# Rotation and gravity

Discussion in 'Physics & Math' started by comedian10001, Sep 27, 2012.

1. ### comedian10001Registered Member

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This might be a strange question, but I really am trying to figure out exactly what gravity is. It's a force I know, but has no kind of physical manifestation. It's just there... So my question is does rotation have anything do do with gravity? I've read that Venus has a slower rotation than earth but has the same gravitational pull or something of the sorts. That's fine but why do celestial bodies rotate? I have a theory(which is what I gather is the same as Einstein's) that massive bodies create dents in space-time. From what I understand Einstein only talked about revolution of bodies, but space is 3 dimensional. I think Neptune(maybe Uranus can't remember) rotates on a y axis vs x like most bodies(I suppose that depends upon your perspective), but ultimately why do bodies rotate? It also seems the more mass a body has the faster it rotates, i.e. stars. Maybe it's as simple as collisions causing the rotation, but I personally think that gravity has to take part in this.... The idea I have is that all objects are like a whirl pool in water, sucking things in. Except in 3 dimensions vs the "two" (although arguably a whirlpool does act in three) am I completely ridiculous or dumb in this evaluation? Gravity is the one thing we know a lot about, but still don't have any idea what it exactly is. It's a Force, and I put it that it's because whatever object happens to be in space creates a 3d whirlpool in space-time attracting anything towards it. I don't know maybe I am just restating what Einstein had in mind, but if any could clarify this for me I would be ever so grateful. It's pretty much the oldest force we as a species have been aware of yet we still don't have any definitive explanation for it. Thoughts, articles, and insights are gladly appreciated. I hope i'm not the only one confused by this concept.

On a final concern where everything gets crazy is on the molecular level, why do electrons revolve around nuclei? is it gravity? That the nucleus causes a gravitational cavity electrons want to fill, but because of the repulsion can't? Universal theory of everything, gravity has to be the key.... In my personal opinion... it's the only constant.

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3. ### Farsight

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No. Regardless of whether a planet is rotating or not, you'll still fall to the ground.

Because they were formed from bodies falling in decaying spiral orbits, and angular momentum is conserved.

That wasn't what Einstein actually said I'm afraid. People say that a gravitational field is "curved spacetime" and they show you the bowling-ball-in-a-rubber-sheet depiction, but that doesn't quite get across what Einstein actually said. He talked about equations of motion. The motion through space is curved, not space. Space isn't the same thing as spacetime. Spacetime is a "mathematical space" rather than that black stuff between the stars.

It isn't like that I'm afraid.

It's pretty simple really, but people don't explain it very well.

No, it's electromagnetism. And take a look at Atomic orbital on wikipedia. See the bit that says 1.The electrons do not orbit the nucleus in the sense of a planet orbiting the sun, but instead exist as standing waves.

No. Electromagnetic force is far more powerful than gravity.

It's good to wonder, and it's good to think, but it's good to learn too. With respect, you need to learn more about this stuff.

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5. ### AlphaNumericFully ionizedRegistered Senior Member

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I haven't the time to go through the thread in detail but this caught my eye....
Oh the irony......

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7. ### kaduseusmelencolia IRegistered Senior Member

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Nobody, and I repeat, nobody knows what gravity is, there are only opinions, and models based on opinions, some are better than others.
Don't let anyone ever tell you what gravity IS, you will of course get bombarded with folk promoting 'current' pet theories (consensus of opinion), and any ideas outside of these theories are not to be tolerated, which is why gravity questions ALWAYS get heated, as you have already seen.
Read ALL theories of gravity, even the daft ones, and make your own damn mind up

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(unless you want a funding grant, then you'd better jump on the band wagon)

The best theory I've come across is attributed to Plato, who when asked by Socrates, why a pebble lay on the beach instead of flying into the air, is supposed to have replied, because it belongs there.
Technically he wasn't wrong.

My own opinion, you did ask for thoughts, is that gravity is a term used to describe a number of different mechanisms, which is why I believe it can't be pinned down under a single 'theory'.
As for rotation (being the basis of one of the mechanisms attributed to the term gravity) , Newton wrote that a gravitational rotation is one where the (tangential) velocity near the center is greater than the (tangential) velocity further out. Basically the tangential velocity increases the closer you get to the center.
So although it cannot be said that gravity is a rotation, a rotation can be gravitational........

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9. ### EmilValued Senior Member

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Of course is known what is gravity.

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10. ### Prof.Laymantotally internally reflectedRegistered Senior Member

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Newton didn't even know what gravity was until an apple fell and hit him on his head.

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He could be the next genius that will improve our understanding of it, lol.

One explaination that stuck with me over the years is that gravity is just the affect of objects trying to travel in a straight line in higher dimensional curved spacetime. But then rotation causes spacetime to drag along with it, so I don't think rotation is caused by this curvature. The curvature is affected by the objects rotation from frame dragging.