Arcadian Functor

occasional meanderings in physics' brave new world

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Location: New Zealand

Marni D. Sheppeard

Sunday, April 13, 2008


Today's pretty picture, from the University of Bristol website, is a convergent beam electron diffraction pattern.


Blogger L. Riofrio said...

Pretty! Very reminiscent of Gareet Lisi's E8 pictures.

April 16, 2008 3:51 AM  
Blogger nige said...

From the source website, presumably the electrons are being diffracted by crystals of a semiconductor, but they don't say which unfortunately. This is pretty fascinating because of course diffraction in crystals allows you to work out the chemical structure, which is how Crick and Watson discovered the structure of DNA (although I think they used X-ray diffraction in DNA crystals, not electrons difraction; however there is little difference in the basic principle because wave-particle duality applies to all particles).

It's a nice clear picture, anyway. One of the first science books I ever read was an awful one by Sir James Jeans, "Our Mysterious Universe" (Cambridge, 1930) which I recall had early photos of diffraction of X-rays and electrons by crystals for comparison. The image quality was really awful, but you could just make out the diffraction effect, demonstrating the physical evidence that electrons and photons both have a wave-like diffraction quality.

(Other things in the book were terrible, however. E.g., Jeans popularised his own half-baked crazy theory that the planets were thrown off the sun like surf from massive tidal waves in the early universe. He presented that like an established fact! He also claimed that radioactivity of uranium is a mathematical consequence of it happening to have 92 protons, and he claimed that God is a "pure mathematician". Wishful thinking!)

April 22, 2008 8:45 AM  

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