Clocks and curivture

[Negeng]

In a place of gravity, where space time is bent "inward" clocks slow down from the prospective of an outsider. But what if you had a region of space time that was bent outward, what would happen to your clocks then?

[Bill_K]

It's hard to know what you mean by "bent inward" or "bent outward." In the Schwarzschild solution, g00 = 1 - 2m/r, which is less than 1, and so for a particle sitting still at finite r the proper time is less than the coordinate time, consequently its clock runs slow. For the Reissner-Nordstrom solution, g00 = 1 - 2m/r + e2/r2, and so for certain values of the parameters (m=0 for example) g00 will be greater than 1, and clocks will run fast.

[harrylin]

Simply put, gravity slows clocks down. Negative gravity would probably speed them up, but that doesn't sound realistic to me. :tongue2:

[Negeng]

Simply put, gravity slows clocks down. Negative gravity would probably speed them up, but that doesn't sound realistic to me. :tongue2:

I got the impression from the cosmology section that there are situations that simulate "Negative gravity" they bend space and time in the oppisate direction than gravity does. For example the inflation of the universe that happened soon after the big bang. Is this impression wrong?

[Naty1]

Inflation did not involve curved spacetime....if anything it's this:

....Inflation answers the classic conundrum of the Big Bang cosmology: why does the universe appear flat, homogeneous and isotropic in accordance with the cosmological principle when one would expect, on the basis of the physics of the Big Bang, a highly curved, heterogeneous universe?

more here: http://en.wikipedia.org/wiki/Cosmological_inflation

But the driving force of inflation, "negative energy vacuum density", I guess could be informally described as "negative gravity" but I have never seen it referred to as such........currently it is usually called the cosmological constant or dark energy. I have not seen cosmological expansion described as resulting from "negative gravity"....but that could be an informal description since "negative energy" seems not so different..