Light, Spherical Orbit, Black Holes
Light is bent by gravitational force. Can a light wave
traveling near a black hole, not at its singularity but very close to it
be bent in a permanent spherical trajectory?
Yes, I believe it could travel in a circular or elliptical trajectory much
as the planets circle the sun. It would not be permanent and might be quite
short lived since the gravitational attraction of the black hole will
increase as it gobbles up more matter. Also the photon might collide with
some bit of matter being swallowed by the black hole and itself be
Also, if the orbit is small enough in diameter, quantum mechanical effects
could become dominant as they are for an electron circulating a proton in a
hydrogen atom. Remember that black holes are small in size, but not, I
believe as small as atomic dimensions. It is also relevant that time is
slowed drastically in the enormous gravitational fields near the event
horizon of a black hole.
My expertise is not sufficient to know exactly what would happen. I have
never seen a discussion of this problem.
Best, Dick Plano, Professor of Physics emeritus, Rutgers University
You are apeaking of a very specific case where the energy of light and
the gravitational force of the Black Hole are in perfect balance. Dr.
Stephen Hawking does a pretty good job of explaining about black holes
and light in his book "A Brief History of Time."
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Update: June 2012