Dark Matter Found? New Study Furthers Stephen Hawking's Predictions About 'Primordial' Black Holes (cnn.com) 86
Where is dark matter, the invisible masses which must exist to bind galaxies together? Stephen Hawking postulated they could be hiding in "primordial" black holes formed during the big bang, writes CNN.
"Now, a new study by researchers with the Massachusetts Institute of Technology has brought the theory back into the spotlight, revealing what these primordial black holes were made of and potentially discovering an entirely new type of exotic black hole in the process." Other recent studies have confirmed the validity of Hawking's hypothesis, but the work of [MIT graduate student Elba] Alonso-Monsalve and [study co-author David] Kaiser, a professor of physics and the Germeshausen Professor of the History of Science at MIT, goes one step further and looks into exactly what happened when primordial black holes first formed. The study, published June 6 in the journal Physical Review Letters, reveals that these black holes must have appeared in the first quintillionth of a second of the big bang: "That is really early, and a lot earlier than the moment when protons and neutrons, the particles everything is made of, were formed," Alonso-Monsalve said... "You cannot find quarks and gluons alone and free in the universe now, because it is too cold," Alonso-Monsalve added. "But early in the big bang, when it was very hot, they could be found alone and free. So the primordial black holes formed by absorbing free quarks and gluons."
Such a formation would make them fundamentally different from the astrophysical black holes that scientists normally observe in the universe, which are the result of collapsing stars. Also, a primordial black hole would be much smaller — only the mass of an asteroid, on average, condensed into the volume of a single atom. But if a sufficient number of these primordial black holes did not evaporate in the early big bang and survived to this day, they could account for all or most dark matter.
During the making of the primordial black holes, another type of previously unseen black hole must have formed as a kind of byproduct, according to the study. These would have been even smaller — just the mass of a rhino, condensed into less than the volume of a single proton... "It's inevitable that these even smaller black holes would have also formed, as a byproduct (of primordial black holes' formation)," Alonso-Monsalve said, "but they would not be around today anymore, as they would have evaporated already." However, if they were still around just ten millionths of a second into the big bang, when protons and neutrons formed, they could have left observable signatures by altering the balance between the two particle types.
Professer Kaiser told CNN the next generation of gravitational detectors "could catch a glimpse of the small-mass black holes — an exotic state of matter that was an unexpected byproduct of the more mundane black holes that could explain dark matter today."
Nico Cappelluti, an assistant professor in the physics department of the University of Miami (who was not involved with the study) confirmed to CNN that "This work is an interesting, viable option for explaining the elusive dark matter."
"Now, a new study by researchers with the Massachusetts Institute of Technology has brought the theory back into the spotlight, revealing what these primordial black holes were made of and potentially discovering an entirely new type of exotic black hole in the process." Other recent studies have confirmed the validity of Hawking's hypothesis, but the work of [MIT graduate student Elba] Alonso-Monsalve and [study co-author David] Kaiser, a professor of physics and the Germeshausen Professor of the History of Science at MIT, goes one step further and looks into exactly what happened when primordial black holes first formed. The study, published June 6 in the journal Physical Review Letters, reveals that these black holes must have appeared in the first quintillionth of a second of the big bang: "That is really early, and a lot earlier than the moment when protons and neutrons, the particles everything is made of, were formed," Alonso-Monsalve said... "You cannot find quarks and gluons alone and free in the universe now, because it is too cold," Alonso-Monsalve added. "But early in the big bang, when it was very hot, they could be found alone and free. So the primordial black holes formed by absorbing free quarks and gluons."
Such a formation would make them fundamentally different from the astrophysical black holes that scientists normally observe in the universe, which are the result of collapsing stars. Also, a primordial black hole would be much smaller — only the mass of an asteroid, on average, condensed into the volume of a single atom. But if a sufficient number of these primordial black holes did not evaporate in the early big bang and survived to this day, they could account for all or most dark matter.
During the making of the primordial black holes, another type of previously unseen black hole must have formed as a kind of byproduct, according to the study. These would have been even smaller — just the mass of a rhino, condensed into less than the volume of a single proton... "It's inevitable that these even smaller black holes would have also formed, as a byproduct (of primordial black holes' formation)," Alonso-Monsalve said, "but they would not be around today anymore, as they would have evaporated already." However, if they were still around just ten millionths of a second into the big bang, when protons and neutrons formed, they could have left observable signatures by altering the balance between the two particle types.
Professer Kaiser told CNN the next generation of gravitational detectors "could catch a glimpse of the small-mass black holes — an exotic state of matter that was an unexpected byproduct of the more mundane black holes that could explain dark matter today."
Nico Cappelluti, an assistant professor in the physics department of the University of Miami (who was not involved with the study) confirmed to CNN that "This work is an interesting, viable option for explaining the elusive dark matter."
Turtles all the way down (Score:4, Insightful)
At this point I've seen a gazillion things that can explain dark matter -- and the universe is weird enough such that all of them are plausible/occam razor compatible. So far none have been proven to the point of being able to exclude other explanations.
Re: Turtles all the way down (Score:2)
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Your assumption is that the little black holes were distributed uniformly. Dark matter appears to congregate in galaxies, so if they are dark matter then that is were we'd expect to find them. Even if not, they still would tend to stick around gravity wells, not flying about with no regard for physics.
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> At this point I've seen a gazillion things that can explain dark matter
Name 250.
Re: Turtles all the way down (Score:2)
I can only think of half of a gazillion.
What else? (Score:3, Funny)
OK. So .. (Score:4, Interesting)
I really get a kick out of any science that claims an overriding effect on practical physics due to its abundance. But when we need to get a satellite within a few thousand miles of an object orbiting beyond Pluto, we can conveniently ignore its effects and succeed with classical Newtonian mechanics. I wish I had discretionary fudge factors to work with like that when I was in engineering.
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Politicians and other blowhards would suddenly disappear into a hole in the ground. It would be glorious!
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Politicians and other blowhards would suddenly disappear into a hole in the ground. It would be glorious!
Heh. See "Everything You Know Is Wrong" - Firesign Theater
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What is the probability that the Earth would be struck by one during some period of time? What would the observable effects be?
IIRC, tiny black holes would pass right through the earth. They might cause small acoustic effects, and people have looked for these in seismic data, with no definitive results yet.
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Ok thanks, another question, would it pass through yourself unnoticed as well aside from maybe an acoustic effect?
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What is the probability that the Earth would be struck by one during some period of time? What would the observable effects be?
IIRC, tiny black holes would pass right through the earth. They might cause small acoustic effects, and people have looked for these in seismic data, with no definitive results yet.
I seem to recall a professor detailing such an event when I was at university circa 2002.
He didn’t refer to it as a black hole, though.
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If an atom size black hole hits the effect would be almost nothing. Asteroid size .. umm we'd be dead. But it's safe to say the universe isn't team with them because if it was we'd see stars or other objects getting hit by them. What's the chance that the universe is teaming with such objects and 1. we haven't been hit in at least a few million years and 2. we don't see other objects that we have been watching for 100 years getting hit by it?
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The limits we can place on black holes in this mass range are primarily from looking for their evaporation signatures. If they hit the you, the Earth, or a neutron star they wouldn't have much effect.
Bigger ones are limited by the effects they'd have on neutron stars, which we do not observe, microlensing, and gravitational waves, in order of increasing mass.
There is a narrow window left between the ones that should be evaporating and the ones that would distrupt neutron stars in which primordial black hole
Re: OK. So .. (Score:2)
That's "teeming".
Re: OK. So .. (Score:2)
we haven't been hit in at least a few million years
That depends on where you draw the line in the size distribution curve. The Barringer crater is 50k years old. Tunguska hit in 1908. Chelyabinsk hit in 2013. I get that atomic-sized, uncharged particles would have minimal effects by comparison. But I'd be really surprised if any of our neutrino detectors or similar equipment would miss an 'anomalous event'. What with dark matter making up about 80% of the mass in the universe.
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My Theory:
FWIW, I think they're overestimating the size.
Black holes evaporate by absorbing HALF of a virtual particle, rendering the other half real at the expense of some energy from the black hole. But if a black hole is small enough it won't be able to absorb anything. because nothing will have a short enough wavelength.
So these things could go right through the earth without causing any problem except a brief fluctuation in gravity. and possibly in EMF They could probably go through a neutron star wi
No dark matter found (Score:2, Troll)
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If you see a wake on the water, you can't tell what made it; ship, whale, or something else entirely. But you see the wake, so you know something passed by.
Theory vs Experiment (Score:5, Interesting)
But you see the wake, so you know something passed by.
Yes, but nobody has seen anything. The idea that Dark Matter could be primordial Black Holes had been around for decades. Indeed it was part of the motivation for the search of MACHOs a few decades ago - looking for massive, compact halo objects orbiting the galaxy and detected by gravitational lensing events.
This paper is just about how such Black Holes might have formed and says nothing about whether they actually exist. Gravitational wave detectors like LIGO should answer whether primordial Black Holes are Dark Matter or not soon as their sensitivity improves. The reason is that if you have all the BHs moving around then some will merge from time-to-time. The smalled the BH mass the more of them that are needed and so the higher the rate of collisions but the smaller the signal so they need to be closer to be detectable. My understanding is that should provide experimental evidence for BHs as DM or else exclude them (at least over a large range of parameter space) regardless of how they might have been produced.
What is interesting about this theoretical paper is that PBHs seemed to have fallen out of favour simply because nobody could figure out how they might have been produced in the Big Bang in the mass ranges that remain experimentally unexcluded. However, you should always do the experiment if you can regardless of what the theorists think possible because, if you do find evidence of PBHs theorists will either quickly come up with an explanation when confronted with their existence or, if not, then it's even more interesting since it means there is likely new physics involved.
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While there are slews of upgrades in progress for LIGO (and VIRGO, and Kagra), the Next Big Step for GWOs is to move away from all the seismic noise of the ground and fly the laser sources and mirrors in space. The technology-proving missions have been flown, and I think the science mission has been green-lit.
Ah, here it is - https://en.wikipedia.org/wiki/... [wikipedia.org],
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Re:No dark matter found (Score:4, Insightful)
Thinking about dark matter won't bring it to light. A direct detection will, no one has detected dark matter.
This obsession with "detecting" dark matter just shows how much people are electromagnetic chauvinists. Since all of our senses work using electromagnetic forces, they believe nothing can possibly exist unless it can somehow be converted to electromagnetic energy.
However, there's no law of physics that says every possible phenomenon in the universe must interact with the electromagnetic field in any particular way. Whatever dark matter is, it already interacts indirectly by causing gravity to bend the paths of light and other particles. Maybe it simply doesn't interact otherwise.
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Whatever dark matter is, it already interacts indirectly by causing gravity to bend the paths of light and other particles.
What? Did I miss a study which showed gravity wasn't causing light to 'bend' (light is technically following the curvature of spacetime due to the mass of an object which has the effect of creating gravity)? When did dark matter enter into the picture?
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OK, to state it more clearly, I should have said: "Whatever dark matter is, it already interacts indirectly because its gravitational force causes spacetime to bend the paths of light and other particles."
Or maybe I should have said "mass". That's enough pedantics. You know what I mean.
Re:No dark matter found (Score:4, Informative)
Whatever dark matter is, it already interacts indirectly by causing gravity to bend the paths of light and other particles. Maybe it simply doesn't interact otherwise.
That is the Weakly Interacting Massive Particle (WIMP) hypothesis, which is still the leading candidate for dark matter.
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But there have been all sorts of experiments to try to detect WIMPs by trying various approaches to convert them into electromagnetic signals, usually hoping that they occasionally collide with normal matter the way neutrinos do.
I was saying that maybe they simply never do that. If so, they could still exist whether most people are willing to believe it or not.
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Searches for WIMPs look for interactions via the weak force, not electromagnetism. That's how you look for WEAKLY interacting massive particles.
Dark matter could absolutely be some particle that does not interact electromagnetically or via the weak force, but you can't really design a lab experiment to look for that.
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We can't detect the weak force directly. We infer weak force interactions by looking at the electromagnetic signatures of their byproducts. (That's the only reason that most people accept the weak force exists. If it weren't for these byproducts that emit light, they'd be saying that the weak force is a myth as well.)
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You can use calorimeters, detect recoil, or look for decay products from weak interactions. You can argue that all of those detectors make use of electromagnetism at some point, but come on.
Not finding a dark matter particle doesn't imply there isn't one, regardless of what kind of detector you're using. If your argument is that people on the internet are dumb, great, but actual searches for dark matter particles aren't a result of "electromagnetic chauvinism."
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Yes, my argument basically is that people on the internet are dumb.
I'm not against them continuing to try to make dark matter interact with the electromagnetic force somehow. My point was, if they fail to do this, that still does not in any way imply that dark matter doesn't exist.
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Searches for WIMPs look for interactions via the weak force, not electromagnetism. That's how you look for WEAKLY interacting massive particles.
The researchers should just come over to Slashdot, which is full of overweight guys too shy to interact with other people or the real world.
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Since all of our senses work using electromagnetic forces
Uh, I only count one.
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All chemical actions and mechanical forces you feel are due to the electrons attached to the atoms that comprise your body. These electrons interact with each other via the electromagnetic force. You can not directly sense the strong force, the weak force, or even gravity (you only feel the mechanical force resisting gravity).
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Uh, yes Einstein. Are you suggesting we just give up? You realize it took like 200 years to get from Copernicus to Isaac Newton. It's not even been 50 years since publication of evidence demonstrating with high definitiveness that dark matter, or at least a serious problem in the theory of gravitation, exists. Maybe there's no hope of detecting it. So what? Until you can prove that, we should allocate at least SOME resources into figuring it out.
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I didn't say that at all. I'm just commenting on people who refuse to consider that dark matter might exist unless and until we somehow make it interact with the electromagnetic field. Maybe someday we'll do that, but if we can't, that still doesn't rule out the possibility that it exists and we'll simply never be able to detect it.
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You mean like it's gravitational effect? That's a direct detection.
Call it "dark matter", "dense invisible stuff", or "Allison Schwartz the Minion of Gozer"- it's still there.
What are you waiting for a proper naming? Because a "direct detection" outside of the gravitational effect may not be possible if it's only property is gravitational.
As another poster mentioned: we are biased by our "electromagnetic experience" which is vast. But gravity... we only see it's effects, we can detect it's waves, but we can
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At this point we'll just go with ""Allison Schwartz the Minion of Gozer"".
Because she can fly right over your head.
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Wait... Einstein. Pop goes your balloon.
Einstein is not wrong. His notations about what he observed are accurate as far as they reach. Many of the conclusions drawn from Einstein's notations are inaccurate due to the limitations of Einstein's observations and the limitations of the person drawing the conclusions.
But gravity... we only see it's effects, we can detect it's waves, but we can't at this point manipulate it like we can with electromagnetism.
It would be interesting to see if we can manipulate gravity using electromagnetic effects. I am uncertain if we are even capable of producing the energy levels needed, since "Gravity" seems to based upon energy levels and spaces far outsi
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How do you think detectors work? To detect anything you need a theory to tell what kind of effect for which to look. Otherwise we'd have the moral equivalent of people watching for UFOs. They have no theory so all we get are non-standardized reports of damn near anything that confuses the observers.
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There seems to be a lack of courage. (Score:2)
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That's not even wrong. Learn some philosophy of science first.
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Doesn't seem to explain halo effect (Score:1)
I thought dark matter tends to be repelled by regular matter, as it appears to stay in a halo around galaxies and avoids the denser centers, based on various studies. But black holes don't normally do this.
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Regular matter piles up in the middle of things like galaxies. Dark matter forms a halo because it doesn't experience friction, so it doesn't clump. Dark matter doesn't appear to "avoid" the centres of galaxies, it's just uniformly distributed relative to the regular matter.
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Galaxies wind significantly tighter over time? This is news to me, other than very near the center where debris is thick.
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? I didn't say anything about winding.
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Let me ask a different way: why does visible matter end up toward the middle of the galaxy but not micro-holes? Wouldn't a hole be subject to the same friction etc. as say an active star?
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Galaxies form through gravitational collapse of large gas clouds, then grow through mergers. Stars and planets form the same way. It's possible because the gas experiences enough friction to dissipate energy and collapse towards a centre point. In galactic mergers there's enough material that manages to collide that a decent amount of it can dissipate energy and stick around.
Stars in a normal galaxy (and planets in a solar system) don't continue to collapse towards the middle because they're much denser tha
new unit of mass (Score:2)
Journalists have now found a new unit of mass, the Rhino, apparently named after a horny physicist.
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Journalists have now found a new unit of mass, the Rhino,
I was unaware that members of the Republican Party with primarily non-Conservative-spectrum political beliefs and activities were all of approximately the same mass.
Weakly interacting? (Score:3)
Unless they can explain why the primordial black holes wouldn't interact with each other, then they essentially have nothing.
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Unless they can explain why the primordial black holes wouldn't interact with each other, then they essentially have nothing.
They interact with each other gravitationally, of course. This results in scattering, if they pass close enough to each other. But if the ones discussed here are only hypothesized to be the mass of an asteroid, this interaction is pretty small.
If they actually collided they would merge, of course, but their Schwarzschild radius is so small that after the universe is a few minutes old the probability of that is pretty low.
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Yeah, but according to the theory there should be far far more mass in these than in normal matter. Due to the sheer scale of time they've been around and their quantity, their small size would mean nothing in terms of interaction probability. The entire concept of dark matter only works if it's weakly interacting. That is not the same as the probability of interacting. You would need matter that just doesn't interact with itself outside of gravitational attraction.
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Yeah, but according to the theory there should be far far more mass in these than in normal matter. Due to the sheer scale of time they've been around and their quantity, their small size would mean nothing in terms of interaction probability. The entire concept of dark matter only works if it's weakly interacting. That is not the same as the probability of interacting. You would need matter that just doesn't interact with itself outside of gravitational attraction.
"Weakly interacting" is not the same as "not interacting." In fact, completely non-interacting matter wouldn't explain the galactic rotation curves; you need some interaction to concentrate matter in the galactic halo.
Gravitational scattering by tiny objects is very, very weak. And to account for galactic rotation curves, you only need a density of about one asteroid-mass black hole per quadrillion cubic kilometers.
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In fact, completely non-interacting matter wouldn't explain the galactic rotation curves; you need some interaction to concentrate matter in the galactic halo.
Do you have anything to cite that backs that up? Because this is counter to everything I've ever read on this subject.
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All I can say is, conservation of energy. Unless the dark matter has some way of losing energy, it will leave the gravity well of a galaxy at the same velocity it entered.
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I'm sorry but this is incorrect. They are still bound gravitationally to the system.
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You're supposing that it starts off bound to the galaxy, he's assuming it starts of free of that, so if it were to slide through a galaxy, it would just leave at the same speed it arrived with. Both are reasonable, and they may both be true.
OTOH, if it is moving above escape velocity, then it should continue moving above escape velocity. Just like an ordinary asteroid would, only beging a lot harder to collide with.
If there were frictional losses in the interaction, one would expect all the matter to even
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According to modern theories dark matter precedes galactic formation. PBS Spacetime did an episode on how non-interacting but gravitationally bound matter would stay together. It's pretty interesting and informative. https://www.youtube.com/watch?... [youtube.com]
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But "preceding" doesn't really say anything about their relative velocities. (But if it's caught in the halo, it can't really be above escape velocity.)
I find it quite plausible that the dark matter has a wide range of velocities. We'd only be detecting the dark matter that was bound to a galaxy (by being below escape velocity).
That said, one way to test this would be to search for galaxy clusters being bound by dark matter that wasn't bound to a particular galaxy.
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I find it quite plausible that the dark matter has a wide range of velocities
Why?
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Why not? I feel there needs to be a reason to exclude a possibility. Just not detecting it doesn't mean much if there's no reason you should expect to detect it.
Re: Weakly interacting? (Score:2)
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Well if it is that little density required, then a real free floating asteroid would do too. It would not need to be either dark or a black hole.
Yes, asteroids would also work in terms of mass. They're not luminous, so you wouldn't see them. The problem is, there's no credible way that enough asteroid material to account for dark matter could be created. Heavy elements-- silicon, oxygen, iron, all the stuff asteroids are made of-- come from nucleosynthesis in stars, and there just weren't enough stars spewing out these elements in the history of the universe to add up to ten times the mass of the stars in a galaxy.
For this source of dark matter to w
Re: Weakly interacting? (Score:2)
Galaxy formation [Re: Weakly interacting?] (Score:2)
The whole dark matter hypothesis implies that everything we know about star formation is wrong also.
Not important in star formation (too weakly interacting to play a role on the small scale of stars, even protostellar nebulae), but dark matter apparently plays a significant role in galaxy formation in the early universe, and the fact that we don't know what it is means that we have only incomplete notions of how galaxies form.
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Asteroids don't work because they do things like occlude stars and collide with each other. Astronomers aren't dumb, they've used every bit of data they can get their hands on to put limits on what dark matter could be. The parameter space formed by the particle size (or interaction distance), mass and prevelence is pretty constrained by observations we've already made. Asteroids, rogue planets and brown dwarfs form some of it, but it's a very, very small fraction because any more is ruled out by things lik
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"Weakly interacting" IS the same as the probability of interacting when you're not looking at individual events. The weak force is just as strong as the other forces but we call it weak because the probability of interactions is small.
https://youtu.be/yOiABZM7wTU?t... [youtu.be]
The leading candidate for dark matter is weakly interacting massive particles: particles that have mass and interact via the weak force. Weak force interactions are typically negligible until two particles are within 10^-17 m. Merging between t
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Unless they can explain why the primordial black holes wouldn't interact with each other, then they essentially have nothing.
That's not particularly hard at all.
If they don't have a net charge (electrical or color(!)), or a nontrivial magnetic field trapped by gravitational time dilation, they won't interact electromagnetically (other than by gravitationally bending light, or grabbing a HYSTERICALLY energetic photon) or by the weak or strong force. With the tiny schwarzschild radius they wouldn't capture
I Wonder If (Score:1)
Aliens (Score:2)