Revisiting: asteroids vs meteors vs meteoroids vs meteorites vs who knows. Still confusing! How much space stuff hits Earth? Like, not just dust but things big enough to be impressed by. Who gets claim to Earth-impacting space rocks?
The idea that life can spread between worlds. Or maybe even stars (maybe not.)? The “soft hypothesis” of panspermia and the utility of primoridla ooze. The possibility of panspermia bringing life to primordial Earth. Cowboy scientists just leaving alien goo everywhere.
Periodic table of the elements
Chemical relationships via the periodic table. Actually-useful alternative periodic tables. Selenium toxicity, testosterone, and Brazil nuts. Arsenic. Marveling at 19th centtury arsenic popularity.