spot won't guarantee you see time the same if some QM effects are in play.

The take home message here is be very careful with classical physics it is wrong and time is something very different to how it represents it.

If you only understood half of the above you should get why no scientist is remotely interested in your idea or wasting time with it. You are like the flat earth society a little bit out of date with science and understanding.

Last edited by Orac; 11/08/15 02:18 PM.

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Originally Posted By: Orac
You are like the flat earth society a little bit out of date with science and understanding.


Doesn't the flat Earth concept depend on how you define "flat"?


There never was nothing.
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Originally Posted By: Orac
Bill S I was very impressed you picked up the layman misrepresentation of Feynmann ... thank you for that.


Sadly, I have to hand the laurels to Matt Strassler for that one.


There never was nothing.

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