Quote:
Originally Posted by skwinty
The force of gravity does not exist. This force was a newtonian construct to explain why apples fall from trees to the ground and why we don't fall of the earth.
The earth is in freefall around the sun (due to the curvature of space time caused by the suns mass) and bodies in free fall feel no "gravity". As far as the earth is concerned it is travelling in a straight line in curved space time.
ie the shortest distance between 2 points which is a straight line.
We dont fall off the earth due to the inertia and acceleration of the earth.
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Pretty good answer, Steve, but not quite correct. For every day situations, such as an apple falling from a tree, tripping over a crack in the pavement etc, gravity can still be called a force (although, technically, it still isn't....if you like to be pedantic about it
). However, gravity is really no more than a curvature of the local spacetime field caused by a massive object, Caleb. As Steve said, the Earth and everything else in the Solar System, is in free fall about the Sun and is traveling along straight lines in curved space caused by the Sun's mass.
The reason why we don't feel the Earth's motion about the Sun, or fall off the Earth is due to the fact we're a part of the inertial system which is the Earth and its gravitational well. Really, we're far to small to notice as for all intents and purposes, everything on the planet is just the one object in the system.
However, if you were to produce some sort of rippling effect in the curved space around the Sun (or the Earth, for that matter), you would be generating a gravitational wave, and this wave would travel at the speed of light....it's characteristics are the same as for a light wave except the propagating agent in this case is a graviton and not a photon.