Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Do photons gain mass in the presense of a black hole?

  1. Feb 6, 2012 #1
    I understand how gravity can affect photons or light waves (Einstein's equivalence principle). But I was wondering if there are any theories that predict that a photon might somehow acquire mass in the presence of a singularity.
  2. jcsd
  3. Feb 6, 2012 #2
    I'm going to assume that you mean black-hole, when you say singularity. The central point of the BH should have no relevance---unless I misunderstand you.

    Note that there isn't anything special about the gravity of a BH. If a BH's gravity somehow gave light mass, then a star, or even a planet would also.

    Nothing, however, can give a photon rest-mass. In general relativity, 'mass' (in-general) is not always well-defined. A photon will (presumably) exert a gravitational force on other-particles, regardless of the local gravity (e.g. a black-hole).
  4. Feb 6, 2012 #3
    My understanding is that light waves flatline when trying to leave a BH - they can not escape. I was not sure if this had an effect on the photons. - Thank you for your answer.
  5. Feb 6, 2012 #4
    Black-holes don't change anything about the photons themselves; instead they're drastically deforming the shape of space-time itself. At (and within) the event horizon, the photons are exactly the same, but spacetime is bent so much that nothing can move outward.
  6. Feb 8, 2012 #5
    I was not sure if this had an effect on the photons. http://www.bosin.info/g.gif [Broken]
    Last edited by a moderator: May 5, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - photons gain mass Date
I Two coherent sources Sunday at 10:20 PM
I Photons and Frequency Sunday at 12:29 PM
B Amplitude of a photon's E and B fields Saturday at 10:49 AM
I Photon and electron Friday at 8:50 AM
How does a photon gain momentum? Aug 25, 2011