For those similarly confused by the title as I.
> astronomers use the word metals as convenient shorthand for all elements except hydrogen and helium
what, ok
I've looked up why before, tldr it's just because historically astronomers have never had to care in any detail about chemical reactions (this is not strictly true of course, but somewhat close for at least a large subset). So they just need a term for "crap that came from stars".
In fact, I'm guessing "metal" (noun) came from use of "metallic" (adjective). The mention of helium betrays it - helium is what hydrogen behaves like normally "due to the insane pressures" (and heat), so what it basically says is just "not hydrogen".
Nb. The subset of astronomers who call everything after helium "metals" is mostly disjoint from the subset that’s interested in gas giant interiors.
With some interesting consequences that sort of justify calling it that.
--
[0] - https://michaeldominik.substack.com/p/physics-rediscovered-i...
Never change, HN, never change.
Gravity waves are waves where the restoring force on some medium comes from gravity. Waves you see on the surface of water, for example, are gravity waves.