Based on what little I know of relativity, clocks run faster the farther from Earth they are. So a clock on top of a mountain will run a bit faster than a clock at sea level due to the effect that the stronger gravity has on time. But what if there was a clock at the center of the Earth? Would the clock run slower or faster than the one at sea level?
It would seem that the clock at the center would be weightless, so it seems that it might run faster than even the one at the top of the mountain. Is that the case?
What time it is is determined by longitude, how far east or west you are on the surface of the Earth. It is nothing to do with relativity theory or fast or slow clocks run. For places that are not on the surface of the Earth, and not closely related to any particular position on the surface - this includes both the centre of the Earth and locations in outer space - the only reasonable standard is Greenwich Mean Time, which is the reference against which Earthly local standards are judged.
At the centre of the Earth, it is whatever time it is at Greenwich.
The center of the Earth is younger than the surface of the Earth, so less time has passed for it. Clocks run slower at the center because the passage of time depends on the gravitational potential rather than the force, so while there is no net force at the center, there is potential. If you make some simplifying assumptions, then for the 5 billion years of Earth history, the surface has had approximately 1 year of time pass more than the center has. So, the effect is not all that significant.
The further you get from the center of the Earth, the more quickly you will age relative to an observer in the center of the Earth because of general relativity time dilation. However, due to special relativity time dilation of the velocity you have rotating at the surface of the Earth, you will age more slowly compared to a still observer at the center.
For airplanes and other flying/orbiting objects, the general relativity is the more powerful effect by an order of magnitude or so. Don’t know which one is more powerful in the center versus the surface. I’d think that General would be yet more powerful still, since orbiting objects have a much greater speed differential versus the surface of the Earth than the surface of the Earth does versus the center, and yet orbiting objects have less gravitational potential difference between themselves and the surface versus the surface and the center.
Yumblie hit it: Gravitational time dilation depends on potential, not on the field. To use the height analogy, what’s important is how far down you are in the valley, not how steep the ground is.
And the general relativistic effect is comparable to (but larger than) the special relativistic effect for an object in orbit, but the rotation of the Earth is well less than orbital speed, and so will be close to negligible.
That’s interesting about gravitational potential. I looked at the wiki page and graph of the potential for a spherical body. That helped with the visualization.
Sorry for my poorly-worded OP. I was not wondering about clock time with timezones and such. I was wondering about time dilation with regards to gravity. I was thinking it was dependent on the force the object felt, but that’s not the case. An object at the center of the Earth is weightless but has a greater time dilation effect than an object on the surface. Thanks for all the great answers. I’m still trying to wrap my mind around it.
So the difference in time at the center of the Earth, compared to someone at the surface would be very small… how about at the center of the sun vs at the surface? Would the difference still be negligible?
talking time is done by an established human standard based on longitudinal markers…as seen on a globe. There are political adjustments in some regions.The center would be on GMT as it is the base zone…Aka London
