Newbie vs Einstein: Questions about Time Travel and Quantum Entanglement

[yuiop]

Hi Dalespam and Ich,

Where do you see a contradiction?

Hi kev,

Look carefully, it is not a contradiction. A timelike geodesic is a path which (locally) maximizes proper time. The stay-at-home twin is on a geodesic and the traveling twin is not therefore the home twin ages more. Similarly in a gravitational field, the free-falling twin is on a geodesic and the stationary (proper acceleration) twin is not therefore the free-falling twin ages more.

Ahh.. Ok, that makes more sense. I got the "wrong end of the stick" there somewhere

Thanks :)

I wasn't really confused, I just put a red herring in there to see if anyone actually reads my posts...

OK.. I'm lying.. I was confused

 

[Dale]

I wasn't really confused, I just put a red herring in there to see if anyone actually reads my posts...

Nice cover!

 

[Al68]

Hi Dalespam and Ich,






Ahh.. Ok, that makes more sense. I got the "wrong end of the stick" there somewhere

Thanks :)

I wasn't really confused, I just put a red herring in there to see if anyone actually reads my posts...

OK.. I'm lying.. I was confused

Hi kev

I read your post, too, but others responded before I could.

See, lots of people read your posts.

Al

 

[Charlie G]

What if the twin paradox begins with the twin heading to Earth at a constant speed close to that of light, this way no acceleration is necessary. Then he sees Earth's clock slower than his but Earth sees the opposite. So what happens, why aren't the twins younger than each other (I know that that isn't possible, but it seems to me that this is what would be the case) Can someone explain this to me? I ve been troubled by it ever since I came across the twin paradox.

 

[russ_watters]

Does the twin in the spaceship ever stop? How did they synchronize their clocks in the first place?

 

[A.T.]

It does sort of seem like a consequence of math, rather than reality

Math is merely used to describe reality.

This is something that my logical brain will probably never be able to accept as reality.

Math is quite logical. It's not your "logical brain" that fails to accept, but rather the intuitive part of it.

 

[Emreth]

What if one of the twins travels away and back to his twin on Earth in a non-inertial way all the time, all acceleration and no constant velocity motion?Then do they agree on their clocks?

 

[JesseM]

What if one of the twins travels away and back to his twin on Earth in a non-inertial way all the time, all acceleration and no constant velocity motion?Then do they agree on their clocks?

No. It's analogous to the fact that in a 2D plane, a straight line is always the shortest distance between two points, if you have any non-straight path--whether a path with two straight segments joined by an angle, or a curvy path that's not straight anywhere--then its length will be longer. In just the same way, a "straight" (constant velocity) path through minkowski spacetime always has the largest value for the proper time (time as measured by a clock that takes that path).

 

[Tam Hunt]

tnadys, one thing that hasn't been mentioned is the fact that Einstein argued for a "new ether" as the basis for differentiating between frames of reference in the Twin Paradox, from 1916 on. His 1905 paper dismissed the 19th Century "old ether" as superfluous, but after further discussions with Lorentz, Einstein became a strong advocate for the new, non-mechanical, ether, as a means for distinguishing worldlines in different reference frames. Without this ether, you are correct that there is complete symmetry between any two observers and the asserted time dilation in SR and GR. The new ether, according to Einstein, was the medium by which inertia, for SR, and acceleration, for GR, could be distinguished in different reference frames. So while there is complete symmetry from an epistemological point of view, between different reference frames, in SR and GR, there is not complete symmetry in terms of relativistic effects. But also see Lorentzian relativity for a different interpretation of relativistic effects - the jury is still, in my view, out on whether Einsteinan relativity or Lorentzian relativity is the better theory.

 

[JesseM]

tnadys, one thing that hasn't been mentioned is the fact that Einstein argued for a "new ether" as the basis for differentiating between frames of reference in the Twin Paradox, from 1916 on. His 1905 paper dismissed the 19th Century "old ether" as superfluous, but after further discussions with Lorentz, Einstein became a strong advocate for the new, non-mechanical, ether, as a means for distinguishing worldlines in different reference frames.

Einstein was using "ether" just to refer to the notion that spacetime has intrinsic properties of its own like curvature, he was not suggesting a medium which would have its own distinct rest frame, and where we could define some notion of absolute velocity relative to that frame. See here:

It may be added that the whole change in the conception of the ether which the special theory of relativity brought about, consisted in taking away from the ether its last mechanical quality, namely, its immobility.

...More careful reflection teaches us, however, that the special theory of relativity does not compel us to deny ether. We may assume the existence of an ether; only we must give up ascribing a definite state of motion to it, i.e. we must by abstraction take from it the last mechanical characteristic which Lorentz had still left it.

...Recapitulating, we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense. But this ether may not be thought of as endowed with the quality characteristic of ponderable inedia, as consisting of parts which may be tracked through time. The idea of motion may not be applied to it.

 

[Tam Hunt]

JesseM, I agree that Einstein was always very clear that his "new ether" could not be the basis for absolute motion - it was a relativistic ether. Others have, however, reintroduced a non-material ether that can be the basis for absolute motion (Hermann Weyl, for example, in 1918, praised by Einstein in his 1920 speech on the ether, in Leiden, Lorentz's university).

And I've long puzzled over this issue: if Einstein's new ether allows inertia and acceleration, can't it also allow for distinguishing what is at absolute rest? This seems to be the case because if inertia prevents a moving object from freely moving from its path when a force is applied to it (a kind of "stickiness" of a given object for its existing path), couldn't we in theory identify an object that is absolute rest with respect to the new ether by identifying an object that has no inertia? I am speculating rampantly here, but hopefully you can indulge me.

 

[Sam Park]

Others have, however, reintroduced a non-material ether that can be the basis for absolute motion (Hermann Weyl, for example, in 1918, praised by Einstein in his 1920 speech on the ether, in Leiden, Lorentz's university).

Weyl's 1918 theory did not "re-introduce a non-material ether that can be the basis for absolute motion".

 

[Tam Hunt]

Sam, in Kostro's book Einstein and the Ether, he quotes Weyl's ether theory as leading to "absolute space," which of course is directly related to absolute rest and absolute motion. I don't have the book here at work, but I'll post the quote later. Einstein praised Weyl, and then said Weyl was on the wrong track, presumably because Weyl's ether was not a relativistic ether, at least not in its 1918 version.

 

[Sam Park]

Sam, in Kostro's book Einstein and the Ether, he quotes Weyl's ether theory as leading to "absolute space," which of course is directly related to absolute rest and absolute motion. I don't have the book here at work, but I'll post the quote later. Einstein praised Weyl, and then said Weyl was on the wrong track, presumably because Weyl's ether was not a relativistic ether, at least not in its 1918 version.

Unlike you, I'm actually familiar with Weyl's 1918 theory, and with what was wrong with it. Weyl and everyone else ultimately agreed that it was a failure, although it did lead to the concept of gauge invariance, which has become a fundamental aspect of later theories. (Does your source think gauge invariance is tantamount to "absolute space"? Sheesh!) In its original form (as an attempt to unify gravity and electromagnetism) the frequencies of light emitted by an atom (for example) would be variable, dependent on the history of the atom. This is precisely the feature of the theory that made it empirically falsified. If THIS is what your source choses to describe as "leading to absolute space", I would say you should seek better sources. (By the way, the book you cited was published by Apeiron... enough said.)

In addition, for you to have originally cited Weyl's "leading to absolute space" as something "praised by Einstein", without mentioning that this unphysical "history-dependence" is precisely the aspect of Weyl's theory to which Einstein objected (as well as being empirically falsified by countless observations) is just intellectually dishonest. I think your post was not only technically and historically inaccurate, but also personally dishonest (and your latest post clearly reveals your mens rea).

 

[Tam Hunt]

Whoa whoa whoa. Sam, check the attitude. It's not helpful and certainly not warranted given my posts thus far. Go back and read what I wrote. I was providing a historical note that had not been thus far provided. I did not say Weyl's theory was accepted, by Einstein or anyone else. Check what I wrote.

And my question remains: doesn't Einstein's new ether allow, in theory, ascertaining absolute rest?

 

[JustinLevy]

Once again, you cannot ascertain your motion relative to empty space according to GR. If you continue to disagree, please state a specific example of how you would measure such a thing so that we can discuss the science, instead of debating history.

And my question remains: doesn't Einstein's new ether allow, in theory, ascertaining absolute rest?

The question does not remain. It has been answered many times. Your previous thread was first moved, and then locked. Why don't you take heed of the moderators.

Heck, you even admitted what Einstein's answer was on this question, stating previously in this very thread:
"I agree that Einstein was always very clear that his "new ether" could not be the basis for absolute motion"

[in response to Tam](By the way, the book you cited was published by Apeiron... enough said.)

Thanks for pointing that out.

 

[Tam Hunt]

Justin, the question has most definitely not been answered. I'm not asking what Einstein said on this topic. I'm asking how Einstein's conception of the new ether can be reconciled with GR. Einstein believed it could, as you know, but I'm following a line of reasoning that may contradict his view - or not, as I'm probably just not thinking it through clearly enough. Here's what I wrote to you before, showing that Einstein himself did not subscribe to the view you suggest - that the fixed stars form the basis for Newton's bucket phenomena. Rather, he states very clearly that it is space itself, with its inherent metric properties (what he often described as his new ether) that provides the basis for the bucket's water's inertia. Here's the passage from his 1920 speech on the ether at Leiden University:

Mach's idea finds its full development in the ether of the general theory of relativity. According to this theory the metrical qualities of the continuum of space-time differ in the environment of different points of space-time, and are partly conditioned by the matter existing outside of the territory under consideration. This space-time variability of the reciprocal relations of the standards of space and time, or, perhaps, the recognition of the fact that ``empty space'' in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitation potentials g), has, I think, finally disposed of the view that space is physically empty. But therewith the conception of the ether has again acquired an intelligible content, although this content differs widely from that of the ether of the mechanical undulatory theory of light. The ether of the general theory of relativity is a medium which is itself devoid of all mechanical and kinematical qualities, but helps to determine mechanical (and electromagnetic) events.

 

[Tam Hunt]

PS. As for a book being published by Apeiron as somehow indicting the worth of the book, let's not become McCarthyists here please. The book is a thorough, and fully Einsteinian, review of Einstein's thinking on the ether, throughout his career. It quotes Einstein in the original German, and in English translations, throughout. And we are now today at the point where the Higgs field is the newest name for Einstein's new ether - see Wilczek's Lightness of Being for more on this.

 

[JustinLevy]

Here's the problem, your question is:

I'm asking how Einstein's conception of the new ether can be reconciled with GR.

This inherently is assuming that there is some idea of a "new ether" that is separate from GR.

We can never get anywhere with this, because no matter what we say, you will feel that we only considered GR and not whatever you feel is this "new ether".

If you are proposing a theory different from GR then we cannot answer your question without knowing this theory. Can you state this theory mathematically for us? Does it make any predictions for experiment different from GR? If so, experiment has most likely already proved your new theory wrong, and there would be your definitive answer.

Why do I call it "your" new theory, and not Einstein's new aether? Because I and others have told your repeatedly that you are not understanding the physics and therefore not understanding what Einstein was saying. You are taking a popularist presentation and skewing it to fit some bizarre notions of absolute space that you have.

As I mentioned before, try reading this:
http://en.wikipedia.org/wiki/Hole_argument
to get a better understanding of what properties space does and does not have according to GR for the context of your question.

 

[JustinLevy]

And we are now today at the point where the Higgs field is the newest name for Einstein's new ether - see Wilczek's Lightness of Being for more on this.

Ugg. Stop misintrepretting stuff. The standard model including the higgs field is still a relativistic theory.

In your mind non-zero vacuum expectation value = Lorentz violation? Because no, it doesn't. But it DOES mean empty space (vaccuum) has properties... just not the kind you keep thinking.

 

[RandallB]

.. my question remains: doesn't Einstein's new ether allow, in theory, ascertaining absolute rest?

TIM
I would say YES
IF, by “absolute rest” you in effect mean changing his mind to accept some form of “absolute space” and some form of “absolute time” sufficient to recognize Newton as in general correct on those issues would be required with accepting any form of an “ether”.

MY Problem with History - is who really changed their minds;
Accepting a new idea to “change his mind” and considering one are two different things:

I am a little more interested in the HISTORY of ideas and how they changed;

First point; was Lorentz “a lifelong advocate of the ether concept”

Often you can find those that claim Lorentz (& friends) “invented relativity first”
But historically that claim is quashed by by Lorentz himself as he acknowledged his transforms were based on length counteractions of matter moving though an ether rendering M&M efforts to measure an ether unable to show results.
But the addition of time dilation based on rejecting absolute space and time Lorentz sited not partial but full credit to Einstein alone.
I had taken this a Lorentz changing is mind on the point and accepting the rejection of the Newton Absolutes. I take him as a GR advocate not an ether supporter!
Does the book you site contradict this view of history, and site some referenced examples of Lorentz arguing for a more “dependent background” that cannot be supported by Background Independent GR. (I understand they would not have used the terms “dependent background” vs. “background independent” back then) . Thus arguing for some form of Newton absolute space and independent absolute time.

MY READ ON THIS: Lorentz changed to accept a “background independent” GR.
---- Do you feel the Kostro book documents a good case to refute this assumption.

Second Point can we really say Einstein advocated for an “Aether” concept?”

Does Kostro give anything in the way of a verifiable Einstein quote or paper indicating GR needed revision toward a more “dependent background” or Newton friendly reinterpretation?

RB

 

[Tam Hunt]

Justin, I have stated clearly and consistently that Einstein's new ether is a relativistic ether - and he always advocated a relativistic ether, not an ether that would allow for detection of absolute space.

My question has been all along: can Einstein's new ether truly be a relativistic ether if it has the properties he assigned to it (inertia, acceleration, etc.)?

The Higgs field, as Wilczek described, is akin to a new ether, but it is still considered to be relativistic. And this leads to the primary problem in modern physics: how do we reconcile the Standard Model with GR?

One possibility and my humble (and probably poorly informed) suggestion: we may "reconcile" these two pillars of modern physics by throwing out GR, or at the least accepting a Lorentzian interpretation of GR that includes an ether that allows absolute rest.

 

[Tam Hunt]

RandallB, yes, Einstein stated very clearly on a number of occasions his support for a new, relativistic, ether. His two major statements on this are "Ether and the theory of relativity," a 1920 speech delivered in Leiden, and his 1924 talk "On the Ether." You can google these.

No, Lorentz never accepted Einstein's interpretation of GR. He went to his grave in 1928 still firmly believing in the non-relativistic ether. He did praise Einstein's achievements profusely, but he never entirely agreed with Einstein's version of GR. See Michael Janssen's writings for more on this complex topic, in particular his 1995 doctoral dissertation (also online).

 

[JesseM]

And I've long puzzled over this issue: if Einstein's new ether allows inertia and acceleration, can't it also allow for distinguishing what is at absolute rest? This seems to be the case because if inertia prevents a moving object from freely moving from its path when a force is applied to it (a kind of "stickiness" of a given object for its existing path), couldn't we in theory identify an object that is absolute rest with respect to the new ether by identifying an object that has no inertia? I am speculating rampantly here, but hopefully you can indulge me.

I don't understand, why would the existence of inertia imply there should be an object with no inertia? Inertia is only detected by applying a force to an object and observing its resistance to acceleration (it has nothing to do with resisting constant-velocity motion), and all objects with equal rest mass will resist acceleration in the same way as seen in the frame where they were previously at rest before the force was applied.

 

[Tam Hunt]

Jesse, my speculation here is that absolute rest could, in theory, be detected by testing a chosen object's resistance to acceleration. Imagine a very small asteroid traveling through space. For the sake of simplicity, let's eliminate any substantial matter near enough to have much of a gravitational influence, so let's imagine we're in the depths of inter-galactic space. We could, in theory, apply a force to the small asteroid while it is traveling through various vectors and find out which vector (there would only be one) led to a much larger acceleration in response to the same force applied to the asteroid than for other asteroid vectors. This is the case because if the new ether is the source of inertia, as Einstein believed after 1916, there seems to be one, and only one, vector that would represent absolute rest with respect to this ether. This follows because the asteroid's inertia increases (and thus its resistance to acceleration) as its speed with respect to the new ether increases. Which leads to the conclusion that there must be a point at which the inertia is zero. And that is absolute rest. Or am I way off base here?

Justin will state that space's (new ether) properties depend on matter. But this does not seem to be Einstein's own interpretation from 1916 on. To the contrary, he argued, as demonstrated by the quote in my earlier post from the 1920 speech on the ether, that space itself has properties (which is also the modern view, re the vacuum and virtual particles, etc.). I'll agree with Justin that Einstein presented different views on this key point throughout his career, claiming as late as 1952 (in his paper "Relativity and the Problem of Space," added to his 1916 book on SR and GR as Appendix V) that space does not have any independent existence. But Justin gets it wrong in stating that Einstein thought space required matter for its existence. Rather, Einstein believed that fields could explain both matter and the ether and would allow for the distinction between ether and matter to melt away. Fields were, in Einstein's later work, considered irreducible. But he never succeeded in creating a unified field theory, which he struggled mightily to find for 30 years. I suspect that he ultimately failed because of his insistence that the "total field," his later term for what he had earlier referred to as the new ether, had to be relativistic. But that's still purely speculation on my part.

 

[JesseM]

Jesse, my speculation here is that absolute rest could, in theory, be detected by testing a chosen object's resistance to acceleration. Imagine a very small asteroid traveling through space. For the sake of simplicity, let's eliminate any substantial matter near enough to have much of a gravitational influence, so let's imagine we're in the depths of inter-galactic space. We could, in theory, apply a force to the small asteroid while it is traveling through various vectors and find out which vector (there would only be one) led to a much larger acceleration in response to the same force applied to the asteroid than for other asteroid vectors. This is the case because if the new ether is the source of inertia, as Einstein believed after 1916, there seems to be one, and only one, vector that would represent absolute rest with respect to this ether. This follows because the asteroid's inertia increases (and thus its resistance to acceleration) as its speed with respect to the new ether increases. Which leads to the conclusion that there must be a point at which the inertia is zero. And that is absolute rest. Or am I way off base here?

Your speculations don't make any sense to me--why would the new ether being the "source of inertia" imply it has its own rest frame? That certainly wasn't what Einstein believed. And even if there was an ether with a definite rest frame, I fail to see how the ether being the "source of inertia" implies that an object's inertia would increase as its speed relative to the ether increased--that just seems like a total non sequitur.

 

[RandallB]

Tam
Thanks for the extra History on Lorentz (prefered frame) – for others interested see:
http://www.mpiwg-berlin.mpg.de/litserv/diss/janssen_diss/
Title page has Table of Contents ref chapt 3 & 4

By the way welcome to the forum:
No need to respond to my earlier PM (Private Message system see top right of Forum Page) on the book. If I come across it I’ll look it over but I’m satisfied there is not that much new in it.

… the asteroid's inertia increases (and thus its resistance to acceleration) as its speed with respect to the new ether increases. Which leads to the conclusion that there must be a point at which the inertia is zero. And that is absolute rest. Or am I way off base here?

Way off base.
If “inertia” were to become “zero” at any point it would mean even the slightest force would impart an infinite speed or nearly so.
That Lorentz remained on a version of his transforms that demanded what we now refer to as a “Preferred Frame” is what I believe any ether “Constructive Theory” would require. IMO this is what Lorentz expected and what you are talking about. This requires a fairly COMPLETE model to describe things before it will be accepted as a Theory and IMO would need to include a more complete model of Classical Maxwell Fields as well.

Fields were, in Einstein's later work, considered irreducible. But he never succeeded in creating a unified field theory, which he struggled mightily to find for 30 years.

IMO this is where Einstein Theory is unrealistic and incompatible with Lorentz.
Which it must be since as Einstein explained his was a “Theory of Principle” (although he hoped for a way to find “Constructive Evidence” to support it.) A Theory of Principle does not need to show constructive explanations or direct constructive evidence of a unrealistic “truth” of extra dimension(s) (invisible to us) to allow for “Space-Time” warping etc.
Although unrealistic in a Euclidian Reality if we assume that such a unrealistic thing were in fact true and “real”; a “Constructive Theory” could hardly be expected to reveal it. Thus the Principles based theories starting with SR that Einstein developed.

To describe Einstein as “strongly advocating” for a “new ether” is over stating it.
IMO it is clear he was trying to find a means to better describe the required continuous fields, in field which must be considered “unrealistic” with no physical model to adequately describe them. I do not thing it is fair to describe his efforts in this area as establishing a version of an ether. Rather more like trying to find a view into the unseen dimension(s) with as “Constructive Like “Principle Model” as possible. I’m sure he felt that was needed to refute the path QM was using and to enable the desired “Unifications”.

 

[Tam Hunt]

Jesse, a quick response (all I have time for): inertia = kinetic energy, so as speed increases with respect to the ether, inertia increases. Which leads to my speculation that there is an "at rest" speed, with respect to the ether, as the inertia diminishes to zero. Again, just speculation, so I welcome your thoughts.

 

[Tam Hunt]

RandallB, a body at rest, in my hypothetical, would not reach infinite acceleration from an external force. Rather, it would accelerate quickly for an instant, and then quickly be slowed due to the inertia it acquires through motion through the ether.

Re Einstein and the ether, I definitely recommend you read Kostro's book, as it describes in detail the history of Einstein's thinking on the ether throughout his career. Einstein was, it is fair to say, a strong advocate of the new ether from 1916 to 1924, responding to Lorentz's encouragements and Lenard's harsh critiques. From 1924 on, he still used the term, but also talked about "physical space" and, eventually, the "total field" (which included gravity and EM) as a new term for the ether. He always asserted the ether was relativistic. It ultimately comes down to semantics and there is a long-fought argument over whether the "ether" should be used at all due to its baggage.

 

[JesseM]

inertia = kinetic energy

How is inertia equal to kinetic energy? Inertia is resistance to acceleration (essentially just the m in F=ma), kinetic energy is (1/2)*mv^2 (the nonrelativistic version anyway, which is close to the relativistic version when v << c).

so as speed increases with respect to the ether, inertia increases.

Again, this makes zero sense to me, just a complete non sequitur. You might as well say "inertia is gravitational potential energy, so as distance from a source of gravity increases, inertia increases."