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

Monday, June 17, 2024

Epicycles are Real

A reader cites Carl Sagan's 1980 Cosmos a personal journey Ep. 3. Harmony of the Worlds (video, transcript).
This little machine shows Ptolemy’s model. The planets were imagined to go around the Earth, attached to perfect crystal spheres — but not attached directly to the spheres, but indirectly, through a kind of off-center wheel. The sphere turns, the little wheel rotates, and — as seen from the Earth — Mars does its loop-the-loop. This model permitted reasonably accurate predictions of planetary motion: where a planet would be on a given day. Certainly good enough predictions for the precision of measurement in Ptolemy’s time and much later. Supported by the church through the Dark Ages, Ptolemy’s model effectively prevented the advance of astronomy for 1,500 years.

Finally, in 1543, a quite different explanation of the apparent motion of the planets was published by a Polish cleric named Nicolaus Copernicus. Its most daring feature was the proposition that the sun, not the Earth, was the center of the universe. The Earth was demoted to just one of the planets. The retrograde (or loop-the-loop) motion happens as the Earth overtakes Mars in its orbit. You can see that, from the standpoint of the Earth, Mars is now going slightly backwards and now it is going in its original direction. This Copernican model worked at least as well as Ptolemy’s crystal spheres, but it annoyed an awful lot of people. The Catholic Church later put Copernicus’s work on its list of forbidden books.

So Ptolemy developed a reasonably accurate model, but it was somehow used by the Catholic Church to keep everyone in the Dark Ages?

No, this is mostly nonsense. The Church only objected to nine sentences in the Copernicus book, and not to publication of the model. Ptolemy did not require crystal spheres.

The Wikipedia article on epicycles is much more sensible:

Epicycles worked very well and were highly accurate, because, as Fourier analysis later showed, any smooth curve can be approximated to arbitrary accuracy with a sufficient number of epicycles. However, they fell out of favor with the discovery that planetary motions were largely elliptical from a heliocentric frame of reference, which led to the discovery that gravity obeying a simple inverse square law could better explain all planetary motions.
The first Ptolemy epicycle for each planet is the orbit of the Earth, and is used to explain the retrograde modtion. People can argue that this epicycle is not real, because Mars never really goes backwards. But Mars does go backwards, as viewed from the Earth, and that is what Ptolemy was modeling.

Subsequent epicycles were used to model variations in speed and direction from uniform circular motion. The Copernicus model did not need the first epicycle, as the Earth had its own orbit, but needed the subseqent epicycles, as deviations from uniform circular motion was observable at the time.

As Sagan later explained, Tycho Brahe made the observations that enabled models superior to Ptolemy's. Astronomy was not held back by epicycles, but by a lack of more precise data. That data came from Tycho, and later the invention of the telescope

Sagan pushes his anti-religion beliefs, but all these advances took places in Christendom, and not elsewhere.

Tuesday, June 11, 2024

Situational Awareness

The AI world is buzzing with the predictions of Leopold Aschenbrenner. It has some overlap with the AI doomsayers who say AGI superintelligence will take over the world, except that he has inside knowledge from OpenAI, and he has specific arguments how it is all going to happen in the next five years.

Scott Aaronson raves about the analysis.

Interestingly, Aschenbrenner sees his fellow AI researchers as being among the first to be put out of work by the new superintelligence. There is a global arms race to create the best AI, and by 2030, the winner will be doing its own research to improve itself. No humans needed, except to keep mounting Nvidia computers into server farms.

Update: Sabine Hossenfelder posts her critique. She agrees with some of it, but gets off the bus with the wild predictions of scientific progress.

Monday, June 10, 2024

Carroll tries to defend Many-Worlds again

Physicis Sean M. Carroll tries to answer this question:
Joel remok says if we can't access any of the many worlds, what 2:31:07 is the purpose of studying it, when there are still many discoveries to be investigated in the reality we exist in?
Good question. There is no point in talking about parallel worlds that we can never see or know anthing about.

The transcript of his answer:

2:31:13 look I've said before I don't care about the other worlds I care about the laws of physics the question is we have 2:31:20 problems with quantum mechanics as it is taught it is not a sensible rigorous coherent Theory. we make things up like 2:31:28 observations and wave function collapse that aren't rigorously defined. many worlds is a well-defined theory that 2:31:37 replaces the ill defined Copenhagen interpretation and lets us actually do science with it. the point of many worlds 2:31:44 is not the other worlds. it's that we've answered the question of what is a measurement, why do you get probability, 2:31:50 and things like that, and equally importantly there's the fact that we don't know the fundamental laws of 2:31:56 physics. we're not done with physics yet we're trying to build better laws of physics and I strongly think that taking 2:32:02 quantum mechanics seriously and thinking about what is the correct foundational version of quantum mechanics will be 2:32:09 useful to that program. so again it's not about the worlds. people who really 2:32:15 obsess about the other worlds are the ones who haven't really internalized many world worlds many worlds is just 2:32:22 it's always obeying the Sher equation that's the essence of the theory
No, this is nonsense on every level.

Many-worlds does not answer the question of what is a measurement. It says that a measurement splits the worlds, but there is no explanation of how the worlds split, how many worlds there are, how you knowt he worlds have split, or anything. It is no better than how bohr explained it.

Many-words says nothing about how we get probabilities. The many-worlds folks do not even believe in probabilities.

Saying that Copenhagen is ill-defined to do science is backwards. Copenhagen has had successes worth trillions of dollars. No one has ever done any science with many-worlds.

I don't know how Carroll says this junk with a straight face. It is like saying Astrology is the only true science.

Here is the distinction. Copenhagen says you can predict an experiment, with probabilities for different outcomes. Once you observet the outcome, you discard the other possibilites as events that did not happen.

Many-worlds is just like that, except that there are no probabilities for the outcomes, because they all happen, and no world is any more likely than any other. Once you see an outcome, the parallel worlds with the other outcomes go out of reach. A prediction might seem true or false, but that is only because you are trapped on one of the worlds. It is not possible to do any science, because no prediction can ever be falsified.

Copenhagen makes sense and is scientific. Many-worlds is an unscientific fantasy.

Saturday, June 8, 2024

AI Models will maintain String Research

Peter Woit reports that the top string theorists are retiring, and they are worried that the younger generation will not carry on as before.

Not to worry! One suggests that AI large language models like ChatGPT will come to the rescue, because they can

train an LLM with the very best papers written by the founding members, so that it can continue to set the trend of the community.
Okay, maybe this was a joke, but it is likely to happen anyway. We may have reached peak knowledge. Already journals are being tricked into publishing AI-generated articles. The LLMs of the future will be trained on the LLMs of the past.

There is no experimental data that has any bearing on string research. Ed Witten cannot live forever. Advanced AI LLMs may be able to carry on string papers indefinitely.

Wednesday, June 5, 2024

SciAm gets Trump Derangement Syndrome

Scientific American used to be the worlds greatest popular science magazine, but now it is filled with politics and pseudoscience.

Now it has this article from an Australian Politics professor:

Donald Trump is now leading in many polls and could retake the U.S. presidency, despite numerous scandals, indictments and erratic behavior. Explanations for his popularity focus on factors like white identity, right-wing authoritarianism, nationalism and populism.

U.S. politics has included people with these predilections for many decades, however, so the puzzle of Trump’s appeal remains. ...

We differentiated the most loyal Trump supporters from the rest of the American population, including those who merely voted for Trump and supported his policies, by measuring three aspects of Trump support: unquestioning credulity, exemplified by the belief that he was in fact the legitimate winner of the 2020 election; ...

Most strikingly, we find they are highly conscientious, a measure of self-reported characteristics including carefulness, dependability, orderliness and self-discipline. Conscientiousness is significantly associated with all the three cultlike aspects of Trump support.

Support for Pres. Trump is not so tricky to explain. Pres. Biden is one of the worst Presidents ever. He is responsible for foreign policy disasters in Afghanistan, Ukraine, and Gaza. His reckless spending has caused high inflation. He has allowed the USA to be invaded by millions of foreigners. He is too senile to do the job. His VP is even worse. He has pursued bogus prosecutions of his political enemics. He appoints incompetent leftist minorities. He supports the sexual mutilation of children.

Pres. Trump, on the other hand, presided over four years of peace and prosperity. He would have been re-elected, but for changed voting rules that allowed the collection of million of votes whose casting and counting could not be verified. Trump won a majority of the votes cast and counted on Election Day.

This professor even found that most Trump supporters had conscientiously examined the evidence, and found Trump to be the better man. But this article makes no mention of all the objective reasons for concluding that Trump was a better President than Biden. He blames authoritarianism, while Biden is much more authoritarian then Biden.

As an example, those who resisted covid vaccine mandates nearly all support Trump over Biden. This shows that Biden is the authoritarian, and his supporters like his authoritarianism. Also, only an auhoritarian would prosecute his political enemies.

The Scientific American of a few years ago would never have published such a trashy partisan and illogical article.

Thursday, May 30, 2024

History on Many Worlds Theory

This new paper gives some history and arguments in favor of many-worlds:
Revolutionizing Quantum Mechanics: The Birth and Evolution of the Many-Worlds Interpretation

Arnub Ghosh

The Many-worlds Interpretation (MWI) of quantum mechanics has captivated physicists and philosophers alike since its inception in the mid-20th century. This paper explores the historical roots, evolution, and implications of the MWI within the context of quantum theory. ...

In reflecting on the significance of studying the historical development of quantum interpretations, it becomes evident that the MWI represents more than just a theoretical framework—it embodies a paradigm shift in our understanding of the quantum world and its implications for the nature of reality. ... Moving forward, further research and exploration in this area hold immense potential for advancing our knowledge of quantum mechanics and its applications.

Okay, you know it is garbage when it pushes revolutions and paradigm shifts, but cannot find any actual utility to the theory.

A big problem is probability:

Moreover, the MWI has led to new insights into the nature of probability in quantum mechanics. In the MWI, probabilities arise from the relative frequencies of different outcomes across multiple branches of the multiverse, rather than from inherent randomness or observer-dependent collapses of the wavefunction. This perspective offers a coherent and objective interpretation of probability in quantum mechanics, resolving longstanding debates about the nature of quantum uncertainty. ...

Furthermore, the MWI has implications for our understanding of probability and randomness. In the MWI, probabilities arise from the relative frequencies of different outcomes across multiple branches of the multiverse, rather than from inherent randomness or observer-dependent collapses of the wavefunction. This perspective offers a coherent and objective interpretation of probability in quantum mechanics, resolving longstanding debates about the nature of quantum uncertainty. However, it also challenges traditional views of probability as a measure of uncertainty or ignorance, suggesting that probabilities are ontologically real and arise from the fundamental structure of the multiverse.

(This is repetitive.) Yes, you might think that MWI gets probabilities from comparing outcomes across branches, but no one has ever gotten this to work. It is a myth. You cannot count the branches, or calculate probabilities of outcomes, or do anything objectively. It is all a big sham.

The people who pursue many-worlds do not even believe in probabilities. If pressed, they will admit that some things seem more probable than others, but they say it is all an illusion. Some subscribe to crazy arguments that Born's rule seems more natural than other rules, but they have no good explanation for why probability works at all.

If the weather man says there is an 80% chance of rain tomorrow, then he means that his data has resulted in rain 80% of the time in the past. Once it rains, you can discard the possibility of a sunny day.

But the MWI fans reject this. They refuse to say that it will rain in 80% of the branches. And if it does rain, they refuse to reject the sunny day, because they argue that it is sunny in another part of the wave function.

Go ahead and read the article, and tell me if you find one reason to accept that MWI nonsense.

Monday, May 27, 2024

Free Will in the Block Universe

Some say that there is no free will because of the way relativity uses time as the fourth dimension.

The philsophical questions about free will go back to the ancient Greeks. Modern science has not settled those questions. The questions are certainly not settled by just declaring that time is a coordinate.

SciAm reports:

As troubling as quantum mechanics (or at least certain versions of it) may be for the idea of free will, relativity—the other pillar of modern physics—isn’t off the hook. Many theorists think of relativity as describing a universe in which past, present and future are all equally real: a static cosmos that just sits there like a big block of spacetime (sometimes called the “block universe”). It’s not that time disappears in this picture—but it no longer “passes” or “flows.” (As Albert Einstein famously put it, the passage of time is a “stubbornly persistent illusion.”) Conceptually speaking, the strongly deterministic quantum universe and the block universe of relativity may not be so far apart. The quantum version can be thought of as “a kind of enriched block universe,” says Alastair Wilson, a philosopher of science at the University of Leeds in England. “Imagine taking a block universe and adding an extra dimension to it—the dimension of possibility.” ...

Even without relativity, you could use a time coordinate to make a block universe. You can use any coordinates you want. Choosing some coordinates cannot possibly say anything about free will.

Many-worlds theory takes this to the next step, if you put all those many worlds in a big block multiverse.

While physicists continue to debate the idea of strong determinism, Emily Adlam, a philosopher of physics at Chapman University, agrees with Chen that it appears to present more of a threat to free will than traditional determinism, particularly because of its ties to the Everettian multiverse. “In a standard deterministic picture, sure, everything that happens was determined from the past—but your mind was a key part of the causal process by which future events get realized,” Adlam says. “So in some meaningful sense, future events—even though they were predetermined—were mediated through processes that you identify with yourself.” But in the Everettian picture, she says, it’s harder to see where decision-making would fit in. “If you always make every possible decision, that does seem to severely undermine the sense in which you are exercising any meaningful kind of choice,” she says. “So in that sense, you do seem worse off than in the standard picture, where one outcome occurs and you play a role in bringing it about.”
It goes on to say that this is controversial, as there are compatibilists who can rationalize belief in free will no matter what soft of determinism there is.

There is no mention of anyone who believes in true free will, now called libertarian free will.

The whole point of the article is to say that many-worlds theory presents a new argument against free will. Since all choices happen in parallel worlds simultaneously, then all choice possibilities are real, and humans cannot make any free will choices. That are all illusions.

This is absurd.

I wonder what Plato and Aristotle would say if we could go back in time, and tell them about our progress. We could tell them about rockets, cars, lasers, electronics, and drugs, and they would be impressed.

And then we would tell them that our best and finest theory of matter, quantum mechanics, has been interpreted to say that there is no free will, because we can imagine parallel universes where alternative decisions are made. They would rightfully conclude that we have made no progress in philosophy at all, and even regressed to some very silly ideas.

Thursday, May 23, 2024

There is Nothing Non-entangled in QM

Supposedly entanglement is the most important thing in quantum mechanics (QM). It is said to be the key feature that distinguishes QM from classical mechanics.

But what is it?

New paper:

Everything is Entangled in Quantum Mechanics: Are the Orthodox Measures Physically Meaningful?

Christian de Ronde, Raimundo Fernandez Moujan, Cesar Massri

Even though quantum entanglement is today's most essential concept within the new technological era of quantum information processing, we do not only lack a consistent definition of this kernel notion, we are also far from understanding its physical meaning [35]. These failures have lead to many problems when attempting to provide a consistent measure or quantification of entanglement. I

According to a lot of modern scholars, entanglement is a resource that can be exploited to give secure communication and super-Turing computability.

The paper discuss various definitions in the literature and concludes:

We have shown how entanglement, as the unitary multiscreen effect of a single power, is an irreducible aspect of the operational content of the theory of quanta. The theory talks about powers of action each one them producing a multiscreen (non-local) effect that can be observed in the lab. Consequently, there is nothing non-entangled in QM. There is no meaningful distinction between something that is entangled and something that is not entangled within the theory of quanta. The attempt of quantifying or measuring the level of entanglement becomes meaningless.
I think that entanglement is not something real. It is an artifact of how QM works, but there is no way to objectively say whether a particle is entangled or not. So we should not talk about entanglement as if it is some mysterious resource.

Maybe I will be proved wrong by some quantum computer that uses entanglement to break RSA or some other calculation that cannot be done otherwise. Then I will have to admit that entanglement is real and useful. But nothing like that has ever been done.

Sean M. Carroll tries to explain entanglement in a recent podcast:

I 0:20 think you know entanglement arises 0:22 directly from that statement we made 0:23 long ago that when you have a Quantum 0:25 system you do not have separate wave 0:27 functions for each part of it you only 0:29 have one wave function for the whole 0:30 thing and the job of the wave function 0:33 is to make predictions for observational 0:35 outcomes so if that's all true then it 0:38 could be the case that if you predict 0:41 the outcome for one thing and another 0:43 thing particle a and particle B there 0:46 might be correlations or connections 0:48 between those measurement outcomes so I 0:50 don't know what I'm going to see when I 0:52 ask what is the spin of particle a and I 0:54 don't know what I'm going to see when I 0:56 ask what is the spin of particle B but I 0:58 know they're going to be opposite so 1:00 then that's entanglement and it tells me 1:02 were I to measure particle a I have no 1:04 idea what I'm going to observe but as 1:06 soon as I do I know what the outcome is 1:08 for particle B and this bugs people 1:11 because how does particle B know what 1:13 its outcome is supposed to be it could 1:15 be light years away
If this is the definition of entanglement, then there is nothing quantum mechanical about it. Classical physics shows the same phenomenon.

If split a classical system with angular momentum zero, separate the halves, and measure the angular momentum of one half, then the other half will have the opposite angular momentum. Just like how Carroll described QM.

When asked for more explanation, he says that he prefers the Everett many-worlds interpretation. However he admits that no one knows whether the effect of a measurement propagates at the speed of light or less in the universal wave function, or propagates instantaneously.

What? I thought that the whole point of Everett was to clarify what happens quantum mechanically when a measurement takes place. But if he cannot tell how the result propagates, then I do not see how it can tell me anything.

See also this podcast, where he starts by saying the Everestt theory is the most straightforwad interpretation of the Schroedinger equation, but it requires splittings into parallel worlds and we do not know what a world is. We also do not know if the wave function is real. Later, at 45:30 he says, "I mean the real answer there is I don't think about all those other worlds, that much again the worlds are a prediction of the theory they're not what the theory is fundamentally about."

Carroll goes on to explain the Bell tests:

also in the 1960s John Bell proved his 6:17 theorems he proved theorems about the 6:20 different predictions between a local 6:22 Theory and a non-local theory like 6:24 quantum mechanics and that made it an 6:27 experimentally accessible question so 6:29 people did the experiment and they just 6:31 won the Nobel Prize a couple years ago 6:33 so physicists are very interested now 6:35 because there's an experiment you can do 6:37 of course the experimental result was 6:38 exactly what schrodinger would have 6:40 predicted back in the 1920s it didn't 6:42 change our idea of quantum mechanics but 6:44 as long as you can do an experiment 6:45 they're happy having said that because 6:48 physicists have ignored the foundations 6:49 of quantum mechanics for so long even 6:52 the Nobel Prize press release botched it 6:55 they gave the wrong explanation for what 6:57 was going on because they didn't really 6:59 understand what they just give the Nobel 7:00 Prize
Again, this is startlingly foolish. He correctly says that the prize-winning experiments just confirmed what quantum mechanics would have predicted in the 1920s, and did not change our idea of quantum mechanics.

So how did the Nobel press release botch it? It certainly did not say that the experiment changed our view of QM. That would have been big news. See my earlier post for more details.

Carroll's real gripe is that he wants to fund more research in the foundations of QM, and the Nobel committee refused to acknowledge that the experiments left unsettled issued. In particular, he wants to push many-worlds theory, but it gets no Nobel endorsement. The Nobel committee correctly said that the experiments confirmed what everyone thought for many decades.

Monday, May 20, 2024

Einstein's Futile Search for Unified Field Theory

Sabine Hossenfelder posted her latest video:
Einstein’s Other Theory of Everything

Einstein completed his theory of general relativity in 1915 when he was 37 years old. What did he do for the remaining 40 years of his life? He continued developing his masterwork of course! Feeling that his theory was incomplete, Einstein pursued a unified field theory. Though he ultimately failed, the ideas he came up with were quite interesting. I have read a lot of old Einstein papers in the past weeks and here is my summary of what I believe he tried to do.

She insists on pronouncing his name INE-shtine. Maybe Germans pronounce it that way, but not Americans.

She summarizes Einstein's foolish and misguided unified field theories. If he did not already have a fancy reputation, this would be considered crackpot work.

She also mentions the more successful Kaluza–Klein theory:

In physics, Kaluza–Klein theory (KK theory) is a classical unified field theory of gravitation and electromagnetism built around the idea of a fifth dimension beyond the common 4D of space and time and considered an important precursor to string theory. In their setup, the vacuum has the usual 3 dimensions of space and one dimension of time but with another microscopic extra spatial dimension in the shape of a tiny circle. Gunnar Nordström had an earlier, similar idea.
This is also described as a failure. She says you need supersymmetry to make it work, but that has been rejected.

That theory is a minor variant of a 1918 H. Weyl proposal to unify gravity (general relativity) and electromagnetism. That was promptly attacked by Einstein, and mostly forgotten.

There the story ends. But not really. Einstein's ideas were, in fact, worthless, and led several generations of physicists astray. I wrote a whole book about it.

But Weyl's idea was essentially correct. In the modern Standard Model, that everyone accepts, there is an extra tiny circle at every spacetime point (event) to account for electromagnetism. In modern lingo, it is a circle bundle over a spacetime manifold. Gravity is a connection on the tangent bundle, and electromagnetism is a connection on the circle bundle. In both cases, the field is the curvature. It is the simplest and most natural relativistic theory.

Physicists studied Weyl and Kaluza-Klein for decades, without ever figuring out that they were just adding extra terms that ruined the theory. I guess they wanted to unify the gravity with the electromagnetism by hypothesizing some interactions, but that was just foolishness.

If Weyl were really smart, he would have conjectured using other Lie groups form the strong and weak interactions, alongside the circle for electromagnetism. Then we could have had the Standard Model, before quantization, about 50 years before we did.

One of the Lessons of the Standard Model is that all four forces (gravity, electromagnetism, weak, and strong) all have the same math structure (field strength is curvature of a bundle connection), but the force are essentially orthogonal. They do not have much to do with each other. There is some twisting between the weak and electromagnetism, but that's all. Many people thought that they would be unified like electricity and magnetism, where you cannot study one without the other.