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

Big Bang and Black Holes

  1. Jun 30, 2005 #1
    I had a thought while I was driving to work this morning. If the Big Bang bundled up the universe into a massive structure, shouldn't the sheer gravitational force of such a structure turned such a structure into a huge black hole?? Or maybe it did, and we're living inside of a black hole. And by that same reasonsing, maybe the universe is an infinite regression of black holes. Weird.

    Assuming of course the existence of the Big Bang and black holes...
  2. jcsd
  3. Jun 30, 2005 #2
    A massive star/body would turn into a black hole when all its fuel has been consumed and after that when a star is left with no fuel , it further cannot counteract its own gravitational field and sucks itself into a black hole.Did 'Big Bang Lump' lose all its fuel?
    ... No we are not inside a black hole , otherwise we all could have hit singularity(if it exists..)

  4. Jun 30, 2005 #3


    User Avatar
    Science Advisor

    Black holes are static solutions of general relativity (Schwarzschild spacetime). The universe is a dynamic solution (Robertson-Walker spacetime). The expansion velocity near the singularity was infinite (and is decreasing since then) and it does not collapse into a black hole. However, there are some analogies between both solutions as both have spherical symmetry and under some circumstances it is possible to have a change of coordinates between both.
  5. Jun 30, 2005 #4
    The simple reason is that there is no center point for all matter to collapse back into. It takes time for gravitational attraction to occur and some objects get pulled away before they can be attracted.
  6. Jun 30, 2005 #5


    User Avatar
    Gold Member

    That's a pretty good assumption, since all current evidence leads that way. In some ways, it can be considered that the universe is a black hole. After all, nothing can escape it. The difference is that there's nothing outside of it to fall in (unless that's what quasars are doing :uhh: ).
    The Big Bang, by the way, didn't 'bundle up' anything into a 'massive structure'. As far as I've ever read, the initial conditions were a singularity (mathematical point size-wise). The Bang was the escape of the universe from that singularity.
  7. Jul 1, 2005 #6

    This would seem to imply that all matter originated from one centrally located point. Observations of the CMBR show that the creation of matter happened everywhere at the same time. Areas separated by large distances were not gravitationally bound, and this caused some matter to be attracted while other matter escaped only to be attracted somewhere else. If the universe emerged from a single singularity I imagine things would look quite different. Also it seems that in that model all matter would be gravitationally bound (as it escapes the singularity at less than C) and we would be able to see more of the universe than we can.

    I'm probably way off base here so please help if you can. :eek:
  8. Jul 1, 2005 #7


    User Avatar
    Gold Member

    The two concepts are not incompatible. The BB consisted of energy and time; at what point matter began to condense out of the energy is a separate issue.
  9. Jul 2, 2005 #8
    This is interesting to think that we might be living inside a black hole, however, due to various physical raesons this is not true.

    Yes, there is a great resemblence between our universe and black holes and that is both have "event horizons": limits beyond which one cannot communicate.
  10. Jul 6, 2005 #9
    I don't really see how we CANT be living in a black hole... what evidence is there that says otherwise? I mean, we really have no clue whatsoever what is beyond the universe, and we have no clue whatsoever as to whats hiding in a black hole... I think it would be pretty nifty an idea if black holes were all little universes unto themselves. :smile:
  11. Aug 3, 2005 #10
    Everybody's hung up over the point-singularity. Step down one dimension and look at a near-degenerate torus. Draw a large circle on paper. Extend a radius outside of the circle by an amount very small as compared to the radius. Using the endpoint of the radius as center, revolve the circle perpendicular to the page through a full revolution. You have formed a torus (doughnut shape) with a very tiny centerhole. If you try to evolute the torus (make it try to rotate as if it were a cylinder having two free ends), the surface area from the outside comes 'round to the inside and gets scrunched up into a much smaller area.

    If you did the same rotation about a point on the circumference of the circle, you'd have a truly degenerate torus, analogous to the point-singularity-- and the involution couldn't happen without tearing.

    Step back up a dimension and do the same things to create a near-degenerate hypertorus. Now, you can have a Big Crunch without the point-singularity. Ah, that's better! Steve
  12. Aug 3, 2005 #11
    1. When we say Space is infinitely curved around a black hole, we compare it to the space wrap around less massive objects...... Its a relative term.
    2. Observational Evidence suggest that the expanding Universe is accelerating over time, so theres no question of having a Big crunch.
    3. The fact that 'SPACE' itself expanded rapidly after the big bang (according to the standard Big-Bang model and the Inflation Theory), the questions, 'What is beyond our Universe?, Where does the Universe End? carry no meaning..
    4. alsoo... the fact that a Black hole is infinitely dense would be good enough for us to believe we are not living inside one..(we cant have Black noles inside a Black hole)
    5. Applying general relativity,, @ the Event horizon of a Black hole space is infinitely curved ==> our relative time of any event is streached to infinity ==> all the events tht happened ATB (after the bang) never end, people born never die(people cant be born, there are no events, no begining)...etc... etc..(RELATIVE TIME!!,, if we were inside a Black hole, there nothing relative, the question of having something beyond our Universe has no meaning, ...sooo the above point would not carry any meaning).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook