Popadoo said:
When I was first taught about general relativity I found it hard to believe. I mean, come on, simply by being in low-gravity you age faster and time just general moves quicker?
But it's true, as it turns out. They have to reset the ATOMIC CLOCKS (super accurate clocks) on satellites every day, lest GPS be miles and miles off.
It could be so hard to believe because general relativity isnt true. At least certain aspects you have to use special relativity to get a sensible answer. If we ever get one theory that actually works for everything it may well be a whole lot easier to understnad.
Also, the actually US GPS system, I dont know about GLONASS, GNSS or future Galileo, Compass or IRNSS systems, but I suspect they are the same, you don't actually alter the clock on the satellites (I misspelt this as satalites and auto correct has suggest to me Australites, Natality, Satanism and Satanist.....Go go autocorrect...) they check them individually against known location ground station and then work out the time error based on the error in position, the satalite then as part of the ping it sends out of its position says "I have an error of this" which the handheld devices then compensate for.
Also, I'm fairly sure the standard theory for the loss of time is due to the speed they are travelling relative to the earth is that much greater and the closer you get to the speed of light the slower you age (Though this could just be the special theory of relativity). The actual loss of time per day for satellites is negligible but it does become significant over time. For one day however the inaccuracies generated by the bending of the signal path as it travels through the atmosphere is significantly greater. Compensating for this bending is one of the biggest problems in satellite navigation as the difference it can make is huge.
