Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: contrived gravitational fields



At 04:59 AM 10/23/00 +0530, D.V.N.Sarma wrote:
What type of mass distribution in an inertial frame will produce
gravitational effects similar to the effects produced in the noninertial
frame of a rotating platform?

See below.

Is there a symmetry between inertial forces and gravitational
forces such that one can always be replaced by another?

Good question. The answer is "No and yes and no".
1) Rotation presumably means rigid rotation of the frame. (If it's not
rigid, you will notice the tearing immediately.) This cannot mimic a
general mass distribution.
2) Very theoretically speaking, there is a mass distribution that can
mimic the centrifugal field. If you have a "spare dimension" this may even
be semi-practical: imagine motion confined to a (nonrotating) plane. Just
below the plane you distribute a bunch of mass. The mass density increases
(rapidly) as a function of distance from some designated point. If you do
it right, the acceleration as a function of position goes like 1/r^2. OTOH
the Coriolis effects (acceleration as a function of _velocity_) are broken,
so it doesn't mimic rotation perfectly.
3) If you tried to do this in full dimensionality, you would need
cylinders of mass, and you couldn't move around without bumping into the mass.