Poincare screwed out of history books

Cracked lists 23 Amazing People Who Were Screwed Out of History Books, citing http://plato.stanford.edu/entries/poincare/.

It drew some criticism:

#21 is objectively false. AuntieMeme must have misunderstood the literature. Poincare argued that LORENTZ should be credited with the invention of special relativity. The cited source describes how he PHILOSOPHICALLY argued that spacetime should warp as it does in general relativity, but did not formulate any kind of model or equations. Source: https://en.wikipedia.org/wiki/Relativity_priority_dispute

Poincare certainly published the equations for the special relativity of spacetime. He proposed some equation for general relativity, but died before they were perfected. That Wikipedia article has a lot of useful info on the subject.

Another comment:

The thing about Einstein and Henri Poincare is a bit misleading. First of all, Poincare had only helped to develop the theory of Special Relativity (which can be derived simply from trigonometry and some fundamental kinematics). Poincare had NOTHING to do with General Relativity which is a far more powerful theory.

Second, at the time Einstein published his research, Poincare hadn't formally published his, rather he only published a short blurb about using the concept of relativity to interpret some of Lorrentz's work on four dimensional transformations. So although he discussed the concept that objects don't act any different if they are still or moving, he didn't derive any equations to explain how that affects the universe.

Third, Poincare did absolutely nothing to try to prove it was correct. Einstein was the first one to propose an experiment for confirming it.

All three points are false. Poincare help develop general relativity by introducing a spacetime metric and geometry, by presenting relativistic theories of gravity, by formulating gravity waves, and by partially explaining an anomaly in Mercury's orbit.

Poincare's work was mostly published before Einstein, with one big 1905 paper being published at about the same time. He certainly had all the equations Einstein did.

Poincare agreed with Lorentz that the Michelson-Morley and other experiments forced special relativity. Einstein was the one who ignored the experimental evidence, and is famous for just postulating it in his 1905 paper.

Another comment:

Poincare is one of the most famous mathematicians of all time, but he didn't invent Special Relativity. Even he gladly admitted to that. He was toying with the right mathematical ideas, but it was Einstein who went all-in on the concepts and really got what was going on conceptually for the first time. That was where Einstein's genius really shown. (And shown again, several times, with the development of Quantum Mechanics.) ...

As for QM, until 1926, most of the work on Quantum could quite reasonably be said to have been Einstein's. Bohr and others had done some, but all had quite quickly retreated from the implications of their work. Einstein was the single person who was interested in exploring what QM really implied and making sense of it as a really complete theory and not an ad hoc hypothesis. (Much as people had been doing with SR before he arrived.) Unfortunately, after 1926 and the advent of Schrodinger's Wave Mechanics and Heisenberg's Matrix Mechanics (equivalent approaches, of course), Einstein got fed up with where things were going. To a fair extend, I'd argue he was fed up with the Copenhagen interpretation in particular, although I don't know how he'd have dealt with the alternatives. That's when he seems to have turned on QM, although, again, it's a lot more subtle that "his disagreed". And remember, Schrodinger *also* didn't like how things went. That's why he cooked up the cat thought experiment, after all.

No, it was Poincare who went all-in on the relativity concepts, and worked out the spacetime geometry. Einstein did not dare contradict Lorentz's theory. Einstein's work on quantum mechanics was mostly to disagree with it.

Another comment:

The one about Einstein and Poincare is complete falsehood. Poincare's first paper on relativity came out three months before Einstein's. There is no way Einstein could have used it for the basis of his own paper, as is implied. (Do you know how long it takes to get a paper submitted and published?) Also, Poincare was wrong about relativity. He denied until his death that energy carried mass, considering mathematics that indicated this 'fictitious'.

However, he was a brilliant mathematician and physicist, and Einstein had acknowledged that his and Poincare's mathematical treatment as equivalent in his 1906 paper, "The principle of the conservation of center of mass motion and the inertia of energy." Einstein continued to acknowledge Poincare publicly for the rest of his life.

In fact this is exactly backwards. It was Poincare who refused to acknowledge Einstein. And just to reiterate, Poincare was wrong about relativity and Einstein was right. Poincare interpreted mathematics that indicated time dilation and mass-energy equivalence as fallacious variables that had no real world effect, rather than real physical effects as Einstein correctly did.

Einstein's papers were not refereed, and were published it quickly. In interviews, he claims that he wrote it in about the 6 weeks before his submission date, and he could have studied Poincare's short 1905 paper for about 4 weeks of that. Einstein understood that he had to publish quickly.

Einstein did not acknowledge Poincare publicly. All his life, Einstein denied reading Poincare's papers, even tho that 1906 paper does credit Poincare for E=mc².

Saying that Poincare had "fallacious variables that had no real world effect" is backwards. I think he means fictitious variables. Lorentz and Poincare derived their formulas from real physical experiments. Einstein derived his from postulates.

Poincare did refuse to mention Einstein. Poincare's major relativity papers were all submitted for Einstein had published anything on the subject. Poincare never used any of Einstein's ideas. Poincare did once write a gracious letter of recommendation for Einstein.

Simple teleportation over-hyped again

LiveScience reports:

A new distance record has been set in the strange world of quantum teleportation.

In a recent experiment, the quantum state (the direction it was spinning) of a light particle instantly traveled 15.5 miles (25 kilometers) across an optical fiber, becoming the farthest successful quantum teleportation feat yet. Advances in quantum teleportation could lead to better Internet and communication security, and get scientists closer to developing quantum computers.

No, almost every part of this story is wrong. There is no such thing as teleportation. The quantum state is not just the direction a particle is spinning. Nothing traveled instantly. This cannot lead to better Internet and communication security, or get scientists closer to developing quantum computers.

All they did was to split a laser beam into two identical light pulses, send one 15 miles thru optical fiber, and detect the polarization at both ends to see that they match.

The light pulse goes at the speed of light, not instantly. The only teleportation is that a bit of info is being conveyed by the polarization to the detection device at the other end of the fiber.

The application to cryptography and quantum computers is all a big hoax. It does not exist.

Quantum teleportation doesn't mean it's possible for a person to instantly pop from New York to London, or be instantly beamed aboard a spacecraft like in television's "Star Trek." Physicists can't instantly transport matter, but they can instantly transport information through quantum teleportation. This works thanks to a bizarre quantum mechanics property called entanglement.

It is not that bizarre. As you read this, you got the info as light pulses were transmitted over fiber in massive internet trunk lines.

The only addition in the new experiment is that a copy of the polarized light pulse is at both ends. This is a cute demonstration of quantum mechanics, but the effect has been well understood for decades and there are no practical applications.

Quantum entanglement happens when two subatomic particles stay connected no matter how far apart they are. When one particle is disturbed, it instantly affects the entangled partner. It's impossible to tell the state of either particle until one is directly measured, but measuring one particle instantly determines the state of its partner.

They are only connected in the sense that they were produced in a way that produces equal and opposite light pulses. No one has ever done an experiment to prove that disturbing one particle has any effect on the other.

That last sentence may surprise you if you read popularizations of quantum mechanics. But I fully accept quantum mechanics, as described by the textbooks. I assure you that Nobel prizes would be given if anyone did such an experiment.

What we do know is that it is possible to put two particles in an entangled state such that measurements give equal (or opposite) results. Measuring one might tell you what the other measurement is going to be, but there is no causal effect.

Physicists think quantum teleportation will lead to secure wireless communication — something that is extremely difficult but important in an increasingly digital world. Advances in quantum teleportation could also help make online banking more secure.

We already have secure online communication for banking. Confidential and authenticated messages can be sent all over the world using the internet.

The above technology, if perfected, might be able to send a few bits confidentially from one router to another. It cannot send messages across routers, and it cannot authenticate messages. It is commercially worthless.

Update on Tyson quotes

I mentioned Neil Tyson getting caught using some bogus quotes, and now a NY Times op-ed puts a charitable spin on it:

The science of memory distortion has become rigorous and reliable enough to help guide public policy. It should also guide our personal attitudes and actions. In Dr. Tyson’s case, once the evidence of his error was undeniable, he didn’t dig his hole deeper or wish the controversy away. He realized that his memory had conflated his experiences of two memorable and personally significant events that both involved speeches by Mr. Bush. He probably still remembers it the way he described it in his talks — but to his credit, he recognizes that the evidence outweighs his experience, and he has publicly apologized.

Dr. Tyson’s decision is especially apt, coming from a scientist. Good scientists remain open to the possibility that they are wrong, and should question their own beliefs until the evidence is overwhelming. We would all be wise to do the same. ...

Politicians should respond as Dr. Tyson eventually did: Stop stonewalling, admit error, note that such things happen, apologize and move on.

Eventually? I don't want to beat a dead horse, but the only one to call Tyson on his quotes was not even mentioned in this article, due to editing. It was TheFederalist blog, and it fills in the details. It will be interesting to see whether he continues to use the misquotes.

Philosophical realism is not what you think

One of the themes of this blog is to counter bad ideas of science. I am not interested in the fringe pseudosciences, but the ideas bad enuf to be taught in Harvard classrooms.

The chief offenders are the theoretical physicists pushing wacky untestable ideas, and the philosophers and historians pushing paradigm shift theory.

Philosopher and former biologist Massimo Pigliucci explains how nearly all philosophers and historians of science have adopted a view of science that is diametrically opposed to what most scientists think. He attributes the difference to a lack of self-awareness on the part of scientists.

I say that scientists reject modern philosophy because philosophers have turned anti-science, but he just just accuses me of ignorance.

Pigliucci's philosophy of science is the realism-antirealism debate. You might think that this would be something mildly sensible like the Bohr-Einstein debates of the 1930s, but it is not. A realist is someone who decides what is real according to the prevailing paradigm. An anti-realist is someone who relies on empirical evidence. All the modern philosophers of science are realists.

For examples, he says that Ptolemy and Newton were fundamentally wrong, because Copernicus and Einstein respectively replaced them with qualitatively different theories. Likewise classical mechanics wrong because it was replaced by quantum mechanics. Only an anti-realist would say that Newtonian gravity is correct as applied to getting Apollo 11 to the Moon.

The paradigm shifters go further, and say that Newtonian mechanics cannot even be compared to relativity because mass means something different in the two theories.

The philosophers are wrong on many levels. Mass does not mean something different, and Newtonian mechanics certainly is correct in its domain of applicability. More importantly, the philosophers are wrong about the qualitative differences.

These theories do not really contradict. Consider Ptolemy and Copernicus. It is a simple mathematical fact that Sun-centered and Earth-centered coordinate systems are mathematically equivalent. XX century physics recognizes that, and both are considered valid. Ptolemy was considered with the appearance with the sky, and does not attempt a 3D model. He does have some arguments for the Earth being stationary, but that has almost nothing to do with his model. I do not know whether he realized that his main epicycles could be interpreted as the Earth's revolution, but that is essentially what Copernicus did.

Thus Copernicus's contribution was essentially to take Ptolemy's 2D model and turn it into a 3D model by making a frame choice and an interpretation of the major epicycles. That contribution had some conceptual advantages, but it was more or less mathematically equivalent as it did not make much difference to the predictions of what we see in the sky.

This example is crucial to paradigm shift theory, because the Copernicus model had no measurable advantages over Ptolemy. This is used to support the goofy idea that scientific progress is illusory and irrational.

The Einstein story is also crucial to philosophers. They say that Einstein ignored the evidence and created relativity based on what he thought was right, abruptly overthrowing everything beforehand. Nearly all parts of their story is wrong, as I have detailed on this blog and in my book.

The quantum mechanics revolution is cited less often, because T. Kuhn denied that it was a paradigm shift. It had measurable advantages over the previous theories that were immediately accepted, and therefore did not fit his pattern for scientific revolutions and paradigm shifts.

I left this comment on Pigliucci's site:

SciSal, Newtonian mechanics certainly is an approximation to relativity, and this is commonly explained in relativity textbooks and on Wikipedia. Space and time are not two aspects of the same thing in relativity. In spite of your claim that causality does not appear in fundamental physics, space-time in relativity has a causal structure that treats space very differently from time.

It is also not quite right to say that Newtonian mechanics is different because space and time are fixed. Both Newtonian and relativistic mechanics can use coordinate changes in space and time. You say that relativity space-time is continuously dynamic, but it is really the gravitational potential that is continuously dynamic, and a Newtonian potential is also continuously dynamic.

It is true that relativistic gravity has an interpretation in terms of curvature, but so does Newtonian gravity.

You also claim that classical and quantum mechanics are radically different in how they treat space and time, and hence cannot be applied to the same problems. I disagree. See the correspondence principle for how classical mechanics is a macroscopic approximation to quantum mechanics, contrary to Cartwright.

Alexander is quite right that calling Newtonian physics "wrong" is a rather strange use of the word wrong. Perhaps the historian/philosophers use the word to mean something different from everyone else. Phoffman56 explains this correctly, and he is right that the philosopher quibbles have no credibility at all with physicists.

SciSal argues that Einstein space-time is some sort of exception to the view of steady progress in science. I disagree. The history of relativity was one of steady progress over decades, and was not really so radically different. You can still talk about forces as being the rate of change of momentum, and many other Newtonian concepts carry over.

A theme of this blog is the steady progress of science. See my Latin motto above. I thought this progress was obvious, but most philosophers deny it.

Pigliucci promotes his idea of science in his 2010 book, Nonsense on Stilts: How to Tell Science from Bunk, and in this interview promoting the book. In it, he argues that Newtonian theory of gravity is wrong, because it does not have Einstein's concept of space-time. He acknowledges that string theory might be wrong, but it is not pseudoscience because it is done by smart people and it makes all the same predictions as the Standard Model. He attacks Bjorn Lomborg for speaking about global warming alarmism because his degree is not in climate science.

This is pretty nutty, and Pigliucci himself would be an example of something speaking outside his expertise. The difference between classical mechanics and relativity is not what he thinks. String theory is not able to make any of the Standard Model prediction, and is pseudoscience in the sense of not making any testable predictions. Lomborg is concerned with the economic choices that people make in response to global warming, and he has expertise in that subject (even with the unpopularity of his view that other problems are more important).

Pigliucci represents a common academic philosophy view of what science is about, and he is way off base. His book has many favorable Amazon reviews, such as this ideological one:

A major political party in America has been taken over by the forces of darkness. Purveyors of scientific illiteracy continue to bombard American citizens with their claims about "legitimate rape," the willful ignorance of creationism, denial of global climate change and other aspects of reality. Pigliucci provides common-sense ammuniton for those who will resist this wave of anti-science reality denial.

But you might want to check out the negative reviews, as they have some very specific and damning criticisms.

Using the disentanglement principle

Yale Law and Psychology professor Dan Kahan writes:

There is a small segment of highly science-literate citizens who can reliably identify what the prevailing scientific view is on the sources and consequences of climate change. But they are no less polarized than the rest of society on whether human activity is causing global warming! ...

Al Gore is right that that climate debate is “a struggle for the soul of America” — and that is exactly the problem. If we could disentangle the question “what do we know” from the question “whose side are you on,” then democratic engagement with the best evidence would be able to proceed. ...

To their immense credit, science education researchers have used empirical methods to address this challenge. What they’ve discovered is that a student’s “disbelief” in evolution in fact poses no barrier whatsoever to his or her learning of how random mutation and genetic variance combine with natural selection to propel adaptive changes in the forms of living creatures, including humans.

After mastering this material, the students who said they “disbelieved” still say they “disbelieve” in evolution. That’s because what people say in response to the “do you believe in evolution” question doesn’t measure what they know; it measures who they are.

Indeed, the key to enabling disbelievers to learn the modern synthesis, this research shows, is to disentangle those two things — to make it plain to students that the point of the instruction isn’t to make them change their “beliefs but to impart knowledge; isn’t to make them into some other kind of person but to give them evidence along with the power of critical discernment essential to make of it what they will.

What he is saying here is that if you disentangle the science from the politics and religion, then students readily learn and accept the science!

I would have thought this would be obvious, but empirical evidence has turned this into a big revelation.

Apparently teachers of evolution and climate science cannot resist inserting assertions of belief that students do not necessarily accept. Cut that out, and students are not so anti-science after all.

The catch here is that you might train one of those highly science-literate citizens, but he might not accept your policy conclusions.

The current Atlantic magazine has an article on You Can't Educate People Into Believing in Evolution. Why are they so eager to "educate people into believing"? They would do better if they educated people into learning the facts, and letting them believe what they want.

“The psychological need to see purpose, that is really interesting," said Jeffrey Hardin, a professor of zoology at the University of Wisconsin, at the Faith Angle Forum in Miami on Tuesday. “Many Christians consider Neo-Darwinian theory to be dysteleological, or lacking in purpose." Hardin is himself an evangelical Christian; he often speaks with church communities about evolution in his work with the BioLogos Foundation. In these conversations, he said, many evangelicals point to statements like that of paleontologist George Gaylord Simpson, who wrote in his 1967 book, The Meaning of Evolution, "Man is the result of a purposeless and materialistic process that did not have him in mind. He was not planned." When this is echoed by outspoken atheists like Richard Dawkins and Sam Harris, Hardin said, "Evangelicals look at it and go, ‘I can’t accept that, and therefore I cannot accept thinking at all about evolutionary biology.'"

Physicist-atheist Steven Weinberg famously said at the end of a book about the Big Bang:

It is very hard to realize that this all is just a tiny part of an overwhelming hostile universe. It is even harder to realize that this present universe has evolved from an unspeakably unfamiliar early condition, and faces a future extinction of endless cold or intolerable heat. The more the universe seems comprehensible, the more it also seems pointless.

Maybe if they disentangle the science from the leftist-atheist dogma, then people will at least learn the science. But to many leftist professors, putting political spin on evolutionary science is essential to their worldview.

Philosophers reject physics causality

Massimo Pigliucci is a biologist-turned-philosopher who posts opinions on a variety of philosophical topics, with his favorites being in philosophy of science. He attacks pseudoscience like creationism, of course, but also blasts mainstream scientists for ignoring the philosophy of the last 50 years.

In my opinion, scientists of the last 50 years have rightfully ignored philosophers because they have nearly all adopted an anti-science agenda that has become irrelevant to modern science.

His latest is On the (dis)unity of the sciences:

Fodor’s target was, essentially, the logical positivist idea (still exceedingly common among scientists, despite the philosophical demise of logical positivism a number of decades ago) that the natural sciences form a hierarchy of fields and theories that are (potentially) reducible to each next level, forming a chain of reduction that ends up with fundamental physics at the bottom. So, for instance, sociology should be reducible to psychology, which in turn collapses into biology, the latter into chemistry, and then we are almost there.

But what does “reducing” mean, anyway?

He mostly complains about reductionism as believed by most scientists, and expressed in extreme form by Steven Weinberg.

The main gripe is that scientists usually feel that they are part of a collective enterprise that is systematically progressing towards the true workings of the universe, as part of one coherent methodology called science. But academic philosophers have all concluded decades ago that there is no such thing as scientific truth, that science does not make progress, that scientists jump on paradigms like fads, that science is a huge hodge-podge of contradictory theories, and that even within a subject like physics, science is just a bunch of loosely-related ideas that have little to do with each other. Scientists are just not self-aware enuf to see what they are doing.

When you discover that most scientists subscribe to a philosophy that all philosophers reject, that should be a clue that the philosophers are on the wrong track.

This is why scientists ignore modern philosophers: the philosophers are crackpots, and are so completely wrong it is hard to explain why they are so wrong. The simplest way to see it is that scientists accomplish things, and philosophers have zero influence on science or anything else.

He also says, in response to a commenter:

“I think the philosophical debate over scientific realism vs anti-realism is itself confused”

I beg to differ. It is one of the clearest debates one can find in philosophy.

But another pointed out that the Stanford encyclodia says:

It is perhaps only a slight exaggeration to say that scientific realism is characterized differently by every author who discusses it, and this presents a challenge to anyone hoping to learn what it is.

So nobody knows what realism means, and yet its virtue is one of philosophy's clearest debates.

Pigliucci responds, referring to this study:

Richard, yeah, it’s not just a slight exaggeration, it’s a pretty serious misrepresentation of the situation. A recent survey of a number of opinions of philosophers, co-authored by David Chlamers, clearly pointed to realism having won the day, especially within the epistemically relevant community, philosophers of science.

Yes, the big majority said that they favor scientific realism, but the survey did not define it or establish that there was a common definition. These philosophers can babble for 100s of pages on the subject, but never clarify their terminology enuf to say who was the realist and anti-realist in the Bohr-Einstein debates. The whole subject has the flavor of people who have never heard of XX-century science.

Several years ago I would have said that of course I was a scientific realist. But then I learned that when the term is applied to quantum mechanics, it usually means people like Einstein, Bohm, and Bell who believe that some hidden variable theory was going to disprove quantum mechanics. I do not know how "realism" came to mean a mystical belief that have never been seen or found any useful application to the real world, but because of that, put me down as an anti-realist, and the philosophers as being hopelessly confused.

Crazy as all that is, here is where Pigliucci really goes off the deep end:

Ah, yes, causality! I stayed away from that one too, partly because I’m thinking of a separate essay about it. The interesting thing is that the concept of causality plays an irreplaceable role in the special sciences, but hardly appears at all in fundamental physics. That’s something to explain, of course, and I’d like to hear a physicist’s opinion of it.

I responded:

I am baffled by this comment, as causality is absolutely central to fundamental physics. I cannot think of any part of physics that can function without it. Saying that causality does not appear in physics is like saying energy does not appear in physics. What is physics without energy and causality?

Perhaps you have been influenced by some misguided philosopher like Bertrand Russell. He wrote a 1913 essay saying that “the law of causality, as usually stated by philosophers, is false, and is not employed in science.” He also said that physics never even seeks causes. I do not know how he could say anything so silly, as all the physics textbooks use causality.

Vojinovic: “notion of causality is related to the notion of determinism”

Not really. There are people who work on deterministic and non-causal interpretations of quantum mechanics, and non-deterministic and causal interpretations. So they are not so tightly related.

I also disagree with your claim that radioactive decay is causeless, and that a causal chain of events makes no sense with quantum phenomena. The atomic nucleus consists of oscillating quarks and gluons, and the decay might be predictable if we could get a wave function for everything in that nucleus. That seems impossible, but there is still a causal theory for how that decay takes place, and the decay can be analyzed as a causal chain of events. Saying that radioactive decay is causeless is like saying a coin toss is causeless. It may seem like it has a random outcome to the casual observer, but there are causal explanations for everything involved.

Quantum mechanics is all about finding causal explanations for things like discrete atomic spectra, where such an explanation must have seemed impossible.

Yes, there are philosophers of physics today who work on those non-causal interpretations. As far as I know, nothing worthwhile has ever come out of that work.

Pigliucci posted this response:

No, it is your comment that is one more example of groundless condescending while refusing to engage with the actual argument in a way that may persuade others to actually take you seriously. ...

I’m afraid you either don’t get what Cartwright is saying or you don’t understand physics. Or possibly both. ...

It isn’t a question of what type of causality, it is an issue of causality period. According to my understanding of fundamental physics (and yes, I did check this with several physicists, Sean Carroll among them) the concept of causality plays little or no role at that level of description / explanation. Quantum mechanical phenomena “occur” with this or that probability, following the predictions of a set of deterministic equation, but one doesn’t need to deploy talk of causality at all.

On the contrary, one simply can’t do anything in the special sciences without bringing up causes. This is true for non fundamental physics, chemistry, biology (especially ecology and evolutionary biology), and so forth.

How did Sean M. Carroll get to be a bigger physics authority than Steve Weinberg? Carroll is just some sort of lab assistant at Caltech, not part of the regular faculty, and he trolls the internet to fund his kooky ideas, likes the many-worlds interpretation and his take on the arrow of time. He is not sure whether your behavior has been determined by the Big Bang and the laws of physics, but he is sure that causality has no place in physics?

I realize how people can disagree with me on quantum computing, and even free will. But I really do not see how anyone can deny that causality is central to physics.

If I really misunderstand physics that badly, maybe I should shut down this blog. Can someone please give me some example of some part of physics that does not involve causality?

The only example given was radioactive decay, but you can find causal explanations from modern quantum field theory on the Wikipedia page. Someone claimed that there are no causal chains in quantum mechanics, but Feynman diagrams do exactly that.

It is true that physics textbooks do not use the word "causality" a lot. Instead of "A causes B", they might say "solving the equations of motion with initial conditions A gives B" or "A is the Cauchy data for B". Instead of saying "A has no causal effect on B" they might say "B is outside the light cone of A" or "A and B are are space-like separated".

It doesn't matter whether the theory is deterministic or not. Even if you are using a wave function to predict a probability, you still have to solve an initial value problem for the Schroedinger equation, which means that a wave function at one time is causing a wave function at future times. When explaining a laser, you still say that it is causing electrons to jump to excited states, and then causing emission of coherent photons.

Causality is so important in quantum field theory that it is one of the four Wightman axioms for such theories.

At the cosmological scale, physicists are always talking about things like what causes supernovas, even if they have never predicted one.

Why would someone think that causality is important in chemistry, but not fundamental physics? I am really trying to understand how someone could be so wrongheaded. What do they think physics is all about, if not causality?

Please tell me if I am wrong about causality. If so, I might have to post a correction, like Scott or Neil.

Aaronson lecture on Computational Physics

MIT complexity theorist Scott Aaronson posts a video lecture (download here) on "Computational Phenomena in Physics":

Scott Aaronson discusses the quest to understand the limits of efficient computation in the physical universe, and how that quest has been giving us new insights into physics over the last two decades. He explores the following questions: Can scalable quantum computers be built? Can they teach us anything new about physics? Is there some new physical principle that explains why they cannot be built? What would quantum computers be good for? Can quantum computing help us resolve which interpretation of quantum mechanics is the right one? Which systems in nature can be universal computers, and which cannot? Aaronson will end by describing a striking recent application of computational complexity theory to the black hole information loss problem.

At 37:00 he says he takes the "conservative" view that quantum computers (QC) are possible, or else "we would have to rewrite all the physics books."

For me, I like to say the single most important application of a quantum computer, even more important than a quantum simulation, is disproving the people who said it was impossible. The rest is icing.

You think his personal biases are clouding his judgment?

I say QC are impossible, and that no textbooks will have to be rewritten. I defy him to show me one quantum textbook that would need more than one page of change.

I doubt that his audience was convinced that QC is possible. He compared it to other impossibilities like faster-than-light travel, and perpetual motion machines. He also proposed that P!=NP might be a principle of physics. That is, even a QC would not be able to solve the traveling salesman problem or other NP-hard problems.

It is just as plausible that it is a principle of physics that no super-Turing computation is possible, and QC is like that perpetual motion machine or faster-than-light travel.

At 45:10, he says D-Wave has spent $150M to build a QC, but it is really no faster than a Turing machine. He explains how D-Wave could be running into physical limits that could prevent it from ever achieving its computational goals.

So why is it so hard to believe that other QC attempts will also run into physical limits?

He quotes David Deutsch as saying that QC should be possible because the computation can take place in parallel worlds of the many-worlds interpretation. But he also explains the flaw that such reasoning would lead you to believe that QC could solve NP-hard problems, and thus is more powerful than it really is.

I should not be too hard on Aaronson because at least he appears to desperately afraid that QC will turn out to be impossible. Almost everyone else refuses to admit the possibility.

Aaronson's latest post is somewhat embarrassing. He says that he is most known for a theorem in quantum computer complexity theory. He says it was easy, and he proved it in about an hour, and published it ten years ago. It is widely cited, but recently people found serious errors in the proof. To fix it, he posted a query publicly on MathOverflow, and people found clever work-arounds for his problem. He also says that some serious errors were found in other papers he wrote ten years ago. Hmmmm. I don't want to pile on here, but he is obviously not always right about everything, and he may not be right about his predictions for QC.