# What happens to time when gravity is absent

1. Jan 27, 2008

### quantify

If it has been determined that time/space is always relative to gravity as observed in several equations (correct me if i'm wrong), then does time cease to exist if viewed from a relative plane perspective that lacks any form of gravity? Could a relative plane perspective even exist without being relative to a mass that observes gravity?

edit: and say you can never have rule out gravity, can a comparable state be formed by having to gravitational fields directly and perfectly counter act each other creating some sort of equilibrium?

Last edited: Jan 27, 2008
2. Jan 27, 2008

### smallphi

Special Relativity is space/time without gravity(curvature).

3. Jan 27, 2008

### quantify

so i guess my question would be what is time in relation to special relativity

edit: According to newton when you enter into the exact center of earth you observe an equal gravitation pull on all sides, so does time stop there?

Last edited: Jan 28, 2008
4. Jan 28, 2008

### yuiop

The force of gravity at the centre of the Earth (or anywhere inside the hollow of a sphere with a solid shell) is zero. Gravitational time dilation is determined by gravitational potential, sqrt(GM/R) and the potential does not go to zero at the centre of the Earth. As an object goes towards the centre of the Earth its gravitational potential is always increasing, reaching a maximum at the centre of the Earth.

5. Jan 28, 2008

### 1effect

As kev points out, the gravitational potential increases. GR predicts that the clock rate will decrease with respect to the surface. The clocks will not stop, their rate will decrease by a very small amount. See also here: http://en.wikipedia.org/wiki/Pound-Rebka_falling_photon_experiment

6. Jan 28, 2008

### JesseM

I think you're wrong, I've never heard general relativity described in this way.

7. Jan 28, 2008

### HallsofIvy

It is true that, in general relativity, if two clocks are at rest relative to one another but one is in a stronger gravitational field, it will tick more slowly than the one in the weaker gravitational field. I presume that was what was meant.

8. Jan 28, 2008

### JesseM

I initially took "time/space is always relative to gravity" to mean something more--that in some sense they can't even be defined except in relation to gravity--but you may be right.

9. Jan 28, 2008

### petm1

How can you define space-time without gravity? Isn't every clock embedded in mass, And so too the observers?

10. Jan 29, 2008

### yogi

All clocks and observers are contained within the gravitational affect of all matter in the universe - Mach and many modern theorists claim this defines the magnitude of the inertial reaction force (commonly condensed to F = ma). But since the G field is isotropic, we don't have a good way of investigating its local influence upon mass - specifically no one has yet related the magnitude of Newton's reaction to distant matter in a way that does not at some point require some ad hoc physics. You might take a look at Garth's paper "SCC" if you have an interest in seeing how difficult it is to arrive at plausible syllogism

11. Feb 10, 2008

### morphine

So I just signed up to post on this topic, and I'm sorry to swing it into a philosophical direction, but this seems the best way to make the question feasible.

In reference to the mind-body problem, Descartes proposed that the mind exists in time and not in space. The mind has no mass and no gravitational force is being exerted on it - so does this even make sense with reference to relativity?

12. Feb 11, 2008

### masudr

There is no evidence for the mind existing as something independent of the brain. Descartes didn't have the knowledge of human physiology that we have now.

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