this post was submitted on 05 Oct 2024
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Showerthoughts

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A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. The best ones are thoughts that many people can relate to and they find something funny or interesting in regular stuff.

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It was only in 1969 (nice) that fungi officially became its own separate kingdom.

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[–] [email protected] 10 points 1 month ago (2 children)

Let's just acknowledge that anything big enough to be round is a planet. That's the bare minimum criteria.

Orbit shapes and clear paths don't matter, the Solar system isn't a typical stellar system, many aren't so stable and ordered, especially in binary and triplet star systems. So the pedantry around the shapes of the orbits of the outer kuiper planets is a very silly thing to argue about. After all most orbits in binary and triplet systems aren't even predictable long term, let alone not circular.

[–] [email protected] 8 points 1 month ago (1 children)

So that makes Earth and Moon a binary planet system. I'm cool with that

[–] [email protected] 5 points 1 month ago* (last edited 1 month ago) (2 children)

I believe the rule of thumb is binary planets' barycentre is external to either body. This is the case with Pluto/Charon, ~~I think it's also the case with Earth/Moon.~~

[–] [email protected] 9 points 1 month ago (1 children)

It is not the case with the earth and the moon. It would be if the moon was 40% more massive

[–] [email protected] 1 points 1 month ago (1 children)

Yeah, I went and checked after posting.

My hunch is that if the moon was closer it would 'drag' the barycentre closer to the moon.

Which, given the moon is slowly receeding, means it was probably a binary early on in the formation of the solar system.

[–] [email protected] 2 points 1 month ago* (last edited 1 month ago) (1 children)

Other way around, the further apart the objects are the less likely the barycentre is to be inside one of them, you can picture it as a rubber band with a dot drawn on it, the more you stretch it the further the dot gets from both ends even if it gets further from one end faster.

[–] [email protected] 1 points 1 month ago

Nice analogy.

TYVM!

[–] [email protected] 1 points 1 month ago

That's a good rule of thumb... but it's probably not enough; no reasonable definition would call Jupiter a star, or even a brown dwarf, or the Solar System a binary system, yet the Sol - Jupiter barycentre is outside the sun... (the whole system's barycentre is sometimes inside the sun, but that's due to Saturn's, Uranus', and Neptune's pulls cancelling Jupiter's).

I'd call the barycentre thing a necessary but not sufficient requirement; a proper definition of double planet should probably also take into account other factors like the relative mass and density of the bodies, and their minimum and maximum distance.

[–] [email protected] 2 points 1 month ago (1 children)

OK, can you name all planets in the solar system?

[–] [email protected] 5 points 1 month ago

Sure. Jeff, Darryl, Norma, Luanne, I got lotsa names.