OCCOM BILL wrote:
Does anyone know of an experiment in which multiple methods of measuring time in space was done
with the control obviously being that they measure nearly precisely in sync here on earth. Specifically, a digital watch, a geared mechanical watch and a watch that uses centrifugal force acting on tiny break pads to create resistance to an excessive drive force (I don't know what you would call that). And, if so, what were the results?
We have done experiments like this using at least three different mechanisms. Note that these experiments have to be very precise to be of any value. We don't have the ability to go anywhere near light speed (except in one case below) so the effect of time dilation is very small.
We have done a very similar experiment to the one you suggested with atomic clocks on airplanes. Atomic clocks are extremely accurate and precise. As predicted by Einstein the one clock experienced less time.
We have also seen a natural experiment with particles. A pi meson is a subatomic particle that is created when radiation strikes our atmosphere. It travels at near the speed of light. We know that it has a very short lifetime and decays to other particles in a precise amount of time. Thus the pi meson is a built in stop watch.
We know where the pi mesons are created, we know how long they exist and we know their speed. Using this information we can simply calculate how deep in the atmosphere we should be able to detect pi mesons. Of course we detect pi mesons much deeper than you would expect using Newtonian physics. The pi mesons are going near the speed of light (from the Earth frame of reference) and thus age slower from our point of view. This allows them to travel farther in the atmosphere. Of course this type of experiment with particles has been duplicated in the lab.
There have also experiments that involve the fact that light acts like a wave and can interfere with itself. Think of light as a sine wave. If you have two "waves" of light that are lined up with all of the "peaks" together. The sine wave adds together and is twice as strong. If the sine waves happen to line up with the peaks of one over the valleys of the other, they "cancel" and the light actually will not be measurable at that point.
With a very precise piece of equipment we can set up an experiment that "times" a beam of light (laser) reflecting between two points. If the light goes out of phase it is very easy to measure (since the beam and its reflection will either add, or darken). This apparatus has shown that the more complex "general relativity" is correct.
Relativity has also been used in countless astronomical calculations. Many of these things have been measured in other ways. An example is the orbit of Mercury. 100 years ago the orbit of Mercury baffled astronomers since the orbital period does not follow the pattern suggested by Newton. Some suggested there was another planet inside the orbit of Mercury.
However, Relativity explains the orbit of Mercury perfectly. Each of these examples is another reason why scientists trust and use the theory of relativity.