I saw the exact same question here but the answer is beyond my limited knowledge. Gravity is not a force as general relativity explained. then why an object always has to move along a geodesic? I mean if were to make an artificial vacuum space little bit higher from the ground top of a pole, can we keep and object stationary inside of that vacuum floating? If cant is it cos its rotating along with the earth? Do geodesics also have some wave like motion?
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Gravity is not a force as general relativity explained.
This is true for large masses and energies, not for your example.
For large masses and energies a new frame is needed, General Relativity, but this does not destroy the low mass and energy theory of Newtonian Mechanics. At the region of low mass and energy GR converges mathematically to Newtonian mechanics , so the modeling of gravity as a force still holds for your example. (this is what the mathematics of the answer you link to is saying).
For GR to be needed one has to go to planetary dimensions, as with the GPS numbers GR corrections are needed.
anna v
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A geodesic in this context is a path in spacetime, that is, essentially, a location changing over time. In effect, saying this means that objects in a particular place will accelerate in a particular way. Which is not that much different in terms of what you see than the idea that gravity is a force. Making a vacuum chamber does not remove the curvature of spacetime. In effect - you cannot shield gravity. The curvature is still pretty close to that associated with the Earth. The idea that gravity is not a force is more related to 1) that every object accelerates the same way, so it is not a material property (unlike electric forces) and 2) that you can ascribe this behaviour to the shape of spacetime - the geometrization of mechanics. In many ways, it is a mathematical trick. (I say that with not intention of deriding the idea, it is a good trick that has many advantages).
Bruce
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