Saturday, June 27, 2009

Physics Quote of the Day (June 21 - June 27)

"Great physics does not automatically imply complicated mathematics!" Martinus Veltman, born 27 June 1931.

"The life and soul of science is its practical application." William Thomson, Lord Kelvin, born 26 June 1924.

"If they can, in their proposals, write the word nano, the chances for funding increase." Alexei Alexeyevich Abrikosov, born 25 June 1928.

"The experimenter dealing with nature faces an outside and often hard world. Natures' curriculum cannot be changed." Martin Perl, born 24 June 1927.

"If you can’t reduce a difficult engineering problem to just one 8-1/2 x 11-inch sheet of paper, you will probably never understand it." Ralph Brazelton Peck, born 23 June 1912.

"To understand is to marvel." Larkin Kerwin, born 22 June 1924.

"That which can affect our senses in any manner whatever, is termed matter." Siméon Denis Poisson, born 21 June 1781.

Saturday, June 20, 2009

Physics Quote of the Day (June 14 - June 20)

"Physics does not ask which is better: the proton or neutron, baryon or lepton, helium or neon, the conductor or insulator. These are simply properties of nature. Rather, physics asks: “Why?”" Isaac Abella, born 20 June 1934.

"To make light of philosophy is to be a true philosopher." Blaise Pascal, born 19 June 1623.

"We certainly don't yet know all the answers. But the universe is about to be pried open." Lisa Randall, born 18 June 1962.

"To stop short in any research that bids fair to widen the gates of knowledge, to recoil from fear of difficulty or adverse criticism, is to bring reproach on science." William Crookes, born 17 June 1832.

"... self-study, in a sense of learning by yourself without anybody teaching you anything, has an enormous value." Robert P. Kraft, born 16 June 1927.

"The main difficulty to popularize quantum physics is that we do not really know how to make images of it in our world. In this sense it is really counterintuitive." Alain Aspect, born 15 June 1947.

"On graduating from the school, a studious young man who would withstand the tedium and monotony of his duties has no choice but to lose himself in some branch of science or literature completely irrelevant to his assignment." Charles de Coulomb, born 14 June 1736.

Saturday, June 13, 2009

Physics Quote of the Day (June 7 - June 13)

"The experimental verification of the mathematical results therefore is no evidence for or against the peculiar doctrines of this theory." James Clerk Maxwell, born 13 June 1831.

"In the labs, the young make things move, and the older ones follow like parents evolving with their children." Catherine Bréchignac, born 12 June 1946.

"Each time the discovery of new facts, the reversal or extension of accepted theories, reminded us that science is never finished." Charles Fabry, born 11 June 1867.

"... if the aim of physical theories is to explain experimental laws, theoretical physics is not an autonomous science; it is subordinate to metaphysics." Pierre Duhem, born 10 June 1861.

"In mesoscopic physics, you really need to build up intuition, because it is not the world you know." Carlo Beenakker, born 9 June 1960.

"The Web does not just connect machines, it connects people." Tim Berners-Lee, born 8 June 1955.

"... the more accurate the calculations became, the more the concepts tended to vanish into thin air." Robert S. Mulliken, born 7 June 1896.

Friday, June 5, 2009

Feynman and what comes next...

As you may be aware of, I am a Feynman aficionado:
  1. My scientific motto is a (not so famous) quote of Feynman: "All we do is draw little arrows on a piece of paper - that's all!"
  2. My Twitter visual profile is dedicated to him.
  3. I love viewing videos of his lectures or his interviews.
  4. I regularly go across his written works.
  5. I've spotted errata in his Physics Lectures, volume III (Quantum mechanics), most of them typo, but some substantial errors.

Curiously, I discovered him relatively late. When I followed quantum mechanics courses at university (somewhere between 1985 and 1989), my courses didn't refer to his lectures. I consider that as a missing. It was only after I took time to dig deeper into the quantum foundations (after 1996) that I came across his works. Reading his works was so enlightening for my comprehension of the fundamental laws of nature, that there are pieces that I could read tens of times and each time I would learn new things. Or better said: approach known things from a new point of view.

Feynman is deservedly one of the most quoted people (at the Selected Pages section of Wikiquote, he figures along with people like Aristotle, Buddha, Confucius, Einstein, Jesus or Shakespeare...). His words are inspiring and often explain physical truths in plain language, comprehensible to the layman. As for all quotes, there is a caveat: they must not be seen as an absolute truth. Or as Feynman stated it himself: Learn from science that you must doubt the experts.

Very early I was skeptic about one of Feynman's most famous quotes: nobody understands quantum mechanics. This is often requoted in a more or less transformed way (for example Dawkins' version: "If you think you understand quantum mechanics, you don't understand quantum mechanics"). Does this quote have a general and definitive value of truth? Or was it just that Feynman didn't know of anyone who could explain quantum mechanics in an understandable common sense way?

Chapter 1 of Feynman's quantum lectures gives some insight in the reasons of his belief that nobody understands quantum mechanics: "We choose to examine a phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics." He goes on to describe the double-slit experiment (with electrons), showing that it is impossible to think of waves alone or of bullets alone (such explanations have been taken over by popular media like that given by "Granddaddy of all Quantum Weirdness"). And Feynman concludes with "No one has found any machinery behind the law. No one can explain any more than we have just explained. No one will give you any deeper representation of the situation." These are terrible sentences when repeated to hundreds of thousands, maybe millions of physics students since 1965. They mark a halt for any further investigation of the subject.

Fortunately, there are inventive unconventional physicists. There were already deeper theoretical representations given by physicists like De Broglie or David Bohm, showing how a particle may be directed by a guiding wave and thus yield all the experimental results of the double slit experiment, but this had never been put to proof during their lifetime with an experimental model.

Today, I think I can safely say that the quote "nobody understands quantum mechanics" is experimentally outdated. Couder and Fort, two French physicists, experimented with bouncing droplets on a liquid subtract and discovered that they exhibited quantum behaviour, without looking for any quantum analogy:
  • droplet travelling in its wave,
  • diffraction and interference patterns of travelling droplets similar to photon and electron diffraction patterns,
  • attraction and repulsion of droplets embedded in their waves,
  • symmetric and anti-symmetric orbital motion of droplets.
Visuals presented by Couder are breathtaking. Even if you don't understand french, I highly recommend watching bouncing droplets orbiting around each other (for example at 25:35 of his 2006 presentation).

An upcoming paper of Couder's group in Physical Review Letters even suggests a quantum tunneling analogy with ordinary droplets: "Unpredictable tunneling of a classical wave-particle association", by A. Eddi, E. Fort, F. Moisy, and Y. Couder.

So today, Feynman's defeatist words about nobody understanding quantum mechanics are outdated. Please, experimental physicists, go ahead, be inventive and focus on experiments where ordinary macroscopic individual particles simulate quantum behaviour, polarization, bosonic and fermionic behaviour, inward bound forces, entanglement, quantum erasure, coupling of ordinary particles to their pilot-wave fields (gravitation, electromagnetism). Because all these quantum phenomena may be rationally understood with the help of experimental models. It's just a matter of inventivity. And we "will find someday that, after all, it isn't as horrible as it looks." ~ Feynman's Epilogue to his Lectures on Physics.

Physics Quote of the Day (May 31 - June 6)

"We live of novelty in science. So when you do something new, you have to overcome certain beliefs that it cannot be done, that it's not interesting and so on." Heinrich Rohrer, born 6 June 1933.

"The future cannot be predicted, but futures can be invented. It was man's ability to invent which has made human society what it is." Dennis Gabor, born 5 June 1900.

"The national research effort, upon which so much depends, will remain healthy only so long as there is sound core of disinterested search for new knowledge..." Alan Waterman, born 4 June 1892.

"Too much equipment can be, however, something that hampers scientific development." Georg von Békésy, born 3 June 1899.

""Have we discovered our Galaxy yet?" And I think the answer to this question is "No, not quite". There is plenty of work ahead for the next generation of astronomers." Heather Couper, born 2 June 1949.

"Simplicity is the touchstone in finding new physical laws." Kip Thorne, born 1 June 1940.

"A theory is only as good as its assumptions. If the premises are false, the theory has no real scientific value. The only scientific criterion for judging the validity of a scientific theory is a confrontation with the data of experience." Maurice Allais, born 31 May 1911.