Gravity: Someone Explain!

Okay, I get that the massive objects distort space/time ... (the whole rubber mat stretched w/a rock in the center and the marble circling)...

So WTF keeps "orbits" ? If the mass of the sun is so great, what keeps Mercury and other small planetoids from eventually "falling into" our sun?

Is our orbit speeding up as we spiral closer? If not, why not?

This to me defeats my logical (and limited) understanding of general relativity.

Can someone here explain why we are not slowing spiraling closer to the sun over eons of galactic time?

Thanks!

I mean, even the largest planet in our solar system's mass is a fraction of the sun ... how can it's own curvature of space-time offset our sun?

This does not make logical sense.

[edit on 19-2-2009 by MystikMushroom]

You can create a sustained orbit by picking the path correctly. Alot of orbits do decay..... it just takes billions or trillions of years. In space there is much less friction... so while a bowling ball on a trampline is a good example.. you are still dealing with wind resistance.

Thank you ....

But that still does not answer my question in clear, logical terms.

Are we spiraling to the sun slowly, over billions of years? If not -- why?

Is our distance in concordance with our own space-time displacement just "right"?

If that is so -- then what enables smaller planets closer such as Venus and Mercury with smaller space/time displacements (mass) enable their orbits?

This logic is flawed (what I have been taught/shown).

The parrots are going to tell you to tie something heavy to a string, and swing/spin the heavy object around in a circle while holding the string.

Centrifugal force.

reply to post by MystikMushroom


The sun becomes a red giant in a billion years or so. I'd say spiraling in isn't really a big problem.

Originally posted by ALLis0NE
The parrots are going to tell you to tie something heavy to a string, and swing/spin the heavy object around in a circle while holding the string.

Centrifugal force.

And they're right--sort of. The centrifugal force is imaginary; a fabrication of convenience. The real reason is that the various celestial bodies have momentum, and the component of their velocity away from the body they're orbiting balances with the acceleration towards the body they're orbiting.

Look outside this medium star and see the big galaxy there is a reflex gravity that supports the mass that is traveling out into the universe.

I thought I read an article a while back on here about the earth being held in place by some electric/magnetic waves coming from the sun. I'll look around.

reply to post by MystikMushroom

And the winner is ... (Drum roll, please....)
mdiinican! .. (Sort of..)

And they're right--sort of. The centrifugal force

Right concept, wrong force. "Centripetal" force

is the external force required to make a body follow a curved path

However, it is not, in itself, gravity. Centripetal force is the "product" of gravity's attraction to a body in kinetic motion (Already moving ... presumably in a straight line) and the resulting curve in its trajectory.
I'll let Wikipedia explain centripetal force further:
Centripetal force - Wikipedia

Get it? Got it?
Then the question now is,- "How do you get rid of it?"

Originally posted by pteridine
reply to post by MystikMushroom

 

The sun becomes a red giant in a billion years or so. I'd say spiraling in isn't really a big problem.

You took the words out of my mouth

reply to post by LatentElement


Obviously I am not a parrot.

I have many other theories of gravity that seem to make much more sense. So excuse me for being incorrect.

[edit on 20-2-2009 by ALLis0NE]

Are we spiraling to the sun slowly, over billions of years? If not -- why?

reply to post by MystikMushroom


The most logical answer is that the sun is slowly loosing mass allowing the planets to slip outward due to less gravitational attraction.

The sun is an energy source and since E=MC2, as energy is expended, mass is decreased allowing planets to slowly widen their orbits.

Also, in general, stellar masses can an will eject solar material (to form planets, etc.), this has been observed on other stars. Less mass obviously allows existing planet to widen their orbits.

Originally posted by LatentElement
reply to post by MystikMushroom

 

And the winner is ... (Drum roll, please....)
mdiinican! .. (Sort of..)

And they're right--sort of. The centrifugal force

Right concept, wrong force. "Centripetal" force

is the external force required to make a body follow a curved path

However, it is not, in itself, gravity. Centripetal force is the "product" of gravity's attraction to a body in kinetic motion (Already moving ... presumably in a straight line) and the resulting curve in its trajectory.
I'll let Wikipedia explain centripetal force further:
Centripetal force - Wikipedia

Get it? Got it?
Then the question now is,- "How do you get rid of it?"

No, I meant what I said. The centripetal force is a real force, in this case, assuming the form of gravity, which keeps things from flying away. The OP wanted to know what keeps things from spiraling down into the sun. That's a different question. The Centrifugal force is an imaginary force that applies in rotating reference frames that represents the outward push of inertia.

If you were to do a force diagram from a non-rotating frame of reference, there is no force balancing the force of gravity. In an orbit, gravity bends the path of an object traveling perpendicular to it, so that the object's path is always more or less tangential to the acceleration of gravity.

en.wikipedia.org...

Of course, if the OP thinks it that the planets might spiral down into the sun, and not just fall down into it, he has his answer right there. The planets are going at a sufficient speed that they move in a complete orbit, and there's negligable friction to slow them to make them fall.