k-nearest neighbors algorithm Updated 2025-07-16
One of the most simply classification algorithm one can think of: just see whatever kind of point your new point seems to be closer to, and say it is also of that type! Then it is just a question of defining "close".
Light Updated 2025-07-16
Why is it there such a clear separation of phases?
Why do people with mild symptoms go on to die? It is a great mystery.
Ciro Santilli's theory is that COVID is extremely effective at avoiding immune response. Then, in people where this is effective, things reach a point where there is so much virus, that the body notices and moves on to take a more drastic approach. This is compatible with the virus killing older people more, as they have weaker immunes systems. This is however incompatible with the fact that people don't seem to be contagious after the viral phase is over...
Xerox PARC Updated 2025-07-16
What a legendary place.
The best way to watch a television series is: wait for the thing to end. Then watch the first and last episodes of each season. The rest is fluff. And then pick up any missing interesting clips from YouTube. If a series holds you more than those episodes, it is one of the few amazing ones!
Ten ancient famous songs of China Updated 2025-07-16
This is a good place to start your journey, though it misses a lot, and some songs are not as memorable as others, there is huge variability in that list.
Video 1.
The Ten Most Famous Melodies in Ancient China
. Source. A single video with a collage of all ten songs.
All GitHub Commit Emails Updated 2025-07-16
In this project Ciro Santilli extracted (almost) all Git commit emails from GitHub with Google BigQuery! The repo was later taken down by GitHub. Newbs, censoring publicly available data!
Ciro also created a beautifully named variant with one email per commit: github.com/cirosantilli/imagine-all-the-people. True art. It also had the effect of breaking this "what's my first commit tracker": twitter.com/NachoSoto/status/1761873362706698469
Figure 1.
GitHub Archive query showing hashed emails
. It was Ciro Santilli that made them hash the emails. They weren't hashed before he published the emails publicly.
Figure 2.
All GitHub Commit Emails repo before takedown
. Screenshot from archive.is.
First we can observe that the exact matrices are different. For example, taking the standard matrix of :
and:
both have the same metric signature. However, we notice that a rotation of 90 degrees, which preserves the first form, does not preserve the second one! E.g. consider the vector , then . But after a rotation of 90 degrees, it becomes , and now ! Therefore, we have to search for an isomorphism between the two sets of matrices.
For example, consider the orthogonal group, which can be defined as shown at the orthogonal group is the group of all matrices that preserve the dot product can be defined as:

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