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To be more specific, if the relativity of time is governed by the mass and gravity of objects (I.E the satellites orbiting earth experience minor time dilation compared to us on the ground), how is it experienced in deep space, the space that separates the galaxies? Is time only relevant if gravity is present?

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    $\begingroup$ this would probably go best on the physics site. If others agree it will be migrated there. $\endgroup$ – kim holder Mar 19 '15 at 0:26
  • $\begingroup$ My bad, any suggestions for a site? New to the whole stackexchange $\endgroup$ – Jon Philbin Mar 19 '15 at 0:32
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    $\begingroup$ Oh, no worries. And maybe others will disagree - it is a vote system. Just sit tight, you'll get your answer. If it is decided to file it under physics, it will be moved intact - you don't need to do anything. (Better you don't actually, to avoid duplicates.) It will still show up on the main page here but with a note that it has been migrated. Welcome :) $\endgroup$ – kim holder Mar 19 '15 at 0:39
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    $\begingroup$ Awesome, thanks for the advice, looking forward to making use of this site for furthering my knowledge on all things related to the cosmos. $\endgroup$ – Jon Philbin Mar 19 '15 at 0:47
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    $\begingroup$ In general, time dilation or "relativity of time" is only significant at really high gravity or really fast speed. The time dilation due to the gravity of earth or the orbital speed of earth around the sun, or the sun around the center of the Milky Way, are pretty small. But your theory is correct, if you got out of the solar system into mostly empty space and essentially no G and assuming no velocity, then time would travel faster - but you'd probably need an atomic clock to notice. Maybe 1 second a week. The earth's gravity and velocity slow down time, but only a very tiny bit. $\endgroup$ – userLTK Mar 19 '15 at 5:39
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Well, it's not my answer, but I came across a pretty good answer to this question. http://www.askamathematician.com/2015/02/q-since-the-earth-is-spinning-and-orbiting-and-whatnot-are-we-experiencing-time-wrong-because-of-time-dilation/

One thing they don't take into account in the link above is the speed of the Milky-Way, based on cosmic background radiation. The site below says the Milky-Way is moving at 1.3 million miles per hour, which, in and of itself, if I've done my math right is 1 second every 6 days.

How fast are we moving?: http://astrosociety.org/edu/publications/tnl/71/howfast.html#6

There's another time dilation to consider, the dilation in relation to the gravitation of the entire universe - we are in the universe and so we are, by definition, in the gravitational field of the universe, so there would be a time dilation from the entire universe as well, but that calculation is above my pay grade.

As to your final question, no, time is relevant without gravity, well, er, kind of. That's sort of a trick question because there is nowhere in the universe without gravity. You can experience no gravity - in orbit for example, you feel weightless, but you are in a gravitational field even if you don't "feel it" - so there's gravity everywhere and as a result, time is slowed down everywhere, at least, a little bit.

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