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Black holes ruled out as universe’s missing dark matter
- andrewflnr 8y agoAssuming this pans out, is there anything left but WIMPs?
- erik_landerholm 8y agoAXIONS
- nautilus12 8y agoDoes this mean that black holes possibly might not even exist? Aren't there examples of them being directly observed?
- sulam 8y agoWe have observed their x-ray jets directly and have observed their creation (recently). Pretty sure they exist. :)
- oldandtired 8y agoLet's change this a little bit. We have observed specific phenomena but not that which created such phenomena. As far as "Black Holes" as per theoretical descriptions are concerned, they cannot exist in a finite time universe as far as we (the observers) are concerned. The theoretical models used all have as a basic assumption that increasing gravity (whatever that may be) will cause a slow down in time as observed at distances away from such increase. As such, all phenomena involved in the creation of such entities will slow to a complete stop as far as we are concerned. Hence, if the universe is of any finite duration, we will not have seen the creation of even 1 black hole of any kind. On the other hand, if the universe has existed eternally, it is still likely that these entities are still in the process of formation and not yet in existence. I don't doubt we are seeing some interesting phenomena, but not the entities called "Black Holes". The argument for the creation involves changing perspective to some observer who is falling into or through the event horizon (choose which one of these you want, as there are apparently a couple of choices here in the theoretical models). Since we are not such observers, that perspective is actually irrelevant to us. What is relevant is what we observe in the universe at large. The basic problems (irrespective of mathematical assumptions) with the processes of "Black Hole" generation relate to non-uniformity of compression, time dilation and other basic assumptions for the "Black Hole" models. I find the reasoning used for the existence of "Black Holes" in our universe to be lacking in logical rigour and appears to have a lot of hand-waviness to it. I am currently reading the documentation for the Metamath system and there are some quite enlightening comments in that about mathematics and those who study it. Especially as it relates to us who are not mathematicians as our career. One of these relates to the amount of "faith" we have to exhibit when trusting that specific "proofs" are in point of fact true. Even mathematicians who are not in that specific speciality do not have the necessary background to verify any proof outside of their own mathematical area. Mathematics is a profoundly useful tool but as we have seen in the past and we will see in the future, it has problems (like all areas).
- InclinedPlane 8y agoWe have observed matter falling into a black hole. We've watched "hot spots" in orbit of a black hole in the accretion disk shine their light at us as they orbited the black hole. We've watched as the orbit got tighter and tighter and the light was dimmed by gravitational red shifting, then we've watched the light blink out and disappear as the blob of gas fell below the event horizon. The evidence for the existence of black holes is incredibly strong at the moment. In fact in some ways it's stronger than the evidence for the existence of atoms about a century ago. Nobody except cranks or extreme contrarians seriously disputes the theory these days.
- roywiggins 8y agoI believe the argument is that event horizons exist but inside is not a singularity, but an eternally collapsing mass of the original star. From the point of view of the star, it does collapse all the way, but from our point of view that final singularity collapse is in the indefinite future. https://en.m.wikipedia.org/wiki/Magnetospheric_eternally_collapsing_object https://en.m.wikipedia.org/wiki/Magnetospheric_eternally_col...
- roywiggins 8y agoUpdate: I am mistaken. The classic GR black hole behaves this way. MECOs supposedly never fully collapse into a singularity, even for infalling observers. That's the difference. I rather think we'd have noticed the difference from LIGO gravitational wave measurements of BH mergers, but maybe not?
- perl4ever 8y agoFrom your point of view, if so-called black holes are "fuzzballs"[1] is that a vindication or a refutation of the existence of black holes? Without a deep understanding of physics, I have the general attitude that infinities must be a mathematical error, and therefore something must stop black holes from collapsing totally, but whether they "exist" is only a matter of definitions. [1]https://en.wikipedia.org/wiki/Fuzzball_(string_theory) https://en.wikipedia.org/wiki/Fuzzball_(string_theory)
- TrainedMonkey 8y agoNo 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.
- sulam 8y agoThis 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!
- myinnerbanjo 8y agoI 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_any_black_holes_created_immediately_after/ https://www.reddit.com/r/askscience/comments/8p7hnn/where_an...
- DougWebb 8y agoI'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.
- twiceaday 8y agoDoesnt E=mc^2 form an equivalence? I would expect energy to warp space-time just as mass does.
- waterhouse 8y agoI believe it does. If you have a bottle full of chemicals with potential energy, and then you make them react and get the energy from them (via, I dunno, heat), while all the particles remain in the bottle, then I think the bottle weighs less afterwards—though probably by an undetectably small amount. I think I read that the change in mass is detectable after, say, nuclear fission.
- brink 8y agoSorry if this question is naive or ignorant or just doesn't make sense; but could this dark matter be influence from higher "spatial" dimensions that we can't see? I mean - doesn't string theory demand something like 10 dimensions in total?
- jngreenlee 8y agoI can't wait for the n-gate synopsis of this one. Get back to social mining you minions, you.
- swframe2 8y agoSince, we can only see "the observable universe", how do we know how much mass is beyond our view? If we don't know what is there, why do we think there is missing mass?
- mort96 8y agoWhen we measure the amount of mass in a galaxy, we see that the galaxy's rotation is way faster than the amount of mass would indicate.
- chopin 8y agoOne thing I do not understand: If a black hole in line-of-sight increases intensity, the intensity for other view points must decrease (the total number of emitted photons needs to stay constant). If black holes make up a substantial part of the dark matter, there should be (statistically) few in the line-of-sight and many more slightly off. Therefore I'd expect that this cancels out. Does anyone know how it is accounted for this?
- prmph 8y agoOne question I have: is it not possible that the big bang occurred an infinite time ago? If the expansion of the universe is accelerating with time, does it not indicate that, if we reverse the time, the deceleration is asymptotic? In that case the big bang is compatible with a universe that has always existed and did not have a beginning
- smithmayowa 8y agoThat is a really interesting way to look at it, and yes since in reverse time, the acceleration never quite reaches zero, the universe can then be though of as an infinite occurrence that has always been expanding with no starting point.
- peeters 8y agoThe question is, does causality require time? I understand that physics can give us a definition of time as far as "happens-before" relationships go, but are "happens-before" and "happens-because-of" necessarily the same thing?
- sdegutis 8y agoIf the world has begun with a single quantum, the notions of space and time would altogether fail to have any meaning at the beginning; they would only begin to have a sensible meaning when the original quantum had been divided into a sufficient number of quanta. If this suggestion is correct, the beginning of the world happened a little before the beginning of space and time. Lemaître, G. (1931). "The Beginning of the World from the Point of View of Quantum Theory"
- gpderetta 8y agoEven a car constantly accelerating for a long time was still at t0.
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- GarrisonPrime 8y agoIsn’t “dark matter” just a way to account for an unexplained behavior? It bothers me that its existence is treated as a given, when it could be a case of mistaken assumptions. If calculations say the universe is acting as if it contained much more mass than we observe, we should also consider the possibility that our method of calculation may be flawed. I’m not claiming dark matter doesn’t exist, only that I fear the human tendency to run with a hypothesis too eagerly and discard alternate options. Similar to how everyone seems to speak as if Hawking radiation is a given fact, when it is thus far completely unproven and nothing more than a suggested idea.
- empath75 8y agoDark matter is an observed phenomenon that can be explain by the existence of an additional, unknown kind of matter. I don't think scientists are unduly hung up on that explanation, though. It's merely the most likely. Plenty of scientists are looking for alternative explanations and I'm sure the rest will get on board if they find something convincing.
- posterboy 8y agoSo far, dark matter is just the label for an incongruence in the calculation that needs to be falsified. With regard to the article, it could still be that there are many young smaller black holes, too small or even too short lived for the methods employed here.
- mattydoincode 8y agoI think that from the optic of someone who is not a physicist (like myself!) it's natural to think "hey... we can't actually know that it's dark matter vs some other unexplained way that gravity works". And in fact there are many physicists working on trying to figure that out, but there is actually a ton of evidence that what we're seeing is in fact particles, and most physicists consider it to be the most likely current theory. I don't think anyone in the physics community treats anything about dark matter as a given either (or hawking radation for that matter). In fact part of being a true scientist is keeping an open mind.
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- mpc755 8y agoDark matter is a supersolid that fills 'empty' space, strongly interacts with ordinary matter and is displaced by ordinary matter. What is referred to geometrically as curved spacetime physically exists in nature as the state of displacement of the supersolid dark matter. The state of displacement of the supersolid dark matter is gravity. The supersolid dark matter displaced by a galaxy pushes back, causing the stars in the outer arms of the galaxy to orbit the galactic center at the rate in which they do. Displaced supersolid dark matter is curved spacetime.
- ravar 8y agowhat are you talking about dude, could you point to something on the arxiv?
- mpc755 8y agoAnother way to think of this is that spacetime has mass. Spacetime and dark matter are both referring to the same 'stuff'. The stuff is a supersolid that is displaced by ordinary matter. The Earth displaces the 'stuff'. The displaced 'stuff' pushes back. The displaced 'stuff' pushing back is gravity. Curved spacetime = Geometrical representation of gravity. Displaced supersolid dark matter = Physical representation of gravity.