1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why doesnt a photon escape from a black hole?

  1. Apr 2, 2006 #1
    Explain why elight emitted at a point inside the Scwarzschild radius (r<a) cannot be seen by a distant observer. (by one at r-> infinity)
    well we know the trajectory of a photon is given by


    [tex] \dot{r}^2 = c^2 \lambda^2 - \left( 1 - \frac{a}{r}\right) \frac{J^2}{r^2} [/tex]

    where J repsents the angular momentum in units of mass
    lambda is [tex] \lambda = \dot{t} \left( 1 - \frac{a}{r} \right) [/tex]

    so when r < a does the expression for r dot become imaginary? Is that what i am aiming to prove?
     
  2. jcsd
  3. Apr 3, 2006 #2

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    See the argument given by Dirac in its GR book when discussing black holes.

    Daniel.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Why doesnt a photon escape from a black hole?
  1. Black Holes (Replies: 3)

  2. Black Holes (Replies: 0)

Loading...