Approaching the Photon Sphere

As before, from this orientation, the black hole's enormous gravity bends light to make two discernible images of the constellation Orion. You now descend to the photon sphere. A photon sphere is a location where gravity is so strong that light can travel in circles. Photons orbit the black hole at the distance of the photon sphere. A photon could leave the back of your head, go once around the black hole, and be seen by your eye - you can see the back of your head.

At the photon sphere, no light emitted outside can reach you from below - you look into the vast emptiness of the black hole. The sky you once knew is now behind you, compacted to occupy only half its original area.

Next: Looking up at the photon sphere.


Replay the movie segment: Approaching the Photon Sphere.
Play the next movie segment: Looking Up at the Photon Sphere.
Go to the hypertext describing the next movie segment: Looking Up at the Photon Sphere.
Peruse the American Journal of Physics Article on this subject.

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