Shut up and think

Quantum mechanics is peculiar in that many people think that it has faulty foundations, and others do not and wonder why so many people expend so much effort philosophizing about misguided questions.

Pablo Echenique-Robba writes a paper with the title: Shut up and let me think! Or why you should work on the foundations of quantum mechanics as much as you please:

If you have a restless intellect, it is very likely that you have played at some point with the idea of investigating the meaning and conceptual foundations of quantum mechanics. It is also probable (albeit not certain) that your intentions have been stopped on their tracks by an encounter with some version of the "Shut up and calculate!" command. You may have heard that everything is already understood. That understanding is not your job. Or, if it is, it is either impossible or very difficult. Maybe somebody explained to you that physics is concerned with "hows" and not with "whys"; that whys are the business of "philosophy" --- you know, that dirty word. That what you call "understanding" is just being Newtonian; which of course you cannot ask quantum mechanics to be. Perhaps they also added some norms: The important thing a theory must do is predict; a theory must only talk about measurable quantities. It may also be the case that you almost asked "OK, and why is that?", but you finally bit your tongue. If you persisted in your intentions and the debate got a little heated up, it is even possible that it was suggested that you suffered of some type of moral or epistemic weakness that tend to disappear as you grow up. Maybe you received some job advice such as "Don't work in that if you ever want to own a house".

When people argue about whether an issue is a scientific question, then it is a good bet that it is not. For a truly scientific question, someone can propose a way for physically resolving it. Most of this quantum philosophy is just people complaining about issues that were scientifically settled 80 years ago.

R.P. Feynman supposedly said "shut up and calculate", but actually wrote in his textbook:

So we must talk about what we can predict. (Feynman, 1963a, p. 2-3)

The basis of a science is its ability to predict. To predict means to tell what will happen in an experiment that has never been done. (Feynman, 1963a, p. 2-8)

The problem has been raised: if a tree falls in a forest and there is nobody there to hear it, does it make a noise? A real tree falling in a real forest makes a sound, of course, even if nobody is there. Even if no one is present to hear it, there are other traces left. The sound will shake some leaves, and if we were careful enough we might find somewhere that some thorn had rubbed against a leaf and made a tiny scratch that could not be explained unless we assumed the leaf were vibrating. So in a certain sense we would have to admit that there is a sound made. (Feynman, 1963a, p. 2-8)

So at the present time we must limit ourselves to computing probabilities. We say "at the present time", but we suspect very strongly that it is something that will be with us forever -- that it is impossible to beat that puzzle -- that this is the way nature really is. (Feynman, 1963a, p. 10-1)

The quantum philosophers blame Feynman for being content with a lack of understanding of quantum mechanics, but that is not what he said. He is saying that quantum mechanics may be counter-intuitive, but that is because nature is counter-intuitive.

They believe that quantum mechanics would be more understandable if it were supplemented with a theory of hidden variables. But it appears that the hidden variable concept is just wrong, and contrary to nature.

Update: Lumo also attacks the above paper, and agrees with Feynman:

The discovery of the framework of quantum mechanics is the most important advance in physics of the 20th century – and probably the most groundbreaking development in the history of science – and Feynman just summarized one of its key properties. ...

And the argument that no need for a probabilistic description was found before quantum mechanics? It's partly true, partly false – the microscopic understanding of thermodynamics, statistical physics, makes it necessary to think in terms of probabilistic distributions and probabilistic interpretations of statements – but even if we decided that quantum mechanics was the first theory that showed that the probabilistic reasoning was fundamental, there wouldn't be anything wrong about it. Every important insight is discovered for the first time at some moment. Quantum mechanics is the first scientific framework that makes probabilities fundamental. It's also the last one because there won't be any non-quantum framework in physics, ever.

I do not agree with that Feynman emphasis on probabilities.

Quantum does not contradict probability laws

Statistician Andrew Gelman writes:

Classical probability does not apply to quantum systems (causal inference edition) ...

If you recall your college physics, you’ll realize that the results of the two-slit experiment violate the laws of joint probability, ...

I discuss this in my linked blog post. But, in brief, the intuitive application of probability theory to the 2-slit experiment is that, if y is the position of the photon and x is the slit that the photon goes through, that p(y) = p(y|x=1)p(x=1) + p(y|x=2)p(x=2). But this is not true. As we all know, the superposition works not with the probabilities but with the probability amplitudes. Classical probabilities don’t have phases, hence you can just superimpose them via the familiar law of total probability. Quantum probabilities work differently.

This seems to be a widespread misconception. As Tim Maudlin explains in the comments, there is no contradiction with classical probability theory. In quantum mechanics, a photon is not a classical particle, but also has wave properties. The photon history is not just the sum of two particle possibilities. It can also be a wave that passes thru both slits at once.

The double slit experiment does show that light has wave properties. Everyone has agreed to that since 1803. If you deny that light is a wave that can go thru both slits at once, then you can get a contradiction. That is another way of saying the same thing. But the contradiction is with the classical particle theory of light, and not with probability theory.

There are people who have tried to make sense of quantum mechanics by using quantum logic or some modification to the laws of probability. These approaches have never worked.

I can't blame Gelman too much. There are a lot of physicists who, like Einstein, really want to believe that quantum mechanics is really a theory of imperfect info about hidden variables. It is not.

He argues:

Sure, a physical experiment can violate a mathematical law. The classic example is, if in a universe with closed curvature, you construct a large enough triangle, its angles will not add up to 180 degrees. Another classic example is that, for various particles, Boltzmann statistics do not apply, instead you have to use Fermi-Dirac or Bose-Einstein statistics. Boltzmann statistics is a mathematical probability model that does not apply in these settings. Another example is, in the two-slit experiment, p(A) does not equal the sum over B of p(A|B)p(B). In all these cases, you have a mathematical model that works (or approximately works) in some areas of application but not others. The math is not wrong but it does not apply to all settings.

This is silly. Yes, the math of flat space does not necessarily apply to curved space. Probability is a funny subject with multiple interpretations, but none of them are contradicted by light having wave properties.

He insists:

The 2-slit data indeed violate the laws of joint probability. I learned about this in physics class in college. In quantum mechanics, it is the complex functions that superimpose, not the probabilities. It is the application of the mathematics of wave mechanics to particles. The open question is whether it might make sense to apply wave mechanics to macroscopic measurements.

I would be interested in any textbooks say it wrong in this way.

Surely it must seem odd that we have a notion of probability that works in all situations except quantum mechanics, and we have some other notion that applies to quantum mechanics, but no one has figured out a way to make that probability notion apply to anything other than quantum mechanics. The answer is that quantum mechanics uses the same logic and probability that everyone else does.

Maudlin writes:

It ought to cause some pause that Feynman himself makes exactly this erroneous claim about the 2-slit experiment in the Lectures. Feynman does not mention locality, unitarity, or causality. He makes a straight claim about the data, based on a bad argument—exactly the argument I was attributing to Andrew. So if Feynman screwed this up, it would not be odd of many other physicists do too.

Feynman was a big advocate of particle interpretations of quantum mechanics. So he thought that the strangest part of quantum mechanics is the experiments showing wave behavior, like the double-slit experiment.

LHC blows string theory out of the water

I intended to post this 3 months ago, but somehow I did not.

Physicist Matt Strassler writes:

Over the weekend, someone said to me, breathlessly, that they’d read that “Results from the Large Hadron Collider [LHC] have blown string theory out of the water.” ...

Now what’s so silly about this notion that the LHC has ruled out string theory is that the whole reason a lot of people hate string theory is that it doesn’t make any testable predictions! So obviously you can’t rule it out with current experiments… that would require testable predictions!

Be sure and read the knowledgeable comments. There are pretty much two possibilities -- that string theory makes no testable predictions, and that the LHC has disproved the theory.

Strassler defends string theory, but is not a string theorist himself. For a hard core enthusiast and hater of anyone else, see Lumo:

When Michio Kaku or even Brian Greene were explicitly or at least implicitly promising you time machines that will produced because of advances in string theory, they oversold the practical power of string theory. When someone would "promise" that it's guaranteed that an experiment that has already been performed would have to observe some beyond-the-Standard-Model physics, they surely oversold the "urgency" of string-theoretical predictions as well – simply because no BSM physics has been observed yet.

However, when Edward Witten "guessed" that the single right string theory compactification capable of predicting all particles' properties would be found within weeks back in 1985, it was just a guess that turned out to be overly optimistic but that reflected this top scientist's best judgement at the moment. There were very good reasons to think so.

Lumo brags about how well the theory works, but cites no published papers to back it up.

New hype for quantum crypto

The Economist magazine reports:

In 1964 Bell proposed a test to settle once and for all whether quantum mechanics really is as weird as it famously appears to be, in that it allows for instantaneous communication between two particles, no matter how far apart they are, on condition that they were once entangled together in the same place. The short answer, as experiments carried out over subsequent decades have shown, is yes, it is.

No that is not correct. The theory and experiments show a correlation between measurements of the particles, but correlation does not imply causation. There is a Nobel Prize waiting for anyone who can show instantaneous communication, but no one ever has.

Bell’s test, however, also led physicists like Dr Ekert to a remarkable insight: made sufficiently sensitive the Bell test could be used to guarantee perfectly secure communication — even if the equipment used to send and receive those communications had been sold to you by a manufacturer subverted by your enemies.

More nonsense. Quantum cryptography does not even need entanglement. Yes, it can be done with entanglement, but there is no advantage to doing so.

None of these quantum crypto systems have ever been good for anything. The only argument for them is the belief that a physical assumption is somehow better than a mathematical assumption. But it is not.

Einstein's miraculous year

The paper Einstein's Miraculous Year, recently put online, has glowing praise for Albert Einstein and adds:

Many scientists attempted to reconcile Newtonian mechanics with the Maxwell theory, the most prominent being Lorentz, Fitzgerald and Poincare. But their efforts were unconvincing, and ultimately unsuccessful. The definitive answer came with Einstein’s work in 1905, where he re-analyzed the nature of space and time. They are not individually absolute and the same for everybody, as Newton had visualized; rather, it is only the combined space-time continuum which is common to all, but each inertial observer divides it up into a space and a time in her own way.

This is nonsense. That understanding of space-time comes almost entirely from Lorentz, Fitzgerald, and Poincare, and not Einstein. The paper is not able to give a single example of any aspect of relativity where Einstein's work was superior.

Big-shots losing faith in string theory

String theorist Lubos Motl

Lenny Susskind's most eye-catching comments were summarized by Matt Strassler as follows:

In fact, we heard this from none other than Lenny Susskind (famous for his efforts, along with those of ‘t Hooft and many others, to oppose Hawking’s view that black holes require no revision of quantum mechanics, but now himself deeply puzzled by the firewall problem — the failure of what Susskind called `complementarity’). Susskind stated clearly his view that string theory, as currently understood, does not appear to provide a complete picture of how quantum gravity works.

Bizarre. And it's not just Susskind; Joe Polchinski said very similar things recently. ...

Again, let me point out that the error that Susskind, Polchinski, and others were doing in recent years is a special case of Einstein's error in the EPR papers. Einstein was assuming that once the two parts of an entangled photon pair separate, they must have objective properties in the classical sense which, via Bell's-theorem-like reasoning (if I use the equivalent "newer" toolkit), implies that the correlations can't be too large or too universal. In the same way, the "firewall problem" advocates think that the properties of a black hole such as its positions may be treated as classical observables once the black hole is created. While Einstein (and EPR) would think about small systems and pairs of particles, their point was much more general and the "firewall problem" champions' mistake (or two related mistakes, in the counting done above) is not just analogous but it is a special case of Einstein's error.

As you can see, I think that most of these misunderstandings, especially by the big shots, boil down to their subtle (?) misunderstandings of quantum mechanics, more precisely attempts to treat certain questions classically even though it is totally paramount to treat them quantum mechanically to avoid "paradoxes" they want (?) to avoid in their final understanding of quantum gravity.

Lumo defends quantum mechanics and string theory, of course.

Peter Woit has more detail on the failure of string theory.

With all the good reasons to give up on string theory, the black hole firewall paradox is an odd one. They all seem to have an Einsteinian preconception of a complete unified theory.

Physicist Matt Strassler writes:

Over the weekend, someone said to me, breathlessly, that they’d read that “Results from the Large Hadron Collider [LHC] have blown string theory out of the water.” ...

Now what’s so silly about this notion that the LHC has ruled out string theory is that the whole reason a lot of people hate string theory is that it doesn’t make any testable predictions! So obviously you can’t rule it out with current experiments… that would require testable predictions!

Be sure and read the knowledgeable comments. There are pretty much two possibilities -- that string theory makes no testable predictions, and that the LHC has disproved the theory.

All the string theorists seem to have believed that there ought to be supersymmetric (SUSY) particles in the range of energies accessible to the LHC. The LHC has not found any such particle, and is systematically eliminating the possibility. There are different reasons for believing in SUSY. For some of those reasons, the LHC should have found a SUSY particle.

Strassler defends string theory, but is not a string theorist himself. For a hard core enthusiast and hater of anyone else, see Lumo:

When Michio Kaku or even Brian Greene were explicitly or at least implicitly promising you time machines that will produced because of advances in string theory, they oversold the practical power of string theory. When someone would "promise" that it's guaranteed that an experiment that has already been performed would have to observe some beyond-the-Standard-Model physics, they surely oversold the "urgency" of string-theoretical predictions as well – simply because no BSM physics has been observed yet.

However, when Edward Witten "guessed" that the single right string theory compactification capable of predicting all particles' properties would be found within weeks back in 1985, it was just a guess that turned out to be overly optimistic but that reflected this top scientist's best judgement at the moment. There were very good reasons to think so.

Lumo brags about how well the theory works, but cites no published papers to back it up.

Theoretical physics reached ultimate catastrophe

A Perimeter Institute pitch said:

Theoretical physics is at a crossroads right now…In a sense we’ve entered a very deep crisis.

You may have heard of some of these models…There’ve been grand unified models, there’ve been super-symmetric models, super-string models, loop quantum gravity models… Well, nature turns out to be simpler than all of these models.

If you ask most theorists working on particle physics, they’re in a state of confusion.

The extensions of the standard model, like grand unified theories, they were supposed to simplify it. But in fact they made it more complicated. The number of parameters in the standard model is about 18. The number in grand unified theories is typically 100. In super-symmetric theories, the minimum is 120. And as you may have heard, string theory seems to predict 10 to the power of 1,000 different possible laws of physics. It’s called the multiverse. It’s the ultimate catastrophe: that theoretical physics has led to this crazy situation where the physicists are utterly confused and seem not to have any predictions at all.

That is the problem with all these theories that aim to replace the Standard Model. The main reason for their existence is that they are supposed to simplify physics, but they are actually much more complicated. The Standard Model is by far the simplest model that has any similarity to reality.

A comment said:

My guess is that the crucial insight will be more philosophical/interpretational than mathematical. Likewise, the Lorentz transformations were discovered and analyzed in the context of electromagnetism almost 2 decades before Einstein came up with special relativity.

We should get the History of Lorentz transformations correct, if it is going to be used as an excuse for useless theoretical investigations.

Lorentz was not just pursuing some mathematical exercise that was detached from the physical world. From the very start, he and FitzGerald were using the transformations to give a physical explanation for the Michelson-Morley experiment. It is true that Einstein was mainly regurgitating ideas that had been published many years earlier.

I think that the commenter was trying to say that 20 years of mathematical theorizing could be justified by some Einstein genius finally figuring out how to apply it to physics. But the relativity history is more nearly the opposite. After 20 years of applying relativity to physics, the consensus among historians is that Einstein used postulates instead of experimental evidence.

Tony Rothman defends Einstein

A reader writes:

Dear Roger,
I just discovered your writings recently even though your last name of course is known to me. I stumbled upon Dark Buzz and things have looked very differently for me after reading a bunch of your columns in Dark Buzz! I then read an essay by this Princeton fellow, Tony Rothman, about Einstein and Poincare. I was delighted that I was able to follow his argument and somewhat critically because of your essays. So I wrote him and told him that I had read his essay. However, I didn't get a clear idea of why Poincare should be dismissed as the founder of relativity as opposed to Einstein. That was he saying that because Einstein came along and stitched so to speak all of these disparate notions together, he should claim the throne. I also told him that Einstein's friend, Maurice Solovine, said they read Poincare thoroughly, something about how his writings left them breathless.

I know you are busy but here is what he wrote me. May I ask you to comment if you have the time. Like the character in Sherwood Anderson's short story, I Want To Know!

Mr. Larkin,
I'm not quite sure what you're looking for. It is quite clear that at the time Einstein couldn't have known about Poincare's paper (although he had read his book Science and Hypotheses) because the two wrote their papers within weeks of each other. The main point is that relativity is a physical theory, not just a collection of equations. Poincare had all the equations, but he failed to understand that they all resulted from two physical postulates: the constancy of the speed of light and the principle of relativity. Poincare just wrote down all these equations, postulated separately. You are correct that Poincare enunciated the principle of relativity before Einstein, but he did not fully appreciate its consequences. (He was mostly concerned with the behavior of electrons, not space and time. In fact his paper is called, "On the Dynamics of Electrons.") It is possible that if Einstein hadn't done it, Poincare would have eventually attached a transparent physical meaning to all his equations, but he didn't do that. Mathematically, the two theories are equivalent. Einstein certainly could have been more gracious to Poincare later in life.

Tony Rothman
Physics Department
Princeton University
Jadwin Hall ...
homepage: http://www.physics.princeton.edu/~trothman/

Yes, it is baffling why people go to such great lengths to credit Einstein, and to badmouth rivals. I wrote a book about it.

Rothman has published similar comments, so I don't think he'll mind being quoted here.

I consider Rothman's points individually.

I'm not quite sure what you're looking for.

Just some objective evidence that Einstein had some part of relativity before his rivals.

It is quite clear that at the time Einstein couldn't have known about Poincare's paper (although he had read his book Science and Hypotheses) because the two wrote their papers within weeks of each other.

He is referring to their 1905 papers. Poincare published on clock synchronization, relativity principle, E=mc2, and Lorentz local time years earlier, and Einstein could have relied on that.

Poincare's 1905 results were announced in Paris in May 1905 (I think), and a 5-page summary was published published on June 5, 1905 in Comptes rendus, a leading European science journal. It was immediately sent to the library where Einstein studied, a few weeks before Einstein submitted his first relativity paper on June 30, 1905. So Einstein certainly could have known about much of what Poincare did. See History of special relativity.

The main point is that relativity is a physical theory, not just a collection of equations. Poincare had all the equations, but he failed to understand that they all resulted from two physical postulates: the constancy of the speed of light and the principle of relativity. Poincare just wrote down all these equations, postulated separately.

This is backwards. The consensus among Einstein historians is that Einstein was the one who ignored the physical evidence like the Michelson-Morley experiment. In the words of Lorentz, Einstein simply postulated what his predecessors had deduced from theory and experiment. So it was Lorentz and Poincare who had the more physical interpretation.

The term "postulate" is a math term, not a physics term. If the complaint is about treating the equations mathematically, then the complaint should be against whoever was doing the postulating, and that was Einstein.

You are correct that Poincare enunciated the principle of relativity before Einstein, but he did not fully appreciate its consequences.

Poincare spent about 5 years convincing Lorentz of the consequences of the relativity principle. What did he miss?

(He was mostly concerned with the behavior of electrons, not space and time. In fact his paper is called, "On the Dynamics of Electrons.")

The title of Einstein's famous 1905 paper was On the Electrodynamics of Moving Bodies.

It is possible that if Einstein hadn't done it, Poincare would have eventually attached a transparent physical meaning to all his equations, but he didn't do that.

Poincare got the 4-dimensional non-Eudlidean geometry of spacetime, and the covariance of Maxwell's equations for electromagnetism. That is the essence of special relativity, as it was understood in textbooks from about 1910 on. Einstein did not have any of that.

Mathematically, the two theories are equivalent. Einstein certainly could have been more gracious to Poincare later in life.

There is nothing Einstein could have said about Poincare, without making himself look bad. Einstein lied about the origin of relativity his entire life, not just his later life.

Rothman is just showing the standard Einstein idol worship. No one wants to admit that the greatest paper from the 20th century's greatest physicist was not even the best paper written on the subject that year. It takes some imagination to believe that Poincare somehow got all the equations correct without understanding what he was doing.

Rothman would be more credible if he acknowledged what Poincare got right, and pointed to some shortcoming in his papers. Instead the Poincare critics just make vague arguments that do not make any sense.

Einstein hated referees

A reader recommends an article by physicist John Moffat:

It is interesting to note that the most famous physicist of the 20th century, Albert Einstein, only faced the anonymous peer-review system once, for a 1936 paper he wrote, with his collaborator Nathan Rosen, disputing the existence of gravity waves in general relativity, Einstein's famous theory of gravitation. This paper, considered controversial at the time, was submitted to the Physical Review, the premier American physics journal then and now, and was duly rejected by the anonymous referee. Einstein wrote an angry letter to the editor, complaining that he had not been warned that he would have to face an anonymous review system when he submitted the paper for publication, and declaring that he would never submit a paper to Physical Review again. He was good to his word, sending future papers only to journals in which the editor made the decision to accept or reject papers. Unfortunately, there are no such journals remaining today. An obvious question arises: Would Einstein have succeeded so phenomenally as a physicist with his typically iconoclastic approach to physics, in which he was usually outside the box of mainstream physics of the day, if he had been subjected to the peer-review system of publication as it exists today? In my opinion, the answer is no.

That Einstein paper was rejected for good reason, as the anonymous referee wrote a detailed analysis showing that it was wrong. While Einstein complained about it, he ultimately decided that the referee was right, and stole his analysis for the revision that was published.

Very few of Einstein's famous papers were really outside the box. His special relativity papers were affirming the theory of the leading physicists of the day.

A large part of Einstein's success was his ability to steal the ideas of others and publish them as his own. Perhaps better refereeing and editing would have forced him to cite the previous work in his papers. If that had happened, he would not have been such a phenomenal success.

Most of Einstein's later papers on unified field theory were garbage, unfit for publication.

Maffat has his own complaints about refereees. He got his start by writing letters to Einstein in the 1950s. He has published a number of far-fetched theories, but none of them have any experimental verification, as far as I know.

The reader has his own theories for going faster than light. I do not see how that is possible.

The special theory is more fundamental

Physics bloggers Sabine Hossenfelder and Lubos Motl quibble about the definition of special relativity (SR). They agree on this:

Is SR applicable to phenomena in which objects accelerate?

The answer is, of course, Yes. Special relativity would be useless if it were requiring all objects to move without any acceleration; after all, almost everything in the real world accelerates, otherwise the world would be useless. The correct claim similar to the proposition above is that special relativity has the same, simpler form in coordinate systems associated with non-accelerating observers. But that doesn't mean that we can't translate the predictions of a special relativistic theory to an accelerating frame. Yes, we can. It's as straightforward as a coordinate transformation. Fictitious forces will appear in the description. All of them are fully calculable.

The earliest papers on SR considered accelerating electrons, so there is no good reason to exclude acceleration.

Acceleration might be excluded because Einstein's 1905 paper had a section on kinematics, and that is sometimes regarded as the simplest and purest version of the theory. With that view, general relativity (GR) is the real theory, and SR is just a special and idealized case of little practical significance.

As Lubos explains, SR is the big theory. Its change to physics was broad and deep. GR is just the logical extension to gravity. GR is a lot more difficult mathematically, but most of the physics is in SR.

Book on big questions in science

A UK newspaper asks The 20 big questions in science, based on a new book. The list is not too bad, but some are silly:

8 Are there other universes?

Our universe is a very unlikely place. Alter some of its settings even slightly and life as we know it becomes impossible. In an attempt to unravel this "fine-tuning" problem, physicists are increasingly turning to the notion of other universes. If there is an infinite number of them in a "multiverse" then every combination of settings would be played out somewhere and, of course, you find yourself in the universe where you are able to exist. It may sound crazy, but evidence from cosmology and quantum physics is pointing in that direction.

11 What's so weird about prime numbers?

The fact you can shop safely on the internet is thanks to prime numbers – those digits that can only be divided by themselves and one. Public key encryption – the heartbeat of internet commerce – uses prime numbers to fashion keys capable of locking away your sensitive information from prying eyes. And yet, despite their fundamental importance to our everyday lives, the primes remain an enigma. An apparent pattern within them – the Riemann hypothesis – has tantalised some of the brightest minds in mathematics for centuries. However, as yet, no one has been able to tame their weirdness. Doing so might just break the internet.

No, this is not a scientific question and a solution will not affect the internet.

17 What's at the bottom of a black hole?

It's a question we don't yet have the tools to answer. Einstein's general relativity says that when a black hole is created by a dying, collapsing massive star, it continues caving in until it forms an infinitely small, infinitely dense point called a singularity. But on such scales quantum physics probably has something to say too. Except that general relativity and quantum physics have never been the happiest of bedfellows – for decades they have withstood all attempts to unify them. However, a recent idea – called M-Theory – may one day explain the unseen centre of one of the universe's most extreme creations.

No, relativity teaches that we can never know what happens inside a black hole. M-theory cannot tell us anything about it.

20 Is time travel possible?

Time travellers already walk among us. Thanks to Einstein's theory of special relativity, astronauts orbiting on the International Space Station experience time ticking more slowly. At that speed the effect is minuscule, but ramp up the velocity and the effect means that one day humans might travel thousands of years into the future. Nature seems to be less fond of people going the other way and returning to the past, however some physicists have concocted an elaborate blueprint for a way to do it using wormholes and spaceships. It could even be used to hand yourself a present on Christmas Day, or answer some of the many questions that surround the universe's great unknowns.

Time travel to the past is science fiction. Simple thought experiments show that the concept does not make sense.

Paradigm argument for quantum interpretation

Papers on crackpot physics often start by invoking Kuhnian paradigm shifts, Galileo, and Einstein.

A new paper on a peculiar interpretation of quantum mechanics, Rovelli's relational quantum mechanics, monism and quantum becoming, starts:

According to Kuhn (1996, p. 85), a radical change in our physical worldview is not just due to the invention of a mathematical formalism or to new empirical information coming from novel experiments, but it also implies a thorough modification of the fundamental concepts with which we interpret the world of our experience. This is particularly evident in the scientific revolution ushered by Galileo (Koyré 1978), which consisted essentially in the discovery of the equivalence between uniform motion and rest, two notions that had always been sharply contrasted, but whose indistinguishability is essential to attribute our planet a counterintuitive state of motion.

The same moral applies to Einstein’s Special Theory of Relativity (STR). Not by chance, Rovelli’s relational interpretation of quantum mechanics (Rovelli 1996, 1998) draws inspiration from the latter theory, by correctly claiming that Einstein’s 1905 paper did not change the existing physics, but provided a new interpretation of an already available formalism. As is well-known, this interpretation was obtained via a critique of an implicit conceptual assumption - absolute simultaneity - that is inappropriate to describe the physical world when velocities are significantly close to that of light. It is important to note that it was only thanks to the abandonment of such an assumption – that depends on the “manifest image of the world” (Sellars 1962), and in particular on that belief in a cosmically extended now that percolated in Newton’s Principia - that Einstein could postulate the two axioms of the theory, namely the invariance of the speed of light from the motion of the source and the universal validity of the principle of relativity. What is relevant here is to recall that not only do these axioms imply the relativization of velocity, already theorized by Galilei, but also that of the spatial and temporal intervals (separately considered), a fact that became particular clear with Minkowski (1908) geometrization of the theory.

The historical theme of the relativization of quantities that were previously regarded as absolute is central also in Rovelli’s relational approach to quantum mechanics (RQM), whose metaphysical consequences, strangely enough, have not yet been explored in depth,

Because of arguments like this, we ought to get the history right. The above history is confused.

It is true that Einstein's 1905 paper did not change existing physics. But it did not provide a new interpretation either. That was done by Poincare in 1905, and extended by Minkowski in 1908. Einstein's theory was called the Lorentz-Einstein theory, and neither Einstein nor anyway else saw any significant difference between Lorentz's and Einstein's interpretation.

The author is promoting a new interpretation as a Kuhnian paradigm shift. The advantage of this is that no evidence, experiment, or logical argument is needed. No change to existing physics is needed. According to Kuhn, scientists jump on these shifts as big fads, as the new paradigm is not comparable to the old.

Galileo's main argument for the motion of the Earth was that the motion caused the tides. If he had accepted the relativity of motion, he never would have had his dispute with the Catholic Church. The Pope even asked him to write a book that describes theories of the Earth in motion and at rest, without advocating either as correct. Galileo wrote a book making fun of the Pope as Simplicio, and ridiculed the idea that the Earth could be at rest.

Causalist-Statisticalist Debate

Physicists debate whether the laws of physics are deterministic or not. My impression is that most believe that quantum mechanics has proved that nature is inherently random, while a few (like Einstein) believe in determinism and that quantum mechanics must be replaced by a deterministic theories. I posted some polls here. I believe both view are wrong, as explained in my FQXi essay.

The July 24 episode of Through the Wormhole on the Science TV channel argued that we do not have free will.

A similar debate occurs in biology. Darwin was a determinist, and did not appreciate statistics. Evolution is usually described today in terms of random mutations and natural selection. A new paper on The Early History of Chance in Evolution says:

For those who have been following contemporary philosophy of biology in the last decade, the novel question I posit here will not seem so novel after all. Precisely the same worry about the relationship between statistical theories and biological processes has been hotly debated, under the guise of the “causalist/statisticalist debate.” On the one side, we have “causalists,” who argue that natural selection and genetic drift describe causally efficacious processes (e.g., Brandon, 1978; Mills and Beatty, 1979; Hodge, 1987; Stephens, 2004; Ramsey, 2006; Abrams, 2009; Otsuka et al., 2011). They are opposed by the “statisticalists,” who claim on the contrary that these theories are merely statistical summaries of genuinely causal events at the level of the individual organism (e.g., Matthen and Ariew, 2002; Walsh et al., 2002; Ariew and Lewontin, 2004; Krimbas, 2004; Walsh, 2007; Ariew and Ernst, 2009; Walsh, 2010).

Here is an example of confusion about randomness:

This modern view was summarised by one of the greatest ever advocates for neo-Darwinism, Richard Dawkins, when in an article in New Scientist magazine he wrote, ‘Natural selection is quintessentially non-random, yet it is lamentably often miscalled random. This one mistake underlies much of the sceptical backlash against evolution. Chance cannot explain life. Design is as bad an explanation as chance because it raises bigger questions than it answers. Evolution by natural selection is the only workable theory ever proposed that is capable of explaining life, and it does so brilliantly.’

Dawkins disagreed with S.J. Gould on this and other points. Here is a recent blog with a confused argument about whether mutations are random in biological evolution. I listed other confusions about randomness last week.

Ball State censors intelligent design

One topic is being censored from science:

Ball State University president Jo Ann Gora announced that the school would no longer teach intelligent design in science classes following a complaint about the curriculum at the public university.

In a statement released Wednesday, Gora said "intelligent design and creation science do not qualify as science," and that it would no longer be a part of the university's science classes.

"Intelligent design is overwhelmingly deemed by the scientific community as a religious belief and not a scientific theory,” Gora said. “Therefore, intelligent design is not appropriate content for science courses.” ...

"Incredibly, Gora insists that her university's 'commitment to academic freedom is unflinching,' even while she imposes a gag order on science faculty who think there is evidence of intelligent design in nature," West wrote on the institute's blog. "Memo to President Gora: Academic freedom was designed to protect dissenting and unpopular views among faculty."

Apparently intelligent design was one of many topics in an interdisciplinary course on "The Boundaries of Science". The supplementary reading list had books for and against intelligent design.

I have no idea whether this was a worthwhile course, but I wonder about all the other unscientific topics being taught in physics departments today. In particular, I wonder about anthropic principle, fine-tuning, many worlds, other multiverses, string and M-theory, black hole firewalls, Laplace's demon, quantum cryptography, scalable quantum computing, Bohmian mechanics and other nonlocal theories, hidden variable theory, Boltzman brains, cold fusion, intelligent extraterrestial life, supersymmetry, quantum gravity and other unified field theories, etc.

And of course other departments are loaded with pseudoscientific courses on Sigmund Freud, Karl Marx, Margaret Mead, Immanuel Kant, Jacques Derrida, Stephen Jay Gould, feminist studies, etc. If I were Gora, I would be more interested in getting rid of some of those classes.

Physics is the study of symmetry

Physicist Dave Goldberg writes in SLate, plugging his book:

The history of physics, in fact, is a marvel of using simple symmetry principles to construct complicated laws of the universe. Einstein quite famously was able to construct his entire theory of special relativity—the idea that ultimately gave us E=mc² and explained the heat of the sun—from nothing more than the simple idea that there was no measurable distinction to be made between observers at rest and observers in uniform motion.

The long-overlooked 20^th-century mathematician Emmy Noether proved the centrality of symmetry as a physical principle. And what is symmetry—at least as scientists understand it? The mathematician Hermann Weyl gave perhaps the most succinct definition:

“A thing is symmetrical if there is something you can do to it so that after you have finished doing it, it looks the same as before.”

Which sounds innocuous enough until you realize that if the entire universe were made symmetric, then all of the good features (e.g., you) are decidedly asymmetric lumps that ruin the otherwise perfect beauty of the cosmos.

The seemingly simple idea that the laws of the universe are the same everywhere in space and time turns out to yield justification for long-observed properties of the universe, like Newton’s first law of motion (“An object in motion stays in motion,” etc.) and first law of thermodynamics (the conservation of energy).

As the Nobel laureate Phil Anderson put it:

“It is only slightly overstating the case to say that physics is the study of symmetry.”

I do agree that the application of symmetry to physics is the biggest and most pervasive accomplishment of 20th century physics.

So who introduced symmetry to physics? Noether's theorem, published in 1918. Hermann Weyl invented gauge theory, and applications of group theory to quantum mechanics.

Einstein did notice in 1905 that the inverse to a Lorentz transformation is a Lorentz transformation. Lorentz credited Einstein for detailing this. This fact would seem to be implicit in Lorentz's explanation of the Michelson-Morley experiment, but Lorentz had not stated or proved it.

The mathematics of symmetry was central to Henri Poincaré's 1905 relativity paper, and that is largely why he deserves the credit for creating special relativity.

The relativity principle and Lorentz group were both named by Poincare. The relativity principle expresses the symmetry between different moving frames of reference, and was defined by Poincare at the 1904 St. Louis Worlds Fair as:

The principle of relativity, according to which the laws of physical phenomena should be the same, whether for an observer fixed, or for an observer carried along in a uniform movement of translation; so that we have not and could not have any means of discerning whether or not we are carried along in such a motion.

Einstein took this as one of his postulates in 1905. The Lorentz group is the mathematical expression of those symmetry operations, and Poincare was the first to point out that it was a symmetry group.

These facts are widely acknowledged, even by Einstein scholars. What is not so well known is how much further Poincare took his symmetry analysis. He used the symmetry group to define a non-Euclidean geometry on 4-dimensional spacetime. He proved that Maxwell's equeations for electromagnetism respected those symmetries, and thus could be geometrically realized on spacetime. He looked for a law of gravity that was similarly invariant under the symmetries. For decades afterwards, physicists followed Poincare's example, and used Lorentz invariance as a guiding principle for finding laws of physics.

Einstein has none of this, and showed no sign of even understanding it until hafter Minkowski spelled in out more clearly in 1908. The closest he got was to understand that the Lorentz transformations in one particular direction formed a 1-dimentional group, altho he probably got that from Poincare as Einstein had access to Poincare's first 1905 paper before submitting his own.

Noether, Weyl, and Poincare are three of the most important theoretical physicists of the 20th century. These three are primarily known as mathematicians who only occasionally dabbled in physics, but their theoretical physics was some of the most profound of the time.

This is all detailed in my book, How Einstein Ruined Physics.