The key thing in a good system of units is to define units in a way that depends only on physical properties of nature.
Ideally (or basically necessarily?) the starting point generally has to be discrete phenomena, e.g.
- number of times some light oscillates per second
- number of steps in a quantum Hall effect or Josephson junction
What we don't want is to have macroscopic measurement artifacts, (or even worse, the size of body parts! Inset dick joke) as you can always make a bar slightly more or less wide. And even metals evaporate over time! Though the mad people of the Avogadro project still attempted otherwise well into the 2010s!
Computational physics is a good way to get valuable intuition about the key equations of physics, and train your numerical analysis skills:
- classical mechanics
- "Real-time heat equation OpenGL visualization with interactive mouse cursor using relaxation method" under the best articles by Ciro Articles
- phet.colorado.edu PhET simulations from University of Colorado Boulder
Other child sections:
Two Photon Microscopy by Nemonic NeuroNex (2019)
Source. Shows a prototype of a two-photon electron microscope on an optical table, and describes it in good detail, well done.Since images are large, they bring the following challenges:
To solve those problems, the following alternatives appear to be stable enough and should be used decreasing preference:
- This way, the entire website is relies on a single third party: GitHub, so we have a simple single point of failure.We are at the mercy of GitHub's 1GB size policy: help.github.com/en/articles/what-is-my-disk-quota, but it will take a while to hit that.GitLab however has a 10Gb maximum size: about.gitlab.com/2015/04/08/gitlab-dot-com-storage-limit-raised-to-10gb-per-repo/ so we could move there is we ever blow up 1Gb on GitHub.
- Wikimedia Commons for videos if the following conditions are met:
- in scope: "educational material in a broad sense", but not e.g. "Private image collections, e.g. private party photos, photos of yourself and your friends, your collection of holiday snaps and so on.". I don't think they will be too picky even with low quality photos.
- allowed format, e.g. images or videos, but not ZIPs
- allowed license: CC BY SA, but no fair use
Since Wikimedia Commons has a higher level of curation and is an educational not-for-profit, it is the method most likely to remain available for the longest time.For this reason, we highly recommend uploading any acceptable files there as well as an additional backup.The downside is that its tooling is not as good, e.g. there are a bunch of messy unofficial tools for batch operations, and upload takes more effort.Another downside of Wikimedia Commons is that while we can choose the basename of files, it also adds some extra SHA crap to the beginning of URLs, making them harder to predict.Another serious downside is that they randomly rename images without redirects... e.g. they renamed upload.wikimedia.org/wikipedia/en/0/03/STJ_SVG_file.svg to upload.wikimedia.org/wikipedia/commons/8/81/Superconducting_tunnel_junction.svgAnother "downside" is that they are extremely strict about copyright compliance. This is good because you can be pretty sure that they are correct in general, but it also means that they are very conservative, and delete things where fair use would be OK. And if those fair uses have no Wikipedia page, they won't show up anywhere. - All content will be tracked under the
cirosantillicollection: archive.org/details/cirosantilliarchive.org has a very convenient upload and lax requirements. The generated URLs are predictable (single SHA prefix for the entire collection).Never trust a website that is not on GitHub Pages, for-profit companies will take down everything immediately as soon as it stops making them money.Every external link to non-GitHub pages must be archived. And GitHub links must be forked.We should also backup images that Wikimedia Commons does not accept here in addition to the github.com/cirosantilli/media repository.
The following alternatives seem impossible because Ciro could not find if they expose direct links to the images:
The following do have direct links:
- www.flickr.com e.g. live.staticflickr.com/7437/27402357162_7d91b73cd5_z.jpg documented at help.flickr.com/en_us/get-the-url-of-a-flickr-photo-S1Hnnmjym Also does automatic image size conversion. But only provides ugly autogenerated URLs.
- Instagram does not support upload from computer? Lol?
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