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Black Holes and Dark Matter

  1. May 24, 2005 #1
    1)Ok.I was wondering ..what happens after we reach singularity inside black hole?...Do we become part of the black hole and strengthen it by increasing its mass in the same amount of volume?

    2) Is Dark Matter only confined to the outer stretches of the Galaxy?..or is it also found elsewhere in the Universe?.
  2. jcsd
  3. May 24, 2005 #2


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    1) I will mention in passing that there is some debate as to whether or not singularities actually exist, but the answer to that question is not vital to finding the answer to your question. In theory, yes, once you cross the event Horizon of a black hole you increase its total mass, and add to its gravitational pull.

    2) Dark matter is any matter that we cannot see with our telescopes. All of the planets that we cannot see orbiting distant (and nearby) stars are dark matter. The Pioneer 10 anomaly (the space probe Pioneer 10 is decelerating slightly more than predicted as it leaves our solar system) may imply that there is considerably more matter right here in our own solar system than we have accounted for so far.
  4. May 24, 2005 #3


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    I agree with Lurch on the first point. On the second point, his definition of Dark matter is a legitimate one, but is not normally what one means when discussing Dark Matter in the context of modern astronomy, for example in the context of a statement that "30% of the matter in the universe is dark matter".

    Ordinary stuff like hydrogen gas in free space and stray asteroids and planets and such are believed to be on the order of 5% or so of the mass of visible matter, maybe more if you include massive neutrinos.

    Usually, and I suspect in the case of your question, what you are referring to is that presence of matter inferred from observations such as the dynamics of galaxies and lensing of galaxies and galactic clusters and cosmic background radiation measurements.

    Theory infers that this kind of dark matter primarily exists in "halos" around certain kinds of galaxies (some kinds tend to have more than others), with galactic clusters having a particularly large does of the stuff. It is also hypothesized that the large scale structure observed in the universe may be driven by filaments of dark matter which may or may not be the same stuff as the stuff believed to cause galactic dynamics.

    These halos are not believed to extend to the cores of galaxies in most cases.

    The Pioneer 10 case could be explained by many, many phenomena, dark matter is one of them. I wouldn't call it a leading theory, however.

    Certainly, dark matter is not only inferred from the dynamics of the Milky Way galaxy. It is inferred, at least, from almost every largish spiral galaxy and many other types of galaxies throughout the universe.

    Dark matter is a mainstream theory of physics but does not have all the kinks worked out. Among the most pressing issues in dark matter theory are: "What is it made of, if it exists?" (The prevailing view is that it is "non-baryonic" (i.e. not made up of protons, neutrons or other three quark particles)) and "Why is it distributed in characteristic ways?"
  5. May 24, 2005 #4

    I'm new here, I really enjoy reading the posts and finally decided to participate.
    I do have a question. Does a black hole have a capacity or limit to its ultimate size? Or the speed or time frame which it can take in a set amount of matter? I thought maybe the jets release what is above what it can take in during a particular time frame. Over time the bh can grow, but at what rate can it grow? If a hundred sun mass black hole merged with another hundred mass object, can it continue as before or will it increase mass ( ratio ) being ejected?
    Thanks, Roy
  6. May 24, 2005 #5


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    I can't speak to rate of growth except to note that there is a volumetric limit (speed of light time event horizon area), and that there is no known or theoretical limit on ultimate size. Mass density would be a big factor in rate of growth.
  7. May 24, 2005 #6


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    And welcome to posting to these Forums pjb59!
  8. May 24, 2005 #7


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    Actually, his is the more correct definition and is used frequently by astronomers, but I agree that they are often used interchangably. By the way, I think you mean "30% of the energy density of the universe is dark matter".
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