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Old 07-23-2012, 03:16 PM
Lumpy Lumpy is offline
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The Big Rip and black holes

According to a recent article, the universe will probably end when dark energy rips the universe apart. This is bad news for galaxies, solar systems, stars, planets, people, atoms, nuclei, and hadrons- but what about black holes? A black hole has no known structure, but what happens when the red shift limit is less than a black hole's radius? Is there in fact no dark energy within an event horizon?
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Old 07-23-2012, 03:50 PM
Yumblie Yumblie is online now
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What would happen would depend on the explicit properties of both dark energy and the center of black holes, neither of which is known, so we can only speculate. If we posit dark energy as a kind of anti-gravity, then my guess would be that as it got stronger, the event horizon of a black hole would shrink, until you had a naked singularity. If the black hole has any kind of structure it would be ripped apart. If the black hole were literally a singularity with 0 volume then dark energy wouldn't be able do anything to it from there and it would just be carried through space away from everything else, like every other fundamental particle.

Note that the Big Rip scenario is far from conclusive. Until we better understand dark energy we can't really say whether we'll have a long drawn-out Heat Death or an explosive Big Rip ending.
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Old 07-23-2012, 04:35 PM
ZenBeam ZenBeam is offline
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Can the OP provide a link? The latest I've seen, the dark energy was a constant, overwhelming gravity on intergalactic scales over time, but local groups stayed bound.
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Old 07-23-2012, 05:00 PM
dracoi dracoi is offline
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Quote:
Originally Posted by ZenBeam View Post
Can the OP provide a link? The latest I've seen, the dark energy was a constant, overwhelming gravity on intergalactic scales over time, but local groups stayed bound.
https://en.wikipedia.org/wiki/Big_Rip
And for what it's worth, Dark Energy (i.e. the expansion of the universe) is not constant over time. It's commonly believed that early stages of the universe had a much higher rate, which slowed down for a time and then starting increasing again. Since it is still increasing, it's possible that it will continue to increase to infinity... but since it has slowed down in the past, it's also possible that it will not continue to increase.
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Old 07-23-2012, 06:32 PM
Enola Straight Enola Straight is offline
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An earlier post of mine:
http://boards.straightdope.com/sdmb/...ght=black+hole
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Old 07-24-2012, 12:37 PM
Half Man Half Wit Half Man Half Wit is offline
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Quote:
Originally Posted by dracoi View Post
https://en.wikipedia.org/wiki/Big_Rip
And for what it's worth, Dark Energy (i.e. the expansion of the universe) is not constant over time. It's commonly believed that early stages of the universe had a much higher rate, which slowed down for a time and then starting increasing again. Since it is still increasing, it's possible that it will continue to increase to infinity... but since it has slowed down in the past, it's also possible that it will not continue to increase.
The Big Rip is a hypothetical scenario, in which the dark energy is of a specific ('phantom') kind; the simplest scenario consistent with observation is indeed that of a cosmological constant, i.e. a term of constant energy density. This yields the so-called lambda-CDM model, often referred to as the 'standard model of cosmology' (CDM stands for 'cold dark matter', the prevailing hypothesis on the kind of stuff that messes up galactic rotation curves).

As for what happens to black holes, apparently, they dissolve: basically, the phantom energy is accreted by the black hole, which thus looses mass, until it's gone, or at least so this article argues.
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Old 07-24-2012, 02:25 PM
fiddlesticks fiddlesticks is offline
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If the recent study is right, the Rip will happen long before decent-sized black holes evaporate, the "worst case" scenario apparently says the Universe has only 17 billion years left.

I presume the dark energy will tear apart black holes too, but I'm guessing there is a Nobel Prize in explaining exactly how that would happen.

Last edited by fiddlesticks; 07-24-2012 at 02:26 PM..
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Old 03-18-2014, 03:26 AM
tetrisd tetrisd is offline
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I presume the dark energy will tear apart black holes too, but I'm guessing there is a Nobel Prize in explaining exactly how that would happen.
Could a black hole / singularity torn apart by a big rip look end up looking something like the big bang that started our universe?
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Old 03-18-2014, 05:01 AM
Mangetout Mangetout is offline
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Quote:
Originally Posted by dracoi View Post
https://en.wikipedia.org/wiki/Big_Rip
And for what it's worth, Dark Energy (i.e. the expansion of the universe) is not constant over time. It's commonly believed that early stages of the universe had a much higher rate, which slowed down for a time and then starting increasing again. Since it is still increasing, it's possible that it will continue to increase to infinity... but since it has slowed down in the past, it's also possible that it will not continue to increase.
How can anything that is finite increase until infinite? Do you mean increase indefintely?
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Old 03-18-2014, 08:41 AM
Chronos Chronos is offline
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How can anything that is finite increase until infinite?
It has a vertical asymptote. Compare to the behavior of the function y = 1/x as you approach the origin from the right.
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