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The equivalence principle only holds for extremely small regions of spacetime. Which means they hold for short time intervals as well as small spatial regions. Consider an event near the event horizon. If the event is outside the horizon there might be a frame moving away from it that cover a very small region that is also completely outside the horizon and ...


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An object inside a black hole horizon cannot send signals outside of the horizon, but something falling into the black hole can fall through the signal. Take the example of the camera attached to the astronaut's foot. When the astronaut is halfway through the horizon, the camera is about a meter inside the horizon and the transmitter is about a meter ...


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The simple answer is that if an object falls and accelerates, its X-T graph will be curved so its worldline would be curved so movement of the object will be a curve through space time and we only see space so we see it as a straight line. But we can see curvature of spacetime in Earth revolving around the Sun


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So far, there is no experimental evidence that tells against the weak equivalence principle. The consequences of any real violation would be deep indeed: general relativity would instantly be falsified because GTR encodes the principle by saying for any path through spacetime, there is a Lorentz local frame (the "momentarily comoving inertial frame (MCIF)") ...


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"a stationary rocket ship in close proximity to ours, stationary relative to our reference frame" If the two ships are stationary with respect to one another, then their clocks will run identically (in fact, all physics will be identical in both ships) unless there are actual sources of gravity with non-negligible tidal forces across the distance separating ...


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I think you are imagining the earth as one giant rigid inertial frame and that creates problems. Let's look at the atmosphere, a giant doldrum over the pole to make it simple. What keeps the air up there a certain height. Well there is a stronger pressure from the air below it than from the air above it. Newtonian gravity would say the air stays at rest ...


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I was confused by this too -- pop descriptions of the equivalence principle don't mention the problem where the gravitational field points in different directions in different places. It is true that gravity is equivalent to acceleration, and that as a result, if you are freely falling, you feel like you're in an inertial frame. But this frame is only ...


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The Earth's gravitational field extends inward from all of space to the Earth's surface, with it's origin at the center of the Earth. The Earth's gravitational field is characteristic of space-time that has been "curved" by a massive object. If you stand on the ground and let go of a ball, it falls away from you at the acceleration of 9.8 m/sec^2. ...



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