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Ask an Astrophysicist

The Question

(Submitted February 28, 2003)

If light doesn't have a mass, how can it get sucked into a black hole?

The Answer

In a Black Hole, light traveling outwards towards an event horizon is pulled back by the very strong gravitational field, because of the warping of space-time inside the event horizon, regardless of the lack of a photon mass. This prevents light from ever escaping the Black Hole.

This is also explained in one of our previous answers, "How Gravity Affects Photons," at:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/961102.html

-Kevin Boyce and Koji Mukai
for "Ask an Astrophysicist"

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