Suppose I am an observer inside the event horizon of a black hole, and I am part of a system comprising myself, an object and a singularity. Now I throw the object towards the singularity; what happens to the entropy of this system from my perspective?

Has the number of possible microstates reduced, violating the 2nd law of thermodynamics?

  • $\begingroup$ Related: physics.stackexchange.com/questions/210846/… $\endgroup$
    – exp ikx
    Apr 25, 2019 at 14:10
  • $\begingroup$ When you are in a non-charged, non-rotating black hole, the singularity is not a place in space where you could throw things, but a future moment of time, say, "noon" by your wristwatch. So before "noon", there is no singularity inside a black hole, but the space around you is shrinking in 2 out of 3 dimensions thus becoming an increasingly tight cylinder. At "noon", this cylinder becomes a line squashing you thin and then time and existence end. This infinitely long line that exists for a zero period of time exactly at your "noon" is the singularity. Thus your question is not well defined. $\endgroup$
    – safesphere
    Apr 25, 2019 at 16:58
  • $\begingroup$ @safesphere I don't understand your comment. My world lines end at the singularity, but I can still look towards and away from it, and I can delay the onset of "noon" by exchanging momentum with the object and causing it to reach the singularity before me, from my perspective. Perhaps I'm missing something. $\endgroup$
    – quant
    Apr 26, 2019 at 11:50
  • $\begingroup$ @quant Yes you are missing the point that the direction toward the singularity inside the horizon is a direction in time. There is no spatial direction to the singularity, so no, you cannot look at it. The singularity is not an object that sits there, but a moment of time that happens to you when you reach it in time, not in space. The distance along your worldline is measured in seconds. You can make it just a bit longer by stopping your movement in space (not toward the singularity) to avoid the time dilation of special relativity. Everything hits the singularity at the same coordinate time. $\endgroup$
    – safesphere
    Apr 26, 2019 at 15:12


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.