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This question is, once again, open to all.

Some time ago, I read this book on space being curved by gravity. The stronger the gravitation, the greater the degree of curvature. No problem with grasping this. Big question is...................am I supposed to abandon my previous understanding that a spacecraft or planet's orbit is a balance between gravity and centrifugal force? Or the freefall thing where the spacecraft is always falling to earth but the curvature of the earth always recedes?

MR

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In a word, "yes".

But that's not so bad, because imagining orbits as a balance between gravity and centrifugal force is wrong anyhow. Centrifugal force doesn't exit - it's a non-intertial force in Newtonian mechanics. A better way to think about this in Newtonian terms is that the force of gravity supplies the needed acceleration to constantly change the velocity vector of the orbiting object so that it orbits with a constant speed and a curved path.

Relativity solves the real problem of gravity doing it's action at a distance. (In other words, how does the satellite know which way is down?) Thinking relativistically, the satellite is merely traveling along a line of constant space-time curvature. It doesn't have to know about the "gravitating" object at all - it merely "goes with the flow" as it were...

2 posts :: Page 1 of 1