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Difference between micro black hole and primordial black hole

  1. Jan 29, 2014 #1
    If the amount of hidden information inside a black hole, depends on the size of the hole, one would expect from general principles, that the black hole would have a temperature, and would glow like a piece of hot metal. But that was impossible, because as everyone knew, nothing could get out of a black hole. Or so it was thought, but stephen hawking discovered that particles can leak out of a black hole. The reason is, that on a very small scale, things are a bit fuzzy. This is summed up in the uncertainty relation, discovered by Werner Heisenberg in 1923, which says that the more precisely you know the position of a particle, the less precisely you can know its speed, and vice versa. This means that if a particle is in a small black hole, you know its position fairly accurately. Its speed therefore will be rather uncertain, and can be more than the peed of light, which would allow the particle to escape from the black hole. The larger the black hole, the less accurately the position of a particle in it is defined, so the more precisely the speed is defined, and the less chance there is that it will be more than the speed of light,. A black hole of the mass of the sun, would leak particles at such a slow rate, it would be impossible to detect. However, there could be much smaller mini black holes. These might have formed in the very early universe, if it had been chaotic and irregular.these are what called primordial black holes, aren't they?

    then in what way a micro black hole is different from a primordial black hole?
  2. jcsd
  3. Jan 29, 2014 #2


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    I don't think Hawking radiation is the result of particles traveling faster than light.

    As for the difference between the two types of black holes, I think the only difference is that primordial black holes formed in the very early universe, whereas micro black holes are simply small black holes, irrelevant of how they formed. A primordial black hole could be a micro black hole and vice versa.
  4. Feb 22, 2014 #3
    What Hawking's ia saying is that if a particle or anti particle pair came into existence near the horizon of a black hole it can fall into the black hole and the other particle could then escape the black hole. It would then appear as radiation. He isn't implying that particles could just escape a black hole at any time.
    Yeah the only difference between the two black holes are that a primordial black hole was formed at the begining of the universe and not by the collapse of a star. It was formed by the density of matter durning the expansion of the universe.
  5. Feb 22, 2014 #4


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    Here is the deal, no black hole can form in the present day universe via natural processes that is not at least around 5 solar masses. That is what the observational evidence implies. So, micro and primordial black holes can only form under exotic conditions. Primordial black holes are considered a possibility because conditions in the early universe are unclear. There are no known exotic conditions that can produce micro black holes.
  6. Feb 22, 2014 #5
    That does not make it impossible, just unobservable. Black holes could very well be extremely dense quark-gluon plasma soup, but gravity is so great that none of the electromagnetic radiation can escape, except in the form of Hawking radiation.

    Primordial black holes are certainly possible. They would had to have formed prior to the end of the Hadron epoch (10-6 seconds after the Big Bang). Before the universe had the opportunity to cool off below 1013° K. Primordial black holes smaller than ~7.34 × 1022 kg in mass (about the mass of the moon) would have evaporated in the 13.78 billion years since the Big Bang.
    Last edited: Feb 22, 2014
  7. Feb 22, 2014 #6


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    dheeraj, your whole concept of particles moving faster than c due to the HUP is nonsense. You have either been badly misinformed or you misunderstood what you read.

    Also, as has already been pointed out, the HUP has nothing at all to do with Hawking radiation.
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