[Archy (George)]

Originally Posted by sjastro

A non inertial frame of reference is accelerated in gravity free space.
The pseudo force is your gravity.
It simply confirms that the effects of gravity can occur in flat space for the reasons I have already given.



Changes to space-time doesn't make any sense.

Corrections to GPS systems involve the synchronization of Earth clocks and GPS satellite clocks.

GR predicts a clock at a higher gravitational potential (ie a clock on the Earths surface) will run slower than one at a lower potential (satellite clock).

This is an example of gravitational red shift which has nothing to do with the geometry of space-time. In fact the original concept of gravitational red shift was devised using SR which assumes that space is flat.

1. An acceleration produces a real force, not a pseudo force.
2. Mass distorts space see: Slide 17 http://www.physics.ucsd.edu/~tmurphy...15_gen_rel.ppt. from which we see the statement "Mass tells space-time how to curve and Space tells mass how to move....Gravity is a property of the geometry of spacetime"
3. Since frequency is a function of inverse time (eg beats per second) a change in frequency, which is what is implied by a redshift, requires a change in time (since there are the same number of beats), which agrees with what I have said that the mass of the earth causes a change in space-time
4. Re the GPS see: Pogge, Richard W., “Real-World Relativity: The GPS Navigation System” where in the seventh para graph there is the statement:
   "Further, the satellites are in orbits high above the Earth, where the curvature of spacetime due to the Earth's mass is less than it is at the Earth's surface. A prediction of General Relativity is that clocks closer to a massive object will seem to tick more slowly than those located further away (see the Black Holes lecture). As such, when viewed from the surface of the Earth, the clocks on the satellites appear to be ticking faster than identical clocks on the ground. A calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day." (Bold and underlining are mine.)

You, of course, are free to believe that the earth does not distort spacetime because it is not dense enough, or whatever else you wish.