Wednesday, October 31, 2012

Einstein agreed with Lorentz

Sometimes Einstein books give the impression that he created a new relativity theory in 1905, and it was only later noticed that Lorentz had the same formulas earlier. In fact, the prevailing opinion in 1905 was the Einstein's theory was the same as Lorentz's. Neither Einstein, nor Lorentz, nor anyone said that there was any significant difference between Lorentz's and Einstein's theories.

Galina Weinstein has a new paper on Variation of Mass with Velocity: "Kugeltheorie" or "Relativtheorie":
Kaufmann concluded, from 1905 onwards, that the mathematical expression proposed by Alfred Bücherer could also be in accord with his measurements and that one could not definitively decide between that expression and that of Abraham as it was derived from his experiments. In the same paper, Kaufmann noted that the two theories of Lorentz and Einstein yielded the same equations of motion for the electron, and he gave the first clear account of the basic theoretical difference between Lorentz's and Einstein's views.29

In the annual general meeting of the German Society of Scientists and Physicists (Deutsche Gesellschaft der Naturforscher und Ärrzte) in Stuttgart, on the 19th of September 1906, scientists discussed three world pictures, the electromagnetic theories of Abraham, Bücherer, or the other picture based on Lorentz and Einstein's "Principle of Relativity". A discussion revolving around the foundations of physics was held after Planck's lecture. The participants in the discussion were, among others, Kaufmann, Planck, Bücherer, Abraham, Arnold Sommerfeld and others. Scientists did not yet distinguish between Lorentz's theory and Einstein's theory. There were two main theories relating to the electron: Abraham's and Lorentz-Einstein's. An inclination towards Einstein and Lorentz's theories, on the part of scientists such as Planck and Max Laue, was evident.
Lorentz did credit Einstein with having a slightly different approach, but neither expressed any differences in the conclusions, except for minor technical errors. Lorentz said that the chief difference was that Einstein postulated what he had proved. No one saw much difference until several years later when Minkowski's approach became popular, and Einstein adopted it.

Walter Kaufmann's 1906 paper says:
Then, a work by H. A. Lorentz[13] appeared in the year 1904, in which the attempt was made to remove the difficulties which sill existed in the optics of moving bodies, by somewhat modified fundamental assumptions on the electron and also on the molecular forces acting in-between the material body-particles. ... Lorentz now showed, that one could arrive at such a result, when it is assumed that the dimensions of all physical bodies, including their individual molecules and electrons, would change their shape in a very specific way with velocity ...

It is now very remarkable, that, starting from quite different [492] assumptions, Einstein[17] recently arrived at results, which are in agreement with those of Lorentz concerning the consequences accessible to observation, though in which the previously mentioned difficulties of epistemological kind have been avoided. Einstein introduced the principle of relative motion, at least as regards translations, as a postulate. He thus places the theorem at the top, that physical phenomena observable in any rigid system, must be independent from whether the system (together with the observer) is moving relatively to any other system. ... The results accessible to observation are thus the same with respect to both authors; however, while Lorentz only shows that his hypotheses lead to the desired result without excluding that the same can also be achieved in another way, it is shown by Einstein, that when the desired result, namely the principle of relative motion, is placed at the top of the whole of physics, then the kinematics of the rigid [493] body must necessarily be changed in the way stated, and that the equations of electrodynamics[18] must assume the form stated by Lorentz. ...

The measurement results are not compatible with the fundamental assumption of Lorentz-Einstein.
Note that Kaufmann is trying to refute Lorentz and Einstein, and considers refuting one the same as refuting the other. Most of the paper just mentions Lorentz without Einstein, such as the section titled, "Comparison with the theories of Abraham, Lorentz and Bucherer."

Kaufmann appears to be not aware of Poincare's theory, or how Einstein got the relativity postulate from Poincare.

Kaufmann says Einstein "places the theorem at the top". That is his version of Lorentz's famous statement that Einstein simply postulates what we have deduced. I give a more technical explanation of what this means.

Kaufmann's argument is a little misleading where he says that Einstein showed "that the equations of electrodynamics must assume the form stated by Lorentz." This sounds like a strong statement, but if you read the footnote, Einstein assumes Maxwell's equations in the rest frame, and hence in the moving frame via the relativity principle. So Einstein is really postulating the equations of electrodynamics. It was Lorentz and Poincare who tried to prove the equations for the moving frame, assuming the equations for the rest frame.

Monday, October 29, 2012

Dyson trashes multiverse and philosophy

Famous mathematician and physicist Freeman Dyson writes in the NY Review of Books:
The essence of quantum physics is unpredictability. At every instant, the objects in our physical environment — the atoms in our lungs and the light in our eyes — are making unpredictable choices, deciding what to do next. According to Everett and Deutsch, the multiverse contains a universe for every combination of choices. There are so many universes that every possible sequence of choices occurs in at least one of them. Each universe is constantly splitting into many alternative universes, and the alternatives are recombining when they arrive at the same final state by different routes. The multiverse is a huge network of possible histories diverging and reconverging as time goes on. The “quantum weirdness” that we observe in the behavior of atoms, the “spooky action at a distance” that Einstein famously disliked, is the result of universes recombining in unexpected ways.

According to Deutsch, each of us exists in the multiverse as a crowd of almost identical creatures, traveling together through time along closely related histories, splitting and recombining constantly like the atoms of which we are composed. ...

Opinions vary widely concerning the proper limits of science. For me, the multiverse is philosophy and not science. Science is about facts that can be tested and mysteries that can be explored, and I see no way of testing hypotheses of the multiverse. Philosophy is about ideas that can be imagined and stories that can be told.
He is right. The multiverse is not science, as I have explained.

Not sure what he means by "unpredictability". I argued below that probability is not the essence of quantum physics, and I got some criticisms in the comments. You can read the exchange, and make up your own mind.

Dyson ends by trashing modern philosophy:
When and why did philosophy lose its bite? How did it become a toothless relic of past glories? ... As a result, science grew to a dominant position in public life, and philosophy shrank. Philosophy shrank even further when it became detached from religion and from literature. ...
Philosophers of science get science badly wrong, as I explain in my book. Other physicists have opposed philosophy. They will continue to have no respect for philosophy as long as all the philosophers deny that physicists are seeking truth and making progress.Cuisinart Smart Stick Stainless Steel Hand Blender & Chopper (Google Affiliate Ad)

Wednesday, October 24, 2012

Revelation from Einstein's brain

A Wired magazine reporter explains to NPR radio:
INSKEEP: So as you're talking, I'm thinking about cloud computing, the Internet cloud. And many of us are getting used to this idea that if we have an email account, it might not be saved in the machine where we are at; it's going off somewhere. But once you actually got in to look at one of these places and hear it, feel it, did it change your perceptions of what's going on in the world when you went back to your computer screen at home?

LEVY: It actually did. You know, many, many years ago I went on a journalistic quest for Einstein's brain, which was lost then. And I felt if I saw it, it might be an anticlimax. But when I actually did see it, it really opened up my eyes; it was a revelation. This is where, you know, the power of the atom came from and relativity and all those other things. And I had the same kind of experience inside that Google data center. Here was the ephemeral made real, you know, the cloud really was something and it was something quite remarkable and breathtaking.

INSKEEP: Steven Levy, thanks very much.
Is this a sarcastic joke? He looked at a 50-year-old jar of chopped up brain tissue, and had a revelation about it being the source of "the power of the atom came from and relativity and all those other things"?

No, Einstein's brain was not the source of any of those things. This is crazy idol worship, as I explain in my book and this blog.

Tuesday, October 23, 2012

Geologists sentenced for bad advice

Science bloggers are complaining:
Seven scientists have been found guilty of the manslaughter of some 308 people following the 6.3-magnitude earthquake that struck the city of L’Aquila in Italy on 6 April 2009. All seven have been sentenced to six years in prison.
It is true that the scientists failed to predict the devastating L’Aquila earthquake, which killed 308 people in 2009.

But it is equally true that the decision to convict these scientists was based upon a fundamental misunderstanding of scientific uncertainty. It is equally true that jailing them for being “falsely reassuring” is a preposterous decision.
No, this is not Galileo Inquisition II.

I would take the side of the geologists if they gave competent scientific advice. But the charge is that they gave false reassurance about tremors in order to silence an earthquake predictor, and 300 people died.

Nature magazine reported last year:
From when he was a young boy growing up in a house on Via Antinori in the medieval heart of this earthquake-prone Italian city, Vincenzo Vittorini remembers the ritual whenever the family felt a seismic tremor overnight. "My father was afraid of earthquakes, so whenever the ground shook, even a little, he would gather us and take us out of the house," he says. "We would walk to a little piazza nearby, and the children — we were four brothers — and my mother would sleep in the car. My father would stand outside, smoking cigarettes with the other fathers, until morning." That, he says, represented the age-old, cautionary "culture" of living in an earthquake zone.

Vittorini, a 48-year-old surgeon who has lived in L'Aquila all his life, will never forgive himself for breaking with that tradition on the night of 5 April 2009. After hundreds of low-level tremors over several months, L'Aquila shook with a strong, magnitude-3.9 tremor shortly before 11 p.m. on that Palm Sunday evening. Vittorini debated with his wife Claudia and his terrified nine-year-old daughter Fabrizia whether to spend the rest of the night outside. Swayed by what he describes as "anaesthetizing" public assurances by government officials that there was no imminent danger, and recalling scientific statements claiming that each shock diminished the potential for a major earthquake, he persuaded his family to remain in their apartment on Via Luigi Sturzo. All three of them were huddled together in the master bed when, at 3:32 a.m. on 6 April, a devastating magnitude-6.3 earthquake struck the city. ...

Prosecutors and the families of victims alike say that the trial has nothing to do with the ability to predict earthquakes, and everything to do with the failure of government-appointed scientists serving on an advisory panel to adequately evaluate, and then communicate, the potential risk to the local population. The charges, detailed in a 224-page document filed by Picuti, allege that members of the National Commission for Forecasting and Predicting Great Risks, who held a special meeting in L'Aquila the week before the earthquake, provided "incomplete, imprecise, and contradictory information" to a public that had been unnerved by months of persistent, low-level tremors. Picuti says that the commission was more interested in pacifying the local population than in giving clear advice about earthquake preparedness.

"I'm not crazy," Picuti says. "I know they can't predict earthquakes. The basis of the charges is not that they didn't predict the earthquake. As functionaries of the state, they had certain duties imposed by law: to evaluate and characterize the risks that were present in L'Aquila."
I have not reviewed the evidence, so I don't know whether the geologists are guilty. But this is not the attack on science that various organizations are pretending.

Update: In other news about the legal free speech of scientists, FoxNews reports:
Controversial climate scientist Michael Mann, who helped raise global warming’s profile by representing temperatures as a rapidly escalating “hockey stick,” has filed a defamation lawsuit against skeptics at the National Review and the Competitive Enterprise Institute.

Mann said statements by the two organizations that compared him to convicted child molester Jerry Sandusky were offensive and defamatory, and called them the latest in a series of attacks he and other climate scientists have faced.
Even if Mann's hockey stick science is rock solid, American law makes it nearly impossible for him to win a libel suit like this. He will surely lose.

Update: A SciAm blogger writes:
It is ludicrous and naïve for the American Association for the Advancement of Science to condemn the verdict, as they did the charges when they were filed, as a misunderstanding about the science behind earthquake probabilities. That this was never about the ability of seismologists to predict earthquakes is clear from the very indictment itself; the defendants were accused of giving “inexact, incomplete and contradictory information” about whether small tremors prior to the April 6 quake should have constituted grounds for a warning.

It was never about whether the scientists could or could not predict earthquakes.

Monday, October 22, 2012

Explaining entanglement

Lumo explains quantum entanglement and adds:
Anti-quantum zealots are like children

The more I interact with them, the more I feel that the people who keep on talking about hidden variables, many worlds, pilot waves, mechanisms of collapses etc. – people who refuse to understand that the most fundamental description of the Universe is intrinsically probabilistic in character – resemble children who just can't live with the insight that the tooth fairy was just an illusion, a trick, an approximation in which playful parents are equated with the most divine layer of the Cosmos.
I agree with what he says, except for "intrinsically probabilistic in character". There is no proof that the universe is intrinsically probabilistic. Quantum mechanics describes the universe, but is not intrinsically probabilistic. It is not helpful to think of either as being intrinsically probabilistic.

Mathematically, probability is always understood in terms of an underlying measure space. But thinking about that underlying measure space leads to talking about hidden variables and all the other concepts that Lumo rights decries. There is no underlying measure space, as I explain in my FQXi essay.

I would rather say that our most fundamental description of the Universe gives a Hilbert space formalism for predicting observations, but we have no complete mathematization of the Universe itself.

Saturday, October 20, 2012

What's wrong with many-worlds

I posted before (and in Oct. 10, Aug., Jan.) about how I think the Many-worlds interpretation (MWI) is unscientific philosophy at best.

The paradigm is the Double-slit experiment. Quantum mechanics teaches that if you shine light or an electron beam thru a double-slit onto a detector screen, then detection probabilities can be calculated. The light is neither a particle nor a wave, but you can represent it as either for doing the calculation. All of this has been well-understood for almost a century.

MWI makes a series of assumptions: (1) light is a particle (photon); (2) the photon can be two places at once as it passes thru the double-slit; (3) all photons have ghostly partners that we never see; and (4) when the photon is detected, the ghostly partners disappear into other worlds where they are detected by other ghosts.

Assumptions (1-3) seem harmless and unprovable;. They are useful for calculations, as long as you do not take them too seriously. That is, you can think of light as photons, but those photons are not like marbles or specks of sand or any other particles in your everyday experience.

Assumption (4) has no physical consequences or computational utility. There is no scientific value to the assumption.

These assumptions make the double-slit harder to understand because the probabilities are harder to interpret. If quantum mechanics says that a detector has a 30% chance of detecting a photon, then the usual interpretation is that you can run the experiment 100 times, and detect about 30 photons. But under MWI, the photon is detected 100% of the time in some universe, and we don't know which universe we are in.

MWI is a joke. It shows that physics is in a sorry state that so many take MWI seriously.

Thursday, October 18, 2012

Einstein now in public domain

A lawsuit against use of this image was filed in 2010:
It doesn’t take a rocket scientist to know that you can’t simply use a celebrity’s image without authorization – even if that superstar was, indeed, a scientist who has been dead for more than half a century.

The Hebrew University of Jerusalem has filed suit against General Motors accusing the automaker of making fraudulent use of the image of Albert Einstein. ...

Though Einstein was not known as a particularly material man, his likeness has proved a gold mine for the school, which reportedly earned $10 million on the rights to the likeness of the author of the theory of relativity, last year.

According to Forbes magazine, Einstein ranks ninth on the list of the Top 10 dead celebrities when it comes to annual earnings, just behind Dr. Seuss, at $15 million, but ahead of widely-publisher author Michael Crichton, at $9 million.
The university must regret the lawsuit now, because it lost the case and all publicity rights:
But if it doesn’t die with the person, how long does it last? Some states define this by statute, but New Jersey has no such statute; the right of publicity in New Jersey is a common-law, judge-made right (as it originally was in most states). ...

Life plus 50 years, the court said, so GM wins (since Einstein died in 1955, and the ad ran in 2009).
So Einstein is now in the public domain. So my use of his name and image on the cover of my book is safe.

Tuesday, October 16, 2012

Hope for quantum information

Physicist Adam Frank writes in the NY Times:
Given its importance, many of us in the physics community expected the event to earn this year’s Nobel Prize in Physics. Instead, the award went to achievements in a field far less well known and vastly less expensive: quantum information. ... It could well usher in a radical new era of technology, one that makes today’s fastest computers look like hand-cranked adding machines.
All of our computers today depend on quantum information, so new research is great, but it is not going to do what Frank says.

He tries to summarize the Interpretations of quantum mechanics:
Take the superposition debate. One camp claims that a deeper level of reality lies hidden beneath all the quantum weirdness. Once the so-called hidden variables controlling reality are exposed, they say, the strangeness of superposition will evaporate.

Another camp claims that superposition shows us that potential realities matter just as much as the single, fully manifested one we experience. But what collapses the potential electrons in their two locations into the one electron we actually see? According to this interpretation, it is the very act of looking; the measurement process collapses an ethereal world of potentials into the one real world we experience.

And a third major camp argues that particles can be two places at once only because the universe itself splits into parallel realities at the moment of measurement, one universe for each particle location — and thus an infinite number of ever splitting parallel versions of the universe (and us) are all evolving alongside one another. ...

Soon at least one interpretation, the most common sense version of hidden variables, was completely ruled out.
The hidden variable interpretation has been ruled out by the quantum mechanics textbooks since about 1930. Einstein, Bohm, Bell, and a few others tried to ressurect the idea, but they were always proven wrong.

The third interpretation, many-words (MWI), has several serious defects. First, it postulates zillions of worlds with no observable consequences. Second, it does not make any computation or understanding of our world any easier. Third, it is philosophically self-defeating, like denying free will.
A quantum machine using no more than 300 qubits would be a million, trillion, trillion, trillion times faster than the most modern supercomputer.

Going even further is the seemingly science-fiction possibility of “quantum teleportation.” Based on experiments going on today with simple quantum systems, it is at least a theoretical possibility that one day objects could be reconstituted — beamed — across a space without ever crossing the distance.
This is fiction. No one has even made one scalable qubit. Even a 300-qubit quantum computer would only be faster on certain obscure search functions of limited utility. And no one has found any use for quantum teleportation.

Update: Greg Kuperberg writes in Slate:
Of course, I was thrilled that the Nobel Foundation recognized this field. However, I was dismayed to read in the press release that "a quantum computer of only 300 qubits could hold 2³°° values simultaneously." Actually, 300 qubits can't hold so many zillion values; it is a mathematical fact that 300 qubits can store only 300 bits. This press release is part of a larger pattern of breathless exaggerations. In the name of accessibility, many popular accounts take quantum computing to implausible levels of hype.
A comment says:
Basically, once we have a fully scaled up quantum computer we will have cures for all sorts of diseases(protein folding problems will be solved quickly), space travel and worm holes, teleportation advances, nuclear fusion. This will be the biggest technological revolution that the planet has ever seen. Believe it or not, that day is coming and soon 5-10 yrs.
No, I do not believe that day is coming in the 1000 years.

Monday, October 15, 2012

Debating Pythagoreanism

Here is a video debate:
Pythagoras thought he had discovered the key to universe: mathematics. Was Pythagoras right? Should we see mathematics as the ultimate character of the world or is this a limited vision?
As Peter Woit points out:
An interesting debate, but maybe they should have had some mathematicians involved…
Physicist Lee Smolin accepts Pythagoreanism, but rejects Max Tegmark's Mathematical universe hypothesis. He implies that most people agree with him.

My FQXi essay expresses a contrary view.

The video server was buggy, so I could only watch part of it. The arguments seemed weak to me.

To give an idea of the philosophical ideas of the speakers, here is Peter Hacker:
Peter Hacker is one of the most powerful contemporary exponents of the linguistic-therapeutic approach to philosophy pioneered by Ludwig Wittgenstein. In this approach, the words and concepts used by the language community are taken as given, and the role of philosophy is to resolve or dissolve philosophical problems by giving an overview of the uses of these words and the structural relationships between these concepts. Philosophical inquiry is therefore very different from scientific inquiry, and Hacker maintains accordingly that there is a sharp dividing line between the two: "Philosophy is not a contribution to human knowledge, but to human understanding"
And Hilary Lawson:
Lawson's theory 'Closure' proposes that the human condition is to find ourselves on the cusp of openness and closure. The world is open and we, along with other living organisms, are able to apprehend and make sense of it through the process of closure. The theory, described by Don Cupitt as the first attempt to offer a non-realist metaphysics[10] shifts the focus of philosophy away from language and towards an exploration of the relationship between openness and closure. An important element of the theory of closure is its own self-referential character.
I am sure these guys do not have anything serious to say about math or science.

Wednesday, October 10, 2012

Copenhagen more coherent than many-worlds

Cosmologist Sean M. Carroll writes:
For a long time, quantum mechanics could be treated as a black box. You had an atomic nucleus sitting their quietly, not really deviating from your classical intuition, and then some quantum magic would occur, and now you have several decay products flying away. The remoteness of the quantum effects themselves is what has enabled physicists to get away for so long using quantum mechanics without really understanding it. (Thereby enabling such monstrosities as the “Copenhagen interpretation” of quantum mechanics, and its unholy offspring “shut up and calculate.”) ...

The objection to Copenhagen is just that it’s completely incoherent. It imagines a distinct “classical” realm, doesn’t tell you what’s in that realm and what’s truly quantum, doesn’t explain when wave functions collapse, etc. The Born Rule isn’t “explained” at all — it’s just postulated. And the Uncertainty Principle is exactly the same in MWI as it is in Copenhagen, so I’m not sure what the distinction is there.

MWI has its own issues, certainly, as do all other known versions of QM. But at least it’s well-defined, whereas Copenhagen is kind of a joke.
No, the Copenhagen interpretation is not a joke. It is a lot more coherent than the Many-worlds interpretation (MWI).

Copenhagen does not postulate the Born rule, but at least it explains the probabilities. The MWI does not explain probabilities at all, and has no experimental evidence for it.

The core of the problem is that Niels Bohr was a positivist while Carroll subscribes to this view:
The basic scientific assumption is that there is exists a complete and coherent description of how the world works. ... Given what we know about the universe, there seems to be no reason to invoke God as part of this description.
This view lead Carroll to believe in zillions of unobesrvable alternate universes and all sorts of other bizarre hypotheses, but he refuses to accept a scientific explanation that he regards as incomplete.

There is no reason to accept MWI.

A recent essay asks, Has Science Established that the Cosmos is Physically Comprehensible? The answer is no.

Science is all about testing hypotheses, and not leaping to unverifiable conclusions just because you pursue a more complete and coherent description of how the world works. I say Carroll has a very wrong idea of science. That is why he subscribes to string theory and other nonsense.

Tuesday, October 9, 2012

Albert Einstein's Methodology

Galina Weinstein has posted a paper on Albert Einstein's Methodology. She details how Einstein needed his friends for his most famous papers, but he refused to give them the credit they deserved. He wrote:
I am now occupied exclusively with the gravitational problem, and believe that I can overcome all difficulties with the help of a local mathematician friend. But one thing is certain, never before in my life have I troubled myself over anything so much, and that I have gained great respect for mathematics, whose more subtle parts I considered until now, in my ignorance, as pure luxury! ...

With this task in mind, in 1912, I was looking for my old student friend Marcel Grossmann, who had meanwhile become a professor of mathematics in the Swiss Federal Polytechnic institute. He was immediately caught in the fire, even though he had as a real mathematician a somewhat skeptical attitude towards physics. ...

He looked through the literature, and soon discovered that the particular implied mathematical problem was already solved by Riemann, Ricci and Levi-Civita. ...

Grossman will never claim to be considered a co-discoverer. He only helped in guiding me through the mathematical literature, but contributed nothing of substance to the results.
She writes about his refusal to credit another long-time friend:
During a visit by Besso to Einstein in 1913 they both tried to solve the Einstein-Grossmann field equations to find the perihelion advance of Mercury. The theory predicted a wrong perihelion advance.

Towards the end of 1915 Einstein abandoned the Einstein-Grossmann theory, and with his new General Theory of Relativity got the correct precession so quickly because he was able to apply the methods he had already worked out two years earlier with Besso. Einstein did not mention Besso, probably because he still considered him as a sounding board; this as opposed to his other friend, Grossmann, who was his active partner since 1912 in creating the Einstein-Grossmann theory.
This is not quite right, as this "correct precession" was derived from Grossmann's 1913 equation that empty space is Ricci-flat. The Mercury precession is regarded as Einstein's most original contribution to general relativity, but only because he refused to credit his friends.

She also explains how Einstein used words to exaggerate the originality of his work:
Alberto Martínez asks in his latest book Kinematics, "Was the formulation of the special theory of relativity a discovery [Entdeckung] or an invention [Erfindung]? Nowadays, many writers call it a 'discovery'. But throughout his life, Einstein emphasized the importance of invention, when characterizing his theoretical
Yes, I think that most people would say that non-Euclidean geometry, and its application to relativity, was a discovery, not an invention. Einstein did not discover or invent it. He was a big egomaniac to claim all the credit that he did.

Sunday, October 7, 2012

Cold water on quantum hype

Charlie Bennett writes:
Throwing cold water on the Quantum Internet

The most common misconception about entanglement is that it can be used to communicate—transmit information from a sender to a receiver—perhaps even instantaneously. In fact it cannot communicate at all, except when assisted by a classical or quantum channel, neither of which communicate faster than the speed of light. So a future Internet will need wires, radio links, optical fibers, or other kinds of communications links, mostly classical, but also including a few quantum channels.

How soon before the quantum internet could arrive?
I don’t think there will ever be an all-quantum or mostly-quantum internet. Quantum cryptographic systems are already in use in a few places, and I think can fairly be said to have proven potential for improving cybersecurity. Within a few decades I think there will be practical large-scale quantum computers, which will be used to solve some problems intractable on any present or foreseeable classical computer, but they will not replace classical computers for most problems. I think the Internet as a whole will continue to consist mostly of classical computers, communications links, and data storage devices.
He is right that there will never be a quantum internet, but it is not true that quantum cryptographic systems have proven potential for improving cybersecurity. Nobody has ever shown that quantum cryptography has any cybersecurity value at all.

I do not believe that we will see practical large-scale quantum computers either. Others disagree with me, but we are still waiting for a proof of concept that any such computers are possible.

Update: Some are buying into the hype:
Jeff Bezos has put money into a robot factory worker, a 10,000 year clock and private car service. And he’s not done yet.

Bezos Expeditions and In-Q-Tel, the venture arm of the CIA, announced Thursday a $30 million investment in D-Wave Systems, a Vancouver-based company that develops quantum-computing applications.

D-Wave Systems integrates computer science and physics discoveries with new-age computational processes. It’s focused on solving “optimization” problems, like finding out the most efficient delivery routes or how protein atoms interact with drug compounds. Some say the technology is more efficient than classical computing.
D-Wave does not have the qubit computer that everyone wants. I guess they somehow convinced Bezos that they can do some useful computations anyway.

Update: Soott Aaronson writes:
D-Wave still hasn’t demonstrated 2-qubit entanglement, which I see as one of the non-negotiable “sanity checks” for scalable quantum computing. ... Keep in mind that D-Wave has now spent ~$100 million and ~10 years of effort on a highly-optimized, special-purpose computer for solving one specific optimization problem.

Tuesday, October 2, 2012

Reality: Is everything made of numbers?

Amanda Gefter writes in the current NewScientist:
How is it possible that mathematics "knows" about Higgs particles or any other feature of physical reality? "Maybe it's because math is reality," says physicist Brian Greene of Columbia University, New York. Perhaps if we dig deep enough, we would find that physical objects like tables and chairs are ultimately not made of particles or strings, but of numbers.

"These are very difficult issues," says philosopher of science James Ladyman of the University of Bristol, UK, "but it might be less misleading to say that the universe is made of maths than to say it is made of matter."

Difficult indeed. What does it mean to say that the universe is "made of mathematics"? An obvious starting point is to ask what mathematics is made of. The late physicist John Wheeler said that the "basis of all mathematics is 0 = 0". All mathematical structures can be derived from something called "the empty set", the set that contains no elements. Say this set corresponds to zero; you can then define the number 1 as the set that contains only the empty set, 2 as the set containing the sets corresponding to 0 and 1, and so on. Keep nesting the nothingness like invisible Russian dolls and eventually all of mathematics appears. Mathematician Ian Stewart of the University of Warwick, UK, calls this "the dreadful secret of mathematics: it's all based on nothing" (New Scientist, 19 November 2011, p 44). Reality may come down to mathematics, but mathematics comes down to nothing at all.

That may be the ultimate clue to existence - after all, a universe made of nothing doesn't require an explanation. Indeed, mathematical structures don't seem to require a physical origin at all. "A dodecahedron was never created," says Max Tegmark of the Massachusetts Institute of Technology. "To be created, something first has to not exist in space or time and then exist." A dodecahedron doesn't exist in space or time at all, he says - it exists independently of them. "Space and time themselves are contained within larger mathematical structures," he adds. These structures just exist; they can't be created or destroyed.

That raises a big question: why is the universe only made of some of the available mathematics? "There's a lot of math out there," Greene says. "Today only a tiny sliver of it has a realisation in the physical world. Pull any math book off the shelf and most of the equations in it don't correspond to any physical object or physical process."

It is true that seemingly arcane and unphysical mathematics does, sometimes, turn out to correspond to the real world. Imaginary numbers, for instance, were once considered totally deserving of their name, but are now used to describe the behaviour of elementary particles; non-Euclidean geometry eventually showed up as gravity. Even so, these phenomena represent a tiny slice of all the mathematics out there.

Not so fast, says Tegmark. "I believe that physical existence and mathematical existence are the same, so any structure that exists mathematically is also real," he says.

So what about the mathematics our universe doesn't use? "Other mathematical structures correspond to other universes," Tegmark says. He calls this the "level 4 multiverse", and it is far stranger than the multiverses that cosmologists often discuss. Their common-or-garden multiverses are governed by the same basic mathematical rules as our universe, but Tegmark's level 4 multiverse operates with completely different mathematics.

All of this sounds bizarre, but the hypothesis that physical reality is fundamentally mathematical has passed every test. "If physics hits a roadblock at which point it turns out that it's impossible to proceed, we might find that nature can't be captured mathematically," Tegmark says. "But it's really remarkable that that hasn't happened. Galileo said that the book of nature was written in the language of mathematics - and that was 400 years ago."

If reality isn't, at bottom, mathematics, what is it? "Maybe someday we'll encounter an alien civilisation and we'll show them what we've discovered about the universe," Greene says. "They'll say, 'Ah, math. We tried that. It only takes you so far. Here's the real thing.' What would that be? It's hard to imagine. Our understanding of fundamental reality is at an early stage."
My FQXi essay argues that reality, at bottom is not mathematics. I say that Tegmark is wrong in the most extreme way. There is no real object that is also a mathematical structure. Not even an electron or a photon.

This is the last week for the public rating of the FQXi essays. My essay has consistently been in the top 10 on the community rating.

Tegmark says, "we might find that nature can't be captured mathematically," but I say that has already happened with quantum mechanics. Niels Bohr said:
It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we say about Nature.

Everything we call real is made of things that cannot be regarded as real.
I think that Bohr was saying that observations about nature can be described mathematically, but nature itself cannot be captured mathematically.