Explaining Planetary Spin: Insights and Mathematical Considerations

In summary, the planets rotate at their particular velocities because of the asymmetrical rotation of the cloud of gas and dust the solar system collapsed from. This makes it difficult to determine exact mathematical relationships between mass and rotation velocity, as the starting conditions and slight variations can greatly impact the outcome. While there may be a correlation between mass and rotation velocity, it is unlikely that a tight relationship would naturally arise from the process of planet formation. Therefore, accurately modeling and simulating the formation of our solar system is still a complex and ongoing task.
  • #1
Ian
88
1
I was hoping that someone might give an insight to this on another thread concerning the moon, but no luck there.
Can anyone give me a plausible reason as to why the planets rotate at their particular velocities, e.g. why does the Earth spin ~365 times per orbital revolution, or why does Jupiter spin ~1200 times per orbital revolution?
If anyone has an answer can they please back their views up with some maths.

Thanks.
 
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  • #2
The planets spin for the same reason they orbit: the cloud of gas and dust the solar system collapsed from was asymetrical and therefore rotating.

The particular maths are tough though: you need to infer some starting conditions and small changes in starting conditions lead to big changes in the result. People are working on it, but I don't think there yet exists an accurate computer model/simulation of our solar system's formation.
 
  • #3
That was a bit quick on the draw! I only posted this a few minutes ago.
Thanks for your ideas. By what you said it sounds as though the rotation is related to the planetary mass or density. If this is so then there ought to be some relation between mass and rotation velocity.
 
  • #4
Maybe, but if you think about how the planets were formed - accretion followed by planetisimal collisions (except the gas giants?) - it would seem quite unlikely that a tight relationship would fall out naturally.

The Earth may be a good example - either way! No doubt there is a fairly well bounded region in the proto-Earth/proto-Moon parameter space that would give rise to an Earth-Moon system, and that region may also pretty much determine the initial rotation period of the Earth (and period of revolution of the Moon) - which, ~4.5 billion years later, gives us today's rates - but the extent to which the parameter space region is determined by the initial conditions of the proto-solar nebula?
 
  • #5
Nereid's explanation was what I meant when I said it was tough to model: there was a lot going on when the solar system formed.
 

1. Why do the planets spin in the first place?

The planets spin due to their initial formation from a rotating cloud of gas and dust. As gravity pulled these materials together, the conservation of angular momentum caused the resulting planet to spin.

2. Do all planets spin in the same direction?

No, not all planets spin in the same direction. The direction of a planet's spin is determined by the direction of the initial rotation of the gas and dust cloud that formed it. Some planets may have also been affected by collisions or gravitational interactions with other objects, causing them to spin in a different direction.

3. What exactly causes the planets to continue spinning?

The planets continue spinning due to inertia, which is the tendency of an object to maintain its state of motion. Once a planet is set in motion, there is no force acting on it to stop or change its spin, so it continues to spin at a constant rate.

4. Are there any exceptions to the planets spinning?

Yes, there are some exceptions to the planets spinning. For example, Venus has a very slow and retrograde (backwards) rotation compared to the other planets. This is thought to be due to a collision early in its formation that caused it to change its spin direction. Additionally, some dwarf planets and moons do not spin at all, but instead have a synchronous rotation where one side always faces their parent planet.

5. Could the planets ever stop spinning?

It is unlikely that the planets will stop spinning, as there are no significant forces acting on them to slow down or stop their rotation. However, some factors such as tidal forces from other objects or changes in their mass distribution could potentially cause changes in their spin rate over a long period of time.

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