Main Question or Discussion Point
This is a quote from Victor Stenger's the Fallacy of Fine Tuning, let me know if you think it is true. He claims that gravity is fictitious (typos are due to the fact that I scanned and OCR'ed the book:
One of the several great insights of Einstein was that gravity is indistinguishable from acceleration. Imagine a closed chamber far out in space accelerating at exactly 9.81 meters per second per second, the acceleration we experience from gravity on the surface of Earth. If you were to wake up inside that chamber,
which has no windows to the outside, with no memory of how /ou got there, you would think you were just sitting in a room :>n Earth.
Now, technically, if you had some accurate measuring equipment, you would be able to detect the fact that the paths of falling objects were not converging as they would on Earth, pointing to the center of Earth. So this equivalence is “local,” that is, limited to an infinitesimal volume.
Consider the law of motion F = ma for a freely falling body in terms of a coordinate system falling along with the body. Since the body does not change position in its own reference frame, both its velocity and its acceleration in that reference frame are zero. Zero acceleration means that a freely falling body experiences no external force. An observer in that refer-snce frame has no sense of gravity.
Next, let us consider a second coordinate system fixed to a second body such as Earth. This could be any coordinate system accelerating with respect to the first. An observer on Earth witnesses a body accelerating toward Earth and interprets it as the action of a “gravitational force.”
Ask yourself this: If the gravitational force can be transformed away by going to a different reference frame, how can it be “real”? It can’t.
We see that the gravitational force is an artifact, a “fictitious” force just like the centrifugal and Coriolis forces. These forces ire introduced in physics so that we can still write a law of motion like F = ma in an accelerating reference frame. We sit on a spinning Earth, which puts us in an accelerated reference frame. By introducing the centrifugal and Coriolis forces we >till can use all the machinery of Newtonian mechanics.
The point, though, is that if we want to make all our models point-of-view invariant, then we should not include non-invariant concepts in our basic models. We can still use the notion of a gravitational force mat has proved so powerful from
the time of Newton, as long as we keep in mind that it is fictitious.
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