Maudlin Explains Special Relativity

New interview:

Tim Maudlin is Professor of Philosophy at NYU and Founder and Director of the John Bell Institute for the Foundations of Physics. This is Tim’s seventh appearance on the show. He last appeared on episode 210 with David Albert for a discussion of the measurement problem in quantum mechanics. In this episode, Tim and Robinson talk about Albert Einstein’s theory of special relativity, explaining it from the ground up and elucidating some common misconceptions. More particularly, they get into Einstein’s magnificent mind, how special relativity displaced the theory of the ether, absolute and relative space, the speed and nature of light, the possibility of time travel, relativistic quantum mechanics, and more. If you’re interested in the foundations of physics, then please check out the JBI, which is devoted to providing a home for research and education in this important area. Any donations are immensely helpful at this early stage in the institute’s life.

Maudlin explains several relativity issues very well. I have a couple of quibbles.

Towards the end, at 1:50:00, he reveals that he does not believe in relativity, because he says John Bell (and subsequent experiments) proved that the world is nonlocal. He says he prefers the Bohm pilot wave theory because it is nonlocal. He elaborates in this lecture of a few months ago.

This is an eccentric opinion, as most physicists believe in locality, and there no convincing evidence against it. And they nearly all reject pilot wave theory as unphysical and useless.

He explains how relativity originated in the Michelson-Morley experiment, but acknowledges a dispute about whether Einstein knew anything about it.

That seems puzzling, but I think there is a simple explanation. The original papers on relativity, by Lorentz, Poincare, and Minkowski, all refer to the experiment. Einstein later wrote that relativity was based on the experiment, but his 1905 paper was not. The obvious explanation is that Einstein relied on the analysis of the experiment by Lorentz and Poincare, and did not look at it himself.

He explains the development of 4D spacetime:

24:08 it it [Einstein's famous 1905 relativity paper] doesn't present itself as a revolutionary theory about the structure 24:13 of space and time exactly and the title of it again nothing about relativity on the 24:19 electrodynamics of moving bodies you can see why that's the example I've got some moving bodies and they have electric and 24:25 magnetic fields um. his math teacher 24:31 minkovski reads the paper and minkovski understands how to represent 24:39 the paper as it were in terms of SpaceTime geometry and that's why we call it manovski SpaceTime and not 24:45 Einstein SpaceTime and it actually takes a little while for Einstein to accept this 24:51 because that wasn't how he was thinking about it but eventually he comes around and says oh yeah um really what I'm 24:58 doing is postulating a different SpaceTime structure.

He is right that Minkowski presents spacetime as a radical new theory and Einstein does not. But I think that it is unlikely that Minkowski was influenced by Einstein at all. Minkowski cites Poincare's 1905 paper that does present spacetime as a radical new theory, so Minkowski got it from Poincare, or rediscovered it himself. Minkowski's papers are not an exposition of Einstein's ideas at all.

The story of special relativity is largely about the leap from Maxwell's equations and the Michelson-Morley experiment to Minkowski 4D spacetime. Einstien didn't have anything to do with it, so I wonder why Maudlin talks about him at all.

Lorentz showed how to reconcile Michelson-Morley with Maxwell by modifying space and time. That is why we call it the Lorentz transformation. Poincare showed how to synchronize moving clocks and to turn Lorentz's theory into a symmetry theory of spacetime. Minkowski perfected Poincare's spacetime theory, and popularized it to a wider audience. Minkowski's theory is what became quickly accepted, and is what is called special relativity today. All Einstein did in 1905 was to give an exposition of Lorentz's theory, but Einstein's version was immediately obsoleted by Poincare and Minkowski.

Maudlin likes pilot wave theory because it supposedly tells us what is really going on, as opposed to Copenhagen "shut up and calculate".

Einstein of course wanted to have that 58:32 kind of clarity about Quantum Theory once it got going and he never got 58:38 it. uh he was never satisfied with quantum theory because he didn't have a 58:44 clear, he didn't have what he thought to be a clear physical account of even what the theory was saying, what it was 58:52 postulating um and the response to that as We Know was shut up and 58:57 calculate. I've given you you know. I I'll tell you how to calculate and make the predictions. I mean maybe this would help. 59:04 you could imagine Einstein. I mean we can play this little game Einstein goes to his physics teacher with this 59:10 electromagnetic problem. he says look physics teacher if I hold the coil and move the magnet I get this current if I 59:18 hold the magnet and move the coil I get the same current. how do I you know what's the difference? why is it so 59:24 different that the that teacher could have said to Young Einstein Einstein, shut up and calculate. right yeah use 59:31 Maxwell's equations yeah you'll use them differently in the two cases you'll get the right result. both times shut up stop 59:38 worrying about what's really going on and then we would have never had relativity. we have it because he 59:44 wouldn't shut up because he was trying to think it through, trying to understand it. yeah I think that is absolutely the 59:50 mark uh of of great physics is to try to get clear about 59:57 really what you're postulating and how it works and having some equations that you 1:00:04 can grind numbers out of that happen to be correct in terms of their predictions. that's not what physics should be 1:00:11 about. physics should be about understanding comprehension 1:00:17 intelligibility things like that and and that requires conceptual Clarity. it 1:00:24 requires Clarity and argumentation all the things it make for a good philosopher that was great.

No, this is completely wrong. Whatever Einstein thought about magnets had no bearing on the development of special relativity. Relativity would not have been delayed one second. The really big insights of length contraction, local time, constant speed of light, simultaneity conventions, covariance of Maxwell's equations, symmetry of spacetime, etc. were all published by others years ahead of Einstein.

As for quantum mechanics, the clarity that Einstein seemed to want was the local hidden variable theory that John Bell sought, and proved impossible. Instead Maudlin settles for Bohm's nonlocal hidden variable theory. But that theory gives no clarity, and is much more confusing than regular Copenhagen quantum mechanics. Einstein would have hated it.

I have previously posted about this disagreement on what Bell proved, such as here, here, here, and here. And how Maudlin is against positivism. Maudlin has argued these points with others in the past, such as here.

Maudlin also has an argument, at 1:20:00 to 1:32:00, that Feynman explains the twins paradox wrong:

This is called a “paradox” only by the people who believe that the principle of relativity means that all motion is relative; they say, “Heh, heh, heh, from the point of view of Paul, can’t we say that Peter was moving and should therefore appear to age more slowly? By symmetry, the only possible result is that both should be the same age when they meet.” ...

So the way to state the rule is to say that the man who has felt the accelerations, who has seen things fall against the walls, and so on, is the one who would be the younger;

Maudlin argues that you get their ages by integrating proper time, and that relative motion and acceleration are irrelevant.

He has a point in that you might be misled into thinking that if both twins are accelerated, then the more accelerated one will be younger. The acceleration is not really causing the twin to be younger.

Some try to explain the paradox by saying that special relativity does not apply to acceleration. But that is not true either. As Maudlin explains, it applies perfectly well to accelerated objects.

I don't think Feynman said anything literally wrong. It is true that there is not a symmetry between the twins because one is accelerated. I would prefer to say that the explanation is incomplete, because he does not say what to do if both twins are accelerated.

Maudlin says the twins' clocks are like odometers on cars. If two identical cars take different routes to a destination, then no one is surprised when they have different odometer readings.

People usually call it the twin paradox, but I guess Maudlin is being more precise by calling it the twins paradox. You need both twins to have a paradox.

The interviewer mentions how Feynman has a god-like status. I do not think that they saw the recent podcast trashing him.

A related excellent point Maudlin makes is that many people say that Newton had an absolute spacetime, and Einstein or Minkowski had a relative spacetime, and this is incorrect. Both are absolute in the same way. Relativistic spacetime just has a different geometry. Just as the Earth's surface has a geometry reflected by odometer readings on cars, spacetime has a geometry reflected by clock readings on spaceships.

Sometimes the core concept of relativity is misleadingly summed up as: there is no absolute frame of reference in the universe; all motion is relative to the observer. There is no such thing as absolute rest or absolute motion.

But the cosmic microwave background defines an absolute rest in the universe, and no one thought that its discovery contradicted special relativity.

No, the crucial idea is that spacetime has a non-euclidean geometry. That geometry implies symmetries between different inertial frames of reference, making motion seem relative.

Perhaps people say that there is no absolute frame because they are reject aether models that defined such a frame. It is true that special relativity rejected certain aether models that used to have followers. But it does not reject the CMB, or Lorentz-invariant aethers. Saying that there is no absolute reference frame is not even a scientifically useful statement.