Teaching relativity to the general public

[David Cooper]

You are focusing on SR here, but it's worth noting that, in the context of GR, where spacetime is curved, the notion of "absolute space" becomes much more problematic, because there are no longer any global inertial frames.

There is no universal absolute frame anyway, but at every point in space there could be a local absolute frame. One way to imagine it would be to think of the three dimensions of space tied up in the surface of a balloon with that balloon expanding within another kind of space (which I'm not suggesting is the actual nature of reality - this is just to illustrate the point). The real absolute frame there would be in that other kind of space while the absolute frame imagined to exist at any point within the universe would only be correct for that single point and would be different for the locations around it. This means that even if an absolute frame could be identified, it would serve no useful role in carrying out calculations of how things will interact within the universe. What is important though is to have a mechanistic understanding of how things might actually work, and LET provides a different mechanistic understanding from SR.

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I should make it clear that LET should not be taught in addition to SR. LET and Minkowski spacetime are two different ways of presenting SR.

What is meant by "there is no absolute frame" is the local laws of physics are Poincare invariant. This is a property of SR, and it is therefore a property of LET.

If "there is no absolute frame" merely has a technical meaning within SR (with a terrible wording), then that is not ideal but we have to work with it regardless. It cannot be used in discussion of LET unless it is reworded because it that wording directly clashes with a requirement of LET. The wording is highly misleading whenever it is used in such a way that it may be taken literally, and it's doubtless that kind of thing that has lead to a lot of people believing things to be facts which are not facts. This is something that education needs to address, because wording does matter and bad wording does mislead people.

No theory can ever be proven by experiment, but a theory can be shown to hold to extremely good approximation in some regime. Poincare invariance has survived all experimental tests to date. ... Have we tested Lorentz invariance enough?

Experiments appear to support SR and LET, so what's your point there?

 

[David Cooper]

... Are you actually suggesting that a logically drawn conclusion is someone's opinion? Drawing conclusions through reasoning is perhaps the most important part of the scientific method! I understand that you think experiment should be used to justify a claim, but by your logic that wouldn't work either, since technically you are only reasoning that the experiment holds true outside of the literal exact context you performed it in.

I am not opposed to logical reasoning being fully applied to the scientific method. In the case of LET's absolute frame though, it is something that is tied up in a philosophical interpretation and which is beyond the reach of experimental verification.

Clearly your mind is set so there is not much point in this discussion, but I fail to see how teaching absolute space, i.e. an hypothetical entity for which there is neither proof nor necessity, furthers the goal of education any more than teaching that there is an army of invisible goblins floating in the ether that are under strict orders to never interact in any way with anything else so their presence cannot be detected even in principle.

I fail to see how teaching against absolute space is acceptable when it too is just part of a philosophical interpretation. If one side is allowed to sneak in ideas which are merely unbacked assertions and to push them as facts, the other side should clearly not be banned from presenting its ideas and describing them as propositions. The idea must be brought in when looking at the contradictions generated by the accounts of events using different frames of reference - it is a logical imperative that they cannot all be true. The same applies to SR, regardless of what Einstein thought - there must be a specal frame where no longer path into the future can be taken by accelerating, because otherwise you must determine that 2 = 1/2 on the basis that a clock being accelerated to 87% the speed of light is at the same time both halving and doubling the length of the path it is following through the time dimension into the future. A proper grounding in relativity ought to explore the logical implications of the claims being put forward. There is nothing that implies the existence of invisible goblins, but all attempts to explain relativity run into a point where they have to bring in some kind of special frame in order to explain the contradictions in the accounts of events from the analysis by different frames. Not to do so is to accept that 2 = 1/2 (and indeed that any number you like = any other nunmber of your choice). It is a requirement of reason, and while that may push it into the realms of philosophy, that is fine as it is only being applied to philosophical interpretations where theorists are attempting to create mechanistic, explanatory models. Here's the key point - if you feel the need to reject the idea of an absolute frame and to do so in a mocking way, you are duty bound to do the same with Einstein's claim that there is no special frame in SR, because that too is mere philosophical baggage (only unlike LET's absolute frame, it is baggage which endorses contradictions rather than rejecting them). We have to remove all of this unjustifiable bias from science education and be evenhanded instead.

 

[wabbit]

Education is not about sides competing for the right to influence students, it is about how best to further the students' progress. So the fact the "one side is allowed..." is irrelevant. What matters is what is in the students' best interests.

Other than that, I don't think anyone suggested to teach that absolute space is an impossibility. Relative space is a necessity, it is present as soon as one starts talking about the building blocks of space - contiguity, distance, orientation.,. All are relative notions. The construction of absolute space can be a useful tool and there is nothing wrong with introducing it as such - and nothing wrong either with mentionning that it might even actually exist as more than a tool. But it is not doing a service to students to try to convince them that it actually exists, or pretend that it is necessary. This only makes their progress more difficult.

 

[atyy]

If "there is no absolute frame" merely has a technical meaning within SR (with a terrible wording), then that is not ideal but we have to work with it regardless. It cannot be used in discussion of LET unless it is reworded because it that wording directly clashes with a requirement of LET. The wording is highly misleading whenever it is used in such a way that it may be taken literally, and it's doubtless that kind of thing that has lead to a lot of people believing things to be facts which are not facts. This is something that education needs to address, because wording does matter and bad wording does mislead people.

It's easy, just make it "there is no detectable single preferred frame".

Experiments appear to support SR and LET, so what's your point there?

My point is that LET and SR are not different theories. SR is a consequence of LET. And SR is consistent with LET - as the Rindler reference I gave in post #19 says, "in SR every inertial frame is as good as absolute space".

As before, there are very interesting subtleties when it comes to QM. Although it is probably not mentioned in the Bell reference I gave in post #19 that advocates a Lorentzian approach to special relativity, my guess is that Bell had the QM subtleties in mind when he wrote it, because the QM subtleties are highlighted by the Bell's theorem.

 

[wabbit]

@atyy, I haven't read those articles you listed before so my question is probably just uninformed - but in short, how much does QM have to teach us about space and time ? The QM theory of space and time is Quantum Gravity and it is still speculative, so how reliable can be QM as a guide here until we step into that most interesting but unsettled area ?

 

[PeterDonis]

The idea must be brought in when looking at the contradictions generated by the accounts of events using different frames of reference - it is a logical imperative that they cannot all be true.

This is not correct, and your claim that it is is an assertion presented as a fact. You are violating your own precepts.

Once again, you appear to have fundamental misunderstandings about relativity, and you should fix those first before trying to decide how other people should be taught.

 

[atyy]

@atyy, I haven't read those articles you listed before so my question is probably just uninformed - but in short, how much does QM have to teach us about space and time ? The QM theory of space and time is Quantum Gravity and it is still speculative, so how reliable can be QM as a guide here until we step into that most interesting but unsettled area ?

Those articles have nothing to do with quantum gravity. QM in Minkowski spacetime already brings up a huge problem

I haven't seen this, but Susskind is usually superb, so here's one of his discussions.



But maybe not insurmountable: http://arxiv.org/abs/1111.1425

 

[wabbit]

But QM doesn't really go very far in Minkowski spacetime does it ? I was under the impression only QFT could truly handle it, which tends at least to suggest that problems of QM in Minkowski spacetime are problems of QM, not of spacetime. Then again I should read before asking, sorry I'm just lazy and you're kind enough to reply so I continue : )

 

[atyy]

But QM doesn't really go very far in Minkowski spacetime does it ? I was under the impression only QFT could truly handle it, which tends at least to suggest that problems of QM in Minkowski spacetime are problems of QM, not of spacetime. Then again I should read before asking, sorry I'm just lazy and you're kind enough to reply so I continue : )

By QM I include relativistic QFT. Relativistic QFT is a special case of the general QM formalism.

 

[wabbit]

Oh OK. So I must really go and read I guess...

 

[atyy]

Oh OK. So I must really go and read I guess...

http://pirsa.org/displayFlash.php?id=14070026
Can Quantum Correlations be Explained Causally?
Robert Spekkens

 

[David Cooper]

Education is not about sides competing for the right to influence students, it is about how best to further the students' progress. So the fact the "one side is allowed..." is irrelevant. What matters is what is in the students' best interests.

It is against their interests to provide them with a distorted picture of how things stand. For illogical philosophical baggage to be presented as good while logical philosophical baggage is presented as bad is not good education.

Other than that, I don't think anyone suggested to teach that absolute space is an impossibility. Relative space is a necessity, it is present as soon as one starts talking about the building blocks of space - contiguity, distance, orientation.,. All are relative notions. The construction of absolute space can be a useful tool and there is nothing wrong with introducing it as such - and nothing wrong either with mentionning that it might even actually exist as more than a tool. But it is not doing a service to students to try to convince them that it actually exists, or pretend that it is necessary. This only makes their progress more difficult.

The aim is not to promote it, but to make it clear that there is an alternative interpretation of the theory available which should be thoroughly understood by anyone who thinks they have a good knowledge of realativity. Most people who claim to have a good knowledge of relativity have a highly warped idea of what LET is and believe it has been disproven. That is not a healthy state of affairs.

It's easy, just make it "there is no detectable single preferred frame".

That's what LET does.

My point is that LET and SR are not different theories. SR is a consequence of LET. And SR is consistent with LET - as the Rindler reference I gave in post #19 says, "in SR every inertial frame is as good as absolute space".

They have very different mechanical explanations underlying them, and understanding one enhances understanding of the other.

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This is not correct, and your claim that it is is an assertion presented as a fact. You are violating your own precepts.

[That refers to "The idea must be brought in when looking at the contradictions generated by the accounts of events using different frames of reference - it is a logical imperative that they cannot all be true."]

Once again, you appear to have fundamental misunderstandings about relativity, and you should fix those first before trying to decide how other people should be taught.

It is not incorrect. If you are to accept that all the accounts of events generated for all frames are equally valid, you have to accept contradictions, and that is not something anyone should be comfortable with. There is no mathematical way to get around it - if you apply reason correctly you are duty bound to determine that not all the accounts are correct. This is one of the key things that education needs to address because it is a common mistake that people make. They are taught to ignore the contradictions and pretend they aren't there and they're told they don't understand relativity if they continue to object to the contradictions.

 

[PeterDonis]

If you are to accept that all the accounts of events generated for all frames are equally valid, you have to accept contradictions

Please give a specific example, and point out exactly where the logical contradiction is. Just a bare assertion is not enough. Think carefully about your example: you are aware, I take it, that there is a completely self-consistent mathematical model in which all of the accounts in different frames can be consistently represented. Since a self-consistent mathematical model is in itself a demonstration of logical consistency, you have an extremely heavy burden of proof.

 

[wabbit]

...

Thanks. I started looking at the last article. I usually find these discussions puzzling because they seem to have no operational consequence, so I find it hard to get the point of them.

 

[berkeman]

Thread closed for Moderation...

 

[PeterDonis]

This thread will remain closed. Proposals for teaching relativity that are based on misunderstandings of relativity cannot be discussed or endorsed here on PF.