:: Home  :: Sections :: Experiments  ::  Blog  ::  Contact  ::

Now let’s do something unorthodox.  Let’s send a rocket to the same altitude as a GPS satellite orbit, but let’s have this rocket just hover in space like a space helicopter, with no side to side motion.  The force exerted by the engine on the rocket equals the gravitational attraction; therefore the rocket is not moving.  The gravitational time dilations for both the GPS satellite and the rocket are the same; but the occupants of the rocket are in an accelerated state.  We have to conclude that there are no time dilation effects due to acceleration.  The acceleration is real, think what would happen if the planet below were to suddenly disappear:  the satellite would abandon its orbital path but the occupants would feel no changes to their inertial state; there are no new accelerations.  The rocket, freed from the gravitational pull, would start to move, but the occupants would feel no difference in their accelerated state.  The gravitational time dilations disappear for both them, and only Special Relativity time dilations would be present.  Admittedly, no rocket has been sent to hover like a helicopter and measure the gravitational time dilations in space, but in a way this experiment has already been done.  The gravitational time dilations for an orbiting GPS satellite and for a ground based GPS receiver are calculated using the same formula; no additional time dilations are added due to the accelerated state of the receiver.  There is good certainty that this discussion has already happened.  See Figure 7 for an illustration of this event.


Another piece of evidence comes from the Pound-Rebka experiment performed at Harvard University in 1959.  When doing the calculations for gravitational time dilations for this experiment, no consideration is given to any additional time dilations due to the accelerated state of doing the experiment on the ground.  If R. Pound and G. Rebka Jr. had boarded the zero gravity plane; this is the plane that takes you high up in the air and then accelerates downwards simulating zero gravity, and they had done their experiment while in free fall, they would have done the same calculation and the results would be expected to be the same (assuming negligible free falling speeds).  This again confirms that there are no additional time dilations by doing the experiment on the ground in an accelerated state.

It is also important to note that there is no formula for time dilations due to acceleration.  GR does not provide such formula, nor has any real or thought experiment associated a math relation between the two..