Don't repeat yourself Updated 2025-07-16
B2 Oxford physics course Updated 2025-07-16
www-thphys.physics.ox.ac.uk/people/AndreiStarinets/sr_mt_2022.html (archive) contains 2022 problem sets and notes, well done Mr Andrei Starinets!
Axiom Updated 2025-07-16
AWS service Updated 2025-07-16
Author Updated 2025-07-16
Aum Shinrikyo Updated 2025-07-16
Atomic clock Updated 2025-07-16
A similar model was used in the Hafele-Keating experiment to test special relativity on two planes flying in opposite directions. Miniaturization was key.
Contains a disposable tube with 6g of Caesium. You boil it, so when it runs out, you change the tube, 40k USD. Their tube is made by Agilent Technologies, so a replacement since that opened in 1999, and the original machine is from the 60s.
Detection is done with an electron multiplier.
youtu.be/eOti3kKWX-c?t=1166 They compare it with their 100 dollar GPS disciplined oscillator, since GPS satellites have atomic clocks in them.
Lab vs cyclotron X-ray crystallography Updated 2025-07-16
cyclotrons produce the better images, but they are expensive/you have to move to them and order a timeslot.
Lab-based just use some X-ray source from the lab, so it is much move convenient e.g. for a pharmaceutical company doing a bunch of images. The Wikipedia image shows such a self-contained lab system: en.wikipedia.org/wiki/File:Freezed_XRD.jpg
Convex polytope Updated 2025-07-16
Binary tree Updated 2025-07-16
Binary translation Updated 2025-07-16
Binary-to-text encoding Updated 2025-07-16
Chorus effect Updated 2025-07-16
Biathlon Updated 2025-07-16
Metastable electron Updated 2025-07-16
A fundamental component of three-level lasers.
As mentioned at youtu.be/_JOchLyNO_w?t=581 from Video "How Lasers Work by Scientized (2017)", they stay in that state for a long time compared to non spontaneous emission of metastable states!
phys.libretexts.org/Courses/University_of_California_Davis/UCD%3A_Physics_9HE_-_Modern_Physics/06%3A_Emission_and_Absorption_of_Photons/6.3%3A_Lasers mentions that they are kept in that excited state due to selection rules.
This is also one of mechanisms behind phosphorescence with triplet states.
Metagenomics Updated 2025-07-16
Experiments that involve sequencing bulk DNA found in a sample to determine what species are present, as opposed to sequencing just a single specific specimen. Examples of samples that are often used:
- river water to determine which bacteria are present, notably to determine if the water is free of dangerous bacteria. A concrete example is shown at: Section "How to use an Oxford Nanopore MinION to extract DNA from river water and determine which bacteria live in it".
- sea water biodiversity: ocean-microbiome.embl.de/companion.html
- food, including searching for desirable microorganisms such as in cheese or bread yeast
- poo, e.g. to study how the human microbiome influences health. There are companies actively working on this, e.g.: www.microbiotica.com/
One related application which most people would not consider metagenomics, is that of finding circulating tumor DNA in blood to detect tumors.
Messier 87 Updated 2025-07-16
Messaging software that force you to have a mobile phone Updated 2025-07-16
Chat programs that don't have a proper web-only operation and force you to have a mobile phone, e.g. WhatsApp.
Heck, even Signal, which is supposed to be super secure and good for your privacy, forces you to disclose your freaking cell phone to all contacts! lifehacker.com/how-to-use-signal-without-revealing-your-private-phone-1818996580
Milky Way Updated 2025-07-16
Where to store images Updated 2025-07-16
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?
There are unlisted articles, also show them or only show them.
