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a/M varies

We start a photon in the equatorial plane, tex2html_wrap_inline292 = tex2html_wrap_inline1121 , and with direction radially inwards, tex2html_wrap_inline296 = (-0.5,0,0). Therefore, it will stay in the equaorial plane.

We integrate the geodesic equation in 300 steps, using a step size tex2html_wrap_inline300 = 0.20

In this movie, we vary the rotation parameter a/M from 0.00 (no rotation) to 1.00 (the most extreme rotation possible). In every frame of the movie, we show a null godesic, that is, the trajectory of a photon, so it's proper time axis is along the geodesic, so to speak, and has nothing to do with the time axis of the movie, which shows a change in a/M.

The IDL script is mf_01.

Movie: QuickTime (3.9 Mbyte), MPEG (0.5 Mbyte), or animated GIF (2.2 Mbyte)
First frame: Inventor, VRML, or GIF
Last frame: Inventor, VRML, or GIF
All files: this directory

Note: this movie has a minor problem: frame 000 and 001 are identical, except for the annotation text. This is because something went wrong when running Explorer. The Inventor (and VRML) files are different.

Web Exhibition: Null Geodesics Around a Kerr Black Hole

Bo Milvang-Jensen (
Mon Jun 17 11:54:08 MDT 1996