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Grey Knight

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< o11c> Is there any portable function to convert an integer to a string in a signal handler? `s[n]prinf` is not on the list of async-signal-safe functions ...
< izabera> there is but you're not gonna like it
< izabera> write is safe, fork is safe, execve is safe

Just C things.
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> ',,,' == new Array(4)

Just Javascript things.
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hurf blurf i am website, must require javascript enabled in order to display simple static images plox

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Webcomic forums are definitely the premier place for trying to come up with a firm definition of evil.

One person says they believe all acts are evil, so this rollercoaster is really getting out of hand.
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Never not post about dodecahedra
Kepler, the Hydrogen Atom and the Fourth Dimension

Kepler loved Platonic solids. He even made a theory of the planets' orbits where they moved on spheres between a nested octahedron, icosahedron, dodecahedron, tetrahedron, and cube. It fit the data pretty well... but not perfectly. He eventually realized that the orbits aren't circles: they're ellipses!

We now know that the force of gravity drops off as the inverse square of the distance. That's why planets move in elliptical orbits. Platonic solids have nothing to do with it.

But last week, +Greg Egan, +Layra Idarani and I found a solid mathematical connection between the Platonic solids and the inverse square force law. It involves quantum mechanics, and a detour into the 4th dimension!

The force between the electron and proton in a hydrogen atom also obeys an inverse square law... but we need to use quantum mechanics to understand it. Instead of having a definite position, the electron has a wavefunction saying how likely it is that you'll find it in any location.

Amazingly, the wavefunction for the electron in a hydrogen atom can also be described as a function on a 3-sphere: a sphere in 4 dimensions. We can rotate a sphere in 4 dimensions and turn one wavefunction into another with the same energy.

This is a 'hidden symmetry' of the hydrogen atom. It's sort of obvious how 3-dimensional rotations act on a hydrogen atom. The amazing part is that you can do 4-dimensional rotations.

This picture, made by Egan, shows a wavefunction on the 3-sphere. It's positive in the blue regions, negative in the yellow regions, and almost zero where it's black. We’re seeing a moving slice of the 3-sphere, which is an ordinary sphere. When the image fades to black, our moving slice is passing through a sphere where the function is zero.

This particular function describes a very symmetrical state of a hydrogen atom, where it has a definite energy and 7200 symmetries, coming from the symmetries of the group of symmetries of a dodecahedron.

That's quite a mouthful! Luckily, I've already written a nice gentle explanation of this stuff with lots of pictures, including nice pictures of Kepler's original Platonic solid theory, start here:

Make sure to follow the links to Egan's explanation:

We worked out a lot of this math with +Layra Idarani, so if you're a mathematician you'll also enjoy his work:

It generalizes a lot of this stuff to even higher dimensions!

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BBC News genuinely using as background research.
Is 2018 the real life?
Is this just fantasy?

One thing's for sure, my sides are in orbit.
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"Yamaoroshi – A possessed vegetable grater, almost porcupine-like in appearance."

I don't think I will ever get tired of Japanese mythology.
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npm at it again with breaking the entire world. I love single points of failure.
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