Is Light Composed of Photons?

A popular channel tries to answer What is a Photon?

The simple answer is that light is composed of photons. A photon is a ball of light. A wise guy commenter gives the more sophisticated answer:

The special relativistic wave equation that accurately describes electrons is the Dirac equation. The Dirac Lagrangian density for electrons has got a local U(1) symmetry because of local causality and local charge conservation (Noether's theorem). U(1) symmetry, because we only ever observe the absolute value squared of the wave function.

This can be modeled in gauge theory as an S^1 fiber bundle (or a U(1) Lie-algebra valued principal g-bundle) over a flat Minkowski spacetime base. Wave functions for the electron field are then sections in this fiber bundle.

To make precise the comparison of geometric data between different spacetime points (gauge covariant derivative), we introduce a connection on this fiber bundle; the electromagnetic vector potential, A_mu (just like the Christoffel symbols/Levi—Civita connection of the tangent bundle in general relativity). Basis vectors/phase can change from place to place either bc. we are using some strange coordinate system (like polar coordinates fx.) or bc. our manifold/bundle is curved (to be precise, the connection is curved). So this connection might have a holonomy/curvature (responsible for geometric Berry phase), just like how spacetime can be curved. In this case, the curvature is caused by the 4-current, just like how spacetime curvature is caused by the stress-energy-momentum tensor. We can take the exterior derivative of this Ehresmann connection 1-form (A_mu), which yields a curvature 2-form, called the electromagnetic/Faraday tensor (or the Riemann curvature tensor in the case of general relativity).

This new field, (A_mu) the vector potential has got its own dynamics. If we derive the equations of motion with the help of the Euler—Lagrange equation, we get back the Lorentz force and Maxwell's equations in the 'classical' case. We can also apply canonical quantization and make the 'A' field values into operators. At low energies, this A field behaves like a quantum harmonic oscillator at each point of spacetime; its energy levels are going to be quantized. The number of quanta in a given frequency mode is what we call the number of photons in that mode (pure numer state/Fock state).

Very good, but it is accurate to say light is composed of photons?

I think not. Light is an electromagnetic wave, and small measurements are quantized. A photon is a measured quanta of light.

You might say, this is like saying a falling tree in the forest does not make a noise if no one listens. Likewise light is not made of photons unless measured.

The difference is that our best theories of trees and sounds say that the tree makes a sound whether anyone listens or not. Our best theories of light do not discretize light until a measurement.

You could say: No, that's wrong, QED uses Feynman diagrams of unobserved particles, including photons.

That is a point, but thinking of light as particles leads to faulty conclusions. QED is really a field theory.

Sean M. Carroll does Woo Podcast

From a Jun 2024 podcast interview:

Ellen came out with a new book at the end of last year called The Mindful Body: Thinking Our Way to Chronic Health, which is about the physiological, the health benefits of mindfulness. And it’s very interesting, she has a lot of studies, right? This is very data-based, and some of the results of these studies are kind of amazing. ... You can think of it as kind of like the placebo effect. You take some pill that really isn’t anything at all and your mind coaxes your body into getting better.

The comments are mostly negative, and a statistician responds:

I don’t think the data are there. To be precise, some relevant data exist, but, from the published papers, I don’t see these data providing good evidence for many of the claims being made.

More generally, statements such as “This is very data-based” and “the data are there” are nothing but empty hype if you can’t point to the actual data and their relation to the (justly) controversial scientific claims. Otherwise, you’re just bullshitting. You could just as well interview someone about the Loch Ness Monster or whatever and say “This is very data-based” over and over and hope your listeners don’t go and check.

I would not be too hard on Carroll, as this is out of his expertise. I just post this as a public service, in case you think that you are getting hard science from the podcast. Carroll must know that the podcast is nonsense, as comments to him explain it.

I do criticize him for many-worlds, as that is in his expertise, and there is no data to support that either.

Einstein's Happiest Moment: The Equivalence Principle

From a new paper on Einstein's Happiest Moment: The Equivalence Principle:

Einstein’s happiest thought was his leap from the observation that a falling person feels no gravity to the realization that gravity might be equivalent to acceleration. It affects all bodies in the same way because it is a property of spacetime — its curvature — not a force propagating through spacetime (like electromagnetic or nuclear forces). When expressed in a way that is manifestly independent of the choice of coordinates, this idea became General Relativity. But the ground for what is now known as the “equivalence principle” was laid long before Einstein, affording a fascinating example of the growth of a scientific idea through the continuous interplay between theory and experiment. ...

The earliest hints of something like equivalence came from Aristotle. ...

The EP can be said to have originated with Newton, as did experiments to test it.

So why would Einstein's happiest thought be a simple regurgitation of a principle that had been accepted for centuries? Wouldn't he be happier about unifying space and time, explaining Michelson-Morley, or quantizing the photon? The story is bizarre.

I have a theory about this. Einstein was proudest about relativity, but as far as I could determine, there was only one part of the theory that was original to him. He figured out in 1907 and 1911 papers that gravitational potential affected clocks. He did it by using the equivalence principle to relate it to a non-gravity scenario, where special relativity could be used to relate the clocks. I do not think this occurred to anyone else.

All the rest of relativity he stole from others. The gravity effect on clocks was his happiest because he could genuinely claim the credit.

Apple says LLMs cannot Reason

Since the Nobel Swedes have apparently decided that Physics is dead, and all the action is in Artificial Intelligence, maybe I will switch to posting about that.

Apple is desperately trying to catch up to its competitors in AI, so it is badmouthing the successes:

A new paper from Apple's artificial intelligence scientists has found that engines based on large language models, such as those from Meta and OpenAI, still lack basic reasoning skills.

The group has proposed a new benchmark, GSM-Symbolic, to help others measure the reasoning capabilities of various large language models (LLMs). Their initial testing reveals that slight changes in the wording of queries can result in significantly different answers, undermining the reliability of the models.

The group investigated the "fragility" of mathematical reasoning by adding contextual information to their queries that a human could understand, but which should not affect the fundamental mathematics of the solution. This resulted in varying answers, which shouldn't happen.

The paper uses this typical example of an LLM failure:

Oliver picks 44 kiwis on Friday. Then he picks 58 kiwis on Saturday. On Sunday, he picks double the number of kiwis he did on Friday, but five of them were a bit smaller than average. How many kiwis does Oliver have?

The paper complains that the LLMs subtract the 5 kiwis, even though the statement about them being smaller should be irrelevant.

No, this is a misguided criticism. If the LLM were strictly logical, it would refuse to answer the question as too vague and imprecise. The problem does not say how many kiwis Oliver started with, or whether he got any from other sources, or if he ate any. Without that info, no answer can be given.

The LLMs work by embedding the problem into a convex meaning space. However sloppy the problem is, it gets precise coordinates in the embedding space.

Whoever formulated this problem seemed to be saying that the 5 kiwis should not be counted. Why else is it phrased that way? Okay, it is phrased that way to be a trick question.

What would you want an LLM to do? To assign meaning in the most direct way, or try to interpret the problem as a trick question?

Apple seems to want to benchmark LLMs on trick questions. No thanks.

For another view, see Apple DROPS AI BOMBSHELL: LLMS CANNOT Reason. This video argues that Apple proved that the LLMs are worse that what people thinks, and not likely to get fixed soon.

Update: Dr. Bee discusses the Apple paper.

Aaronson Posts his Manifesto

Dr. Quantum Supremacy Scott Aaronson has posts

In nearly twenty years of blogging, I’ve unfortunately felt more and more isolated and embattled. It now feels like anything I post earns severe blowback,

It appears that I am blocked from commenting there. The following was rejected, so I repost it here:

(7) Goldbach is not a good example because if it is independent of the axioms then there is no counterexample in N, and hence true in N. There are other arithmetical statements that are independent and we have no reason to say they are true or false. "how did we even get started talking about math?" By accepting what is provable. Mathematicians do not need to have an opinion, when there is no proof.

(15) "Everett interpretation ... to result from scientifically conservative choices." By this I assume you mean you can use the Schroedinger equation to predict probabilities, but then reject those probabilities and interpret them as world-splittings instead. No, this is not scientifically conservative. It makes the theory untestable, and introduces vast unobservable worlds.

Yes, I do think his math philosophy, and his many-worlds beliefs, are untenable. In particular, it is a nutty extreme view to say that many-worlds is scientifically conservative.

Sean M. Carroll says that same thing, and I have criticized him for it. He has explained his views in detail on his podcast, so I am sure he is wrong.

The essence of many-worlds is that it takes a scientific theory that predicts probabilities, denies that probabilities exists, and postulates that all possibilities happen in parallel worlds. It is so crazy that any scientist who advocates it should be disregarded on all scientific issues.

Aaronson tries to make his other positions sound moderate, but some are nutty. Item (1) exhibits Trump Derangement Syndrome. He thinks Trump is a threat to the Enlightenment!

He is entitled to his political views, of course, but nothing he says about Trump makes any sense. Some of his viwes seem more aligned with Trump than Harris, except for his Jewish brainwashing against Trump. I say Jewish because a lot of Jews show the same derangement, even though Trump's policies are likely to be much better for the Jews.

Harris and Walz are the most vacuous candidates I can remember. They have low IQ, have nothing to say about anything, and just babble nonsense when asked questions. Surely anyone smart enough to be a professor can see that they are morons. They just support them out of some sort of leftist tribal loyalty.

The Physics News is no New Physics

Physicists must be annoyed that the Nobel Physics prize was for computer science, with no application to Physics.

Here is a defense:

All this sounds nice for computer science, or for building language translators or self-driving cars, but is it Physics? I’d argue the answer is “yes.” These ideas of network properties, stability, and transitions didn’t spring up de novo, but emerged via classic problems in statistical mechanics, one of the fundamental, core areas of physics. Hopfield’s model was, in fact, a “spin glass” model, originally developed to describe magnetic materials and phase transitions.

They were inspired by biological models of the brain also, but today's neural nets are really designed to do what can be made efficient on consumer gaming chips, and do not have much to do with either physics or biology.

I wonder why these guys even take the calls from Sweden. They insisted on interviewing Hinton in a California hotel room at 2am, and keeping him up all morning. He would still get the money if he had slept in.

It is debatable whether these guys did much that was novel. Ignoring that point, look at all the work that Physicists brag out that did not win. There were surely nominations for cosmic inflation, ER=EPR, dark matter, string theory, quantum gravity, holographic principle, supersymmetry, quantum computing, many-worlds. The Swedes have a pretty good record of resisting fads like these.

Is Physics dead? The last big advanced was the discovery of the Higgs boson about 10 years ago, confirming a theory from 50 years before that. There isn't much new and interesting coming out of Physics anymore. Not Big Physics, anyway. I guess there is still lots of good work being done in material science.

Happy Columbus Day. The discovery of the New World to Europeans in 1492 was one of the most important events in all of human history. I cannot think of any other single event that changed the world so much.

Predicted Nobel for Quantum Computing

Dr. Bee predicts:

Which is why my best bet for this year’s 1:35 Physics Nobel is quantum computing. This is clearly on the bingo card, it’s just a 1:40 matter of time until we check this box. Likely candidates are David Deutsch and Peter Shor.

No, not likely. Not yet, anyway.

Nobel prizes for theoretical advances are only given after experimental confirmation. If someone makes a quantum computer that breaks RSA encryption, then that would be an achievement that the Nobel folks would like to recognize.

IK personally think that they should have given a prize for the Higgs mechanism when it proved so essential to the stunning successes of the Standard Model in the 1970s.

Nope. Nobel does not work that way. Higgs could be confirmed by finding a new particle, and no prize was to be given until that particle is found.

There has been no prize for dark matter, despite dozens of brilliant works describing it. Until someone finds a piece of dark matter in a lab.

3:51 And as my fifth and final guess I have a topic that I think should win 3:56 the Nobel Prize but probably won’t, which is modified Newtonian dynamics. That is because, 4:03 regardless of what you think about the maths, it’s been extremely successful in making predictions. 4:09 It has predicted that the Tully-Fisher relation is valid for all types of galaxies, 4:14 it has predicted the height of the second peak of the CMB, it has predicted that galaxies should 4:20 form as early as the James Webb Telescope has observed. Even if these regularities 4:26 will eventually be explained by something else, modified gravity still predicted them correctly.

Interesting opinion, but those people deny that dark matter is a thing, so I don't think they will win a prize as long as people are looking for dark matter particles.

My fourth bet is a topic that I hope will not win, which is cosmological inflation, 3:15 that’s the idea that the early briefly underwent a phase of 3:19 exponential expansion. Astrophysicists talk about inflation as if it’s settled science, 3:25 but the evidence is sketchier than your friend who always ‘forgets’ his wallet.

It is not settled science, because we do not know what the inflation is. Inflation is not getting a prize.

Alfred Wegener discovered continental drift in 1915, one of the great scientific breakthroughs of all time. He got no prizes or respect, because he could not nail down the mechanism in a way that could be accepted and confirmed by others. Like it or not, that's how it works.

So I say, no prizes for quantum computing, inflation, or dark matter.

Here is a new Bloomberg video: The Race to Harness Quantum Computing's Mind-Bending Power | The Future With Hannah Fry. It says our communications systems will be insecure in 5-7 years. And China may be passing us up. The usual hype.

Update: The Physics prize went to two neural net researchers. Following tradition, they were awoken at 2am this morning.

Dr. Bee reports:

0:00 The 2024 Nobel Prize in physics… did not go to physicists. It went to two computer 0:06 scientists for developing the first neural networks, which became the basis 0:11 of what we now call artificial intelligence. If you still doubt that physics is in crisis, 0:16 the fact that the Nobel Prize in physics goes to computer scientists should make you think. Really, 0:21 I’m just grumpy because all my predictions were wrong. I guess my crystal ball needs 0:26 a software update.

The prize work is decades old, and not the large language models like ChatGPT that have gotten so much excitement. I am tempted to infer that the Nobel committee thought that ChatGPT and other LLMs were the hottest advance in science, so it wanted a prize to recognize that, even if the winners never worked on LLMs.

Merits of the Quantum Positivist Instrumentalist Mindset

New video:

Sean Carroll delves into the baffling and beautiful world of quantum mechanics. ...

Under the Umbrella of classical physics of 10:03 course you know that in the beginning of the 20th century quantum mechanics came along and changed everything now there's 10:10 a puzzle with quantum mechanics quantum mechanics is so profound that even though we've known about it for a 10:16 hundred years professional physicists still don't agree on what quantum 10:21 mechanics actually says and that's very embarrassing. I don't know to me anyway. I 10:26 think that we should know what our best theory of nature actually says but the weird thing is even though we don't 10:33 exactly know what the theory says, we do know what it predicts so it's pushed 20 10:39 and 21st century physicists into this sort of positivist instrumentalist mindset, where they say don't ask me 10:46 what's really going on. I can just tell you what you're going to observe in your experiment and you know what I I hate 10:52 that attitude this is very much not much not my attitude but it is the attitude we're going to take for this talk. I 10:59 wrote a whole another book called something deeply hidden about the philosophical mysteries of quantum mechanics but today we're going to be 11:05 hard-nosed physicists and ask what the Theory actually predicts.

Follow that? Sean M. Carroll says that QM was created as a wonderful theory a century ago. It perfectly predicts experiments. It was created by physicists with a positivist instrumentalist mindset. That is, they focused on the science, and not on the philosophizing.

But Carroll and some other philosophers are unhappy about it, and like weird untestable interpretations. That is all such nonsense, that in teaching QM he has to use that Copenhagen mindset of a century ago.

This is bizarre. It is like a Physics professor saying:

I am going to teach the theory of relativity, as understood by Minkowski, Einstein, and others. It passes all the tests. I am going to teach it even though it does not explain the arrow of time, and I personally think it should. It does not, so the theory is unsatifactory. Since nobody properly explains the arrow of time, I will have to teach it that way.

No, that would be ridiculous. No scientist is going to apologize for a scientific theory not answering some vaguely related metaphysical question.