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Why is it considered the 'end of the universe' when the stars go dark?

  1. Dec 30, 2011 #1

    01i

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    Why is it considered the 'end of the universe' when the stars go dark??

    As I understand it, there were two main theories accepted regarding the expansion of the universe after the big bang. One of them assumed that the expansion would start to contract, the other that it would continue to accelerate until all the stars die out leaving the cold black of space. The recent documentaries I've watched suggest that the evidence for the latter is more likely, and that it's quite a sad ending.

    What I don't understand is why the stars going dark is considered the end, rather than fully taking things to their ultimate conclusion.

    When the stars go out their 'dead bodies' will still continue to orbit the black holes in the center of their galaxy. It stands to reason that eventually the black holes at the centre of each 'dead' galaxy will finish consuming all the 'dead' stars. Admittedly they'll probably collide with a few other galaxies on the way, adding some new stars to the mix prolonging the process, but eventually all the black holes will have eaten all the 'dead' stars in the 'dead' universe.

    Once that happens it still isn't the end. There is still the endless void of space, and the super-massive black holes that once were galaxies.

    Based on the idea that the rules of the sub-atomic world allow for a small enough object to appear from nothing, or jump from one place to another, it is not unreasonable to assume that these black holes (no longer tied down by a load of stars) might also be able to act this way. After all, the recent arguments suggesting the big-bang singularity could appear from nothing use exactly the same sub-atomic rules reasoning.

    Even if that's not the case and a supermassive black hole untethered by stars can't jump around, they should still be able to be attracted through gravity to the other black holes in the void of the 'dead' universe. Eventually it would make sense that all the black holes end up as one huge black hole containing the majority of (if not all of) the matter originally released by the big bang.

    Even if a few black holes escape, there are still (as I understand it) tiny black holes appearing from nowhere all around. They have to leave 'something' behind when they disipate that could - over time - be consumed by the ultimate black hole until it reaches the density equal to the entire amount of matter discharged by the big bang.

    That leaves a situation very similar to just before the big bang singularity exploded, and pretty much identical to the ending of the contracting universe idea.

    On a related note, this time going back to the ultimate beginning. A Stephen Hawkin documentary recently argued that the big bang singularity appeared from nothing fully formed at full density. While I'm sure that wouldn't have been argued if not possible, it seems a little strange that fully formed big bang dense singularities have not appeared since.

    However, if you have an empty endless void of nothing, and a rule that allows tiny enough objects to spontaniously exist out of nothingness, the same gradual combination of black holes eating each other in the void can evenqtually create the density for a big bang singularity over time, from the tiny black holes that supposedly appear all around us.

    As I've never seen or read anyone making the same arguments, and as it seems like a pretty logical next step to take, my question is what's wrong with my logic?

    ~ Oliver Piotrowski
     
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  3. Dec 30, 2011 #2

    marcus

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    Oliver,
    the main thing we have to go on (future speculations like this) is the present standard model with its positive cosmological constant. It's the simplest best fit to the data so far, so my response is based on the prevailing model.

    As you acknowledge this provides for continued expansion. Gradually accelerating, in fact.

    This will take the galaxies' clusters (black holes included) out of interactive range, so no chance of galaxies falling into each other except for some already clustered. E.g. for us a small group of galaxies will coalesce early on, like Milky+Andromeda+a few smaller ones.
    But then all the other billions of galaxies will be beyond our horizon---out of causal contact.

    So no chance of one giant allconsuming black holes. Instead, widely scattered ones. Also black holes, over the long term, evaporate.

    So even if there were a chance of dead stars falling in, probably most dead stars would just continue to orbit the former galaxy central black hole until the black hole evaporated.

    Black holes don't pull in stuff unless it gets too close. Something in a wide stable orbit is not destined to fall in barring some weird event like deflection by a near collision knocking it out of stable orbit. I think one has to say that in a dead galaxy only SOME of the dead stars are destined to fall in.

    Then there is the problem of "singularity". Technically a singularity is considered a symptom that something is wrong with the man-made theory that suffers from the problem. It indicates the theory needs improvement to make the singularity go away and find out what really happened.
    So people are working on that. There are various quantized versions of cosmology that do not suffer from singularities at the start of expansion of our universe. So the main thing now is to devise observational tests and collect data so we can distinguish and rule some of the rival (no-singularity) models out.

    So your idea of black holes getting together to make a giant "singularity" which then "explodes" does not really fit in with today's accepted ideas of physics.

    I wouldn't say that is FATAL, the accepted ideas of physics evolve over time and may in future undergo unpredictable revolutions. Science ideas are only provisional, the best we can invent for the time being. So be of good cheer. However your idea being completely outside the realm of conventional research DOES have the disadvantage that it makes it difficult to have a rigorous informed discussion. So (it seems to me) we normally avoid ideas here that are beyond fringe simply for the practical reason of being unsatisfactory to talk about.
     
    Last edited: Dec 30, 2011
  4. Dec 30, 2011 #3

    01i

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    Marcus,

    Thanks for your response. So basically, instead of naturally tying together accepted theories, I've tied them with an additional assumption, that super massive black holes will eventually swallow up the stars orbitting them? Is that right?

    What I dont understand is why that is an assumption.

    Surely the stars in a stable orbit are only stable because of their relative density to the black hole being perfect for their distance away from it.

    As the black hole swallows up the stars too near to escape it'll become denser and have more gravity, pulling in a few further away that were only 'just' stable. Become denser, pull a few more in .. and so on.

    Why would the most powerful thing in the universe just evaporate while still surrounded by 'food'?
     
  5. Dec 30, 2011 #4
    Re: Why is it considered the 'end of the universe' when the stars go dark??

    My assumption has been that due to the infinite amount of time available so far, and in the future, that this event has been repeated an infinite number of times, in an infinite number of locations, and may even be occurring an infinite number of times simultaneously, given the infinite amount of space we are situated within.

    We do not have a good way of knowing our scale relative to the rest of what's out beyond where we can detect. Is our system relatively large, or is our known universe simply riding on another scale's version of a sub-atomic particle.

    We know what we can sense or detect, and we can theorize about what we guess is going on that we can't see directly....but, there are certainly opportunities for things to be out there that we don't even suspect yet. I think we're getting the known universe out pretty far, but, compared to infinity, well, its statistically nothing.

    So, what happens after the infinite numbers of singularity? More singularity...or whatever it is instead.

    :D


    As for ignoring food, well, sometimes BEING the most powerful thing in the universe is why the thing can't last....Suns are pretty powerful to start with, etc. A bomb might be the most powerful thing around it, but they sure do explode. If an object becomes too dense, it may rip itself apart just from the differences between the inner/outer forces for example.
     
    Last edited: Dec 30, 2011
  6. Dec 30, 2011 #5
    Re: Why is it considered the 'end of the universe' when the stars go dark??

    The problem is that space is fairly empty. When a blackhole consumes a star, the event horizon grows, but not as much as you are thinking. Either that or you are thinking that stars are closer together then they are. When a super-massive black holes (millions of times the mass of our sun) consumes a star the size of our sun, the event horizon grows only slightly, this is compounded by how you figure out volume. Then there is the last problem. From our vantage point here on earth, when our super-massive black hole at the center of our galaxy consumes a star, it doesn't effect us at all. Because the gravity already existed. The source of the gravity has changed, but there isn't more gravity then there was to begin with.
     
  7. Dec 30, 2011 #6

    Chronos

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    Supermassive black holes do not consume entire galaxies, so far as we know, so that is an unlikely scenario.
     
  8. Dec 30, 2011 #7

    marcus

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    No that is not right. Your scenario also says that the huge black holes will themselves eventually get together (before they evaporate) into one vast superhuge. That's what I think you said and that is physically impossible according to standard cosmology. Because of the acceleration factor.

    Because of the continued (and gradually accelerating) expansion we expect to be out of causal contact with most of the billions of galaxies out there. So far from them that if you were to set out for one of them at the speed of light you would never get there.
    So it will be physically impossible to have a grand merger.

    We can expect black hole merger involving Milky and Andromeda, and perhaps a halfdozen more galaxies. But that is peanuts. It is like TEN instead of billions.

    So the important thing to realize is your scenario does not work.so you can move on.

    The other thing is a second way it is wrong. I'll get to that later. She eats up all the food in her immediate surrounds and when its cleared she stops growing, basic story.
     
  9. Dec 30, 2011 #8

    01i

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    JonDE, I can't argue with that logic. I hadn't considered that the amount of gravity wouldn't actually change.

    So, the ultimate future of dead galaxies is lone black holes surrounded by a ring of dead stars in stable orbit. The black hole eventually evaporates and I guess the dead stars need to find something else in the dead galaxy to orbit or fly off??

    So what happens to the mass of the galactic black hole when it 'evaporates'?
     
  10. Dec 30, 2011 #9

    01i

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    ooh more posts.

    marcus, I am moving on. you mentioned "The other thing is a second way it is wrong. I'll get to that later" and then swifty concluded your post.

    Interested to hear the other way it's wrong.
     
  11. Dec 31, 2011 #10

    marcus

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    As long as you are moving on from that scenario to ideas, all is well. No need to belabor.
    But in fact a black hole can eat up the matter in immediate neighborhood and stop growing and still have million of stars orbiting around it.

    It is not to be expected that every galaxy eventually turns into a big black hole.

    E.g if the sun were A BLACK HOLE AND BY SOME CURIOUS accident the planet Mercury fell in that would not make significantly more central gravity so as to pull in Venus, which would still continue in roughly the same circular orbit as before

    if the modestsize BH in center of Milky galaxy eats some stuff that is already near it, this does not make more mass in the center of Milky. So stuff like the sun does not feel more drawn to center. Things continue orbiting at about the same radial distance from center.

    But no need to belabor this idea. Learn some more, ask other questions. Get some different ideas. Big subject with lots of room for thought, so have fun.
     
  12. Dec 31, 2011 #11

    Chronos

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    This does not deserve much attention, marcus.
     
  13. Dec 31, 2011 #12

    marcus

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    You've got a point, Chronos. I'm trying to be a mensch. I'm not up on my Yiddish but I think a mensch is the opposite of a grinsch. Something like that :biggrin:
     
  14. Dec 31, 2011 #13

    phinds

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    Marcus, you are always a mensch !
     
  15. Jan 1, 2012 #14

    marcus

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    Hey! It's an ideal to strive for. Still a pretty far off one but thanks!
     
  16. Jan 1, 2012 #15
    Re: Why is it considered the 'end of the universe' when the stars go dark??

    I thought the stars going out meant that thermodynamic engines were no longer possible since all temperatures would soon equilibrate.

    All life ceases and that's that.
     
  17. Jan 2, 2012 #16

    marcus

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    I think by "stars going out" you mean the natural process by which naturally-formed stars use up their fuel and eventually become slowly cooling dead cinders of various sorts---whitedwarf, neutronstar.

    In that case you may have skipped some steps. It seems to me that "stars going out" would not immediately lead to "all life ceases". It might take a very long time (after the natural end of stars) for life to cease. Some people have speculated about this.

    I don't know how interesting it really is to speculate so far into the future, but a key physics fact you might bring into your picture is that the temperature of a 1020 kilogram black hole is 1227 degrees kelvin.

    And the temp goes as the inverse of the mass---so if you cut the mass by half you double the temperature. I think you probably know this, may even have looked up "Hawking radiation" on Wkpd.

    So as long as you have a lot of 1020 kilogram black holes and plenty of matter to feed them you have source of energy. The matter you feed them could, I suppose, be pretty much anything----hydrogen gas, ground-up rock, old copies of the Scientific American...

    So even after your star goes dark you can continue being Life as long as there is extra matter to feed the artificial black holes. Or to annihilate in some other manner that I cannot imagine. If you really enjoy living it might take a long time to annihilate all the extra matter. :biggrin:
     
  18. Jan 2, 2012 #17
    Re: Why is it considered the 'end of the universe' when the stars go dark??

    Concerning the scenario of dead stars in stable orbits around central black holes, wouldn't the orbits eventually decay as energy is radiated away as gravity waves? I realize that would take a ridiculously long time, but we are talking about ridiculously long time scales.
     
  19. Jan 3, 2012 #18

    marcus

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    Re: Why is it considered the 'end of the universe' when the stars go dark??

    I think you are right (the effect has been observed in tight orbit binary pulsars?). In the very very long run in theory you don't have stable orbits even at galactic scale because energy is lost thru gravitational radiation.

    The sun takes 200-250 million years to orbit Milky center. I am trying to imagine a wave with a period of one cycle every 200 million years. :biggrin:
     
  20. Jan 3, 2012 #19
    Re: Why is it considered the 'end of the universe' when the stars go dark??

    This is my understanding of the end of the universe.

    According to the second law of thermodynamics Entropy dictates that the universe will go from a state of low entropy to a state of high entropy over time, because its overwhelmingly more likely that this will happen.
    This concept introduces the arrow of time, cause and effect from order into disorder. A shattered glass never jumps back onto the table into the precise organisation that the glass had when it wasn't shattered, this is a given we know this to be true.
    Towards the end of the end of the universe when even the black dwarves have burnt themselves out and evaporated leaving nothing behind, after that black holes follow suit until only photons remain slowly cooling down to absolute zero, when that is achieved nothing happens ever again no change and the concept of the arrow of time evaporates along with everything else.
    Nothing changes ever, so the passage of time is essentially immeasurable, and that's how we know time we measure it, so essentially time ceases to exist and the universe comes to a halt and 'dead' would be the best way to describe the state of the universe then.


    According to my parroted knowledge this is what will happen tens of trillions and trillions and trillions of years from now so don't worry about it
     
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