- Anonymous

If light had no mass a "Black Hole" would have no effect on it. If it does in fact have mass the hole would have the same effect on it as other mass. It would condence it and add it to the singularity. I guess this would answer my own question about the mass of light.
- Chuck Hess (age 65)
Florence, Arizona

Although light photons have zero 'rest mass', and this has been checked by many many experiments, a photon has an 'effective mass' which is its energy divided by c².   This effective mass is affected by gravity just as well as particles with non-zero rest mass, such as electrons, protons and larger objects like lead bricks and planets.  In 1919, during an eclipse of the sun, light from stars passing close to the sun was observed to deflect in accordance with the theory of general relativity proposed by Einstein in 1905.    As far as light interacting with black holes the same analogy holds. If photons pass by reasonably close to the black hole they will be deflected.  If they pass too close they will get sucked in and contribute to the total mass of the black hole.

LeeH

(published on 06/13/2009)