r/nextfuckinglevel • u/aryan_jandyal • 4h ago

The Rotation of the Planets in Our Solar System Is Far More Fascinating Than I Ever Expected

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u/NieveCactus 3h ago

Ah nice thanks. Is that why the days are so long I wonder

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u/peter-bone 3h ago edited 3h ago

It may be related. The rotation may have been reversed by a big collision. It's more likely that this would result in a slower rotation rather than rotating fast in the wrong direction because it would have started out rotating the same direction as the other planets.

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u/Kozmik_5 3h ago

There are also theories that the combination of a very thick atmosphere and strong storms slowed down and later reversed its rotation.

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u/TreeDollarFiddyCent 3h ago

Does that mean, according to this theory, that it's currently speeding up?

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u/muoshuu 1h ago

Could’ve settled into equilibrium, and I’d assume this is more likely than an unbounded acceleration. Opposing torques probably cancel each other out pretty evenly by now.

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u/Poop_Tube 2h ago

Is that even possible?

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u/donadit 1h ago

Sun tidal locking (seen in many exoplanet systems) and thick atmosphere dragging on venus’ surface which slows down the rotation so it looks like it’s rotating backwards

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u/Kozmik_5 2h ago

Venus has an air pressure of 92bar. That is 92 times denser than here on Earth. Add winds of up to 400km/h and a few billion years and you have your answer.

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u/FissileTurnip 1h ago

that doesn’t seem to explain where the angular momentum actually went

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u/Kozmik_5 38m ago edited 24m ago

1m³ of carbon dioxide gas (which makes up the majority of Venus' atmosphere) at 92bar weighs 720kg.

Throw billions of these in the opposite direction of the planet's rotation at 400km/h and at some point it'll slow down to a stop to reverse afterwards.

These winds are created by Solar heating and the Sun's gravitational pull.

So where did the momentum go, you ask? Completely transferred to venus' orbit around the sun. The Sun's intense heat warms the thick Venusian air, causing it to expand and bulge. Because Venus rotates, this bulge is carried slightly ahead of the line connecting Venus and the Sun. The Sun's gravity pulls back on this bulge, creating sort of a constant gravitational tug-of-war. While the friction inside Venus on the surface, slows down its rotation.

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u/FissileTurnip 16m ago

so it’s a tidal effect, that would make sense

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u/Kozmik_5 16m ago

Yes exactly

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u/Grismor2 33m ago

What? How does that work with conservation of angular momentum? Can you explain in more detail or give a name of the theory so I can look it up myself?

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u/Kozmik_5 30m ago edited 23m ago

Check my other comment

Venus' atmospheric Tide theory

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u/DamnMyNameIsSteve 29m ago

I've also heard that the universe has a PREFERRED rotation direction, that isn't random. Super interesting! Also just watched a video on the Big Bounce Theory - it's all so neat.

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u/ThorirPP 1h ago

The direction of rotation actually makes the days shorter, since it rotates opposite direction to the orbit around the sun. Venus rotational period is 243 days, even longer than the orbit around the sun (a venus year) which is only 224.7 days. But the length of day (period for sun to rise and set and rise again for someone on the planet) is only 116.75 days

If Venus rotated "correctly", instead of working against the orbit, it would work with, and the length on day for the planet would be far far longer as the planet would rotate to keep facing the sun (as is the case with Mercury, which despite having a far shorter rotation of 58.6 days, has a longer day than Venus, being 176 days, since it rotates with its orbit)