Black holes ruled out as universe’s missing dark matter
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Black holes ruled out as universe’s missing dark matter
1–10 of 130 posts
Re: Black holes ruled out as universe’s missing dark matter
#2Assuming this pans out, is there anything left but WIMPs?
Re: Black holes ruled out as universe’s missing dark matter
#3Does this mean that black holes possibly might not even exist? Aren't there examples of them being directly observed?
Re: Black holes ruled out as universe’s missing dark matter
#4This spawned a question for me that seems like it must be nonsensical but I don’t know the answer.
Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole?
I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any mental framework to understand why that would be true. If someone reading this knows the answer and can point me at it, I’d be grateful. TIA!
Re: Black holes ruled out as universe’s missing dark matter
#5Does this mean that black holes possibly might not even exist? Aren't there examples of them being directly observed?
We have observed their x-ray jets directly and have observed their creation (recently). Pretty sure they exist. :)
Re: Black holes ruled out as universe’s missing dark matter
#6This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…
I think inflation had something to do with it, the only time in the history of the universe something faster than the speed of light was possible--but only because space and time itself was expanding so quickly.
Just stumbled upon this: https://www.reddit.com/r/askscience/comments/8p7hnn/where_an...
Re: Black holes ruled out as universe’s missing dark matter
#7Does this mean that black holes possibly might not even exist? Aren't there examples of them being directly observed?
No black holes absolutely exist. The researches have established an upper limit on the fraction of mass of black holes compared to all of the matter in universe. Per quote below this comes out to no more than than 23%.
" An as-yet unpublished reanalysis by the same team using an updated list of 1,048 supernovas cuts the limit in half, to a maximum of about 23 percent, further slamming the door on the dark matter-black hole proposal. "
Since dark matter makes up 85% of total matter this rules out black holes as the primary contributor.
Re: Black holes ruled out as universe’s missing dark matter
#8This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…
I'm absolutely not an expert, but I believe there wasn't any mass at first; it was all energy. It had to slow down to become mass, at which point it was spread out enough. Or something along those lines.
Another possibility is that black holes are places where lots of mass accumulates in the same place in space, while the big bang was a rapid expansion of space itself. Even if there was enough mass in one spot to be what we'd consider a black hole, the space it occupied expanded, dragged the mass along with it, and ripped the black hole apart.
Re: Black holes ruled out as universe’s missing dark matter
#9This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…
Neither space nor time existed prior to the big bang and energy levels were so high that a different set of laws of physics dominated the early evolution.
Re: Black holes ruled out as universe’s missing dark matter
#10This spawned a question for me that seems like it must be nonsensical but I don’t know the answer. Why did the Big Bang not just produce a Big Hole? IOW, if all the current mass of the universe was in a small volume wouldn’t it have promptly created a black hole? I’m assuming the answer has something to do with mass not actually existing in its current form until the universe expanded enough. However I don’t have any…
My naive (and likely wrong) understanding is that cosmological inflation was caused by a "false vacuum" of the higgs field. Think of it as if the energy pressure of a system is higher than a vacuum, but has similar pressure properties of a vacuum. That had the effect of gravitational pressure pushing matter outwardly, instead of pulling it inwardly like we have it today (to answer your question). That caused enormously fast expansion of the universe. Very shortly afterwards, the false vacuum "decayed", and gravity started behaving as you know it.
Check out Alan Guth's inflationary universe - a surprisingly accessible book on a deeply complex subject.
Someone please correct me where I'm wrong!