Black hole properties
M =
(mass)
a/M =
(measure of rotation,
)
Initial position of photon
r =
(you must have
)
=
[radians]
=
[radians] (unimportant, since there is symmetry around the z-axis)
t =
(unimportant, since the metric is time independent)
Note:
You can specify (pi)
as !pi in the normal IDL fasion.
Initial direction of photon
dr =
=
[radians]
=
[radians]
Note:
Here, a null geodesic is obtained by solving
for dt . Therefore, the user cannot specify dt .
Affine parameter control
=
(affine parameter step size)
# steps =
(max 10,000)
3D scene format
Inventor
VRML
Note: you have to manually switch on "Headlight"
(in the "View" menu)
in WebSpace to be able to see the 3D widgets below.
In ivview there seems to be light everywhere.

Drawing style of geodesic
Line
Points
Note: I think that Line looks the best, but Points
allows you too see (more clearly) the spacing between the points.
Try sending the photon directly towards a nonrotating black hole,
e.g.
a/M=0,
dr=-0.5,
=0,
and
=0 .

Color of geodesic
R =
G =
B =
Coordinate system widget
Note: the x , y , and z axis are
red, green, and blue,
respectively, and have a transparency of 0.25.
If you cannot view color, you should enable the x axis labeling,
and then find the y and z axis using the right hand rule.

Horizon widget
Note: you can of course get a black horizon instead of a
yellow one by setting R=G=B=0 !
Static Limit / Ergosphere widget
Note: the static limit is given by
.
It is shown as a wire mesh.
Submit!
(be patient!) or
Note: when your browser says
"Connect: Host www.astro.ku.dk contacted. Waiting for reply...",
my machine is actually calculating the null geodesic you
specified.
Typical calculation time: 10 seconds.