On 18 June 2014 08:43, <jr...@trexenterprises.com> wrote: > I understand clocks in satellites do not run at the same speed as clocks > here on earth. However, I just can't understand why we would use > Einstein's equations to adjust the clocks on satellites when it would be > so easy to adjust them in accordance to the exact time here on earth. >
That isn't the point. For all I know they may adjust them using clocks on Earth. The point is that the satellites provide yet another way to test special and general relativity, and since scientists are always trying to check their theories are correct, they consider it worthwhile to work out how fast or slow these theories say the satellites' clocks will run and compare this to the measured values. The results are in accordance with both theories - working out the time dilation due to the satellites' relative motion and their position in the Earth's gravity field gives the observed result. Note that SR and GR give this result without needing any free parameters to be tweaked. SR involves simple geometry applied to 4 dimensional space-time; as far as I know the only "free" parameter is the speed of light. GR involves the gravitational constant (I think) but I'm told there are no simple ways in which the equations can be modified to give similar results. Hence the clock rate is "forced" to have a particular value in both theories - the result falls out naturally from the theories without any need to introduce any corrections that could equally well have given other results. Here <http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html> is a more detailed description of this effect. If you have a theory that can give the same result (with a similar lack of "wriggle room" for adjusting free parameters) then you should get some serious interest from scientists. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
