Ciro Santilli @cirosantilli  40

Combination of electromagnetism and general relativity. Unlike combining quantum mechanics and general relativity, this combination was easier.

TODO any experiments of interest at all?

In 2020 physics, best explained by general relativity.

TODO: does old Newtonian gravity give different force results than general relativity?

GPIO generally only supports discrete outputs.

But for some types of hardware, like LEDs and some motors, the system has some inertia, and if you switch on and off fast enough, you get a result similar to having an intermediate voltage.

So with pulse width modulation we can fake analog output from digital output in a good enough manner.

general linear group over a finite field of order $m$. Remember that due to the classification of finite fields, there is one single field for each prime power $m$.

Exactly as over the real numbers, you just put the finite field elements into a $n\times n$ matrix, and then take the invertible ones.

Ciro Santilli considered this as the basis for Ciro's 2D reinforcement learning games, but ultimately decided it was a bit too messy. Nice overall though.

Their project lead as of 2018 was pro-CCP: github.com/cirosantilli/china-dictatorship/blob/aa1176c57fc2929465294e520b43b50d44e202ba/communities-that-censor-politics.md

This is apparently the most important III-V semiconductor, it seems to actually have some applications, see also: gallium arsenide vs silicon.

First proper nearest galaxy to the Milky Way. Everything in the middle in the Local group is either a satellite of the Milky Way or Andromeda.

Many Andromeda satellite galaxies are simply numbered Andromeda II, Andromeda III and so on.

As described on Wikipedia, the observational history of Andromeda is fascinating. Little by little, people noticed that it had a different nature to many other objects observed on the sky, and the hypothesis that there are other galaxies like ours grew in force.

Part of our fascination with Andromeda is due to how similar in size and shape and close it is to the Milky Way.

It is clearly the only thing so large and so close.

Andromeda is, without a doubt, our sister galaxy.

One can't help but wonder if there is some alien looking back at us when we are looking at them through our telescope.

Andromeda is also the furthest object from Earth that can be seen with the naked eye.^[ref] Not surprising, as it literally shines with the strength of a trillion suns!

Once again, relies on superconductivity to reach insane magnetic fields. Superconductivity is just so important.

Ciro Santilli saw a good presentation about it once circa 2020, it seems that the main difficulty of the time was turbulence messing things up. They have some nice simulations with cross section pictures e.g. at: www.eurekalert.org/news-releases/937941.

There is a Turing machine that halts for every member of the language with the answer yes, but does not necessarily halt for non-members.

Non-examples: cs.stackexchange.com/questions/52503/non-recursively-enumerable-languages