Another Youtuber attacks Hossenfelder

I mentioned Professor Dave attacking Sabine Hossenfelder, and now here is another:

The Fallacy of Sabine Hossenfelder
Quantverse

Dr. Sabine Hossenfelder is a popular science communicator, with often controversial views. In this video, I have attempted to take a critical look at the rise of Sabine, her involvement in string theory wars, recent controversy, and expert opinions.

she posts a lot of videos. so I am sure she gets some things wrong.

This attacks her on three points.

1. She says black hole information loss will never be measured.

2. She did a video on an unpublished argument about black hole singularities.

3. She believes in superdeterminism.

I agree with her on (1), and on (2) she seemed to be accurately reporting a paper that might be wrong.

For (3), the video relies on Tim Maudlin:

superdeterminism 18:19 explains Quantum Randomness by denying 18:21 statistical Independence

[Hossenfelder] about the 18:23 possible values of the Hidden variables 18:26 think about the hidden variables as 18:28 labels for the possible paths that the 18:30 particle could take say the labels 1 2 3 18:33 go to the left slit and the labels 456 18:36 go to the right slit and the label 7 to 18:38 12 go through both the particle really 18:41 has one of those hidden variables but we 18:43 don't know which then if we measure the 18:47 particles at the left slit that simply 18:49 tells us that the hidden variable was in 18:51 the one 12 three batch if we measure it 18:54 right it was in the 456 batch if we 18:56 measure it on the screen it was than the 18:59 7th to 12th batch no mystery no 19:01 instantaneous collapse no 19:04 non-locality but it means that the 19:06 particles path depends on what 19:08 measurement will take place because the 19:11 particles must have known already when 19:13 they got on the way whether to pick one 19:15 of the two slits or go through both this 19:19 is just what observations tell us and 19:22 that's what super determinism is now you 19:25 may say well drawing lines on YouTube 19:28 isn't proper science and I would agree 19:30 if you'd rather see equations you're 19:32 most welcome to look at my

[Quantverse] instead of 19:35 reading her papers let's see what Tim 19:37 Maudlin, a world leading expert, has to say 19:39 about 19:40 it.

[Maudlin] there are people who for reasons I do 19:43 not fathom, I just literally don't 19:46 understand their reasons, are are so 19:49 deeply committed to 19:52 locality that they're looking for any 19:54 Escape Route. I mean that's more or less 19:56 what we were talking about with these 19:57 with these loopholes with these 19:59 detection loopholes right they don't 20:01 like the idea of non-locality and 20:03 they're looking for any Escape they can 20:05 have from from accepting it and these 20:08 detection loopholes for many years were 20:10 one until the experimentalist just 20:12 closed those loopholes they're gone uh 20:15 so the only other loophole is they look 20:16 at this and they say well I don't want 20:17 to deny locality I guess I have to deny 20:20 statistical 20:21 Independence and the problem with 20:23 denying statistical Independence is that 20:25 it's kind of crazy and it's it's crazy 20:28 in conspiratorial and on top of it you 20:30 know as as you know I've said and other 20:33 people have said it undermines all 20:36 scientific method I 20:38 mean if in order to get out of accepting 20:41 non-locality you 20:44 deny what's required assumptions that 20:47 are required to do 20:50 science that's not a good 20:52 deal right that's a really bad 20:56 deal

I agree with Maudlin that superdeterminism is kinda crazy, and undermines the whole scientific enterprise. But I would say the same about the nonlocal quantum interpretations that Maudlin subscribes to. If nature is nonlocal, then the premises underlying much of science are wrong.

The problem is not that Hossenfelder is committed to locality, but that Hossenfelder and Maudlin are committed to hidden variable theories.

Yes, Hossenfelder has kooky views about superdeterminism that the vast majority of physicists reject. In fairness, she realizes this, and hardly ever talks about those views.

I am all in favor of criticizing science popularizers when they are wrong, but he needs to look up the word "fallacy". There is no fallacy.

She also has a new video attacking Gisin:

This Physicist Says We’re Using Maths Entirely Wrong

Intuitionist mathematics is the idea that the entire discipline of maths is a mental construct based on human thought rather than a platonic realm of eternal truths. According to physicist Nicolas Gisin, one of this idea’s biggest proponents, that maths is based on human intuition is the reason why quantum mechanics seems so strange. Let’s take a look.

I think she misunderstands Gisin. She does not link to him. Here is a Quanta article, and one of his papers. His gripe is about mathematizing nature, and it applies to classical or quantum mechanics.

In this video, Gisin attacks her for saying that free will is meaningless and contrary to science, and for her believing in superdeterminism. He is at the other extreme, and believes that classical and quantum theories are indeterministic.

I partially agree with Gisin, in that I believe in free will, and that the future is indeterminate. Infinities are not realizable in nature, and neither are real numbers having infinitely many decimal places. We only observe approximations to reals.

Albert Einstein’s Political Journey

New video:

Discover the fascinating political journey of Albert Einstein, one of the greatest minds of the 20th century, as he moves from supporting liberalism and the German Democratic Party to advocating for socialism and a democratic world government. In this documentary, we explore Einstein’s critiques of capitalism, his evolving views on Bolshevism, and his admiration for Mahatma Gandhi’s non-violent philosophy. Learn how Einstein's political ideals shaped his legacy beyond physics, making him a global voice for social justice, human rights, and peace.

Albert Einstein's 10:25 political views was as Dynamic and 10:27 impactful as his son scientific 10:30 discoveries from his early support for 10:32 the German Democratic party to his later 10:35 advocacy for socialism and Global 10:38 government Einstein consistently sought 10:40 to align his political beliefs with his 10:42 deep concern for a Humanity's future his 10:45 critiques of capitalism his nuanced 10:48 views on bolshevism his admiration for 10:51 gandi and his call for World governance 10:54 all reflected a mind deeply committed to 10:56 the pursuit of justice and peace

They get a little carried away. Einstein was a pacifist, Communist, Zionist, and determinist.

He continued to belong to Communist front organizations well after the Stalin crimes against humanity were exposed. His political views were horrible.

I do not expect a physicist to have reasonable political views. Most of what he says is too foolish and stupid to be worthy of comment. I just object when people claim he had important opinions, or a deep concern for humanity. No, it is just horrible commie crap.

A lot of physicists today are leftists with Trump Derangement Syndrome. I think of physicists as intelligent, but do not expect any political wisdom.

Survey Paper on Quantum Supremacy

There have been a lot of claims of quantum supremacy experiments, and refutations. It is hard to keep them straight.

New paper:

In this review article we summarize all experiments claiming quantum computational advantage to date. Our review highlights challenges, loopholes, and refutations appearing in subsequent work to provide a complete picture of the current statuses of these experiments. I

It concludes:

Ultimately, any hypothesized computational advantage must be experimentally performed to be substantiated, and we have seen in this review that experiments can be challenged and refuted. It seems at this moment in history we are just on the boundary between quantum and classical computational advantage, and in the near future we expect the status of computational advantage to continue shifting between quantum and classical.

Well, that was unsatisfying. Who is winning, the quantum computers or the classical simulators? Apparently we are right on the edge.

Just wait. Spend a few billion dollars more on experiments. The question may have already been answered in a parallel universe.

It appears that we are also on he edge of artificial general intelligence (AGI). Maybe not yet, but AI has built systems that are better than humans at some tasks. It is not so clear that there are any quantum computers that are better at anything. Stay tuned.

Space Aliens from Another Dimension

Dr. Bee mocks this Congressional testimony:

[Hossenfelder] He also thinks that the aliens might 2:47 come to us from multidimensional space.

[Q] “You have mentioned that there's interdimensional 2:53 potential. Could you expound on that?

[A] “In terms of uh multi-dimensionality 2:59 that kind of thing, the framework that I'm familiar with for example is something called 3:04 the holographic principle. It derives itself from general relativity and quantum mechanics and that 3:11 is if you want to imagine uh 3D objects such as yourself casting a shadow onto a 2d surface 3:18 that's the holographic principle. So you can be projected, quasi-projected from higher dimensional 3:23 space to lower dimensional. It's a scientific trope that you can actually cross literally 3:28 as far as I understand, but there's probably guys with PhDs that… we can probably argue about that.” 3:32

[Q] “But you have not seen any documentation that that's what's occurring.”

[A] 3:36 “Only a theoretical framework discussion.”

Physicists like to make fun of laymen saying stuff like this, but it really isn't much different from what physicists say. For example, Wikipedia:

The holographic principle is a property of string theories and a supposed property of quantum gravity that states that the description of a volume of space can be thought of as encoded on a lower-dimensional boundary to the region – such as a light-like boundary like a gravitational horizon.

Nowhere does the article say that it is all science fiction or fantasy. The closest it gets to saying that is:

Bekenstein asks "Could we, as William Blake memorably penned, 'see a world in a grain of sand', or is that idea no more than 'poetic license'?",[8] referring to the holographic principle.

Dr. Quantum Supremacy writes:

I listened to Google’s technical talks but didn’t watch their movie. From what you say, it sounds better for my mental health if I continue not watching it.

That is because Google says its quantum computer work by spreading all the possibilities over the multiverse, and then trying them all in parallel. It bugs him when the press describes quantum computers this way, as he says it is a distortion of the theoretical subtleties. Okay, but I cannot blame the popular press, when the leaders of the field use the same distortions.

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.

Google Announces Quantum Supremacy Again

Google announces what appears to be quantum supremacy:

Today I’m delighted to announce Willow, our latest quantum chip. Willow has state-of-the-art performance across a number of metrics, enabling two major achievements.

The first is that Willow can reduce errors exponentially as we scale up using more qubits. This cracks a key challenge in quantum error correction that the field has pursued for almost 30 years.

Second, Willow performed a standard benchmark computation in under five minutes that would take one of today’s fastest supercomputers 10 septillion (that is, 1025) years — a number that vastly exceeds the age of the Universe.

We have been down this road before. These results are published in the Nature journal, showing that they are accepted as correct.

This mind-boggling number exceeds known timescales in physics and vastly exceeds the age of the universe. It lends credence to the notion that quantum computation occurs in many parallel universes, in line with the idea that we live in a multiverse, a prediction first made by David Deutsch. ...

Of course, as happened after we announced the first beyond-classical computation in 2019, we expect classical computers to keep improving on this benchmark, but the rapidly growing gap shows that quantum processors are peeling away at a double exponential rate and will continue to vastly outperform classical computers as we scale up.

I reported on these claims of double exponential growth back in 2019.

Have I been proved wrong? Possibly. They are still not computing anything useful, but just using the quantum computer to generate random numbers in a way that is hard to simulate in other ways. I will be interested to see what other skeptics say.

I do not think that this is any evidence for the multiverse. I will also be interested to see if the other many-worlds advocates claim this work.

Update: Gil Kalai reiterates his criticism of Google's big 2019 claim of quantum supremacy, and concludes:

I usually don’t mind “hype” as a reflection of scientists’ enthusiasm for their work and the public’s excitement about scientific endeavors. However, in the case of Google, some caution is warranted, as the premature claims in 2019 may have had significant consequences. For example, following the 2019 “supremacy” announcement, the value of Bitcoin dropped (around October 24, 2019, after a period of stability) from roughly $9,500 to roughly $8,500 in just a few days, representing a loss for investors of more than ten billion dollars. (The value today is around $100,000.) Additionally, Google’s assertions may have imposed unrealistic challenges on other quantum computing efforts and encouraged a culture of undesirable scientific methodologies.

The paper is paywalled and still being editing. All you can download is the abstract and list of about 100 Google authors.

Update: Google promotional video.

Update: Scott Aaronson comments. In short, he thinks Google made a big advance, but there is still a long way to go to get anything useful, or even a true logical qubit.

If someone thinks we’re about to get personal QCs that will speed up everything we do, they need to be told that “the age of QC” is not upon us (and indeed, might never be).

If, on the other hand, someone thinks QC is all a scam or a misconception, and quantum error-correction can never work in the real world, they need to be told that “the age of QC” is now upon us. ...

Gil Kalai #23: So we’re perfectly clear, from my perspective your position has become like that of Saddam Hussein’s information minister, who repeatedly went on TV to explain how Iraq was winning the war even as American tanks rolled into Baghdad. I.e., you are writing to us from an increasingly remote parallel universe.

Okay, tough talk, but Aaronson concedes that all Google did was to generate unverifiable random numbers. They are unverifiable because it would take a classical supercomputer longer than the lifetime of the universe to regenerate them, and there is no other way to verify them. It is not like factoring a large number, where the factorization is easy to verify.

As an analogy that someone gave, you can drop a glass vase onto the floor, shattering it into pieces, and it is nearly impossible for a simulator to reproduce what you have done. But you have not done anything useful, either.

Update: New Scientist video: Does Google’s new quantum computer prove the multiverse exists?

I think 7:57 you know the the consensus from outside 7:59 of Google is that what Harman Nan is 8:02 saying here [about the multiverse] is basically complete 8:04 nonsense okay um so I should say if 8:07 you've not heard of David Deutsch he's 8:09 he's famous for laying the theoretical 8:12 mathematical foundations for uh the 8:14 quantum theory of computation and since 8:17 the that press release mentioned him by 8:19 name I I reached out to him to ask him 8:21 what he made of that and uh you know 8:22 I've had some interaction with him in 8:24 the past and he's always been good value 8:26 once he told me that the evidence that 8:28 we live in a Multiverse is at least as 8:31 strong as the evidence that there were 8:33 dinosaurs once on Earth no I will not 8:36 allow that know that is that is also not 8:39 true yeah but I know but what a what a 8:41 fantastic quote um so you know I thought 8:44 I'd get a good response um from him but 8:46 when I asked him what he made of his 8:48 name coming up in the willow press 8:50 release he said he was the wrong person 8:52 to 8:53 ask.

Glad to see some science journalists express skepticism about the multiverse.

I have argued before that my skepticism for quantum computing is based, in part on the proponents relying on quantum interpretations that are not widely accepted. The Google announcement is an example.

Update: Dr. Bee discusses the QC multiverse claim.

Brains have Difficulty with Zero

SciAm reports:

Zero can be conceptualized at several levels, including as an “absence,” a special category of emptiness, a quantity or as a number used in calculations. Although many animals have a number sense, Nieder, who has studied crows and monkeys, suspects that only humans use zero mathematically.

Furthermore, numeric zero, as used in mathematics, is something that humans need to learn about from others—it’s not an innate concept. Children generally cannot understand it until about age six. That’s roughly two years later than other numbers.

The notion that zero is somehow distinct comes from studies of brain injury as well. About 14 percent of people who have had a stroke may be unable to read or process numbers that include a zero digit, points out Barnett.

Age 6? In my experience, most adults have trouble grasping the zero. Also negative numbers.

The trouble with tracing the origin of zero is that not everyone agrees about what qualifies as understanding zero. There is zero in the sense of lacking whatever is being counted. There is zero as a placeholder in a positional notation, such as the number 105. And there is zero as the number between the positives and negatives.

I think credit for zero should require having a symbol for it, and having text that describes zero just like any other number.

I believe Ptolemy had tables of angles, where a zero angle was in the table just like positive angles. I don't think he had any negative angles, though.

Ancient people did measurements in directions of North, East, South, West. It seems as if they must have understood that if they go 10 miles east and then 20 miles west, they will be 10 miles west, and that is the same as -10 miles east. And if they go back to where they started, then the net displacement is zero. Maps could thus describe locations with positive and negative coordinates. As far as I know, there is no ancient text or map that does this.

All this must have been obvious to Kepler and Newton. But did they really treat zero just like other numbers? I don't know.

Here is a blog post from the world's smartest mathematician, defining the natural numbers as { 1, 2, 3, ... }. Why no zero? Including zero makes much more logical sense. Obviously Terry Tao understand zero as well as anyone, and yet he has a reluctance to call it a natural number.

The Universe is Finite, not Infinite

Dr. Bee addresses the question: Is the Universe Infinite or Finite?

She correctly explains that we do not know. There have been attempts to prove that the universe is finite, but there is no way to prove that it is infinite.

Is the universe really infinite? Or could it close back on itself like a sphere? If it’s infinite, how can it expand? And is it true that there might be copies of you in it? Today I want to explain how much we know about those questions and what the expansion of space has to do with Hilbert's Hotel.

She explains:

3:02 You could ask now, well, if those are all things we measure on the inside, what sense 3:09 does it even make to call this curvature. Couldn’t we just say that spacetime is flat, 3:14 just that these observables have difficult relations that are mediated by some sort of field. 3:20 Indeed, this is a valid interpretation of the maths, that you refuse to give this a geometric 3:26 interpretation and instead just say gravity is determined by some sort of complicated field. 3:32 This is why Steven Weinberg in his book on general relativity famously refused to use a 3:38 geometric interpretation. You don’t need it. And if you don’t need the geometric interpretation, 3:43 why subscribe to it. ...

3:56 That said, most physicists use the geometric interpretation, I believe because it makes it 4:01 easier to visualize things. Either way, the relevant point is that General Relativity is 4:06 entirely about what happens inside of space-time. This also answers the often-asked question, 4:13 if the universe expands, then what does it expand into? The answer is that that’s a meaningless 4:19 question.

I think that it was Poincare, in his very popular 1902 book, Science and Hypothesis, where he made the point that we cannot truly tell whether space is curved. We could just adjust our Physics formulas to account for the curvature. He said flat space was just a convention.

Einstein also had an attitude similar to Weinberg's book. That the geometric interpretation is interesting, but not really essential to the Physics. I was surprised to learn this, as almost everyone credits Einstein with having the geometric interpretation. But he denied it.

Almost everyone else accepts the geometry as being essential to the Physics, and not just a conventional Math interpretation.

Infinities cannot be observed, so mathematical models of spacetime can be finite or infinite, as a matter of convenience. The infinity is physically meaningless.

Here is where she loses me:

9:22 If spacetime is really infinite, then that has the odd consequence that every 9:27 possible configuration of matter appears infinitely many times. That includes you, 9:33 unless you are an impossible configuration of matter, 9:36 in which case, please tell me more about your workout schedule in the comments.

9:41 So in an infinite universe there would be infinitely many copies of you and 9:45 also versions with very small alterations. Somewhat more hair. Somewhat less brain. A 9:52 physics degree or a desire for mathematical self-torture, but then I repeat myself.

9:57 It’s not a new insight. To my best knowledge it was first discussed by George Ellis and 10:02 Graham Brundrit in 1979. George Ellis by the way is one of the people who I 10:07 interviewed about the multiverse for my first book. That an infinitely extended 10:12 universe would have infinitely many copies of each of us is often considered the simplest, 10:18 and least controversial type of multiverse.

She is correct that many astrophysicists accept this multiverse as so self-evident to be not controversial, and yet it is a crazy idea. There are not infinitely copies of each us, and it is almost meaningless to talk about such foolishness. The observable universe is finite, and does not include copies of yourself. Even if the universe were infinite, there is no reason to believe that all possibilities would be replicated indefinitely. You would have to assume that all possible conditions are being recreated infinitely. Any such talk is like theology -- beliefs that are not grounded in science.

She talks about the possibility of the universe being finite and closed, like a torus. Most models have an open spacetime where space has an infinite extent, but there might be only a bounded portion of it with matter in it. The unoccupied space beyond our observation is just a mathematical convenience, with no reality.

Feynman Never Wrote a Book

So says physicist and youtuber Angela Collier, in the sham legacy of Richard Feynman.

She does not like him, and trashes him. She also explains that all his books are ghostwritten.

Several books are attributed to him, especially his two autobiographies.

The books have many amusing stories, and she argues that most of them are made up.

She has a funny personality, different from most physics, and she is entertaining. She makes some good arguments. Watch it, and lower your opinion of Feynman.

She does have a bunch of positive things to say about him. Her main point is that the legend is very misleading.