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, result of black hole?

  1. Jan 15, 2013 #1
    I'm certainly no scientist, but I've always had an interest in Physics & Astronomy, so I read a bit here and there, watch primarily science shows on TV etc...Just an interest.

    I was wondering though, and figured on a site called "Physics Forums" there may be a physicist or two running around here that could clear something up for me.

    Every time I hear of ideas about the big bang, I never hear of one that, to my scientifically untrained mind, just makes sense; why couldn't the big bang just be an event that happens over and over again as a result of black holes being formed, "eating" everything (including each other), then collapsing in on itself (once only one remains) and POOF, another big bang?

    Haven't we pretty much come to the conclusion at this point that black holes are likely at the center of every galaxy? If so, wouldn't that mean that they are consuming their galaxies?

    So, you get the bang, nebula(s) & stars form, then some stars collapse creating black holes, other stars/systems begin to orbit them and form galaxies. The black holes at the center of those galaxies eventually consume the entire galaxy and through gravity and time (obviously, a LOT of time) eventually the only things left are black holes that collide / consume each other etc until just one remains and the "weight" of all matter in the universe (which would remain constant through every "bang", expansion/collapse phase) is just enough to cause the last super massive black hole to collapse in on itself and BANG, another big bang. Repeat.

    Why not? Why couldn't this process occur over hundreds of billions or even trillions of years time?
  2. jcsd
  3. Jan 15, 2013 #2


    User Avatar

    Staff: Mentor

    Because black holes don't work like this.

    1. They don't "eat" everything around them. If you were to magically replace the Sun with a black hole of equal mass the orbits of all objects in the solar system would be unaffected. This is because gravity is based solely off of mass. With equal mass comes equal gravity. The difference between a black hole and the Sun would be the size and density. The Sun is 1.3 million km in diameter, while a black hole of equal mass would be about 3 km across. This is important because 3 km from the center of the Sun most of the mass is equally distributed around you and spread over millions of cubic kilometers. 3 km from a black hole ALL of the mass is in front of you and gravity is pulling on you with incredible force.

    2. Black holes should actually shrink over long periods of time as they lose mass from Hawking Radiation. Eventually they should evaporate completely.
  4. Jan 15, 2013 #3
    Don't black holes explode once they evaporate to a critical level tho?
  5. Jan 15, 2013 #4


    User Avatar
    Science Advisor
    Gold Member

    More like a whimper than a bang. They are probably stable until they approach the Planck mass.
  6. Jan 15, 2013 #5
    Lets say you want a black hole to be at the microwave background temperature ~3K
    that translates to a mass on the order of 10^-23 kg! Even if directly converting that to pure energy (not exactly how Hawking Radiation works) gives you ~5 TeV in total... not very spectacular in terms of bangs...
    Just for a reference: LHC had 7 TeV center of momentum energies.
    Cosmic rays are bombarding our atmosphere with energies up to 10^20 eVs !(without you even noticing...)
  7. Jan 15, 2013 #6


    User Avatar

    Staff: Mentor

    First they shrink and give off almost all of their mass over a long period of time. By the time they "explode" over 99% of their mass and energy are gone. Not much of a boom at all.
  8. Jan 15, 2013 #7


    User Avatar
    Science Advisor
    Gold Member

    A black hole cannot shed mass until its 'temperature' falls below the CMB background temperature.
  9. Jan 16, 2013 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    We have a FAQ about this: https://www.physicsforums.com/showthread.php?t=506992 [Broken]
    Last edited by a moderator: May 6, 2017
  10. Jan 16, 2013 #9
    I stumbled across a recent research paper in which finite 'bangs' emerge when torsion [a type of curvature mathematically associated with particle spin] is included in the Einstein stress energy tensor....and such also describes the possibility of universes being spawned from black holes and even embedded inside them as well..... with connections [wormholes] to other universes.....

    But so far, no one knows with any certainty what started any bangs...neither infinite nor finite....


    Cosmology with torsion: An alternative to cosmic inflation


    So while not a 'mainstream' [widely popular] cosmological model, such descriptions cannot be ruled out entirely....and are interesting enough to some scientists for current research and publication.
  11. Feb 8, 2013 #10
    I've been toying with this conceptually for a while for a short story. So, I took BH evaporation, Tachyons, and the Big Bang and shoved them altogether for no reason other than it seemed elegant. The idea was that the acceleration of matter as it fell past the event horizon shifted some of the particles to a different energy state and spawned tachyons. Tachyons which by default travel faster than light, cause(d) the black hole to evaporate into the past instead of the present where nothing escapes.

    If time didn't exist until the Big Bang, then all of the tachyons that have been or ever will be produced will travel through an ever collapsing universe to a Zero point. The energy of all of the tachyons ever created smashing into one point in time cause(d) the universe spawning explosion.

    If time is a measure of linear forward progression, it doesn't matter that 2 tachyons could be created billions of years apart, they would still reach the Zero point at the same instant. This is analogus to the Galileo expirement of dropping two weights of different mass.

    I was also toying with throwing dark matter in there as well but couldn't come up with an explanation of how to see the effects of a particle that doesn't exist when you measure it, but exists before you do.
  12. Feb 8, 2013 #11
    I thoroughly enjoyed those articles in that thread Naty I highly recommend ppl to read them . Even though it may or may not be BB multiverses the underlying methodology on torsion was informative.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook