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

Can black holes absorb at an infinite rate?

  1. Jan 9, 2008 #1
    This is theoretical, but if we had a black hole with event horizon of radius R, and passed in a continuous stream of stellar matter with a radius of 99% of R or so,
    would the black hole take in everything, no matter how fast it was moving?

    For example, we have a sufficiently long rod of a hard metal (let's say a few light-years long), with a radius near the size of the event horizon. If this rod were rammed into the black hole at nearly light speed, would it just eat up all of it. Or is it possible that some would pass through by virtue of it's momentum or inertia?
  2. jcsd
  3. Jan 9, 2008 #2


    User Avatar
    Science Advisor
    Gold Member

    The rod would not pass through. The momentum would be transferred to the black hole - it would move in the direction of the incoming rod.
  4. Jan 9, 2008 #3
    So we're talking a 100% energy conversion, virtually instantaneously as the horizon is crossed?
  5. Jan 9, 2008 #4


    User Avatar
    Science Advisor

    This also brings up an interesting question about what happens at the event horizon. It is generally said that objects approaching the event horizon appear to slow down, and never appear to cross the horizon. What would we see if we pushed this very long rod itno the black hole? ould the end near the EH appear to stop while the rest of the rod appears to keep moving forward at very high speed, while no bunching up in the middle occurs?
  6. Jan 9, 2008 #5
    This makes me think that the gravitational force would affect the metal rod even before it crosses the horizon. There was a physics show on tv that mentioned if a black hole was as close to us as Jupiter, we would experience earthquakes on Earth.

    I always have to remember there is the conservation of energy. However, when dealing with the QM nature of black holes, this becomes more interesting.
  7. Jan 9, 2008 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The event horizon is the point of no return as it were. But the gravitational force of the black hole will be acting on the rod all the time as it approaches. I'm not sure what the show was referring to but it would depend entirely on the mass of the black hole.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Can black holes absorb at an infinite rate?
  1. Can I be a black hole? (Replies: 6)