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 Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...The Space and Astronomy Agora Re: One Aspect Of Einstein's Theory Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response ToPosted by Bruce on November 23, 2000 07:41:57 UTC

Tidal forces. Curvature of spacetime can be detected by the tide-producing relative accelerations among two or more free test particles (ropes) situated far enough apart or observed for a long enough of time to reveal the non flat nature of non local spacetime. For instance: If your were falling radially (plunging) towards the event horizon of a black hole the center of your body would be the free float frame. As you fall closer the tidal forces increase between the center of your body and your head and feet. Essentially pulling (stretching)you apart. At the same time the tidal forces would be pushing in on both your sides. Its thought that you would become uncomfortable when the tidal accelerations equal about 1 g relative to Earth. After converting mass to a length (1 kilogram equals 7.424x10^-28 meter/kilogram)
For the earth
g=M/r^2
g=.00444m/(6.4x10^6m)^2=1x10^-16m^-1
Taking the deriviative with respect to r of the local acceleration g
dg/dr=|2M|/r^3
dg=2Mdr/r^3
Solving this expression for r(ouch). (the radius when you start to feel uncomfortable due to tidal accelerations as you fall radially towards the event horizon.0
r(ouch)=(2Mdr/dg)^1/3
For a solar mass black hole (1477 meters) the radius at which you would start to feel uncomfortable due to tidal accelerations would be

r(ouch)=[(2)1477m(2m)/1x10^-16m^-1]^1/3
=3894755.168 meters
Even though you are in free fall in the elevator if you can observe the ropes long enough they should reveal the curvature of spacetime by the effects of tidal forces on them. Curvature equals gravity.

Lets say you are pretty tall and dr=2 meters