Slashdot Mirror
Can Primordial Black Holes Alone Account For Dark Matter?
thomst writes: Slashdot stories have reported extensively on the LIGO experiments' initial detection of gravity waves emanating from collisions of primordial black holes, beginning, on February 11, 2016, with the first (and most widely-reported) such detection. Other Slashdot articles have chronicled the second LIGO detection event and the third one. There's even been a Slashdot report on the Synthetic Universe supercomputer model that provided support for the conclusion that the first detection event was, indeed, of a collision between two primordial black holes, rather than the more familiar stellar remnant kind that result from more recent supernovae of large-mass stars.
What interests me is the possibility that black holes of all kinds -- and particularly primordial black holes -- are so commonplace that they may be all that's required to explain the effects of "dark matter." Dark matter, which, according to current models, makes up some 26% of the mass of our Universe, has been firmly established as real, both by calculation of the gravity necessary to hold spiral galaxies like our own together, and by direct observation of gravitational lensing effects produced by the "empty" space between recently-collided galaxies. There's no question that it exists. What is unknown, at this point, is what exactly it consists of.
The leading candidate has, for decades, been something called WIMPs (Weakly-Interacting Massive Particles), a theoretical notion that there are atomic-scale particles that interact with "normal" baryonic matter only via gravity. The problem with WIMPs is that, thus far, not a single one has been detected, despite years of searching for evidence that they exist via multiple, multi-billion-dollar detectors.
With the recent publication of a study of black hole populations in our galaxy (article paywalled, more layman-friendly press release at Phys.org) that indicates there may be as many as 100 million stellar-remnant-type black holes in the Milky Way alone, the question arises, "Is the number of primordial and stellar-remnant black holes in our Universe sufficient to account for the calculated mass of dark matter, without having to invoke WIMPs at all?"
I don't personally have the mathematical knowledge to even begin to answer that question, but I'm curious to find out what the professional cosmologists here think of the idea.
What interests me is the possibility that black holes of all kinds -- and particularly primordial black holes -- are so commonplace that they may be all that's required to explain the effects of "dark matter." Dark matter, which, according to current models, makes up some 26% of the mass of our Universe, has been firmly established as real, both by calculation of the gravity necessary to hold spiral galaxies like our own together, and by direct observation of gravitational lensing effects produced by the "empty" space between recently-collided galaxies. There's no question that it exists. What is unknown, at this point, is what exactly it consists of.
The leading candidate has, for decades, been something called WIMPs (Weakly-Interacting Massive Particles), a theoretical notion that there are atomic-scale particles that interact with "normal" baryonic matter only via gravity. The problem with WIMPs is that, thus far, not a single one has been detected, despite years of searching for evidence that they exist via multiple, multi-billion-dollar detectors.
With the recent publication of a study of black hole populations in our galaxy (article paywalled, more layman-friendly press release at Phys.org) that indicates there may be as many as 100 million stellar-remnant-type black holes in the Milky Way alone, the question arises, "Is the number of primordial and stellar-remnant black holes in our Universe sufficient to account for the calculated mass of dark matter, without having to invoke WIMPs at all?"
I don't personally have the mathematical knowledge to even begin to answer that question, but I'm curious to find out what the professional cosmologists here think of the idea.
Pirmordial
Editors, the word you're looking for is primordial.
editors... really??
See this link: Content of the Universe 2016
So, the problem is that there is so much of it, you would think we'd see it perturbing stallar orbits more, it it were concentated in many, many discrete points of star gravitational influence. There would be a lot more stars orbiting pulsar type objects, perhaps?
A real cosmologist would know the odds of the galaxy looking the way it does if all the extra mass were in scattered black holes of a certain size. Probably low.
You're welcome.
I'm quite sure than as soon as someone figures out the math, a paper will be published. I doubt anyone seeing this question will pull out their pencil, do the computations right now just because you asked, and then publish the result here.
Solutions range from assuming that something of a kind exists that we've never seen, calculating differently (be it MOND or pilot waves or ...), or there simply being something we know but cannot see the instances of. It's physics. You can be sure that some of all 3 (and probably a 4th, correcting some other current assumptions) are needed to solve the riddle or, at least, get the mathematical descriptions closer to reality.
https://phys.org/news/2015-03-... http://www.sciencemag.org/news... If dark matter were simply some existing form of baryonic matter, even if trapped in black holes, then a phenoma like this where dark matter halos separate from collided galaxies and behave under different rules to continue on their existing path should not be possible at all, because it, like all the other ordinary matter involved, it should have followed the same paths gravitationally bound.
Quote: "Dark matter [...] has been firmly established as real [...] There's no question that it exists." There is still plenty of controversy related to the idea of dark matter, and there is no such thing in physics as proving something exists - you can only prove something to be false. I'm not saying dark matter does not exist, only that statements like the above are too assertive.
26% of the mass of the universe is made up of your simplifying assumptions: space is flat and uniform everywhere and everywhen, gravity is constant everywhere and everywhen, the speed of light is constant everywhere and everywhen, the Higgs field isn't really the luminiferous aether with a fancy new name, etc. ...
So so so much of the Standard Model (and astrophysics in general) starts out like "Given a spherical cow of uniform density at STP...".
We can basically derive ALL of chemistry from first principles involving (protons, neutrons, electrons) (and their charges), electron shell configurations, etc. Does the Standard Model provide an explanation for the mass of the electron, or any of the other 92 empirically derived "constants" that make up the current orthodoxy? Does calling the gap between reality and our understanding of it really benefit from calling it "Dark Matter", or "Dark Energy", or should we just call it "phlogiston"?
I'm not trolling, I'm serious. The Standard Model has lots of (statistical) predictive power, but absolutely no explanitory power -- back to the chemistry example, it's as though we have atomic weights and molar values, but no notion of electron shells -- we can predict, but we can't explain, at least not in a meaningful way -- yet.
I want to invoke the Betteridge Law of Headlines here.
See: https://en.wikipedia.org/wiki/Betteridge%27s_law_of_headlines
Anyway, a bit more sientific, not having done large research the following can easily be false reasoing.
In my understanding we need a very special distibution of darkmatter for galaxy formation. This is easier if particle are small.
Primordial Black Holes need a minimum size not to have decayed through Hawking Radiation by now. With the larger size the distribution of dark matter that the models hint at would need to be grainier.
Therfore I find it likely that this is not the solution.
So this is just a question by someone, not a real article or anything. Brilliant. Like a crayon.
I asked some of the professional cosmologists here and they variously talked about Frosty Piss, Gay Wiggers, a lengthy explication of a homosexual encounter, Appy apps and why Hillary, feminists and transgenders in Seattle bathrooms should be blamed. Others called it Fake News and promised that Trump would fix it, possibly with a hosts file, and there was a steady chorus denying any Russian involvement in anything. It's not my field so I can't say if they're right or not.
Dark matter has never been directly proven, it's an hypothesis.
https://www.wired.com/2017/01/case-dark-matter/
"What interests me..."
"I..."
"I..."
Thanks for letting us know in an entirely opinionated piece you lack the science background, but this fascinates you.
My dog feels the same way about asphalt and rabbits.
E
WIMPs are unknown particles with unknown properties and the speculative detectors we hoped might detect them haven't yet ... ...this does not mean they don't exist, it just means the things we don't know the properties of we still don't know the properties of ...
Puteulanus fenestra mortis
These scientists need to get up to date!
Last year saw the death of Dark Matter theory - as finding don't match the theory, and no stretching and contorting of either the findings, or the model could unify them. So this is a null and void assertion from the outset.
Astronomers have observed the gravitational lens effect of dark matter. Dark matter normally surrounds normal matter, but is sometimes found separated. It appears that during galactic collisions, the dark matter can be separated from the normal matter, gas and dust of a galaxy. To do that, dark matter would have to interact with itself in a manner that does not involve gravity. A bunch of black holes would not interact in this way, so it is unlikely that dark matter consists solely of black holes.
I've never understood the emotional response to the theory of dark matter being some sort of mass we can't see. It seems like the theory personally affronts people for some reason.
The idea that a form of matter doesn't interact with three of the four fundamental forces doesn't seem all that crazy to me. I mean, the photon and W and Z bosons don't interact with the strong nuclear force, do they? (I'm actually asking - I'm no particle physicist.) And the neutrino interacts with the weak force and gravity, but not electromagnetism or the strong force. So the precedence exists - why not a particle with mass that interacts only with gravity? It'd be incredibly difficult to isolate and detect and measure of course, but I don't understand the push-back some people exhibit in regards to the concept. (The cool thing about that concept being that it perfectly fits, far as I'm aware, the observations scientists have made so far.)
https://en.wikipedia.org/wiki/...
Let's see: up to 100 million stellar sized (massed) black holes in our galaxy. We know it also has between 100 billion and 400 billion stars. And so, one-one thousandth of the mass in black holes is definitely 6 times the mass (4% vs 24%). The OP is definitely right, it requires the mathematical acumen of a PhD cosmologist to get those numbers to add up. I assume part of the problem is the stress he's under when he wakes up and has to count his feet, it must be quite a strain.
If you get rid of dark energy, you eliminate the need for dark matter as well.
That's completely wrong. Dark energy is needed to explain the acceleration in the expansion of the universe. Matter - either dark or ordinary - is gravitationally attractive and can never cause the expansion to accelerate. Dark Matter is needed to explain the "clumpiness" of the Cosmic Microwave Background, the rotation curves of galaxies and gravitational lensing observations e.g. bullet cluster. Black Holes have been considered a dark matter candidate before (MACHOs) and have been ruled out.
I think that about covers everything.
JANUS model from Jean-Pierre Petit could be the base of alternative possibility.
No, it was not obvious there would be an aether. It was closed to claim fire was an element, since fire comes out of things burning, but when careful measurements were made, THEN it became clear that aether had negative mass, so wasn't real, it was a privative.
However, there never was a clear reason why there should be an aether. Only by maxwell was it known that light was (apparently) a wave, but it was ALSO known to behave like a particle too. But if you thought of it as a wave AND thought that every wave needed a medium to travel through, THEN an aether was obvious.
But only by ignoring evidence (photoelectric effect) and making a claim out of ignorance (all waves need a medium. A thing not shown).
So, in summary, wrong.
And dark matter appears uniformly distributed. This is different than a black hole, which do interact with each other and which over time are pulled together and not left uniformly distributed.
This is the same guy that brought us enlightening articles like:
https://slashdot.org/submissio...
He's not a physicist, or scientist, or anything...
slashdot editors are scrounging badly, please have a clue.
We all love real science/astronomy/physics articles, written by actual specialists who know more than lazy laymen. Please do more of those, and less of these? kthx
there's a lot of interstellar, and intergalactic dust and gas too
Well.... they'd need to be pretty small, and also to not evaporate via Hawking radiation. Tiny black holes evaporating would release light at a known frequency that hasn't been detected (or hadn't been a decade ago, when I was paying attention). And the black holes would need to be primordial, because otherwise they'd affect the proportion of Lithium in the interstellar dust. So they can't have been engaging in nuclear reactions while that was being formed (*quite* early in the process). And they'd need to have a small enough capture cross-section that they wouldn't be capturing matter from a dense cloud back before the hyper inflation finished.
So you aren't talking about any normal black hole, but something rather special. Special enough to probably deserve a new name. I'm not sure what you're thinking the mass that would be necessary to create the gravity to cause the black hole is made from, but it would appear to need to be electrically neutral. The only thing that occurs to me is something like photonium, but how you'd get photons close enough and dense enough to create a Schwartzchild radius, even under those conditions, I can't imagine. Still, a black hole created of bound photons MIGHT not emit Hawking radiation. (I wouldn't want to bet on that, but the things would need to have a radius small enough that it might work.)
I actually think speculations about what exploded to create the big bang are more profitable than this one.
I think we've pushed this "anyone can grow up to be president" thing too far.
Very large stars explode rather than collapse into black holes according to some models.
So that is why some suggest they are primordial.
Others suggest LIGO black holes themselves are the merger of several stellar black holes.
Flavor changing pretty proves they have mass. However experiments give the upper weight bound of an electron volt. This is too light to explain dark matter. Plus neutrinos may be much lighter than an ev. New weighing experiments are planned.
There was a recent interesting paper, "Concordance cosmology without dark energy", which explained how dark energy was actually not required to explain the structure of the universe, if one just used a more accurate numerical model to simulate how the universe evolved. They even resolved a long-standing issue in cosmology whereby different ways of estimating the Hubble constant from observations gave different results. I'm looking forward to seeing how this theory develops, and how their findings are received by the rest of the cosmology community.
Betteridge's law
Q.E.D.
What happens to all the matter sucked up by black holes?
If some of the mass is converted to energy inside the black hole, could that affect our perception of the mass of those black holes?
Essentially, would an amount of mass that is being converted to energy inside the black hole affect the amount of mass we attribute to a black hole from our vantage point on the outside of said black hole?
Would it behave like some sort of "anti-gravity" effect, or would it act as a "gravity enhancing" effect?
I'm just a layman here, so please forgive my ignorance, but I am serious about getting an answer to the questions.
PlaynBass