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The vial contains strontium aluminate. It starts the same, but then the electron gets trapped in a "triplet state" where the drop back down is harder (a "forbidden transition") and it remains there for a long time (up to hours) until it drops, releasing light.pic.twitter.com/o4O5MeDjnu
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The test tube has pieces of uranium glass, containing some U2O3. When hit by a UV photon, electrons jump up to a high energy state, lose some energy through a few small jumps, and then drop back down, releasing a longer wavelength (=visible) photon. https://en.wikipedia.org/wiki/Fluorescence#/media/File:Jablonski_Diagram_of_Fluorescence_Only.png …pic.twitter.com/cUiI7gOGYh
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Friday physics fun: here are two yellowish solids. I shine UV light on them, they respond by shining green back. Afterwards one of the keeps on shining. What is going on? Fluorescence and phosphorescence.pic.twitter.com/jyMY9jZcSv
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Neat animation! But what constitutes a "a sufficiently symmetric tiling"? When I try it on random graphs near percolation the result is very uneven. The heat kernel depends on the graph Laplacian, sensitive to local anisotropy http://homepages.inf.ed.ac.uk/hsun4/PDE.pdf pic.twitter.com/y80I0G6d2M
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Here is a cute idea: MRI tends to be noisy and many patients get nervous from the weird sounds. So manipulate the field gradients to play music. Turn the superconductor into a cello! https://youtu.be/VYAvxe9X3s0 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4715797/ …
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If one uses a disordered graph one does get lines, velocities and circles that look like they should once the scale is big enough: https://arxiv.org/abs/1904.09868 pic.twitter.com/1NfbxZfxaS
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Weyl pointed out that if you have a lattice with a shortest length the Pythagorean theorem does not work. Spheres will not be spheres but cubes, shortest paths follow taxi-cab geometry, space is not isotropic. This generalizes to any regular graph: https://arxiv.org/abs/1109.1963 pic.twitter.com/LW0gwESAO5
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Many dislike the idea that stuff could be truly continuous (you need infinite information to specify a point) and suggest some discrete structure like a lattice or a graph. Others think continuous symmetry is so important (conservation laws) it implies continuous spacetime.pic.twitter.com/D3WJXPA73S
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Friday (theoretical) physics fun: is spacetime discrete or not? Normally we assume space is infinitely divisible just like the real numbers: between two points there will always be at least one more point. It is not obvious this has to be true. Matter turned out to be atoms.pic.twitter.com/kBdTL7nZBW
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Friday physics fun: the crystallogens, alias the tetragens alias Group 14 alias Group IV alias the Carbon group in the periodic table. The name comes from the nice crystals C, Si and Ge make because they have 4 valence electrons, allowing diamondoid crystal structures.pic.twitter.com/2JSystWwJB
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Friday physics fun: Of all the elements in my office these two came about in the weirdest way: cosmic rays whittling down atomic nuclei.pic.twitter.com/ntwh5ZyWww
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Santa gives naughty kids a lump of coal. In my case, I got a cube of beryllium! Thank you santa!pic.twitter.com/R85dtTNbhr
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I Feel Fantastic, Moderaterna styr Stockholms läns landsting. https://youtu.be/zidiWe9yq88 (Oväntat passande)
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Friday physics fun: vanadium crystals. Nicely dendritic, and you can see hints of color from a passivating oxide layer on some crystals.pic.twitter.com/9oU4N0i4jQ
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I was interviewed by Francesca Ferrando on "The Near Future and the Transhuman" https://youtu.be/KKZspUJZQNA and "Far Futures and the Transhuman" https://youtu.be/hrVowCzjv7k for eps. 20 and 21 of the Vlog "Posthumans" http://www.theposthuman.org/vlog-posthumans.html …
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