# Time and gravity

by seb7
Tags: gravity, space, time
 P: 26 Time slows down near gravity (or under acceleration); so if a 100 seconds pass in space, somewhere wheres there is no (near zero) gravity, how many seconds passed on earth over the period? ie. whats the percentage difference does earth experience against time that is not effected by gravity?
 PF Gold P: 10,781 First, there is absolutely nowhere in the universe that is unaffected by gravity. Since the range of gravity is infinite, at best you can say that out there in a huge interstellar void the effect is very very small. The effect of the Earth's gravity on time dilation is very small, but very measurable. The clocks on board GPS satellites tick at a rate of about 40 microseconds faster per day than a clock here on Earth thanks to the lessened effect of gravity at their orbital distance. Way off in an interstellar void there would be an even larger difference, but it would still be very small. http://www.astronomy.ohio-state.edu/...Unit5/gps.html
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Thanks
PF Gold
P: 26,122
hi seb7!
 Quote by seb7 Time slows down near gravity (or under acceleration);
no, time dilation does not depend on acceleration, only on speed (or gravity)
 so if a 100 seconds pass in space, somewhere wheres there is no (near zero) gravity, how many seconds passed on earth over the period? ie. whats the percentage difference does earth experience against time that is not effected by gravity?
time dilation due to gravity is approximately 1 - U = 1 - 2gM/rc2 = 1 - 2gr/c2

P: 26

## Time and gravity

Hi, yes I understand GPS satellites tick faster, but they are hardly out of the earths gravitational field.
So, whats the answer to 1 - U = 1 - 2gM/rc2 = 1 - 2gr/c2 ?
I'm interested to know what, as percentage, is time on earth slowed, compared to a place without gravity.
Mentor
P: 15,395
 Quote by seb7 I'm interested to know what, as percentage, is time on earth slowed, compared to a place without gravity.
 Quote by Drakkith First, there is absolutely nowhere in the universe that is unaffected by gravity