Ciro Santilli @cirosantilli 35

Ciro Santilli often wonders to himself, how much of the natural sciences can one learn in a lifetime? Certainly, a very strong basis, with concrete experimental and physics, chemistry and biology should be attainable to all? How much Ciro manages to learning and teach in those areas is a kind of success metric of Ciro's life.

www-pnp.physics.ox.ac.uk/~barra/teaching.shtml As of 2023, contains some good 2015 materials: web.archive.org/web/20220525094139/http://www-pnp.physics.ox.ac.uk/~barra/teaching.shtml It was called "Subatomic physics" back then.

2015 professor: Alan J. Barr.

Possible 2022 professor: Guy Wilkinson (unconfirmed): www.chch.ox.ac.uk/staff/professor-guy-wilkinson

users.ox.ac.uk/~corp0014/B6-lectures.html gives a syllabus:

Problem set dated 2015: users.ox.ac.uk/~corp0014/B6-materials/B6_Problems.pdf Marked by: A. Ardavan and T. Hesjedal. Some more stuff under: users.ox.ac.uk/~corp0014/B6-materials/

The book is the fully commercial The Oxford Solid State Basics.

The only isotope found on Earth because it occurs as part of the uranium 238 decay chain, i.e., it is not a primordial nuclide.

Interestingly it is a bit less stable than other isotopesL such as Polonium-208 (3 y) and Polonium-209 (124 y), but those aren't in any Earthly radioactive chain so they don't show up on Earth.

A really good option to store educational media such as images and video!

Shame that like the rest of Wikimedia, their interface is so clunky and lacking obvious features.

Gun-type fission weapons are the simplest approach and they work with Uranium-235 bombs as you can ignite it with just one explosion.

But Gun-type fission weapons don't work with plutonium, and weapon grade Plutonium is cheaper than weapon grade Uranium, so it wasn't much used.

Ciro Santilli finds it interesting that radioactive decay basically kickstarted the domain of nuclear physics by essentially providing a natural particle accelerator from a chunk of radioactive element.

The discovery process was particularly interesting, including Henri Becquerel's luck while observing phosphorescence, and Marie Curie's observation that the uranium ore were more radioactive than pure uranium, and must therefore contain other even more radioactive substances, which lead to the discovery of polonium (half-life 138 days) and radium (half-life 1600 years).

The most practical/precise volt standard.

It motivated the definition of the ampere in the 2019 redefinition of the SI base units

Good NIST articles about it: (archive)

The wiki page en.wikipedia.org/wiki/Josephson_voltage_standard contains amazing schematics of the device, apparently made by the US Government.

This situation is the most bizarre thing ever. The dude was fired in 2020, but he refused to be fired, and because he has the company seal, they can't fire him. He is still going to the office as of 2022. It makes one wonder what are the true political causes for this situation. A big warning sign to all companies tring to setup joint ventures in China!

Discovered by Marie Curie when she noticed that there was some yet unknown more radioactive element in their raw samples, after uranium and polonium, which she published 6 months prior, had already been separated. Published on December 1989 as: Section "Sur une nouvelle substance fortement radio-active, contenue dans la pechblende".

The uranium 238 decay chain is the main source of naturally occurring radium.

Contains the University of Cambridge, that's about it really, from that everything follows.

The city appear to exist there because it was a convenient crossing of the Cam. It also lies near the start of the ancient navigable section TODO towards north or south? Castle hill also offered a convenient fortification location near the river, and is part of the reason for the early Roman settlement. The original bridge was presumably in the current Magnalene bridge, just under the castle hill.

TODO why did the University of Oxford scholars flee to after the The hanging of the clerks in 1209? Why not anywhere else?

To Ernest Lawrence for the cyclotron.

Suppose we have a given permutation group that acts on a set of n elements.

If we pick k elements of the set, the stabilizer subgroup of those k elements is a subgroup of the given permutation group that keeps those elements unchanged.

Note that an analogous definition can be given for non-finite groups. Also note that the case for all finite groups is covered by the permutation definition since all groups are isomorphic to a subgroup of the symmetric group

TODO existence and uniqueness. Existence is obvious for the identity permutation, but proper subgroup likely does not exist in general.

Bibliography:

Group of all permutations.