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## Friction in Space

By the way, a curious observation concerning friction.

Have you noticed the spin velocities of Jupiter and Saturn equal their orbital velocities?

As an analogy, the spin velocity of your tire equals the linear velocity of your car -- the cause being friction between the pavement and tire.

Do you think this is a coincidence?

2. Considering most other planets have radically non-matching spins to their orbits, yes, I'm willing to call it coincidence.

3. Originally Posted by marksthespot
By the way, a curious observation concerning friction.

Have you noticed the spin velocities of Jupiter and Saturn equal their orbital velocities?

As an analogy, the spin velocity of your tire equals the linear velocity of your car -- the cause being friction between the pavement and tire.

Do you think this is a coincidence?
I've noticed that they are not equal. For Saturn, it has an average orbital speed of 9.68 km/s and rotational velocity of 9.87 km/s. For Jupiter, it's an average of 13.07 km/s and 12.6 km/s. One number is an average speed and the other is a velocity. Speed is distance over time while velocity is displacement over time.

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1) If this mechanism were possible, I would not expect it to be exact
2) A coefficient of frictions goes from 0 to 1

5. Orbital speeds are not constant, but vary throughout the planet's year, so at best the rotation speed matches the orbital speed twice a planetary year. And the rotation axes are inclined to the orbital plane--so the planet would be skidding rather than rolling in its revolution around the sun.

Grant Hutchison

6. marksthespot,

It almost sounds like you're making a claim and arguing against the answers. That's not what we do here. The Space/Astronomy Questions and Answers forum is where people get mainstream answers to their questions. One may not argue against those answers on an against-the-mainstream basis. Please read our rules, linked in my signature line below.

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