Rotation requires a reference frame, so sitting still I’m still rotating because the Earth is rotating me with it.
The Sun, being a gas ball, rotates at rates that vary with latitude. Deeper inside the Sun, it rotates like a solid.
Helio and catastrophe can you please check. it's just a thought but I don't think spin needs a reference frame or something relative to it to spin. I think spin is an absolute property. I say this because something spinning will have an internal centripetal force ( centrifugal force for non-scientists) to it, and that's an absolute value, regardless of whether it's relative to something else or not.Does everything in space spin - does the Sun spin ?
Yes. Relative to something.
Cat
Helio and Catastrophte,IIRC, there is still a debate about rotation. There is a famous case where a bucket of water is flung by a rope round and round in a universe with no mass, except for the bucket. The question is whether the water would creep up the sides? Mach,I think, said no.
I suppose a rotational can be independent, but to have meaning I would think you need references.
A modified Tychonic model has the Earth at the center. This rotational frame is not in violatiion of GR, surprisingly, but with all other motions, including our galaxy, our current model works much better.
I think the meaning is that Catastrophe has an independant fixed weight regardless of what's going on outside and that he can communicate it.I suppose a rotational can be independent, but to have meaning I would think you need references.
Helio, we on Earth, have proof that we are rotating with respect to the Sun. That proof is the existence of day and night. We know that (probably dozens, if not more planets, dwarf planets, moons, asteroids. TNOs etcetera, are rotating. There are no absolute rotations, but there are thousands of relative rotations - any object viewed from another object shows change of view of surface features. I cannot see any doubt whatsoever about this. It would be, to deny night and day.
Cat
P.S. Is not the bucket of water orbiting = revolving around, not rotation? The bucket is not turning on an axis, but orbiting a central point external to the bucket. It is like the Earth orbiting the Sun, not turning on its axis.
The more I think about it the more I think the opposite is true, i.e all rotations are absolute, because rotation causes an absolute value of internal centripital force proportion to its rotation speed, dependent only on the mass and radius of the object, which can be measured or calculated. It's not dependent on what any outside observers see or measure.There are no absolute rotations, but there are thousands of relative rotations
Yes, but that doesn't disprove the object being viewed doesn't have an absolute rate of spin. How fast you are moving doesn't change the fixed internal centripital force of the object.any object viewed from another object shows change of view of surface features.
Hi Catastrophe,Just to remind you good folks, this thread is entitled:
Does everything in space spin - does the Sun spin ?
Cat
The "Yes. Relative to something." reply was a red flag for me . I think it's fair to challenge something I don't agree with, also it's still about spin.Does everything in space spin - does the Sun spin ?
Yes. Relative to something.
Cat
David, nothing is aimed against you. I do not make personal attacks. What I find (honestly) abhorrent is confusing the idea of spin, which is common to every understood body in the observed universe, spinning around its own axis, with moving around a central point. viz orbiting around another body. Totally different matters.
I do not want to get into trouble with repetition, but I find it impossible for anyone to respond to the following:
THIS IS WHAT THE OP ASKED:
Does everything in space spin - does the Sun spin ?
Post #1 asks: "Does the Sun rotate on an axis-does the Sun spin ?" My emphasis.
May I respectfully suggest that if anyone wants to discuss swinging buckets or other matters relating to one body swinging or orbiting around another, they might like to consider starting an appropriate thread. The question here is not: does the Earth orbit around the Sun?
The Earth, and all astronomical bodies spin on their axes. The Earth spins on its axis in approximately 24 hours. The Earth also orbits the Sun in one year. If anyone thinks that these are the same, then I believe we should agree our definitions before proceeding further. Does this sound a good common sense solution? A little polite agreement here can save pages of confused "discussion" otherwise.
Do we have a problem in distinguishing between "day and night" and "year"?
That is, between spinning and orbiting. Spin = day and night, orbit . year?
I really do believe we should sort out our definitions/ assumptions. PLEASE
Please, David, there is nothing whatsoever personal here. "No good wars." etcetera.
Please can we agree on some premises?
I was serious about this thread.
THIS IS WHAT THE OP ASKED:
Does everything in space spin - does the Sun spin ?
Post #1 asks: "Does the Sun rotate on an axis-does the Sun spin ?" My emphasis.
If you want to discuss "years" instead of "day and night" - I believe this belongs elsewhere. If I start a thread "spinning or orbiting" or something you choose, I will join you there. I think the OP should have the choice here - spin.
With sincere friendly wishes for a good discussion,
Cat
OK. I agree asteroids may "tumble" around a constantly changing axis. Not really relevant.
What I find (honestly) abhorrent is confusing the idea of spin, which is common to every understood body in the observed universe, spinning around its own axis, with moving around a central point. viz orbiting around another body. Totally different matters.
The Earth spins on its axis in approximately 24 hours. The Earth also orbits the Sun in one year. If anyone thinks that these are the same, then I believe we should agree our definitions before proceeding further.
Do we have a problem in distinguishing between "day and night" and "year"?
That is, between spinning and orbiting. Spin = day and night, orbit . year?
I haven't deviated from spin, other than in one sentence. My space station idea was all about spin and try to prove that it's absolute.I think the OP should have the choice here - spin.
Note the force term in the equation is from the bathroom scales on which Catastrophe was standing.If you know your mass, and the radius of the space station you can calculate your absolute rate of spin without looking out of the window, by using the formulae;
Force (centripital) = mass x velocity^2/radius
In this equation, the force, the mass and the radius are absolute values, so the velocity term must also be an absolute value.
As the curtains were closed, all the information Catastrophe had was obtained from inside the space station. So the answer was independent and not relative to anything outside. The spin of the space station is therefore an absolute value.