Time dilation in an acc. vs gr. field

[Reuben Smith]

In a gravitational field time slows this is fact,the area around the gravitational field is affected ,is the space around an accelerating field also effected or only the object itself ,what I really want to ask if you place a clock so it would be in close but not contacting a accelerating mass would it run slower?

 

[zhermes]

No it would not. The equivalence principle only applies to the accelerating observer, not nearby objects.

 

[bcrowell]

GPS satellites show gravitational time dilation, and they're not in contact with the earth.

 

[Mentz114]

A gravitational field pervades space, and clocks at different locations may run at different speeds, certainly.

But I'm not sure what you mean by 'close but not contacting'. Or by 'accelerating field'. Is the clock co-moving with the accelerating body ? Is the accelerating body creating a gravitational field we should take account of ?

 

[bcrowell]

Hmm...zhermes and I seem to be contradicting each other, which probably indicates that Reuben Smith's question was open to differing interpretations.

What does "area around the gravitational field" mean? I would describe a gravitational field as *occupying* the area around some mass.

What does "accelerating field" mean? A field isn't a physical object.

Re "accelerating mass," why would it matter whether the mass creating the field was accelerating or not?

 

[Reuben Smith]

For example we could build an oscillating circuit into the barrel of a machine gun and an oscillating circuit in an object that is levatad in a vacumme by a magnetic force

 

[Reuben Smith]

Am I wrong in thinking that a clock in a high tower would run faster than one on the ground because of the strength differences in gravity due to the distance from the center of gravity force ,Maybe I should have used the word force instead of field?

 

[Jonathan Scott]

Time dilation is caused by differences in gravitational potential or different velocities, or a combination of both. Acceleration has nothing to do with it.

You can analyze time dilation in a rotating system (for example like a space station) either as due to velocity or due to "effective" gravitation caused by the acceleration from the point of view of someone within the system, and both calculations give the same result.

 

[PAllen]

I'm guessing the OP is getting at better defining the equivalence principal. As has come up on many threads here, there are different researches have used many different definitions, of varying precision.

My take on what they are worried about is:

1) hold clock above the the ground, it will run slow compared to a clock far from any gravitating body.

2) What about a clock in rocket not touching any walls?

Some partial answers, for different ways of making this more precise:

a) If a person in a rocket holds the clock above the floor, you get the same slowing as a person holding a clock on earth.

b) If you imagine a free falling clock near the Earth's surface, vs. a free falling clock in the rocket, things get a little complicated. The Earth's gravity is radial and different at different heights. The rocket's pseudogravity is strictly uniform. The best one could say, is that to the extent that span of free fall, the distance of free fall, and size of the clock are small enough that radial (tidal) and altitude effects are below what you can measure, then the free falling clock near the Earth behaves identically to the free falling clock in the rocket.

 

[Reuben Smith]

In open space velocity is null because there is no center of the universe to check your speed by only acceleration can be noted ,for if you are not accelerating you are sitting still other wise all objects in deep space would slow down or at least in my humble opinion.Mass in motion tends to stay in motion.

 

[Dale]

The time dilation between the top and bottom of a uniformly accelerating elevator in flat spacetime will be the same as the time dilation between the top and bottom of the same elevator in a uniform gravitational field of the same proper acceleration.

 

[Reuben Smith]

Yes I can conceive that the two clocks on Earth and the two clocks in space accel. would be effected the same because of the change in length due to accelation,thank this has enlightened me ,bear with me in my future questions for the only stupid question is the one unasked and I feel privilaged to have a forum where I can present my questions.

 

[Dale]

No problem. Such questions are useful to other people who read but may not want to ask.