Physics of critical mass for uranium, mostly the work of Rudolf Peierls on nuclear fission and how a simple question from Otto Frisch led to the realization that an atomic bomb was possible.
Follow-up video: How to calculate an atomic bomb's critical mass https://youtu.be/DIuoFAW9H3E
Playlist Physics of Nuclear Weapons: https://www.youtube.com/playlist?list=PL_UV-wQj1lvUhNttvv4_KsYrQxHygj3Ey
"Critical Assembly Simulator" by Alex Wellerstein https://blog.nuclearsecrecy.com/misc/criticality/
Erratum: at 3:00 the number of protons and neutrons is incorrect, it should say "U-235: 92 protons + 143 neutrons; U-238: 92 protons + 146 neutrons"
00:00 Introduction
01:01 Nuclear Fission
02:20 Critical mass: Bohr
03:25 Critical mass: Perrin
04:27 Critical mass: Peierls
08:29 Cross section & mean free path
09:59 Critical mass: Frisch-Peierls