# Does a clock in free fall through a gravity potential run faster than a clock held at that gravity potential?

• March 5th, 2012, 12:20 PM
mnpguy
Does a clock in free fall through a gravity potential run faster than a clock held at that gravity potential?
Or are clocks slowed by the gravitational potential independent of their acceleration?

General Relativity's Equivalence Principle posits that the viewer in a closed box in free fall will see no difference from being in an accelerating box away from all large masses, even if the clocks are slowed?

The muon storage/acceleration experiments show muon decay time (measured in the lab frame) depends only on the speed of the muons, not the acceleration.

The Vessot Gravity Probe A must have dealt with/predicted/answered that question when their maser was in several hours of free fall, but I find little more than abstracts and summaries on the internet.

Of course, in the initial question, clocks will be slowed by the velocity attained in free fall. Clock effects are multiplied, though at low speeds and potentials addition is a good approximation (??).
• March 6th, 2012, 01:58 AM
granpa
Quote:

Originally Posted by mnpguy
Or are clocks slowed by the gravitational potential independent of their acceleration?

yes it is independent of their acceleration
• March 8th, 2012, 02:02 AM
mnpguy
Thanks - does
Quote:

Originally Posted by granpa
yes it is independent of their acceleration

come from an actual look at experiment, from theory, or from other's reports on experiment?

So when a distant galaxy approaches a black hole, its clocks, vibrating electrons and all, have slowed toward 0, lengths perpendicular to the event horizon have contracted toward 0, and we still see the galaxy disappearing into the black hole with a velocity less than c while radiation is being pulled out. The black hole expands and its average density goes down. Does the gravitational potential at its center, which may move, stay 0?

How do I reconcile that picture with Leonard Susskind's description of a spaceship entering a black hole in free fall which will continue on normally in its own reference frame until it encounters events we cannot see? (L. Susskind, The Black Hole Wars, 2008)