Question on Einstein's General Relativity?

Question

As i know, the reason earth orbits around the sun is due the effect of curved-space. However, i'm curious - How/where did the force come from to keep pushing the planets moving around? It just didn't make sense to me that planets move by itself around the sun.

Your answers are very much appreciated. Thanks =)

Answer 1

Ah...before Einstein there was Newton.

An object in motion will remain in motion unless affected by an outside force.

There is very little friction in space, momentum/inertia carries the planets around.

Think of it like a well balanced bicycle wheel that keeps spinning long after the initial push, except instead of spokes, you have gravity.

Answer 2

Nothing is needed to push the planets around the sun. Space is friction free so they will rotate indefinitely ,and no force is required. A body in mutation will continue in motion unless it is acted on by another force. The sun gravity curves this into an orbit.

Answer 3

Momentum is what keeps a planet moving in orbit (you know, Newton: an object in motion stays in motion blah blah blah). I believe the rate of movement slowly slowly decreases with time because of gravitational friction. I suppose impacts from light also have a cumulative effect over time too, at least in theory. I can't think of any other forces offhand that are acting on the planet.

The original motion came from the rotation of the protostar.

Answer 4

You are quite right to be curious.

In Newton's physics, you need a force (the gravitational force) to keep the earth going round in its orbit and not flying straight off at a tangent. Newton himself said that he had no idea where this force came from (he said it in Latin, "Hypotheses non fingo"). it was just a fundamental property of matter that lumps of matter attract each other.

Einstein's model, which I do not pretend to fully understand, replaces the idea of force by the idea of curved space-time, and the path that the earth follows is the closest it can get to a straight line once this curvature is taken into account.

Answer 5

No force is required to keep pushing planets in their orbits. The inertia of the original movement does that. Einstein's refinement of the laws of gravity does not deal with this, they make calculations that determine the minor variations of planets orbits that Newton's laws can not do.

Answer 6

In an partially empty universe where only the solar system exists, matter with magnetic poles will align with the magnetic poles and behave like a drain, in accordance to diffy-q. There is no other force than gravity acting on the massive objects, be they planets or rock and ice.

Answer 7

Our solar system was created out of dust. All matter in the galaxy is sprialling aroud the centre. It is prehaps this motion that gave the solar system rotational motion and throught a massive amount of time things balanced out into a stable system. Short answer Galaxy spins, solar system spins and planet spins.

Answer 8

Since I read Dune, I fold space now and the freshness dating on Einstein's theories has expired.

Answer 9

Newtonian physics as others have already alluded to, plus the fact that stars and planets must form from rotating clouds of dust and gas. The rotation is believed to be caused by nearby supernovae.

Answer 10

that would be Newton;
an object in motion will remain in motion unless on outside force acts apon that object
Who told you that planets keep going around?
they dont, they slowley spiral in