Archive for the ‘Fun’ Category

Quick video links

November 28, 2009

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.

Copernicus who?

September 29, 2006

This guy is being asked which one of four objects gravitates around the Earth. The price is three thousand euros and, just in case, he has the option to ask the public’s opinion…

Would be funny, if it weren’t so sad. Reminds me of those people that justify their inability to write correctly saying that they are scientists . I had a colleague that always retorted to them: no, you’re not a scientist, you’re just silly!.


September 25, 2006

Thanks to this recent post over at Not Even Wrong, i’ve rediscovered a piece, written a few years ago by the prestigious Professor Allen that has, in a way, ameliorated my prejudices against string theory. The essay is called Strung Out, and will make for an excellent introduction to this fascinating metatheory. Enjoy!


September 8, 2006

Scientists are also sexy, let's not forget that

From xkcd, a webcomic of romance, sarcasm, math and language.

Frogs, science and magic mirrors

August 4, 2006

Levitation without meditationThe 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.

A Makyoh in action. Click for more pictures.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.

The Mark Steel lectures on Physics

August 2, 2006

Here’s Open University’s Mark Steel’s comic (but informative) take on Newton:

and on Einstein:

The whole series includes lectures on Charles Darwin, Rene Descartes, Sigmund Freud and Aristotle. Hat tip Mind Hacks.

Three Feynmans walk into a bar…

July 28, 2006

The first two vanish into the back room to play a game of darts, leaving the third to chat up the barmaid. After emptying a stein, he pulls a bit of ribbon from his pocket and entertains her with a trick hereby he ties the ribbon to the handle, twists the stein around two full turns, and then magically untwists the ribbon without moving the stein. He tells her how particles he studies have a property called “spin”, and that particles whose spin is 1/2 actually behave like the stein with the ribbon tied to it: coming back where they started only after two, but not one, full turns. Feynman then leans closer, and conspiratorially whispers to her why (in language a barmaid can understand), just spin 1/2 particles act this way, and not other particles.

What story does the Feynman tell the barmaid?

(Posted by Edward Green to sci.phys.research. Hints here and here.)

Feynman spinning

Postmodern Prometheus

July 22, 2006

Hiroshi, isn't he?I know i’m wandering a bit off-topic here, but this post over at Mind Hacks was too fun to let it pass unnoticed: according to recent news, Hiroshi Ishiguro, director of the Intelligent Robotics Lab (IRL) at Osaka University in Japan, has created an android double of himself. You can see Hiroshi in the figure on the left (stolen from this recent Scientific American article). If you didn’t recognise the android at first, don’t worry: Ishiguro’s team have been conducting a variation of Turing’s test where androids are shown to humans for around two seconds; 70% of times people take the androids for humans. The experiment is part of a study trying to explain the so-called uncanny valley effect: the emotional response of humans to robots increases as the robot is made more human-like, up to a point where a too close resemblance causes the empathy to abruptly fall. A sort of too good to be true effect. According to the IRL experiments, this may be caused by the stillness of androids: it’s impossible for humans to stand perfectly still, and that’d be what makes robots uncanny. To prove their hypothesis, Ishiguro’s team has added micro movements to their toys. As the result of the experiment with 20 subjects, 70% of the subjects did not become aware they were dealing with an android when the android had micro movements, but 70% became aware with a static android.

SensorsOf course, there’s much more to Android Science (as they call their interdisciplinary endeavours) than micro movements. This beautiful paper gives an introduction to some of the challenges faced by these intrepid researchers, ranging from an understanding of cognition and intelligent behaviour in humans to the technical challenges of creating an adequate sensor system for the robot: besides the piezo-electric films under their silicon skin, the androids use a sensor network distributed over their environment that includes video, sound and infrared motion sensors. (Yes, that’s a bit like cheating, but the results are impressive: you can get a glimpse of the science and technology behind sensors and data processing in these posters by the IRL researchers) The paper also discusses in length the Turing tests mentioned above.

I just wonder, why do the androids look so angry?

Pebble physics

July 20, 2006

From the Curiosities Department comes this news over at PhysicsWeb (see also a previous piece at about recent advancements in our understanding of pebbles:

Aristotle's peeblesA question that has been around since the time of Aristotle — what shape is a pebble? — has now been solved by physicists in France and the US. Douglas Durian of the University of Pennsylvania and colleagues in Strasbourg say that a pebble is “a nearly round object with a near-Gaussian distribution of curvatures”. All pebbles, regardless of their original shape, end up with a similar shape that depends solely on how the pebble was eroded over time. The results could help geologists determine the history of a pebble simply by looking at its geometry (Phys. Rev. Lett. 97 028001).

You can also take a look at this nice presentation for more details, and even see some movies by the people of Strasbourg. For all the nitty-gritty details, the articles can be found in the arXiv, here and here.

steiner.pngThis news reminded me of an older one, The Mistery of the Skipping Stone, where the physics of bouncing stones in water is (more or less) explained (unsurprisingly, the determining factor seems to be the initial velocity of the stone: see this very readable paper, to appear in AJP, by the same author, Lyderic Bocquet). A piece of amazing trivia included in the article: In 2002 an American called Kurt Steiner set a new world record when he threw a stone across a river in Pennsylvania and made it bounce… 40 times. Unbelievable? I thought so, but here’s the proof. By comparison, the team of physicists writing the article were using a specially designed catapult for their experiments, but they got just 20 bounces. What’s your mark?

Update: And, when it comes to talk about physics and throwing, nobody more apt (one would say) than a physicist let loose at the Baseball Major League: in A Magnus Force on the Mound,  Major league pitcher Jeff Francis brings an educated insight to the physics of baseball (besides giving me an excellent excuse to publicize the excellent Symmetry Magazine, a joint SLAC/Fermilab publication about particle physics for the rest of us).

Nature’s nifty tricks

July 10, 2006

Herman BondiA few weeks ago, and thanks to this post over at A Neighborghood of Infinity, i discovered a little jewel: Herman Bondi‘s book Relativity and Common Sense, an insightful and original introduction to special relativity for the layman. The above mentioned post gives an overview of Bondi’s approach, based on what is known as k-calculus, arguably simple enough to be taught at highschools. Bondi makes the case for an understanding of SR as an evolution of Newtonian ideas, rather than as the revolution we all thought it was. Whether successful or not, this attempt leads Bondi to start his book with a delicious review of classical physics, illustrating the concepts and principles with very well chosen common life phenomena and their corresponding explanations. You know, trying to come to grips with quantum mechanics interpretations or finding a unified theory of everything is all very well, but it’s the marvel of being able to explain those other nature’s nifty tricks what draw me to physics in the first place. These little and easy to understand principles convey in a very real and fun sense the magic of ours world’s understandability. Bondi touches a lot of these magic things in the first fifty pages of his book, and i thought some of you may amuse yourselves finding (or just remembering) the explanations to these down-to-earth phenomena:

  • Conservation of momentum. Your baby is sleeping in her pram. Would you put the brakes on or off to ensure she will still be there when you come back and find that she awakened in the meantime?
  • Spinning cats. Can you think of a way of exploiting angular momentum conservation to explain how a cat manages to land always on all fours? (For extra score, how’s this problem related to Yang-Mills theory?)
  • Coriolis force. Can you explain it in simple terms (involving, say, a disk and a little ball)? Does it have anything to do with kitchen sinks? And what about weather? How does it explain cyclones and anticyclones?
  • Wave phenomena: the sonic boom. Can you explain how the explosion associated with a plane travelling at ultrasonic velocities is produced?
  • More on waves: Doppler effect. You surely know about the proverbial band on a train wagon, but what about putting the band on the station and yourself in the train? Will be the frequency shift identical? Why or why not?

These look like simple, even basic, questions, but their solution does not lack subtle points. I’m with Bondi in that one should better understand everyday physics before jumping to the unification of forces or even, more modestly, special relativity. At least in my case, and with the benefit of hindsight, i regret having jumped too early into mathematical physics and abstract stuff, only later learning about funny things like those above: i’m sure i’d be a better physicist had i spent more time in the wonderful world of understandable experiments… but, oh well, you already know the line: you’re never too old… ;-)

Turning back to Bondi’s book, never mind some of the unfavourable comments at Amazon. Even if you don’t buy his claims about SR being common sense (i don’t), the book is just excellent.