Monday, July 29, 2024

Weinberg blamed Religion for Scientific Ignorance

Physicist Steve Weinberg is deceased, and said this in a recently released interview:
7:12 expensive uh we waste enormous amounts 7:14 of money on man space flight which have 7:17 has no uh scientific function 7:21 um I worry about that and maybe a more 7:26 important worry is whether or not um 7:30 the forces of uh religious 7:33 zealotry uh which are 7:36 uh so obvious in the Islamic world but 7:40 not entirely absent in the west uh will 7:44 lead to us turning away from science 7:47 because after all the Scientific 7:49 Revolution uhu of course did occur in 7:53 the uh 16th century and 17th century but 7:58 uh there had been a great period of 8:00 scientific Advance before that in 8:02 helenistic times which then came to an 8:05 end uh it was continued for a while in 8:08 the Arab world it disappeared in the 8:10 Christian world and then after the 13th 8:14 century it really uh did not pick up 8:17 again in any real way until the time of 8:20 Galileo uh we may not 8:23 continue with the great 8:26 um great tradition of science uh for 8:29 reasons which are even deeper and more 8:31 frightening than the lack of funding
Weinberg is putting a lot of blame on Christianity here. He praises ancient Greeks because they were pre-Christian, and Galileo because he had a dispute with the Pope.

Other people do say stuff like this, but I do not agree with it.

This "Scientific Revolution" took place in Christian Europe. The scientists were Christians, and acting under Christian sponsorship. Areas dominated by other religions did not make these scientific advances. Is that just a coincidence? I don't think so.

Monday, July 22, 2024

How Michelson-Morley was Crucial for Relativity

Alejandro Cassini, Leonardo Levinas write a new paper:
How the Michelson and Morley experiment was reinterpreted by special relativity
They note how relativity textbooks describe M-M as being crucial for relativity, and discuss whether this is historically accurate. It includes some interesting history, but omits the most important pieces to the puzzle.

Einstein's 1905 paper does not mention M-M. Later on he admitted that M-M was crucial for special relativity, but denied that he paid any attention to it.

FitzGerald, Lorentz, Poincare, and Minkowski all described relativity as a consequence of M-M. This paper does not even mention Poincare or Minkowski. It discusses Einstein a lot.

A paper on the influence of M-M on relativity should primarily be on those who were influenced, not Einstein.

In the years immediately following the M-M experiment, there was no inclination to conclude that the ether was non-existent, nor that the speed of light was constant even though the light source was in motion relative to the ether. Moreover, no one thought that the principle of relativity - the equivalence of all inertial frames of reference for the description of electromagnetic phenomena- would be confirmed. Nor did anyone think the hypothesis that the speed of light was invariant, that is, the same in any inertial frame of reference, would be confirmed.1 What exactly did this experiment confirm or refute?
Not true. In those years, Lorentz and Poincare did say that the speed of light was constant, and Einstein got that postulate from Lorentz. Poincare did say that the principle of relativity was confirmed, and Einstein got that terminology from him.

Lorentz did think that M-M refuted the aether motion theories.

M-M does not actually refute the aether. Belief in the aether is consistent with relativity. Einstein said so himself. M-M just refuted the idea that the Earth had a measurable motion against the aether.

As is well known, FitzGerald in 1889 and independently Lorentz in 1892 proposed a different interpretation. They argued that the experiment refuted the hypothesis that the length of the arms of the instrument remained unchanged when it was in motion relative to the ether, a tacit assumption of the M-M experiment. They then formulated the hypothesis that the length of rigid bodies that move with respect to the ether is not invariant, but rather contracts in the direction of motion
That's right. They saw the M-M as finding that measuring the speed of light did not depend on the frame of reference, and used that to deduce the Lorentz transformation.

It was similar to what Einstein did in 1905, except that Einstein did not use the M-M, but rather what Lorentz had deduced from Maxwell's equations and M-M -- that the speed of light is constant and appears the same in different frames.

At the time Einstein formulated it, it was the only explanation of the M-M experiment that was compatible with all known phenomena about the propagation of light, such as stellar aberration, Fizeau's experiment, and many others.28
No, that was all done by Lorentz in 1895. Lorentz even got a related Nobel Prize in 1902. Einstein did not attempt to explain M-M at all. You might say that Einstein was trying to give a recapitulation of Lorentz's 1895 theory, without mentioning M-M or other experiments.
The contraction hypothesis is usually considered to be purely ad hoc since it was proposed solely to accommodate the result of the M-M experiment in order to save the quiescent ether hypothesis from refutation. This affirmation is debatable and depends on what is understood by the concept of an ad hoc hypothesis.13
Here, "ad hoc" means deduced from M-M or other experiment. A theory is not ad hoc if it abstracts out principles from the experiment. There are some anti-positivist philosophers who consider ad hoc to be a bad thing.

The M-M really was crucial for relativity. Those who discovered the Lorentz transformations and spacetime all said so.

Monday, July 8, 2024

Posulating the Constant Speed of Light

D V Redžić writes in a new paper:
The historical path to special relativity starts from the second postulate introduced by Einstein in 1905 [10]. Immediately after the publication of reference [10],
No, the historical path starts with Maxwell's 1865 theory, and the motion invariance tests of it by Michelson in the 1880s.

A popular interpretation of the 1887 Michelson-Morley experiment was that the speed of light was the same for all observers.

Newton, and all physicists before Einstein (including Voigt, Larmor, Lorentz and Poincar´e [15-18]), took it for granted that there was only one ‘time,’ absolute Newtonian time, for all observers in motion with respect to one another. Einstein was bold enough to venture that each inertial observer has her/his own absolute Einsteinian time.
No. Moving objects had they own "local time" in Lorentz's 1895 relativity theory. Poincare accepted this, and believed that motion affects time. Not sure about Voigt and Larmor, but they gave equantions for time changing; what else could they have thought?

It is amazing that someone could write a commentary on on the historical path of relativity, and act as if it all started and ended with Eeinstein's 1905 paper.

Thursday, July 4, 2024

Google Quantum Supremacy is Smashed

NewScientist reports:
Google's claim of quantum supremacy has been completely smashed

Google's Sycamore quantum computer was the first to demonstrate quantum supremacy – solving calculations that would be unfeasible on a classical computer – but now ordinary machines have pulled ahead again

In 2019, Google claimed that its Sycamore quantum computer could perform calculations that would take even the world’s most powerful classical supercomputer 10,000 years to complete – but now it seems that a non-quantum computer crunches the numbers several times faster than Google’s machine, and uses less energy doing so.

Quantum computers have the potential to carry out some kinds of calculations vastly more quickly than classical computers, but are still in their infancy. Google announced in 2019 that Sycamore had achieved “quantum supremacy” – the point at which a quantum computer can…

The rest is paywalled, and I haven't read it, but I don't think I need to. Others have said the Google claim was refuted.

I was skeptical in 2019 for the simple reason that Google did not do something that known to be computationally difficult.. It merely generated some random numbers and then claimed that it would be hard for a classical computer to simulate it.

Then some Chinese researchers showed that it was not so hard to simulate it. Meanwhile the Google team moved on to other problems, rather than defend the integrity of their biggest accomplishment.

Without quantum supremacy, the whole field of quantum computing is a sham. No good can come of it.

Monday, July 1, 2024

David Z. Albert Plugs Bohmian Mechanics

New podcast, with a physicist interviewing a philosopher of physics:
Could physics serve as our best guide to metaphysics? What fundamental metaphysics is best motivated by quantum mechanics? And what’s the deal with the age-old feud between philosophers and physicists?

Here to shed light on all these questions and more is none other than David Z. Albert, professor of philosophy and director of the MA program in The Philosophical Foundations of Physics at Columbia University in New York. David is a prominent American philosopher and physicist widely recognized for his contributions to the philosophy of quantum mechanics and the foundations of physics. He has published four popular books and numerous articles on quantum mechanics.

I have some disagreements, but I was especially struck by this comment at the end:
1:19:40 last question, this one comes from my friend Professor Luke Barnes at Western Sydney. Luke. Yeah, he's a great friend of the show. 1:19:47 He's been on multiple times. he has he makes a controversial claim, as if bohmian mechanics have been proposed. First. 1:19:54 No one would have proposed the Copenhagen interpretation. Right. Your thoughts, sir? I think that's absolutely right. 1:19:59 I think, you know, somebody, somebody had discovered about me in mechanics. 1:20:06 And you imagine before then walking into a room and saying, no, I've got a whole new view. 1:20:12 Okay. it's much more elegant. It respects the symmetry between position 1:20:18 space and momentum space, blah, blah, blah. The only little catch is that you have to give up on the idea 1:20:25 that there's a real external world out there. Okay, I think you would have been laughed out of the room, right?
No, this is bizarre. Albert has written a lot about the philosophy of quantum mechanics, but this comment is so foolish that we should disregard everyone he says on the subject.

Bohmian mechanics is weirdly deterministic and nonlocal. While it has its own cult following, it is nearly useless for practical physics. It was invented to make a theoretical point about hidden variables, but not because it is a satisfactor interpretation.

Earlier, Albert said that quantum logics were too confusing, because he doesn't how to reason about it if regular logic is abandoned. I feel similarly about locality. Give it up, and I am not sure what you mean by experiments anymore, because you cannot isolate any physical processes.

Wednesday, June 26, 2024

Does E=mc^2 Require Relativity?

Physicist Tony Rothman has a new paper arguing that one can get the famous Einstein mass-energy equivalience E = mc2 before Einstein's 1905 paper, and without relativity. In particular, it appears in a 1900 Poincare paper.
Many physicists, for instance, are under the impression that ℰ=m⁢c2 can be established by employing the four-vector formalism of special relativity. An early draft of Wikipedia’s page on mass-energy equivalence in fact offered exactly such a “derivation.” Four-vectors, however, are defined in order to be consistent with ℰ=m⁢c2; consequently any argument based on them to prove the relationship is circular. ...

A universal, assumption-free proof of ℰ=m⁢c2 is no more attainable than a universal proof of conservation of energy or momentum, and the very idea that all physics can be derived from a master Lagrangian without experimental input must be doomed to failure. For that reason, all demonstrations of mass-energy equivalence rely on specific assumptions and approximations. The closest thing that exists to a general proof of ℰ=m⁢c2 is the Laue-Klein theorem [16, 17, 18] of 1911 and 1918, which in essence states that if ℰ=m⁢c2 holds for a point mass, then it also holds for an extended closed system, under specified boundary conditions. If radiation can escape to infinity, for example, the boundary conditions are evaded.

Einstein was aware of the inadequacies of his 1905 article and attempted to correct them in six further papers, but as Ohanian argues [19], none is free of errors and inconsistencies. Physicists who have actually read the 1905 paper know that the dubious step is the final one, in which Einstein relies on the Newtonian value for the kinetic energy. ...

Can one arrive at ℰ=m⁢c2 in a consistent and plausible manner using only Galilean mechanics and “perhaps Maxwellian” electrodynamics?

Okay, but Maxwellian electrodynamics is a fully relativistic theory, if interpreted correctly. The whole theory of special relativity is mostly a recognition of that fact.

Monday, June 24, 2024

Another Misreading of Bell's Theorem

There is a steady stream of crackpot papers that misrepresent Bell's Theorem. The Wikipedia description is adequate:
Bell's theorem is a term encompassing a number of closely related results in physics, all of which determine that quantum mechanics is incompatible with local hidden-variable theories, given some basic assumptions about the nature of measurement.
It does not say anything about reality, or quantum mechanics, except that we cannot replace QM with a local hidden variable theory.

Here is a new paper that gets it wrong:

Allori, Valia (2024) “Hidden Variables and Bell’s Theorem: Local or Not?”. [Preprint] ...

Equation (2) might misleadingly suggest that Bell’s reasoning only applies to hidden variable theories. This is not the case, as discussed later: Bell has shown that all quantum theories, not just hidden variable ones, must be nonlocal. ...

To summarize the result of the previous section, Bell’s theorem shows that, assuming locality, the perfect (anti)correlations can only be explained by non-contextual hidden variables; however, non-contextual hidden variable theories have been empirically falsified by the violation of Bell’s inequality, when seen as a constrain that such theories need to obey to. Therefore, they only other option to explain the perfect (anti)correlations is to assume that there are nonlocal interactions. ...

Some have argued that Bell’s nonlocality result is unacceptable and have tried to get around it. One possibility which has recently received attention is to reject a hidden assumption called statistical independence. ...

Let’s grant that Bell’s theorem has proven that reality is nonlocal. One theory which respects this theorem is the pilot-wave theory, a hidden variable theory which is explicitly nonlocal. ...

It has been argued that retaining locality would be a desideratum for making quantum mechanics and relativity compatible. However, since locality has to come together with superdeterminism, it is not going to help with much at all.

No. Bell's reasoning does only apply to hidden variable theories. It only gives reasons to accept QM, and reject Bohm's theory and superdeterminism.

The main point of this paper is to argue that superdeterminism is no better than Bohm's theory. As opposed to people like Sabine Hossenfelder who argue for superdeterminism.

A lot of people, like Sean M. Carroll, were hoping that the 2022 Nobel Prize would endorse Bell nonlocality. But it pointedly did not.

The Wikipedia article occasionally has someone inserting text that Bell figured out how to get rid of the hidden variable hypothesis, and apply the theorem to all theories. But that is nonsense, of course.

New video: The 'spooky' side of quantum physics | Tim Maudlin on astonishment and fear in #quantumphysics.

Maudlin admits at 10:30 that you get a similarly spooky and incomplete theory if you tear a dollar bill in two, and send the halves to Alice and Bob. When Alice opens the envelope, she immediately knows what Bob got.

So the entanglement itself is not spooky or surprising. The only surprising part is that QM cannot be completed with local hidden variables. Maybe Maudlin explains that later. Reply

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