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Black Holes Relation to an Accelerated Expanding Universe

  1. Jan 25, 2012 #1
    Let me first start off by saying that I have no formal Education or background in Physics or Astronomy save for one course during college. This is simply posing an idea I had while reading an article on the acceleration of the expanding universe and how it could have a correlation with "Dark Energy" or "Dark Matter", and again I am only posing this question to see if it is at least reasonable or absolutely ludicrous. While there is debate on what exactly dark matter/energy is, those that stand by the belief of its existence say that it constitutes a large portion of all the matter in the Universe (I believe the average number agreed upon is roughly 80-90% if not more). Although we cannot see it many scientist are claiming that a black hole has some correlation to this phenomenon. I am aware that a black hole does not "suck" but is merely a point of infinite gravitational density and mass, of which not even light can escape.I suppose my main question is if all the matter that enters a singularity is expelled in pure protons or other particles or if some is converted into a form of this dark energy or matter. If some of the matter is converted and it is "emitted" (if that would even be the term for it) then could this be what causes the acceleration? Because while the initial velocity of the Big Bang is unimaginably fast it would stand to reason that it would slow down. However if dark matter/energy is what arguably pushes space and time then as more black holes occur more dark energy would be "emitted" pushing against the dark matter already there then would that add to an increase in the speed of the expanding universe. I am not trying to say that a black hole is some kind of magical portal that automatically turns matter into dark energy, but again I am curious to see if this would be a reasonable guess as to why this occurs. Please give me your thoughts and if I am completely wrong do not worry about offending me I am here for more expert opinions so please tell me if this is ridiculous.

    Thank You
  2. jcsd
  3. Jan 25, 2012 #2


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    No scientists are claiming that black holes are related to either dark energy or dark matter. It might have been possible that black holes could have contributed to the MACHO explanation of dark matter, but that has fallen out of favor, the more popular model being WIMPs.

    All nonsense. When a black hole absorbs some matter, what generally happens is it heats up as it falls in and radiates in the hard x-ray portion of the electromagnetic spectrum. Once the matter has fallen beyond the event horizon, it is classically lost to this universe. Now, a quantum effect known as Hawking radiation allows black holes to VERY VERY slowly emit radiation and lose mass, but this effect is so negligible, that any black holes formed from stellar processes cannot possibly have been effected by it during the lifetime of the universe. (Note, none of this has to do with DM or DE, precisely because there is no connection.)
  4. Jan 25, 2012 #3
    Thank you for the clarification. As i said I make no claims about have any solid background or understanding of these subject matter, but have merely pursued it from an amateur perspective. I apologize for posing such an improper question to a forum consisting of much higher level concepts than the question I posed here, I simply assumed this was a good place to start.
  5. Jan 25, 2012 #4


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    Lighten up, dude. This is actually a very friendly forum and your question was quite reasonable given your understanding, and it was politely and thoughtfully posed. Response terms like "nonsense" used on this forum are not personal attacks, they are a concise statement of response and are not intended to offend.
  6. Jan 25, 2012 #5
    Thanks for encouragement and as I stated in my original post no answer would offend me. I simply apologized because most of the content of this forum is contributed by people who have a very good understanding of this complex subject matter, and describing those mathematical concepts into layman terms to someone must be frustrating after awhile. Especially when the question posed does turn out to be "nonsense" hah.
  7. Jan 25, 2012 #6


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    PVastro: Indeed, I don't mean in my responses to insult or offend, simply to concisely convey my meaning. Honestly, I was unsure where to start in talking about your idea, so I figured it best to simply recount the situation as it is in reality. I don't think I've fully understood quite what it is you're asking, but I hope that my explanations have either clarified some things or allowed you to get a better handle on your question.

    Looking at my response, I think it was a little curt, especially since you admit to having no training in these matters. I'll clarify a few things, but by all means ask if anything is unclear!

    Just as a recap, Dark Matter is the term we use for matter which evidently exists surrounding galaxies in large halos. It is dark in the sense that it does not interact with light, but matter in that it interacts gravitationally (i.e. it has mass). One of the big pieces of evidence for dark matter is the way in which galaxies rotate. Just from intuition it's probably clear to you that the stars farther away from the center of the galaxy should move slowly -- this is in accord with normal observations in the solar system, for example. However, we observe that as you go farther away from the galaxy, the speed is actually roughly constant! What this means is that there's a whole lot of 'stuff' in the galaxy, which continues outwards and does not taper off with distance. We call it dark matter.

    When I say that black holes can be related to dark matter as "MACHOs", what I am referring to is so-called Massive Compact Halo Objects (MACHO)s. These are large objects which, for whatever reason, do not shine very brightly. Things like failed stars, large planets, or black holes all fall into this category. It was thought, for a while, that dark matter could simply be a lot of these objects distributed throughout the galaxy. This turns out to be difficult and does not fit the data very well, so the idea has been abandoned in favor of...

    Weakly Interactive Massive Particles (WIMP)s. This is the opposite approach to dark matter. Whereas MACHOs are large (star-scale) objects, WIMPs are subatomic particles (like electrons or protons). The idea is that the dark matter is some type of particle yet undiscovered which, for whatever reason, does not interact very strongly with light (hence it is dark). These models are better at explaining the data, and there are a multitude of theoretical ways that we can generate these new particles. Currently, there's a large effort to try and detect the WIMPs in Earth-based experiments.

    Dark energy, on the other hand, is what is responsible for the acceleration of the universe as a whole. We've known for some time that the universe is expanding -- things are moving away from each other. However we found out that it's not just expanding, it's accelerating! To achieve this acceleration, you need some kind of negative pressure to push things apart in the overall expansion of the universe. We know such a thing exists, having seen the accelerated expansion, and we call it Dark Energy. But beyond that, we don't really know much about it! We haven't been able to come up with a good explanation of what it actually is, or devise any experiments that might be able to uncover it in a laboratory setting. This stuff is pretty mysterious!

    I hope all of that makes sense, and at the very least we should now be on the same page as to what it is we're talking about. So, all that said, any questions?
  8. Jan 25, 2012 #7
    Thank you that clarifies a lot for me as far as the difference between Dark Energy, Matter and BHs. However now that you have identified them I can reformulate my original question in a way that makes better sense. As you said Dark Energy is the term assigned to the force that is causing the expansion and acceleration of said expansion. While you did state that we do not know very much about the composition of dark energy, my question is better stated as:

    1)If dark energy is accelerating, does it better stand to reason that more is somehow being created, based on an assumption that it can only interact with "itself" (or the "space" is seems to be expanding) therefore adding an accelerated effect from the "new" DE being created.

    2)Is it more plausible that it has some related reaction with matter in the universe, such as the matter we can observe and quantify.
    I understand these are still fairly broad questions and would possibly bleed over into the subject of whether the universe actually has finite borders or if it extends on indefinitely. I apologize for the context of this new question because again, I know that all of these theories are based off detailed observation, and that it has to work out mathematically, which as far as I know it has not been solidly proven for either (though i'm sure there are those who have postulated many mathematical theories about this subject).
  9. Jan 25, 2012 #8


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    No, that's not quite what he said. Dark energy is causing the ACCELERATION of the increase in scale factor but is not responsible for the increase itself, which is apparently a, to use the term loosly, "balistic" effect left over from the big bang itself. Up unil very recently (about 10 years I think) it was assumed that the expansion was slowing down, and when measurements were made to find out how fast it was slowing down, to everyones absolute surprize, it was found to be NOT slowing down but actually speeding up, and the cause for this was called "dark energy", the "dark" in this case meaning "mysterious" / "not understood".

    That's an excellet question and one that is subject to some debate, not about whether more is being created in some sense (it is) but HOW is that happening and exactly WHAT is happening. There is a whole set of discussions around this issue that you can find in various threads on this forum. Some say "space is expanding" but my preference is the ones that say "the scale factor is changing" (that is, "space" isn't actually being created, things are just getting farther apart --- and how weird is that?)

    There have been lots of theories along those lines, all, to the best of my understanding, having been shunted off to cloud cuckoo land

    Good questions, interesting discussion.
  10. Jan 26, 2012 #9
    "That's an excellent question and one that is subject to some debate, not about whether more is being created in some sense (it is) but HOW is that happening and exactly WHAT is happening. There is a whole set of discussions around this issue that you can find in various threads on this forum. Some say "space is expanding" but my preference is the ones that say "the scale factor is changing" (that is, "space" isn't actually being created, things are just getting farther apart --- and how weird is that?)"

    Wow that that is a strange concept, if considering my understanding that all energy and matter in the Universe is the same amount since the beginning of it (as to say that no new energy or matter is being "created" since there is only as much of both as what was initially part of what made up the "big Bang"). Also as far as my understanding of the laws of thermodynamics neither energy more matter is ever lost only changed into another state of the two. Following these lines does it stand to reason that DE is some sort of (for lack of a better understanding of the terminology) "negative" or inverse reaction to matter and energy? Because I can't grasp how "new" DE can essentially be created from (again lack of terminology) "Nothing", since no matter or energy seems to lost in the creation of it. If so to me this would seem to argue that DE is generated simply because of the presence of matter and energy within time and space which I find hard to grasp.
    Also as far as the acceleration goes, the universe is incredibly vast (duh) so does it stand to reason that, viewing the Big Bang from a "ballistic" effect the outward force of the BB would give it incredible speed and as I understand our view of the universe "Nothing" (again applied very loosely) is around the "outside" of the Universe then technically is there nothing to slow its progress? What im getting at is while the universe is incredibly old by our perspective (13.7 Billion yrs is a long time to me), in terms of how long it would take to slow down that kind of incredible energy, might it not take many more billions of years before it started to lose its initial velocity? That is to say that the acceleration from the BBs initial release of energy is still accelerating because it hasn't even begun to hits it peak velocity (maybe even many billions years more before it does), and therefore hasn't begun to slow down.
    Again I am sure that I am butchering the terminology, and I cannot begin to back this up with any kind of mathematical basis, only from my very basic understanding of general physics.
  11. Jan 26, 2012 #10


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    I am NOT really knowledgeable about this, but I will pass on a statement that I have read here many times, which is this: energy conservation is NOT applicable on a universe scale --- it is a relatively small-scale pheonomon.

    The "ballistic" expansion, following inflation (a whole 'nother big story) kept the U moving apart for some 6 to 8 billion years. That's a long time. During that time, it is believed that the expansion was slowing down due to gravity. How gravity slows things down when there's the same amount in all directions, is a whole 'NOTHER thing to try to get your head around.

    At that point, matter was spread out enough so that gravity had less effect and DE took over and the expansion started accelerating. The consensus seems to be that DE has been with us all along, but it is a STUNNINGLY weak force and had no effect for the first 6-8 billion years.

    It STILL has no effect inside gravitationally bound objects. Local clusters and smaller are not affected by DE. It's not that the effect is SMALL, it's that there IS no effect. It's like an ant pushing on a tank. Yes, the ant IS pushing, but the tank doesn't move a tiny amount, it just doesn't move at all.

    My favorite way of keeping DE in perspective is this. Although the universe is expanding, it's still going to be hard to find a parking place. Sounds silly, but the thought behind it is this: if you could magically paint parking space lines in deep space outside of gravitationally bound clusers, it would take something like a billion years before you had enough space to park a 2nd car. It's slow and it's weak. BUT ... the amount of it is pretty much beyond imagination.

    The tricky part seems to be that as the scale factor increases, MORE DE then exists, so the process will apparently snowball.

    There are LOTS of articles about all of this all over the internet.

    The FAQ in the cosmology section should prove very interesting to you as well.
  12. Jan 27, 2012 #11


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    The terms 'dark matter' and 'dark energy' turned out to be unfortunate choices. It would have been so much simpler had they been termed 'Zwicky matter' and 'Einstein energy'. At least then it would merely be a conspiracy theory bereft of any substantive deeper meaning.
  13. Jan 27, 2012 #12


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    :rofl: well said
  14. Jan 27, 2012 #13
    This Phdcomics video on dark matter is pretty nice.
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