Archive for the ‘Physics’ Category
CERN makes available at its web site a truly awesome collection of video lectures and courses. The whole set is browsable here and consists of almost 1500 entries. Naturally enough there’s a bias towards particle physics, but many other topics make cameo appearances. Here’s a list of some of the lectures that caught my attention:
- A passion for discovery, by P. Freund, based on his book
- Albert Einstein, Analogizer Extraordinaire, by D. R. Hosftadter
- The future of gravity, by J. B. Hartle
- The future of physics, by D. J. Gross
- The Quantum theory of fields: effective or fundamental?, by S. Weinberg
- Loop quantum gravity, by C. Rovelli
- Warped extra-dimensional opportunities and signatures, by L. Randall
- Introduction to QCD, a course by B. Webber
- Introduction to general relativity and black holes, a course by T. M. A. G. Damour
- The cosmic microwave background, a course by M. Zaldarriaga
- Quantum teleportation: principles and applications, by N. Gisin
- Cosmology for particle physicists, a course by S. M. Carroll
- A course on string theory, by C. V. Johnson
Yeah, i’m too still trying to decide where to begin! :)
The Royal Society is commemorating its 350th anniversary next year and, as part of the celebrations, has put together a very nice site called Trailblazing. The site presents an interactive time-line highlighting some of the events and publications that have made history during those three and a half centuries. The best part is that one can download, in PDF, a bunch of jewels. Among them: Newton’s letter on light and colors, Faraday’s musings on gravity and electricity, Maxwell’s article presenting his field equations, Bayes’ essay on chance, Eddington’s report on his famous expedition, or Hawking and Penrose’s work on singularities. Talk about the shoulders of giants!
From this press release:
CERN’s Large Hadron Collider has today become the world’s highest energy particle accelerator, having accelerated its twin beams of protons to an energy of 1.18 TeV in the early hours of the morning. This exceeds the previous world record of 0.98 TeV, which had been held by the US Fermi National Accelerator Laboratory’s Tevatron collider since 2001.
There’s also a photographic report.
A couple of interesting links for those of you with a penchant for videos.
MIT World is a free and open site that provides on demand video of significant public events at MIT, including some physics lectures, like this very fun series by Walter Lewin on electromagnetism, music and light; or this one where Robert Laughlin and Steven Weinberg talk about the social aspects of physics.
ScienceDump is a new site devoted to “popular science, technology & digital lifestyle videos”, contributed by its users. Although the site is brand new, it already contains some interesting bits.
The Lindau Nobel Laureate homepage contains lots of videos of this annual gathering in the Constance Lake that brings together consecrated scientists and young researchers. You can find both lectures and short documentaries. In particular, 2008 was devoted to physics: the list of lectures is here, and there’s also a collection of short films featuring Gerardus `t Hooft and David Gross, among others, interviewed by young students. These Lindau meetings have been taking place since the 1950s, and one can find some funny stuff in there: for instance, there’s the recording of a talk by P.A.M Dirac himself, from 1979.
The IOP has just launched a podcast feed (hat tip Yan Feng). Their first post (mp3 here) is a 20 minutes interview with Michael Berry, of the eponymous phase fame, whose work on levitating frogs earned him an IgNobel Price in Physics in 2000. Professor Berry talks neither of his phase nor his frogs in the interview, but of his current research on optics (having to do with conical diffraction and the angular momentum of light), and the relationship between science and art (he is very fond of images representing optical phenomena, as you can see in this beautiful gallery). He has also a couple of things to say about the interplay between theoretical work and practical applications and the part played by science in our society. In this regard, his little piece Living with Physics (pdf) and his unpublished Night thoughts of a theoretical physicist (pdf) are very worth reading; for instance, here’s a quite inspiring musing on the unity of science:
From science come inspiring and magical connections between very different things. This observation counters one of our commonest criticisms: that by the reductionist disarticulation of the world into its parts, which are then studied separately, we lose the sense of the whole. My favourite example starts with the question: Why is matter hard? Atoms consist mostly of empty space, after all, so why doesn’t matter squash down, with all the electrons collapsing into their lowest quantum energy states near the nuclei? Because this is prevented by the Pauli exclusion principle: no two electrons can be in the same state. And where does that come from? It could well originate in a property of rotation in three-dimensional space4: holding a glass of wine, you can turn it completely twice (that is, through 720°) and find at the end of this contortion that your arm is untwisted (this does not work for a single turn). I find that `two into none’ connection, that totally unexpected association of microscopic hardness with geometry5, miraculous.
By the end of the interview, Berry returns to his research and mentions a quite curious recent result of his, the explanation of the workings of the oriental magic mirrors called Makyoh. This bit caught my eye (well, i guess it was my ear) because i had never hear of those magic mirrors before. They’re quite amusing. These cast and polished bronze mirrors, manufactured in China and Japan since at least 500 BC have a pattern embossed on the back that magically appears in a patch of light reflected by the mirror face (which to the naked eye looks as smooth and polished as one can get, except for a bit convexity). You can see a Makyoh in action in the figure on the right (more here): the pattern in the reflected light patch is nowhere to be seen in the mirror’s surface, which reflects images as a regular, slightly convex mirror would do. Credit for explaining the trick usually goes to Ayrthon and Perry, but, according to this article of the 1911 edition of the Encyclopedia Britannica,
The true explanation of the magic mirror was first suggested by the French physicist Charles Cleophas Person in 1847, who observed that the reflecting surface of the mirrors was not uniformly convex, the portions opposite relief surfaces being plane. Therefore, as he says, ‘ the rays reflected from the convex portion diverge and give but a feebly illuminated image,while, on the contrary, the rays reflected from the plane portions of the mirror preserve their parallelism, and appear on the screen as an image by reason of their contrast with the feebler illumination of the rest of the disk. Such differences of plane in the mirror surface are accidental, being due to the manner in which it is prepared, a process explained by W. E. Ayrton and J. Perry (Prot. Roy. Soc., 1878, vol. xxviii.), by whom ample details of the history, process of manufacture and composition of Oriental mirrors have been published.
I haven’t found these original papers on-line, but you can learn more about the history of Ayrton and Perry’s discoveries in this page on magic mirrors from Grand Illusions. A more in-depth treatment of the optics involved is given in Michael Berry’s article Oriental magic mirrors and the Laplace image (pdf), where he explains how the Laplacian of the relief height function gives rise to the image in the reflected patch (see also this article for comments on Berry’s and a bit more on the history of Makyoh).
I find Professor Berry’s willingness to investigate funny, every-day problems refreshing, not to mention his concern on making the physicist’s world closer to outsiders, like, say, taxi drivers. Or, as Berry himself puts it:
A source of delight is uncovering down-to-earth or dramatic and sometimes beautiful examples of abstract mathematical ideas: the arcane in the mundane.
These are the ten most viewed posts during July:
- Geometrically speaking
- You’re never too old
- Quantum probability
- Getting Schwarzschild right
- Nature’s nifty tricks
- Powers of Ten
- The dimensionality of the world
- Pebble physics
- The cyclist team
- Students and quantum mechanics
This has been the best month so far here at physics musings in terms of number of visits, thanks to Sean’s kind plug of Geometrically speaking. A big thanks to Sean, and also to those of you posting encouraging comments or just dropping a mail; and, as always, thanks for reading!
Judging a paper’s quality may be hard for human referees, and people are looking for alternatives. For instance, this recent PhysicsWeb news gives an overview of P. Chen et al. article Finding Scientific Gems with Google, where the authors take advantage of Google’s page rating algorithm to assess the relative importance of all publications in the Physical Review family of journals from 1893 to 2003. Since the rating algorithm weights pages by number of referrers , there’s in principle no value added to traditional citation indexes: both popularity measures are linearly correlated. The catch is that there are exceptions: papers that are not widely cited but that, judging for the number of web pages linking to them, seem to be much more influential than one would think (the article mentions quite a few, Feynman, Murray and Gell-Mann’s one on Fermi interactions being an example). Amusing; although i must confess that this kind of democratic assessments of our scientific endeavours remind me somewhat of a well-known Planck dixit:
A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.
Max Planck, 1858–1947
(I remember i jotted down this same quotation some twenty years ago, together with a note showing my skepticism… nowadays i think i’m much more of a planckian than i used to be.)
Returning to our electronic referees, over at PhysOrg there’s a story about how computer science may help us in detecting bogus papers, where by bogus i mean automatically generated ones (looks like our human referees do sometimes find their task really hard!). Probably the most popular case of such a prank was the article accepted at WMSCI 2005 whose author came out to be SCIgen, an automatic paper generator created by the guy in portrait on the right. And our field is not immune to similar problems, as exemplified by the amusing Bogdanoff Affair (besides, as you’ll see, most probably no computer program would be of much help in this case).
 Of course, i’m oversimplifying: see here for the complete history behind Google’s PageRank.
Update: Andrew Jaffe, in his excellent blog (recommended, but you probably already knew it), has some interesting thoughts about peer review, and a recent initiative by Nature to open a debate on the issue and looking for ways of improvement.