# How much of the universe is black holes?

We all fear black holes, but how many of them are there out there, really? Between the stellar mass black holes and the supermassive ones, just how much of our Universe is black holes?

There are two kinds of in the Universe that we know of: There's stellar black holes, formed from , and a supermassive black holes which lives at the hearts of galaxies.

About 1 in a 1000 stars have enough mass to become a black hole when they die. Our Milky Way has 100 billion stars, this means it could have up to 100 million stellar mass black holes. As there are hundreds of billions of galaxies in the observable Universe, there are lots, lots more out there. In fact, the math suggests there's a new black hole forming every second or so. So just to recap, the entire Universe is about 1/1000th "regular flavor" stellar mass black holes.

Supermassive black holes are a slightly different story. Our central galactic black hole is about 26,000 light years away from us. Formally, it's called Sagittarius A-star, but for our purposes I'm going to call it Kevin. Just so you know they don't throw that term "supermassive" around for no reason, Kevin contains 4.1 million times the mass of the Sun.

Kevin is gigantic and horrible. We can only imagine what it's like to be in the region of space near Kevin. What percentage of the galaxy do you think Kevin makes up, mass wise?

Kevin, whilst absolutely super-massive, is a tiny, tiny 1/10,000 of a percent of the Milky Way galaxy's mass. So, to be precise, if we add Kevin's mass to the mass of all the stellar mass black holes aka. "mini-Kevins", we get a very minor 11/10000s of a %.

As it turns out this ratio holds up on a Universal scale and is approximately the same for all the mass in the Universe. So, 11 ten thousandths of a percent is the answer to the question. As far as we know.

Unless… is black holes. Dark matter accounts for more than ¾ of the mass of the Universe. It doesn't absorb light or interact with matter in any way. We're only aware of its presence through its gravitational influence.

As it turns out, Astronomers think that one explanation for dark matter might be primordial black holes. These microscopic black holes would have the mass of an asteroid or more and could only form in the high pressure, high temperature conditions after the Big Bang.

Experiments to search for primordial black holes have yet to turn up any evidence, and most scientists don't think they're a viable explanation. But if they were, then the Universe is almost entirely composed of the physics inspired nightmare that are black holes.

If it's not the case now, in the far future, everything could be. Given enough time, all those stellar black holes and supermassive Kevins will scoop up all the available material in the Universe.

In 10 quintillion years everything in the Universe will have either fallen into a black hole, or been flung out on an escape trajectory. And then those black holes will slowly evaporate over time, as predicted by Stephen Hawking.

In 10^66 years the smallest stellar black holes will have evaporated. The most massive could take 10^100 years. And then, there won't be any black holes at all.

What do you think? Is it mostly black holes or almost no black holes? Tell us what you suspect in the comments below.

Source: Universe Today

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Jun 17, 2014
|We all fear black holes, but|

Wait, wait. What does fear have to do with the most removed and interesting phenomenon in the Universe? Speak for yourself, bud

Jun 17, 2014
|We all fear black holes, but|

Wait, wait. What does fear have to do with the most removed and interesting phenomenon in the Universe? Speak for yourself, bud

I agree with you Nigel-Skippy. I can't remember the last time ol Ira say to him self "Ira-Skippy I sure don't want one them black holes to swoop down on me today or the meteor either." Somebody tell me the truth. When was the last time you had a worrying about the black holes on your mind making you afraid?

Jun 17, 2014
I'm going to say that the percentage of the universe that is black hole is the same as the percentage of the donut that is donut hole.

Jun 17, 2014
DM being a lot of small ones kinda makes sense if you look at the universe as some bubble in a sea of other bigger bubbles. It would be like the small foamy stuff you see, and those/bubbles always seem attract and pull together.

Jun 17, 2014

"Do mini black holes cause earthquakes? After suggesting two years ago that tiny black holes orbiting inside the Earth may trigger volcanic activity, a Russian physicist has now linked these bizarre objects - whose presence is still only hypothetical - with seismic activity.

A. P. Trofimenko of the Minsk Department of the Astronomical-Geodesical Society of the USSR believes that all cosmic bodies, including the Sun and the Earth, are riddled with 'mini' black holes left over from the big bang (New Scientist, Science, 1 September 1990). Though smaller than atoms, such black holes would each contain as much mass as a mountain, up to about 2 x 1020 grams."

-How would we know? And how wouldnt we know?

Jun 17, 2014
IMO the miniblack holes are common atom nuclei: it's the compromise of relativity and quantum physics theories. They're even formed in LHC routinely - the physicists just don't recognize them so. If you believe in relativity firmly and ignore the quantum mechanics, then all black holes must be tiny pinpoint singularities, because the general relativity predicts the gravitational collapse. Whereas in quantum mechanics all particles expand into infinity instead. Ironically enough, the theories like stringy and susy models are getting dismissed today due to alleged lack of extradimensions, despite the atom nuclei are stabilized just with presence of extradimensions. It just illustrates, that the contemporary mainstream physics based on schematic abstract theories is confused as hell - it cannot be confused more.

Jun 17, 2014
Ok, sure, ignore Kevin as inconsequential. He's just the 362.874kg gorilla in the room. Yeah, he's tiny. He has an event horizon of less than 30km in diameter but he seems to be doing a good job of keeping us in orbit. And what about Stacy, Andromeda's SMBH? Are they an item? Why are they getting closer? Is it random motion or do they have a relationship? Is it animal magnetism, gravity or some unknown causality? What kind of gravitational lensing distortions would two SMBH closing proximity cause? As always, I have more questions than answers.
If one can wrap their head around a human with average sized hands could hold all the black holes in the universe in the palm of one hand, perhaps they'd be closer to unifying relativity with quantum gravity. A simple solution to a complex differential equation would do it.

Jun 17, 2014
As a layman my understanding was that micro BH would be short lived and thus eliminates the idea of MBH being the particles of matter (info from could not cross the micro event horizon etc.). However, it does seem that the 'jury is out' on this one because Hawking radiation may not apply. My idea, with nothing to back it up, would be that virtual particles might be good candidates for MBH, the formation of a micro Gabriel's Horn then poof.

Jun 18, 2014
"I'm going to say that the percentage of the universe that is black hole is the same as the percentage of the donut that is donut hole."
Nice analogy and probably the truest statement ever written about black holes.

"Do mini black holes cause earthquakes?
Come on, everyone knows Pat Robertson proved the acceptance of homosexuality causes earthquakes and hurricanes.

Jun 18, 2014
This is part of a trend of fearmongering in these articles.

Jun 18, 2014
to Bob Osaka: send me a message to joefe777@yahoo.com and I give U many not-official answer at Your questions. Or to anyone...

Jun 18, 2014
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Jun 18, 2014
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Jun 18, 2014
|We all fear black holes, but|

Wait, wait. What does fear have to do with the most removed and interesting phenomenon in the Universe? Speak for yourself, bud

Still, close up they are surely pretty scary. There are a couple of simulations on youtube of flights close to/into a black hole. And I'd certainly pee my pants if I saw one of those suckers looming in the sky.

When was the last time you had a worrying about the black holes on your mind making you afraid?

Depends on the quality of your nightmares, I guess.

Jun 18, 2014
@Sikla 'They indeed should, but the microblack holes aren't concept of relativists. They're primarily the idea of string theorists (Mrs. Randall in particular),....' Yes, quite and therein lies my apprehension. According to Lisa Randall with all these extra dimensions just about anything is possible. Also at the QM level one would have to decide on the representation of the dimensions, 2D,3D,4D (spacetime) or physical dimensions higher than 3 (compactified or not). In the latter, although there are formulations there is yet no evidence that such exists.

Jun 18, 2014
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Jun 18, 2014
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Jun 18, 2014
Considering that an object has to exceed a certain mass below a certain volume of space in order to possess the powerful gravity needed to become a black hole, how is it that primordial black holes are able to remain black holes despite having far less mass as in microscopic black holes this article mentions.

I've never seen an explanation of this, only statements that it is so.

Jun 19, 2014
On the 1st pic there is NO an Black Hole! That is an Accretional Disc in Prestellar Phase. You can watch the supermass Nucleus with strong gravity Force!!!

Jun 22, 2014
The mistake in this calculation is that the proportion of massive stars that ever existed has to be counted, not the current fraction. Since these stars do not last ver long there have been many generations of them since the start of the galaxy. Say they last 10000000 years, then there will have been about 1000 generations of them, amounting to around 50% of the mass or more. (since they amass more than the average star)

Jun 22, 2014
|Wait, wait. What does fear have to do with the most removed and interesting phenomenon in the Universe? Speak for yourself, bud
Actually, however many years ago I first learned about black holes, a time span now best measured in decades, I remember being quite unhappy about the very idea of black holes. It seemed like a terrible waste of perfectly good matter, to me at the time. This was before I really understood just how vast the Universe is, mind you, and while I no longer feel that way now, I can understand why some people would.
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The mistake in this calculation is that the proportion of massive stars that ever existed has to be counted, not the current fraction.
Yes, this bothered me, too, and I was going to mention it if you hadn't.

Jun 23, 2014
How much of the universe is black holes?

Probably the same amount which is unicorns and leprechauns...

Brilliant!
I could not do better.
Anyway, the article shows how much some people love fairy tales.
Do not dare to challenge their wisdom!

Jun 23, 2014
As Halton Arp says "All evidence about Black Holes comes from White Hole"