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Black hole vs. Black hole, who wins?

  1. Mar 19, 2008 #1
    Is there any theory that attempts to answer what would happen if two equally massive black holes collided?

    Also, If one could isolate an entire galaxy like Andromeda, so that no external forces outside of its volume could interact with its contents, would Andromeda's core black hole slowly devour all surrounding galactic matter? Or would this matter simply hold orbit forever, or some other explantion?

  2. jcsd
  3. Mar 20, 2008 #2


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    If two black holes collide, they simply merge into one big black hole.

    The question about a galaxy should be looked at independent of whether or not its massive center is a black hole or not. It is no diffferent from the question of the eventual fate of the solar system. In either case whether or not something falls in depends on it maintaining enough angular momentum. (for the solar system there is the extra problem of the sun becoming a red giant)
  4. Sep 2, 2008 #3
  5. Oct 22, 2008 #4
    Well first of all two black holes coliding is sighly unlikly, but if it did happen what does "who wins mean?" What happens when two singularities conect? They probably just become one singularity infinatly small x 2 is sitll infinatly small.

    as to galaxies colapsing on themselves with no external forces. I supose It COULD happen. But lets look at the with a realistic veiw of gravity, Just because there is nothing pulling things out doesnt mean its going colapse. Take the earth and the sun, do you think if we removed jupiter earth would crash in to the sun? No of course not, we still have the same total energy maybe our orbit would change a little but thats probably it.

    As for galaxies as long as there isnt a colision things dont colapse the two masses orbit around their center of mass, asumedly a glalaxy acts in the same way the galaxy slowly spins((in terms of time not speed)) around its center of mass
  6. Oct 30, 2008 #5
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  7. Oct 30, 2008 #6
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  8. Feb 2, 2010 #7
    If two black holes (though as unlikely as it may be) were to colide, they would most likely become nothing. Dew to the nature of a black hole, whitch is the destruction and consumtion of matter, two outcomes would occure.

    1: Depending on if one of the black holes were larger and more powerful then the other, the less powerful and smaller of the two would be sucked in and become what matter becomes when entering a black hole...nothing.

    2: Now, if both were the same size, had the same power, and could do the same damage, the outcome could be two different things:
    A: They form together and become an evern more powerful and larger black hole.
    B: They start to consume one another until there is nothing left but some left over matter from the outer parte of the black holes.

    Now, I'm not an expert at all, I'm just a 20 year old military wife with a 1 year old daughter. But these things have always interested me. My ideas are only ideas, nothing more.[/
  9. Feb 2, 2010 #8


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    Fairly confident no matter what the mass ratio between two black holes, a collision-event ultimately results in a merger with a black whole whose horizon is of greater or equal size to the sum of the previous two horizons.
  10. Feb 3, 2010 #9
    ...I have no idea what you said...remember, I'm just a military wife and mom...high school education only...
  11. Feb 3, 2010 #10
    what would we see as an outsider sitting far far away when the two collide?
    For each BH, we see objects that fall into it takes infinite time to reach the event horizon. If the event horizons of the two BH touches, the objects that never quite pass the event horizons from our point of view would crash into each other, but it can't happen since the objects had long reach the BH center in some local frame. So what do we actually see? Also, does it take infinite time for them to merge as observed by us outsiders?
  12. Feb 3, 2010 #11
    You seem to have a fairly common misconception about black holes, that they destroy matter. When anything falls into a black hole, matter, energy, or other black holes, it just adds to the mass of the black hole. Black holes are just very dense matter. The more mass they have the greater gravity they have. When some simply piece of matter falls into a black hole that mass is just added to the black hole increases in size slightly.
  13. Sep 14, 2011 #12
  14. Sep 16, 2011 #13
    If two equal mass back holes merge, science and knowledge will be the winner, and gravity temporarily the loser. If two relatively small equal size black holes merge, at the point of contact of each BH's surface there will be no net gravitational force. If each BH contains something located at greater than 70% of the Schwarzchild radius, a large burst will occur. Probably about one of these BH-BH mergers occurs annually in other galaxies, and possibly they are observable and identifiable by a large gamma ray burst. The science of gamma ray bursts is growing rapidly so this might be confirmed in 10 - 20 years.
  15. Nov 8, 2011 #14
    can u please tell me that if there are only four dimensions exists in a black hole then which one of the black hole will be losing its other dimensions (what I understand till now is that there are 4 dimensions exists in a black hole i.e. 3 dimensions are of time and 1 is of space) but whole black hole has all the dimensions from outside.

    Whose gravitational pull will be higher if they are of same mass..................
  16. Nov 8, 2011 #15


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    Nothing will happen to dimensions in either black hole. Dimensions are not something that each object has individually. If dimensions were somehow different in a black hole, then both black holes would be equally different from the rest of the universe and upon merger they would be exactly the same except for being one bigger black hole instead of two.
  17. Nov 8, 2011 #16
    Wow, I really never thought I would get to the point of ever being able to ask a question on a thread this good but... Okay we got universe beginning and ending questions being asked here for the dreamers... So is gravity stronger then the mysterious energy causing the universe to still be expanding at an exponential rate? Say we take 10 then 20 and 40 and an entire galaxy becomes a black hole. Lay that theory on top of the hobbles deep field image and gravity loses up against the force behind the big bang.
  18. Nov 8, 2011 #17
    Actually the thing is when two black holes collides either one of them will suck other one and in that case the black hole which gets sucked will be hitting singularity in other black hole but if both of them are of same mass and with same gravitational pull then what will happen at the time of there collision (which one will get sucked)?
  19. Nov 8, 2011 #18


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    I don't think this is true. Earth does not "suck" meteors to it, they simply fall into the atmosphere due to gravity. Both black holes would be attracted to each other and they would be both fall towards each other until they merged. Honestly they probably wouldn't even collide, at least not initially, but instead spiral around each other until the meet. What happens beyond the event horizon is beyond me.
  20. Nov 8, 2011 #19


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    Current observations show that gravity is not strong enough to avoid the acceleration of the rate of expansion of the Universe. I don't even understand the rest of your question.
  21. Nov 8, 2011 #20


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    One point is that in the very long run, two stellar mass objects closely orbiting (be they black holes, pulsars, stars, whatever) cannot maintain stability. Gravitational radiation will sap the angular momentum, and they will spiral towards each other. Thus, the answer to the original question is: if two black holes approach so as to get into a tight orbit (no need for collision), they will merge into a larger black hole, with immense gravitational radiation approaching merger.
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