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Jan20-13, 03:58 AM
P: 611
What exactly is an inertial reference frame?

While I can understand how objects would seem to accelerate due to an accelerating reference frame and you wouldn't want that, what particularly confuses me is that we use the earth as a reference frame yet the earth accelerates around the sun.

Are we just using the earth as a good enough approximation of an inertial reference frame? Would it be correct in thinking that there isn't an absolute inertial reference frame?
Although Einstein liked to talk about moving trains on Earth, he liked to think about elevators in outer space. And, in fact, that is where most of the thinking about inertial reference frames should take place when you are learning about it. To try to figure this stuff out in a cosmic sense initially using your rotating bedroom on earth as your frame of reference is working harder, not smarter. Start thinking about your 4-vectors in the intergalactic space between the milky way and the andromeda galaxy.