Gravitational Field Surface
gravity - curved space - general relativity
What it shows:
In general relativity, gravity is replaced by a curved space geometry, where the
curvature is determined by the presence and distribution of matter. Objects move
in straight lines, or along geodesics, but because of the curvature of space, their
paths will simulate the effect of gravitational attraction. This demo gives a two
dimensional view of warped space.
How it works:
In this 2-D analog, a 1 meter diameter piece of dental dam forms a sheet that represents
the geometry of space. The sheet is sandwiched between two wooden hoops that act as a
frame to keep things taught (see figure 1). Use a massive ball bearing (say 500g)
as a stationary central object, smaller ball bearings can be rolled in its field. You can
show clearly circular, elliptical or parabolic orbits in this way.
figure 1. The dental dam elastic surface, shown distorted by a ball bearing mass.
Setting it up:
Place the frame so that it is supported a reasonable distance off the ground, with the area
under the sheet open so that it warps without obstruction. Resting on two chairs will do.
Comments:
The dental dam does degrade over time, so test the setup before the class. Make sure the
sheet can take the heaviest ball bearing, or you’ll be creating a singularity demo! Rating *