Clock Dilation: Its cause?

Beginning with a stationary observer on the surface of the earth, the rate at which clocks operate changes with altitude and with speed relative to the observer. The question is: What is the cause for this clock dilation? The clock's operation is a physical occurrence. Does empirical evidence...

So a day spent on the bottom of the ocean is slightly less than a day spent on the top of Mt. Everest right? And if you were to look back at the Earth from an intergalactic void with a giant telescope everyone would be walking around in slow motion with a slightly redish tint? Are the atoms in a clock at the bottom of the ocean squashed more like a pancake, so a pendulum would have to travel further in it's swing? This is interesting stuff.

Exactly.

This type of test doesn't need to be performed. Why bother, we already know what the answer will be. There are already plenty of experiments that have comfirmed time dilation and gravitational redshift.

All you need to do is place the adequate equipment on the top of a tower, and similar equipment on ground level.



CC

Also, there's nothing significant about sea level. It just reflects how much liquid water is on the planet. It's certainly not a boundary concerning time dilation or potential. Nevertheless, I'm sure people have used GPS in places like the dead sea that are significantly below sea level without consequence.

~modest

Previous responses to this post have done, I think, a good job of answering it, but I’ve some additional comments to contribute.

The best modern atomic clocks, such as the NIST-F1 and others in the TAI collaborative, are already sensitive enough that arithmetic correction must be made to their digital counters when their altitude is changed by an amount as slight as that experienced when they are moved from one floor to another of the same building.

Since all of the clocks in the TAI are above sea level, and since it was established as a standard in the 1970s, the TAI is for a clock at mean sea level, all of its clocks must be adjusted using Relativity. A less “geocentric” time standard is BCT, a calculated time that would be measured by a clock infinitely distant from all matter in the universe (ie in truly gravitationally flat space) with exactly the velocity of the barycenter of the solar system.

NIST and other labs are putting a lot of effort, with good results, into making small, inexpensive atomic clocks, so the day is likely not far off when a typical high school class could use one to measure time differences between two clocks on different floors of its building and compare them to calculations made from the formulas of Relativity. Once these become commonplace, they’ll likely be so useful that they’re carried by submarines, making the experiment HydrogenBond describes practical.

Although you’d have to go considerably deeper than the bottom of the deepest ocean trench to begin to see An interesting question that came up in a string of posts ending with Re: More correct, but more approximate, examples of grav time dilation in and around (these posts are about gravitational time dilation as one approaches the center of the Sun, but the principle is the same as with the Earth) is what gravitational time dilation would be experienced by a clock placed at the bottom of a shaft reaching all the way to the center of the Earth, where the net force of gravity relative to the surface is zero. Although one might expect (as I and an erroneous wikipedia article suggested) that such a clock might actually run faster than one on the surface, this is not the case. Gravitational time dilation is at a local maximum at the center of the Earth. Even at this maximum, the speed of a clock at the center of the earth relative to one at its surface is very nearly an unchanged 1, on the order of .

To get large gravitational time dilations (and such a thing could be very useful!), you need either much more mass than can be had with a mere Earth-size planet, or even a star, or you need great, black hole or near black hole, density.

Hi Modest,

A couple of days ago I read about GPS using the triangulation of 3 satellites times with a further one used to check the answer for +/- 10 metres accuracy. Dilation is only a portion of the solution (that increases in proportion as you seek greater accuracy).

On second thought, I do believe you're right. The additional blue shift that GPS receives below sea level would be small enough to not cause anomalies - be it there or not.

~modest