The Naked Scientists

The Naked Scientists Forum

Author Topic: Does a black hole contain zero gravity at its centre?  (Read 1666 times)

Online jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3929
  • Thanked: 55 times
  • The graviton sucks
    • View Profile
The talk of gravitational fields cancelling out in the hollow planet example brings to mind this question. What happens to gravitation at the centre of a black hole? Should the field cancel out?


 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Re: Does a black hole contain zero gravity at its centre?
« Reply #1 on: 09/12/2013 20:00:24 »
There has been many predictions of the density of a black hole, without any good evidence to support it. 

However, any mass with a fixed center would have zero gravity at the middle. 
It is like walking North from the North Pole (no direction), or for that matter, walking South from the North Pole (all directions).

At exceptional density, the center could be extremely small, and slight deviations from the center of mass might make a substantial difference in the gravity.

Is it possible that the center of mass could move, perhaps quickly, in which case there would not be a fixed point in relation to the surface that would be considered the center where gravity cancels out?
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: Does a black hole contain zero gravity at its centre?
« Reply #2 on: 09/12/2013 20:47:00 »
The talk of gravitational fields cancelling out in the hollow planet example brings to mind this question. What happens to gravitation at the centre of a black hole? Should the field cancel out?
The center of a black hole is not the center of a hollow sphere so it doesn't apply. Also a black hole can't be thought of a consisting of point masses, at least not the singularity. It's matter is concentrated at a point. Therefore its not possible to place a test particle at the center and see what happens even in principle, right?
« Last Edit: 09/12/2013 20:52:34 by Pmb »
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Does a black hole contain zero gravity at its centre?
« Reply #3 on: 09/12/2013 21:04:50 »
What is gravity?
 

The Naked Scientists Forum

Re: Does a black hole contain zero gravity at its centre?
« Reply #3 on: 09/12/2013 21:04:50 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums