[HN Gopher] In contrast to Earth, Mars's middle atmosphere appea...
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In contrast to Earth, Mars's middle atmosphere appears driven by
gravity waves
Author : wglb
Score : 71 points
Date : 2025-03-09 03:15 UTC (3 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| wglb wrote:
| Referenced article:
| https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JE00...
| colanderman wrote:
| > Not to be confused with gravitational waves from massive
| stellar bodies, [gravity waves] are an atmospheric phenomenon
| when a packet of air rises and falls due to variations in
| buoyancy.
|
| For those similarly confused by the title as I.
| stronglikedan wrote:
| I used to thing programmers were bad a naming things until I
| became interested in physics.
| DiggyJohnson wrote:
| Related to this discussion, astronomers' usage of 'metal' is
| a fun example.
| hamilyon2 wrote:
| And musicians!
| dylan604 wrote:
| Salts in chemistry too
| dmoy wrote:
| "it can't be that bad, can it?"
|
| > astronomers use the word metals as convenient shorthand
| for all elements except hydrogen and helium
|
| what, ok
| kadoban wrote:
| Yeah, fun, right?
|
| 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".
| adastra22 wrote:
| Eh, that grosses over the defining difference that
| hydrogen, helium, and a little bit of lithium are
| everywhere everywhen all at once because of The Bog Bang,
| whereas everything else is concentrated due to being
| produced in supernovas and neutron stars.
| wavemode wrote:
| Reminds me of: https://xkcd.com/2205/
| dataflow wrote:
| Isn't there predicted to be liquid metallic hydrogen in
| Jupiter's core?
| danparsonson wrote:
| Metallic as an adjective, behaving like a metal - due to
| the insane pressures. Different usage of the word
| "metal".
| TeMPOraL wrote:
| So for astronomers, metallic means "behaving like
| everything else other than hydrogen and helium".
|
| 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".
| Sharlin wrote:
| "Metal" to astronomers simply means "non-primordial". As
| in, not created by the primordial nucleosynthesis.
| layer8 wrote:
| To keep on topic, that makes Earth's and Mars'
| atmospheres consist of metals.
| cjfd wrote:
| Hydrogen can be a metal too.
| https://en.wikipedia.org/wiki/Metallic_hydrogen
| Sharlin wrote:
| Point is, not in the astrophycisists' use of the word
| (and not really in any other use either - metallic
| hydrogen is not a metal, just behaves in some aspects
| like metal). To astrophysicists, hydrogen is not a metal
| by definition, which is literally "everything except
| hydrogen and helium". No matter how exotic a phase.
|
| Nb. The subset of astronomers who call everything after
| helium "metals" is mostly disjoint from the subset that's
| interested in gas giant interiors.
| bane wrote:
| Wait until you spend time learning probability, or worse,
| biology.
| andrewflnr wrote:
| Worse than math, where set theory, type theory, group theory,
| and category theory all exist and refer to barely-related
| things?
| lucasoshiro wrote:
| I really can't see why they are called categories... Do we
| have anything that we categorize and get categories from
| it? Looks like another synonym to "set" and "group" that
| wasn't used so far.
| AnimalMuppet wrote:
| So in a thread about Mars's atmosphere, we wind up at
| category theory.
|
| Never change, HN, never change.
| TeMPOraL wrote:
| Reminds me of that article[0] that says the trebuchet is a
| _gravity weapon_. That 's because it's the gravity that does
| _both_ the launching and the dropping.
|
| With some interesting consequences that sort of justify
| calling it that.
|
| --
|
| [0] - https://michaeldominik.substack.com/p/physics-
| rediscovered-i...
| erkt wrote:
| I am cynical but, I am pretty sure the ambiguity was
| intentional
| NotYourLawyer wrote:
| Seriously, what a dumb title. Anybody who knows what gravity
| waves are is gonna read it and go "what?? no."
| pfdietz wrote:
| You are confusing gravity waves and gravitational waves.
|
| 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.
| NotYourLawyer wrote:
| Ok, that's a good point. But gravity wave is commonly used
| as shorthand for gravitational wave.
| pfdietz wrote:
| But not in this case, so your criticism was unwarranted.
| divbzero wrote:
| One type of gravity waves can be seen on Earth where its
| atmosphere meets large bodies of water. These are commonly
| known as ocean waves.
| fleeb_ wrote:
| As always - relevant XKCD - https://xkcd.com/2340/
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