Friday, March 30, 2018

How Einstein learned about general covariance

Quanta mag reports:
Albert Einstein released his general theory of relativity at the end of 1915. He should have finished it two years earlier. When scholars look at his notebooks from the period, they see the completed equations, minus just a detail or two. “That really should have been the final theory,” said John Norton, an Einstein expert and a historian of science at the University of Pittsburgh.

But Einstein made a critical last-second error that set him on an odyssey of doubt and discovery — one that nearly cost him his greatest scientific achievement. The consequences of his decision continue to reverberate in math and physics today.

Here’s the error. General relativity was meant to supplant Newtonian gravity. This meant it had to explain all the same physical phenomena Newton’s equations could, plus other phenomena that Newton’s equations couldn’t. Yet in mid-1913, Einstein convinced himself, incorrectly, that his new theory couldn’t account for scenarios where the force of gravity was weak — scenarios that Newtonian gravity handled well. “In retrospect, this is just a bizarre mistake,” said Norton.

To correct this perceived flaw, Einstein thought he had to abandon what had been one of the central features of his emerging theory. ...

Einstein initially wanted his equations to be coordinate-independent (a property he called “general covariance”), meaning they’d produce correct, consistent descriptions of the universe regardless of which coordinate system you happened to be using. But Einstein convinced himself that in order to fix the error he thought he’d made, he had to abandon general covariance.

Not only did he fail at this, he doubled down on his error: He tried to show that coordinate independence was not a property that his theory could have, even in principle, because it would violate the laws of cause and effect. As one study of Einstein put it, “Nothing is easier for a first-rate mind than to form plausible arguments that what it cannot do cannot be done.”

Einstein pulled out of this dive just in time. By late 1915 he knew that the influential German mathematician David Hilbert was close to finalizing a theory of general relativity himself. In a few feverish weeks in November 1915, Einstein reverted to the equations of general relativity he’d had in hand for more than two years and applied the finishing touches.
Norton is an Einstein idolizer who makes this all about Einstein.

The problem was that Einstein did not understand general covariance. He only ever settled on it because of persuasion from Levi-Civita, Grossmann, and Hilbert. It was Grossmann who had the correct equations in 1913, that the Ricci tensor is zero. Einstein did not even know about the Ricci tensor.

The problem stems from Einstein not properly understanding special relativity in the first place. The core of the theory, and Poincare explained in 1905 and Minkowski in 1907, was that Maxwell's equations were covariant under Lorentz transformations. Einstein's 1905 paper only had the weaker principle of corresponding states that Lorentz published in 1895. Even as Einstein wrote later review papers on relativity, he never showed that he understood that Poincare and Minkowski proved covariance, or even the definition or importance of covariance.

The article makes it sound as if Einstein was competing with Hilbert, but actually they were collaborating.

The "completed equations", as applied to the solar system, were just Ricci = 0. Ricci is the covariant curvature tensor of the appropriate rank. I would credit the guys who figured out covariance and the Ricci tensor. With the discovery of dark energy, this equation is modified to say that Ricci is a small multiple of the metric tensor.

For details, see a scholarly account of the history of general relativity. One can debate which are the crucial ideas, but general covariance was not Einstein’s.

Thursday, March 29, 2018

Difficult birth of Many Worlds

SciAm reports:
The Difficult Birth of the "Many Worlds" Interpretation of Quantum Mechanics
Hugh Everett, creator of this radical idea during a drunken debate more than 60 years ago, died before he could see his theory gain widespread popularity ...

To solve the problem of superposition, Everett proposed something truly radical, seemingly more appropriate for the pulp sci-fi novels he read in his spare time: he said that quantum physics actually implied an infinite number of near-identical parallel universes, continually splitting off from each other whenever a quantum experiment was performed. This bizarre idea that Everett found lurking in the mathematics of quantum physics came to be known as the “many-worlds” interpretation.

The many-worlds interpretation hit a roadblock almost immediately in the person of Everett’s PhD advisor at Princeton, the eminent physicist John Wheeler. Wheeler was a physicist’s physicist; ...
Wheeler also was very open to wacky ideas. Eg, he promoted "it from bit", that information is somehow more fundamental than fields or matter.

There is a good reason why Everett could not convince Wheeler or Bohr or anyone else. He idea is unscientific nonsense.
The work of DeWitt, Deutsch, and others led the many-worlds interpretation to become much more popular over the ensuing decades. But Everett didn’t live to see the many-worlds interpretation achieve its current status as the most prominent rival to the Copenhagen interpretation. He died of a massive heart attack in 1982, at the age of 51.
If Everett were correct, then he would be still alive in some of those parallel universes. Not even this SciAm story can go as far as to endorse such nuttiness.

The article gives the impression that Everett's idea was so radical that the world was slow to see the genius in it.

On the contrary, theoretical physics ran out of good ideas in about 1980. Professors got desperate for ideas, so they started recycling stupid ideas from the past.

When I attack MWI, I am not just attacking a straw man. As you can see, it is the most prominent rival to Copenhagen.

Wednesday, March 28, 2018

Von Neumann believed in Church's Thesis

John von Neumann is regarded by many as the smartest man of the XX century. Two of his areas of expertise were the foundations of quantum mechanics, and computability theory. He wrote the first QM textbook that clearly explain how observations yield collapse of the wave function, 1932. He was one of the first in the mainstream mathematical community to recognize the significance of Goedel's work on the computability of proofs.

The Church–Turing thesis of the 1930s was the physically computable functions were those defined by Goedel, Church, and Turing.

Not until around 1985 did anyone argue that von Neumann's QM is in direct contradiction to the Church-Turing thesis, and that quantum computers will be able to create computable functions that are beyond what can be done with Turing machines.

How was von Neumann so stupid as to not notice this?

Von Neumann did a lot of work to build early computers, and yet he never commented that with quantum mechanics, he could outdo a Turing machine. Why?

And why didn't anyone else notice it either?

I say that the answer is that there is no such contradiction. The foundations of quantum mechanics do not imply a violation of Church's thesis. It is a myth.

QM says that if you have a system with a |0> state and a |1> state, and if you cannot predict which will be the result of a future measurement, then the formalism represents it as a cat-state, where either is possible. It is like the Schroedinger cat that might be alive or dead, until you open the box and look.

The theory works great, and I don't question it.

But the quantum computing enthusiasts claim that you can some use your uncertainty to do a super-Turing computation. This is like putting a cat in a box, generating some uncertainty about whether the cat is alive, and they trying to use that uncertainty to do a super-Turing computation. At the end, you might open the box to find that the cat was alive all along, but the intervening uncertainty somehow magicly does some super-natural computation.

I don't believe it. The conventional wisdom should be in the validity of Church's thesis, unless someone convincing demonstrates otherwise.

Monday, March 26, 2018

Argument that science, like religion, requires faith

Evolutionary biologist Jerry Coyne attacks a video saying this:
For the second half of the 20th century, the best philosophers of science, philosophers like Sir Karl Popper, Thomas Kuhn, Imre Lakatos and Paul Feyerabend, attempted to explain what science consists in and how it differs from myths and religion. And no matter how hard they tried, eventually, the debate died out their realization that science, much like religion, requires faith. To choose one scientific theory over another, is simply a matter of aesthetics in the hope that this theory and all to the other is going to work out.

But there is no way to disprove or prove in theory. And since there is no way to prove it or disprove it, then there is no point where it becomes irrational for a scientist to stay with a failing theory.
Coyne is right to criticize this, but the video is essentially correct that modern philosophers have abandoned the idea that science discovers objective truths. Popper was one of the last to believe that theories could be disproved, even if they could not be proved true, but his ideas are rejected today.

I used to say that physicists are still believers in hard science, and had not succumbed to philosophers nonsense. But now too many physicists teach the multiverse and all sorts other ideas that have no scientific support at all.
So, the best example of this is the case of heliocentricism. Heliocentricism was first put forward about 2,000 years ago. And for about 1,600 years, it was a failing theory. However, at some point, Kepler and Galileo decided to take it up. And even though it was failing for 1,600 years, they managed to convert it in a very successful theory. The choice, however, to do so, was not because the theory was a good one — since obviously it was failing for a long time — but simply because they liked it and for some reason they had faith in it. So scientists choose to stay, we the few, simply because they have faith in it. So both science and religion seem to require faith, which means that it is not so easy to distinguish between creationism and evolutionary biology.
This example is what convinced Kuhn that scientific revolutions, aka paradigm shifts, are driven by scientists who had an irrational faith (Kuhn preferred the term arational), and other scientists jumping on the bandwagon like a big fad.

As ridiculous as this is, it is the dominant view among philosophers of science today. Even physicists echo this nonsense when it suits them getting papers published.

Coyne replies:
Kepler and Galileo “converted” heliocentrism to a good explanation because of OBSERVATIONS, you moron! It was not because they had “faith” that the Sun was the locus of the solar system.
That is only partially true. Kepler admitted that he could not prove that the Earth goes around the Sun.

Galileo made some excellent observations with his telescope, but his biggest argument for the motion of the Earth was with the daily tides. Galileo claimed that it caused one tide a day, which is nonsense because there are two tides a day, and they are caused by gravity, not motion.

Coyne blames religious influences for undermining views of what science is all about. I am sure that is true in many cases, but the overwhelming attacks on science in academia come from philosophers who hate religious almost as much as he does.

At least the religious folks are up-front about saying that their beliefs are based on faith.

Sunday, March 25, 2018

Trashing the many-worlds interpretation

Lubos Motl trashes the Many Worlds Interpretation:
Bohr told Wheeler that it was a pile of crap because it was a pile of crap. In particular, the "splitting of the worlds" made no sense. Even today, in 2018, it makes absolutely no sense and no fan of these Everett ideas can tell you anything whatsoever about the question whether the worlds split at all, when they split, why they split, how many branches there are. You may suggest several answers to each questions, none of them can be completed to a convincing let alone quantitative theory, and in fact, none of them has a significantly greater support among the Everett fans than others. They don't seem to care. ...

On top of that, even if you solved these problems in some way, the many worlds theory will have nothing to do with science – with predictions. All predictions of quantum mechanics have the form of probabilities, continuous numbers assigned to possible results of experiments, or their functions or functionals. And no Everett's fan has an idea how these probabilities could be written into the many worlds, or extracted from the many worlds. It's just not possible. If this many world theory predicts something, it's the wrong prediction that all probabilities should be rational – the number of worlds would be the denominator because if several worlds obviously exist, they should be "equally likely". Well, the actual outcomes in quantum mechanics are not. It just doesn't make the slightest sense. And all predictions in quantum mechanics are functions of these continuous probabilities. Because the many worlds philosophy can't be reconciled with the continuous probabilities at all (or it seems to predict wrong probabilities), it can't be reconciled with the predictions as such – it cannot possibly have anything to do with science within the quantum mechanical framework.
Motl is correct. I think a lot of people have the misconception that MWI has some way of calculating which worlds or outcomes are more probable, but it has nothing of the kind. MWI does not make any testable predictions.

Peter Woit writes:
The calculation [of the spectrum of the hydrogen atom] in Many Worlds is exactly the same textbook calculation as in Copenhagen. It’s the same Schrodinger equation and you solve for its energy eigenvalues the same way. That is the problem: there’s no difference from the standard QM textbook.
This is just wrong. There is no known way to do a MWI calculation that matches some real world object like a hydrogen atom.

Jim Baggott says:
All this really shouldn’t detract from the main point. The formalism is the formalism and we know it works (and we know furthermore that it doesn’t accommodate local or crypto non-local hidden variables). The formalism is, for now, empirically unassailable. All *interpretations* of the formalism are then exercises in metaphysics, based on different preconceptions of how we think reality could or should be, such as deterministic (‘God does not play dice’). Of course, the aim of such speculations is to open up the possibility that we might learn something new, and I believe extensions which seek to make the ‘collapse’ physical, through spacetime curvature and/or decoherence, are well motivated.

But until such time as one interpretation or extension can be demonstrated to be better than the other through empirical evidence, the debate (in my opinion) is a philosophical one. I’m just disappointed (and rather frustrated) by the apparent rise of a new breed of Many Worlds Taliban who claim – quite without any scientific justification – that the MWI is the only way and the one true faith.

... this endless debate over interpretation is really a philosophical debate, driven by everybody’s very different views on what ‘reality’ ought to be like. And, as such, we’re unlikely to see a resolution anytime soon…
In a sense, this is correct. If an interpretation reproduces all the calculations used to test the theory, then whether to accept it is a philosophical issue, not an empirical one.

For example, the solar system has geocentric and heliocentric interpretation, and preference for heliocentric is philosophical, not scientific.

The trouble with this is that most of these QM interpretations are not really interpretations. MWI does not reproduce any calculations of QM, and does not have any empirical support.

MWI is just like QM except for (1) MWI has no way of making quantitative predictions (like the Born rule), and (2) MWI postulates parallel worlds where all possibilities exist and no world has an effect on any other world.

These two properties make MWI completely disconnected from any scientific analysis. With no predictions, it cannot be tested. And the parallel worlds are just subjective fantasies, with no relation to our world.

More and more, I see physicists argue that the MWI is the only scientific interpretation of QM, because the Copenhagen interpretation somehow fails to solve the "measurement problem" or to define what is "real". Whatever you might think to be shortcomings of the CI, the MWI does not solve any of them, and does not even qualify as a scientific theory. It is a mystery how otherwise-smart physicists could fall for something so ridiculous.

Tim Maudlin attacks Woit:
It is a bit hard to know how to comment on a discussion of a book called “What is Real?” when it has been asserted that

“I’d rather do almost anything with my time than try and moderate a discussion of what is “real” and what isn’t.

Any further discussion of ontology will be ruthlessly suppressed.”

The question “What is real?” just is the question “What exists?” which is in turn just the question “What is the true physical ontology?” which is identical to the question “Which physical theory is true?”. Peter Woit begins by writing “Ever since my high school days, the topic of quantum mechanics and what it really means has been a source of deep fascination to me…”. But that just is the question: What might the empirical success of the quantum formalism imply about what is real? or What exists? or What is the ontology of the world? To say you are interested in understanding the implications of quantum mechanics for physical reality but then ruthlessly suppress discussions of ontology is either to be flatly self-contradictory or to misunderstand the meaning of “ontology” or of “real”. That is also reflected in the quite explicit rejection of any discussion of two of the three possible solutions to the Measurement Problem: pilot wave theories and objective collapse theories.
No, when quantum philosophers ask "what is real?", they are not asking about existence or physical consequences. They are usually searching for a nonlocal hidden variable theory that is supposed to match their nonlocal intuition. They subscribe to a belief that QM is defective, and a hidden variable theory would be better.

At least Maudlin is not defending MWI. But pilot wave theories are nonlocal, and objective collapse theories are hard to reconcile with experiment.

Thursday, March 22, 2018

Hawking also had unsupported beliefs

Evolutionary biologist atheist Jerry Coyne writes:
Stephen Hawking’s body was barely cold (or rather, his ashes were barely cold) when the religionists came muscling in with their tut-tutting and caveats about his accomplishments. For Father Raymond de Souza, a Canadian priest in Ontario (and Catholic Chaplain of Queen’s University), he did his kvetching in yesterday’s National Post. His column, as you see below, claims that “Hawking’s world was rather small.” Really? Why?

Well, because Hawking, while he made big advances in cosmology, couldn’t answer the BIG QUESTIONS about the Universe: namely, why does it exist? Why is there something rather than nothing? ...

But God is de Souza’s answer to this big question, and, further, the priest says that that answer is compatible with science. ...

Those are some questions for Father de Souza, but I have more:

What’s your evidence for God? And why do you adhere to the Catholic conception of God rather than the Muslim conception, which sees Jesus as a prophet but not a divine being? Why aren’t you a polytheist, like Hindus?
If God created the Big Bang, who created God?
If you say that God didn’t need a creator because He was eternal, why couldn’t the Universe be eternal?
And if God was, for some reason, eternal, what was he doing before he created the Universe? And why did he bother to create the Universe? Was he bored?

These questions aren’t original with me; they’re a staple of religious doubters. And of course Father de Souza can’t answer them except by spouting theological nonsense.
The Catholic Church does have all sort of beliefs that are grounded in faith and revelation, not scientific evidence. But so did Hawking, and the physicists that Coyne relies on, like Sean M. Carroll.

Hawking was a proponent of the multiverse and string theory. Hawking spent much of his life arguing about issues that cannot be resolved by any scientific observation.

Most of Coyne's questions, above, are not really scientific questions. There is no known scientific meaning to discussing what preceded the big bang, if anything. It is not clear that such questions make any sense.

Coyne sometimes questions the motives of his fellow humans. If he cannot necessarily figure out human motives, how can he expect to figure out God's motives?

I suspect that priest could give a good explanation for why he is not a Muslim, and not a polytheist.

I don't mind atheists calling out religious believers for having beliefs that are merely compatible with science, but not directly supported by evidence. But why are those atheists so supporting of physicists who do the same thing, with string theory, the multiverse, and black hole information?

Wednesday, March 21, 2018

The blockchain is not efficient

Nature mag reports:
Dexter Hadley thinks that artificial intelligence (AI) could do a far better job at detecting breast cancer than doctors do — if screening algorithms could be trained on millions of mammograms. The problem is getting access to such massive quantities of data. Because of privacy laws in many countries, sensitive medical information remains largely off-limits to researchers and technology companies.

So Hadley, a physician and computational biologist at the University of California, San Francisco, is trying a radical solution. He and his colleagues are building a system that allows people to share their medical data with researchers easily and securely — and retain control over it. Their method, which is based on the blockchain technology that underlies the cryptocurrency Bitcoin, will soon be put to the test. By May, Hadley and his colleagues will launch a study to train their AI algorithm to detect cancer using mammograms that they hope to obtain from between three million and five million US women.

The team joins a growing number of academic scientists and start-ups who are using blockchain to make sharing medical scans, hospital records and genetic data more attractive — and more efficient. Some projects will even pay people to use their information. The ultimate goal of many teams is to train AI algorithms on the data they solicit using the blockchain systems.
No the blockchain is not efficient, and does not offer any advantage to a project like this.

The blockchain is surely the least efficient algorithm ever widely deployed. Today it consumes energy equivalent to the usage of a small country, to maintain what would otherwise be a fairly trivial database.

It appears that someone got some grant money by adding some fashionable buzzwords: AI, blockchain, women's health.

The blockchain does not offer any confidentiality, or give patients any control over their data. This is all a big scam. It is amazing that a leading science journal could be so gullible.

Monday, March 19, 2018

Burned books are lost

"Preposterous" Sean M. Carroll writes, in memory of Stephen Hawking:
Hawking’s result had obvious and profound implications for how we think about black holes. Instead of being a cosmic dead end, where matter and energy disappear forever, they are dynamical objects that will eventually evaporate completely. But more importantly for theoretical physics, this discovery raised a question to which we still don’t know the answer: when matter falls into a black hole, and then the black hole radiates away, where does the information go?

If you take an encyclopedia and toss it into a fire, you might think the information contained inside is lost forever. But according to the laws of quantum mechanics, it isn’t really lost at all; if you were able to capture every bit of light and ash that emerged from the fire, in principle you could exactly reconstruct everything that went into it, even the print on the book pages. But black holes, if Hawking’s result is taken at face value, seem to destroy information, at least from the perspective of the outside world. This conundrum is the “black hole information loss puzzle,” and has been nagging at physicists for decades.

In recent years, progress in understanding quantum gravity (at a purely thought-experiment level) has convinced more people that the information really is preserved.
Common sense tells us that encyclopedia information gets lost in a fire. Quantum gravity thought experiments tell theorists otherwise. Whom are you going to believe?

I believe that the info is lost. I will continue to believe that until someone shows me some empirical evidence that it is not. And there is no law of quantum mechanics that says that info is never lost.

John Preskill (aka. Professor Quantum Supremacy) says otherwise. Info can't disappear because it is needed to make those quantum computers perform super-Turing feats!

Saturday, March 17, 2018

Hype to justify a new particle collider

Physicist Bee explains how theoretical particle physicists are making a phony push for funding billions of dollars for a new collider:
You haven’t seen headlines recently about the Large Hadron Collider, have you? That’s because even the most skilled science writers can’t find much to write about. ...

It’s a PR disaster that particle physics won’t be able to shake off easily. Before the LHC’s launch in 2008, many theorists expressed themselves confident the collider would produce new particles besides the Higgs boson. That hasn’t happened. And the public isn’t remotely as dumb as many academics wish. They’ll remember next time we come ask for money. ...

In an essay some months ago, Adam Falkowski expressed it this way:

“[P]article physics is currently experiencing the most serious crisis in its storied history. The feeling in the field is at best one of confusion and at worst depression”

At present, the best reason to build another particle collider, one with energies above the LHC’s, is to measure the properties of the Higgs-boson, specifically its self-interaction. But it’s difficult to spin a sexy story around such a technical detail. ...

You see what is happening here. Conjecturing a multiverse of any type (string landscape or eternal inflation or what have you) is useless. It doesn’t explain anything and you can’t calculate anything with it. But once you add a probability distribution on that multiverse, you can make calculations. Those calculations are math you can publish. And those publications you can later refer to in proposals read by people who can’t decipher the math. Mission accomplished.

The reason this cycle of empty predictions continues is that everyone involved only stands to benefit. From the particle physicists who write the papers to those who review the papers to those who cite the papers, everyone wants more funding for particle physics, so everyone plays along.
So all this hype about multiverse, susy, naturalness, strings, etc is a hoax to get funding for a new collider?

Theoretical physics peaked in about 1975. They found the Standard Model, and thus had a theory of everything. Instead of being happy with that, they claimed that they need to prove it wrong with proton decay, supersymmetry, grand unified field theories, etc. None of those worked, so they went on to multiverse, black hole firewalls, and other nonsense.

How much longer can this go on? Almost everything theoretical physicists talk about is a scam.

Stephen Hawking was a proponent of all this string theory, multiverse, supersymmetry, black hole information nonsense. I don't think that he did much in the way of serious research in these topics, but he hung out with other theoretical physicists who were all believers.

Friday, March 16, 2018

The blockchain bubble

The Bitcoin blockchain is interesting from cryptological or computing complexity view, but it is solves a problem of no interest to the typical consumer. Other technologies are preferable for the vast majority of applications. The blockchain has become a big scam.

A new essay explains some of the problems:
While much of the tech industry has grown bearish on the volatility of cryptocurrencies, enthusiasm for its underlying technology remains at an all-time high. Nowadays we see “blockchain” cropping up with impressive frequency in even the most unlikely startup pitches. And while blockchain technology does have genuinely interesting and potentially powerful use cases, it has enormous drawbacks for consumer applications that get little mention in media coverage. ...

As it stands, blockchain is caught between three competing objectives: fast, low-cost, and decentralized. It is not yet possible to make one chain that achieves all three. Fast and decentralized chains will incur a high cost because the storage and bandwidth requirements for historical archiving will be enormous and will bloat even with pruning. Aim for fast and low-cost, and you’ll have to introduce a bank-like authority (“Tangles” are a proposed solution, but not yet fully understood).

At high volume, a good credit card processor can settle a typical $2 transaction for somewhere around $0.10. Some of the largest online game economies manage more than a million user-to-user transactions per day, instantaneously, with no fees. And yet, I can name half a dozen startups trying to inject an expensive and slow blockchain into this very problem.

Blockchain is a customer support nightmare

For most consumers, losing a password to an online service is a mild inconvenience they’ve grown accustomed to, since typically, it’s quickly fixed by requesting an email reset, say, or talking with customer service.

Blockchain wallets and their passwords, by contrast, are tied to a file on a user’s hard disk and are absolutely critical to users trying to access the blockchain. By their very nature they have no recovery mechanism. “You lose your password, you lose everything” is an awful user experience for mainstream consumers and a nightmare for companies attempting to build their service on a blockchain. If you use a hosted service, the risk of theft or sudden loss of assets is very real, with central targets and limited traceability. ...

Nothing about blockchain applications is easy for consumers right now. Everyday users accustomed to making digital and online payments would have to be trained to make blockchain purchases, learning to apply the right mix of paranoia and caveat emptor to prevent theft or buying from shady dealers. Irreversible pseudonymous transactions do not lend themselves well to trust and integrity.

Compounding this is the speed and the transaction fees involved. Most public chains have settlements measured in minutes — unless you’re willing to pay high transaction fees. Compare that to the 2-10 seconds for a saved credit card transaction customers are accustomed to in the age of fast mobile interfaces and instant gratification. ...

These points only scratch the surface of what it’ll truly take to make blockchain ready for a mass market.
The Bitcoin blockchain does have some utility for the illicit transfer of money overseas, but it is hard to think of a legitimate use for it.

IBM, big banks, venture capitalists, and others are investing 100s of millions of dollars on this. It is all going to crash, because there aren't any legitimate applications that anyone has found.

Wednesday, March 14, 2018

Hawking had opinions on the black hole info paradox

From the NY Times Stephen Hawking obituary:
The discovery of black hole radiation also led to a 30-year controversy over the fate of things that had fallen into a black hole.

Dr. Hawking initially said that detailed information about whatever had fallen in would be lost forever because the particles coming out would be completely random, erasing whatever patterns had been present when they first fell in. Paraphrasing Einstein’s complaint about the randomness inherent in quantum mechanics, Dr. Hawking said, “God not only plays dice with the universe, but sometimes throws them where they can’t be seen.”

Many particle physicists protested that this violated a tenet of quantum physics, which says that knowledge is always preserved and can be retrieved. Leonard Susskind, a Stanford physicist who carried on the argument for decades, said, “Stephen correctly understood that if this was true, it would lead to the downfall of much of 20th-century physics.”

On another occasion, he characterized Dr. Hawking to his face as “one of the most obstinate people in the world; no, he is the most infuriating person in the universe.” Dr. Hawking grinned.

Dr. Hawking admitted defeat in 2004. Whatever information goes into a black hole will come back out when it explodes. One consequence, he noted sadly, was that one could not use black holes to escape to another universe. “I’m sorry to disappoint science fiction fans,” he said.

Despite his concession, however, the information paradox, as it is known, has become one of the hottest and deepest topics in theoretical physics. Physicists say they still do not know how information gets in or out of black holes.
Not only that, but physicists do not have a sufficiently coherent definition of information in order to make this a paradox. And even if they did, there were be no way to resolve an issue about information leaking out of a black hole.

This shows the sorry state of theoretical physics, that such a non-question could be "one of the hottest and deepest topics".
As a graduate student in 1963, he learned he had amyotrophic lateral sclerosis, a neuromuscular wasting disease also known as Lou Gehrig’s disease. He was given only a few years to live.
He probably had some other degenerative disease.
Dr. Hawking was a strong advocate of space exploration, saying it was essential to the long-term survival of the human race. “Life on Earth is at the ever-increasing risk of being wiped out by a disaster, such as sudden global nuclear war, a genetically engineered virus or other dangers we have not yet thought of,” he told an audience in Hong Kong in 2007.
Mars will always be much more hostile to human life than the Earth, no matter what we do to Earth.
By then string theory, which claimed finally to explain both gravity and the other forces and particles of nature as tiny microscopically vibrating strings, like notes on a violin, was the leading candidate for a “theory of everything.”

In “A Brief History of Time,” Dr. Hawking concluded that “if we do discover a complete theory” of the universe, “it should in time be understandable in broad principle by everyone, not just a few scientists.”

He added, “Then we shall all, philosophers, scientists and just ordinary people, be able to take part in the discussion of why it is that we and the universe exist.”

“If we find the answer to that,” he continued, “it would be the ultimate triumph of human reason — for then we would know the mind of God.”
There is not any hope that string theory will do that.

Hawking's scientific reputation rests on two things: extending the Penrose singularity theorems, and arguing that quantum effects cause black holes to very slowly radiate.

The 20th century mathematics revolution

Mathematician Frank Quinn wrote in 2012:
The physical sciences all went through "revolutions": wrenching transitions in which methods changed radically and became much more powerful. It is not widely realized, but there was a similar transition in mathematics between about 1890 and 1930. The first section briefly describes the changes that took place and why they qualify as a "revolution", and the second describes turmoil and resistance to the changes at the time.

The mathematical event was different from those in science, however. In science, most of the older material was wrong and discarded, while old mathematics needed precision upgrades but was mostly correct. The sciences were completely transformed while mathematics split, with the core changing profoundly but many applied areas, and mathematical science outside the core, relatively unchanged. The strangest difference is that the scientific revolutions were highly visible, while the significance of the mathematical event is essentially unrecognized.
More of his opinions are here. This is essentially correct. Relativity and quantum mechanics radically changed physics in those decades, and math was similarly changed.

I would not say that the older physics was discarded; previous ideas about Newtonian mechanics, thermodynamics, and electromagnetism are still correct within their domains of applicability. The new physics was a revolution in the sense of a turning-around with new views that permitted understandings that were unreachable with the old views.

The essence of the math revolution was precise definitions and logically complete proofs. It was led by Hilbert and some logicians. It was perfected by Bourbaki.

Of course mathematicians used the axiomatic method since Euclid, but only in the early XXc was it formalized to where proofs had no gray areas at all. The 19c still used infinitesimals and other constructs without rigorous justification.

Quinn goes on to complain that educators are almost entirely still stuck in the previous 19c math. I would add that about 90% of physicists today are also.

Quinn goes on to relate this lack of understanding to a lack of respecte for mathematicians:
Many scientists and engineers depend on mathematics, but its reliability makes it transparent rather than appreciated, and they often dismiss core mathematics as meaningless formalism and obsessive-compulsive about details. This is a cultural attitude that reflects feelings of power in their domains and world views that include little else, but it is encouraged by the opposition in elementary education and philosophy. In fact, hostility to mathematics is endemic in our culture. Imagine a conversation:

A: What do you do?
B: I am a --- .

A: Oh, I hate that. Ideally this response would be limited to such occupations as "serial killer", "child pornographer", and maybe "politician", but "mathematician" seems to work. It is common enough that many of us are reluctant to identify ourselves as mathematicians. Paul Halmos is said to have told outsiders that he was in "roofing and siding"!
Yes, mathematicians are widely regarded as freaks and weirdos. Hollywood nearly always portrays us as insane losers. There was another big movie last year doing that.

A new paper takes issue with how mathematician Felix Klein fits into this picture:
Historian Herbert Mehrtens sought to portray the history of turn-of-the-century mathematics as a struggle of modern vs countermodern, led respectively by David Hilbert and Felix Klein. Some of Mehrtens' conclusions have been picked up by both historians (Jeremy Gray) and mathematicians (Frank Quinn).
Klein is mostly famous for his Erlangen program, an 1872 essay that modernized our whole concept of geometry. He embedded geometries into projective spaces, and then charactized a geometry by its symmetry group and its invariants.

Courant wrote in 1926:
This so-called Erlangen Program, entitled `Comparative Considerations on recent geometrical research' has become perhaps the most influential and most-read mathematical text of the last 60 years.
These ideas were crucial for the development of relativity. Lorentz had correctly figured out how to resolve the paradox of Maxwell's equations and the Michelson-Morley experiment, but what really tied the theory together beautifully was the symmetry group and the invariants, as that made it a non-Euclidean geometry under the Erlangen Program. Such thinking clearly guided Poincare, Minkowski, Grossmann, and Hilbert.

No history of relativity even mentions this, as far as I know. The historians focus on Einstein, who never seemed to even understand this essential aspect of relativity.

The above paper argues that Klein was a very modern mathematician who has been unfairly maligned by Marxist historians. Quinn was duped by those historians.

Quinn wants to distinguish 19c non-rigorous math from XXc axiomatic modern math, the Marxist historians instead distinguish Aryan math, Jewish math, Nazi math, racist math, and modern math. Klein was said to be half-Jewish.

The paper has quotes like these:
"This is compounded by a defect which can be found in many very intelligent people, especially those from the semitic tribe[;]8 he [i.e., Kronecker] does not have sufficient imagination (I should rather say: intuition) and it is true to say that a mathematician who is not a little bit of a poet, will never be a consummate mathematician. Comparisons are instructive: the all-encompassing view which is directed towards the Highest, the Ideal,9 marks out, in a very striking manner, Abel as better than Jacobi, marks out Riemann as better than all his contemporaries (Eisenstein, Rosenhain), and marks out Helmholtz as better than Kirchhoff (even though the latter did not have a droplet of semitic blood)."

"When the National Socialists came to power in 1933, [Bieberbach] attempted to find political backing for his counter-modernist perspective on mathematics, and declared both, intuition and concreteness, to be the inborn characteristic of the mathematician of the German race, while the tendency towards abstractness and unconcrete logical subtleties would be the style of Jews and of the French (Mehrtens 1987). He thus turned countermodernism into outright racism and anti-modernism."
I don't know what to make of this. No one talks this way anymore.

Sunday, March 11, 2018

Krauss is being silenced

I posted about metooing Krauss.

Jerry Coyne blogs on The Lawrence Krauss affair:
After that article appeared, I did some digging on my own, and came up with three cases that have convinced me that Krauss engaged in sexual predation of both a physical nature (groping) and of a verbal nature (offensive and harassing comments). The allegations that convinced me are not public, but the accusers are sufficiently credible that I believe their claims to be true. Further, these claims buttress the general allegation of sexual misbehavior made in BuzzFeed. In my view, then, Krauss had a propensity to engage in sexual misconduct. ...

I am taking the step of not allowing comments on this post as I don’t really want any discussion here of my position, which I’ve arrived at after long cogitation. As I said, I don’t want trial by social media, and it would be hypocritical of me to allow that here.
Popular podcaster atheist Sam Harris has canceled a live public interview of Krauss, which was supposed to be a sequel to the last one.

It is not mentioned that Krauss is now apparently happily married to one of those women he supposedly sexually harassed when he was a single man 10 years ago. [According to a comment below, Krauss was divorced 8 years ago.]

Coyne has a popular blog, and probably most of his readers think that he is gay. He denies it, but he blogs a lot about his personal life, and it is obvious that he has no wife, no girlfriend, and no kids. Furthermore, he has stereotypical gay interests in music, arts, clothing, and pets. And his political views are mostly what you would expect from a gay atheist professor.

I am not saying this to criticize, but to give background for his opinions. He does not appear to have any worries that any woman is going to metoo him.

I have no way of knowing how he has flirted with women in the past, and I don't see how it is anyone's business.

I wonder where this is going. Is the Physics community going to sit back and let their colleagues be silenced and destroyed? If he were being ostracized for being a Communist, I am sure that Krauss's colleagues would stick up for him.

Like him or not, Krauss was one of the leading figures in the public image of Physics. Where is this going? He has views which are that of a typical Trump-hating leftist professor, but that is not good enough. Maybe Physics will have to be feminized, with only feminist professors being allowed to explain Physics to the public.

Update: Coyne responds:
What? I must be gay because I’m not worried about being #MeToo’d? ...

If I could have imagined all the ways people would go after me for my stand, I would never have dreamed up this one. Thanks, Roger, for a long moment of amusement. You’re an idiot.
I did not say that he is gay. If he were, then I think that he would probably say so. The point is about ostracizing Krauss.

Update: Commenter Craw writes "Well I think Coyne has simply misread Roger’s post entirely." Coyne replies:
I understand Craw’s post perfectly. I know his point was to defend the person at issue; the part about me being gay was simply his hamhanded attempt to understand why I was part of the “pile on”. But I found that part really humorous and a complete miss on the part of the writer.

Seriously, don’t insult me by saying that I didn’t understand what was a straightforward (though incredibly dumb) post. I picked out one part to show the lengths to which people will go to get at me for what I believe.

As Dark Buzz himself says, the point was not just that people were ostracizing the person at issue (unfairly, he thinks, but he’s wrong), but also to try to understand why I was part of the “pile on”.

You’re insulting the intelligence of not just me, but of everyone here. Best to leave this topic alone and stop posting excerpts from that website here. People can go over there to read any response by this befuddled individual.
Coyne says he wanted "to show the lengths to which people will go to get at me for what I believe."!

Coyne collected some anonymous and confidential gossip about Krauss, accused him of "sexual predation" and "propensity to engage in sexual misconduct", and announced that he is publicly disassociating himself from Krauss. But I am the one who is going to lengths to "get at" Coyne?!

I like Coyne's blog. Sometimes I disagree with him. Sometimes I say so.

Tuesday, March 6, 2018

Google Bristlecone would be compelling

Google just announced a quantum supremacy chip:
This device uses the same scheme for coupling, control, and readout, but is scaled to a square array of 72 qubits. We chose a device of this size to be able to demonstrate quantum supremacy in the future, investigate first and second order error-correction using the surface code, and to facilitate quantum algorithm development on actual hardware. ...

This device uses the same scheme for coupling, control, and readout, but is scaled to a square array of 72 qubits. We chose a device of this size to be able to demonstrate quantum supremacy in the future, investigate first and second order error-correction using the surface code, and to facilitate quantum algorithm development on actual hardware. ...

We believe Bristlecone would then be a compelling proof-of-principle for building larger scale quantum computers. ...

We are cautiously optimistic that quantum supremacy can be achieved with Bristlecone, and feel that learning to build and operate devices at this level of performance is an exciting challenge! We look forward to sharing the results and allowing collaborators to run experiments in the future.
In other words, they are not quite there yet, but any day now they will be announcing a Nobel-prize-worthy computer.

I expect to be reading announcements like this for the next five years. It is like reading that high-energy particle physicists are close to discovering supersymmetry. It is all a pipe dream.

Bell tacitly assumed commuting observables

Physicist N. David Mermin just posted a revision of his 1993 paper, Hidden Variables and the Two Theorems of John Bell:
In all these cases, as Bell pointed out immediately after proving the Bell-KS theorem, we have “tacitly assumed that the measurement of an observable must yield the same value independently of what other measurements must be made simultaneously.” ...

This tacit assumption that a hidden-variables theory has to assign to an observable A the same value whether A is measured as part of the mutually commuting set A, B, C, ... or a second mutually commuting set A, L, M, ... even when some of the L, M, ... fail to commute with some of the B, C, ..., is called “non-contextuality” by the philosophers. Is non-contextuality, as Bell seemed to suggest, as silly a condition as von Neumann’s — a foolish disregard of “the impossibility of any sharp distinction between the behavior of atomic objects and the interaction with the measuring instruments which serve to define the conditions under which the phenomena appear,” as Bohr23 put it?
Yes, it is a silly condition, because it is contrary to everything we know about atomic physics. Many observables do not commute. If you want to measure position and momentum of a particle, then it makes a big difference which you measure first. That is the essence of the Heisenberg uncertainty principle.

Some people try to claim that Bell just made physically reasonable assumptions, but that is false.
To those for whom non-locality is anathema, Bell’s Theorem finally spells the death of the hidden-variables program.31 But not for Bell. None of the no-hidden-variables theorems persuaded him that hidden variables were impossible. What Bell’s Theorem did suggest to Bell was the need to reexamine our understanding of Lorentz invariance, as he argues in his delightful essay on how to teach special relativity* and in Dennis Weaire’s transcription of Bell’s lecture on the Fitzgerald contraction.** “What is proved by impossibility proofs,” Bell declared, “is lack of imagination.”
Bell has his followers today, and they still refuse to accept impossibility proofs.

Update: A reader asks me to elaborate. Check the blog for past postings on this topic, for more detail.

A core tenet of quantum mechanics is that there are no hidden variables. Von Neumann was explicit about this in his textbook from about 1930. Bell, Einstein, and other dissenters have claimed that quantum mechanics is not a realistic theory, and that only a hidden variable theory achieves the sort of philosophical realism that they aspire too. Bell devised a clever way of testing his hidden variable ideas. Experiments have proved his hidden variable theories to be wrong.

I don't think Bell or Einstein ever stopped believing in hidden variable theories. Nearly everyone else, including myself, accepts that they have been proven wrong.

Saturday, March 3, 2018

The death of supersymmetry

The Economist mag reported:
“The great tragedy of science”, said Thomas Huxley, “is the slaying of a beautiful hypothesis by an ugly fact.” That, though, is the scientific method. If nature provides clear evidence that a hypothesis is wrong then you have to abandon it or at least modify it. It is psychologically uncomfortable, no doubt, for those with an interest in the correctness of the hypothesis in question. But at least everybody knows where they stand.

What happens, though, in the opposite case: when nature fails to contradict a hypothesis but stubbornly refuses to provide any facts that support it? Then nobody knows where he stands. This is fast becoming the case for a crucial hypothesis in physics, called Supersymmetry — or Susy, to its friends. Susy attempts to tie up many of the loose ends in physical theory by providing each of the known fundamental particles of matter and energy with a “supersymmetric” partner particle, called a sparticle. It is neat. It is elegant. But it is still unsupported by any actual facts. And 2017 looks like the year when the theory will either be confirmed or dropped.
No, it was not neat or elegant.

Theorists liked it because it could be used to cancel certain anomalies. With SUSY, string theory only need 6 extra dimensions instead of 22.

The Standard Model is neat and elegant because it models the universe with only about 20 parameters. Supersymmetric models all require at least 120 extra parameters, none of which have any connection to any known observational reality.

The SUSY models thus forced a vast and unnecessary complexity. Ptolemaic epicycles made much more sense, as they were only introduced to the extent needed to explain observations.

Sabine Hossenfelder posted that naturalness is nonsense. One could believe in supersymmetry independent of naturalness, but the two concepts seem to have the same followers. They have an almost religious belief that the universe will conform to their peculiar notions of beauty. For an example of such a believer, see Lubos Motl.