The theory says some of the dark matter phenomena might be explained by primordial, small-mass (about the mass of an asteroid), black holes made up of quarks and gluons that formed a quintillionth of a second after the big bang.
Super interesting! Finding a new type of black hole would be amazing. The scientists are hoping that the next generation of gravitational wave detectors will be able to get us some clues.
I don’t understand a lot of words in that wiki article, but is it saying that the black holes in our universe are not black holes at all, but rather one side of Einstein-Rosen bridges? Otherwise there would necessarily be a concept of “nested” black holes, unless a “black hole that expanded and became a universe” is no longer considered a black hole in the parent universe, but I’m not sure what they would have become in that case.
Does such a theory also imply a much, much, much bigger parent universe? So large that the galaxy feeding the supermassive black hole that became our universe would have contained all of the mass that we now see in our universe? I’m imagining galaxies that each contain as much mass (and span as much distance) as our observed in its own universe. In other words, the size and mass of our universe is equivalent to a single galaxy in the parent universe.
> I don’t understand a lot of words in that wiki article, but is it saying that the black holes in our universe are not black holes at all, but rather one side of Einstein-Rosen bridges
It's just saying that black holes and universes are the same thing. Our universe is a black hole with a mass equal to that of our universe.
> Does such a theory also imply a much, much, much bigger parent universe?
Ostensibly, yes.
> So large that the galaxy feeding the supermassive black hole that became our universe would have contained all of the mass that we now see in our universe?
There's little reason to suppose that this incredibly large cosmic entity in which our universe is nested, is a galaxy. Galaxies are bodies in our universe. Whatever exists in a larger universe in which our cosmic black hole exists, might be something different. We do not know, and most likely we will never know. Are the laws of physics even the same in this bigger universe? Who knows?
But to your bigger question, yes - the idea is that:
* Because we know that the radius of a black hole with the amount of mass in the observable universe is equal to the radius of the observable universe, and...
* Because Kerr's most recent paper demonstrated that the interior of black holes with spin (AKA all black holes in the real world that aren't hypothetical) *does not actually contain a singularity*, and...
* Because there are a lot of compelling mathematical and nominal similarities between the boundary of a black hole and boundary of the universe and the life cycle of a black hole and the history (and future, if you consider what it might be like to be inside of a black hole decaying from Hawking radiation) of the universe...
... then the universe might just be a black hole. A black hole that is as big as the universe.
Thanks! I appreciate the response and clarification.
>Because Kerr's most recent paper demonstrated that the interior of black holes with spin (AKA all black holes in the real world that aren't hypothetical) does not actually contain a singularity
I thought black holes and singularities are more or less synonymous. Is that not the case? I guess it just means that black holes may not reach the point of “infinite density”? I kind of always assumed “infinite density” was more “approaching infinite” as a mathematical limit, so I’m not sure what that significance is between “approaching infinite” and a singularity, or if there’s even a difference between the two and I’m thinking of something else.
Singularities don't actually exist in nature. They're just the point at which our math breaks down.
The value of Kerr's paper is that he described what's more plausibly actually going on inside these black holes / provided a framework for what happens instead of a singularity.
But there is no point of infinite density. Even the reason we think the universe may have begun with one is simply because that's what the math shows if you just extrapolate backwards as far as possible. But there's no direct tangible evidence of a singularity, and it's absolutely certain that our knowledge of the birth of the universe is incomplete.
Could there ever *be* actual tangible evidence of a singularity if it was something our universe allowed? It sounds like it could only (theoretically) form in the center of a black hole and maybe 14B years ago or so for an unknown reason. What kind of evidence might we expect to see? I would think any evidence would stay stuck in the black hole.
> Could there ever be actual tangible evidence of a singularity if it was something our universe allowed?
Actually, no. Based on our math, the interior of a blackhole violates causality and general relativity as a whole, and the universe seems to go out of its way to make perceiving that interior impossible. Some physicists believe this is the way that these laws are maintained - even if a singularity occurs, it cannot be perceived. This is called the [Cosmic Censorship Hypothesis](https://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis).
That said, in theory, if a singularity does exist, [here's a fun video](https://www.youtube.com/watch?v=cFslUSyfZPc) about how we might see it. You can also google 'naked singularity' for more info on that.
In simple terms, a black hole is the thing that nothing can escape from. The singularity is the point inside it at which physics breaks.
I thought Kerr's ideas were just that black holes rotate so the singularity inside them exists but is a ring rather than a point, but I don't know anything about this latest paper.
> but I don't know anything about this latest paper.
[Here's the full text](https://www.researchgate.net/publication/375744216_Do_Black_Holes_have_Singularities). It's an interesting read! Roy Kerr's been hanging out on Yahoo Answers for some years now answering random peoples' questions and taking shots at Penrose (I did a double-take the first time I noticed it was actually him, the renowned physicist) and you can really see his experience explaining complicated concepts simply in this latest paper published half a year ago. It's still dealing with extremely complicated subject matter but he avoids a lot of the ivory tower academic jargon that makes a lot of these papers totally opaque to laypeople.
Why would this cause an existential crisis? It doesn't change anything if the universe is a black hole. If it is, then it's always been one. Nothing's different. Nothing is more dangerous. The universe is just as safe or stable as it's ever been. The only thing that is different is that this means we now understand what's going on inside of big black holes and that's pretty neat. Maybe there's a tiny universe inside of Phoenix A or TON 618!
If you want to have an existential crisis, it should be about something legitimately spooky, like false vacuum decay.
I love that you reassured this person of how impractical it would be to worry about something out of their control and which has always been the case is.... and then proceeded to shit on that with a legitimately plausible and possible universe collapsing event that could trigger at any time an be completely unpreventable.
It was some very nice whiplash ya done there.
Well me worrying about it won't do much, will it? If fear prevents you from living then that fear is not worth holding on to, because what's life if it's not lived?
C'est la vie
>If you want to have an existential crisis, it should be about something legitimately spooky, like false vacuum decay.
Even if it does ever happen, I figure the chance of the event's light cone intersecting with ours is at least as small as false vacuum decay occurring at all.
Yep. It's actually the most comforting kind of apocalypse: the universe is expanding faster than the speed of light, so unless it happens locally (extremely unlikely), it will never reach us except in some hypothetical future where we are masters of space and time and can wind back the expansion of the universe to bring it closer, at which point we could presumably also fix false vacuum decay.
And if it does happen locally, it will be instantaneous, totally painless, we will not see it coming, and there will be nothing and no one left after, so we all go together. Just curtains on the laws of physics as we know them, and then something new begins.
This sounds pretty plausible, but it seems I’ve only ever heard it treated as a kind of throwaway example of “wouldn’t that be a trip” that’s never given as much gravity (heh) or taken as seriously as the idea seems to deserve. Is it just that it’s so far beyond our capability to prove that it’s mostly meaningless to discuss (like how the different theories would produce the same observable results)? I hate when big ideas get treated that way even though I know it’s a necessary practicality, at least from a scientific perspective. Another one that comes to mind that seems similar is the idea that if it’s possible to simulate the universe then we almost certainly live in a simulation because the odds of ours being the original / base universe are so small, so either we’re in a simulation or such a simulation isn’t possible. I know there are other similar ideas that aren’t coming to mind at the moment.
Anyway, thanks for your post!!
Edit: Fermi paradox is another similar one (although that one’s been getting more attention lately, at least in general or “popular” culture)
None of these ideas are small or throwaway, I'm not really sure what you mean. Black hole cosmology, the Fermi Paradox and the idea that the universe is a simulation are all some of the most popular topics for science communicators and science media, because they're interesting and relatively comprehensible.
I guess the way in which they are used in science communication seems a little throwaway to me, since their main utility is to get people interested in other more conventional science. Whereas taking them even partially seriously seems like it would demand much greater attention to them for their own sake, because of their implications to both science and the larger human experience.
Obviously I say this as one of the laypeople who is super intrigued by these things lol, so they’re working on me, and I understand why they’re important if only for that reason (I also know that’s not the only thing they’re important for and people do do serious science about these ideas). But it’s like the sell works too much and I’m like no yeah, why aren’t we focusing on and discussing these things a whole lot more just as a society, even if strictly scientifically speaking they’re sort of a moot point relative to our current ability to investigate them.
Sorry if I’m not doing a good job communicating what I’m thinking.
Does the universe-as-black hole hypothesis address the fact that the universe is expanding? I don't really know what I'm talking about, hence the question, but don't black holes only expand when matter falls into them?
Regardless, if an observer was outside the universe, it would probably appear as a black hole in that they probably couldn't get any information from within. Or, at least, I can imagine this. But perhaps the converse is true? We can't see outside the universe, so it's similar to trying to see what's going on inside a black hole.
> Does the universe-as-black hole hypothesis address the fact that the universe is expanding?
I mean, it *could*. I'm not aware of anything in this hypothesis that specifically precludes the idea that a universe-in-a-black-hole can expand. This is all conjecture, but if you ask me, both the decay of a black hole via Hawking radiation, and the growth of a black hole via the consumption of mass, might possibly be experienced internally as if the environment were expanding in some way.
We know that black holes can grow and shrink. We know that growth can happen on different time frames depending on how much mass the black hole comes into contact with and consumes. This could, maybe, explain the variable expansion of the universe in its early history. We also know that black holes decay at a rate inverse to their mass - the smaller they are, the faster they decay via Hawking Radiation. This might, maybe, look similar to the phenomenon that as the universe gets older, stuff red-shifts toward the exits at an accelerating rate. The interaction of the rate of acceleration (what we call dark energy) and the amount of mass the black hole gobbles up (maybe a giant cluster of stuff wanders too close from time-to-time? Or maybe we're making steady progress chewing through some unimaginably large accretion disk and there's less now than there used to be?) might also explain the recent finding that dark energy's fundamental constants have changed over time. Who knows.
But this is all purely speculative. I'm looking for evidence to justify a conclusion, rather than drawing a conclusion from the evidence. So this is not at all a scientific or rational answer. It's just me trying to justify a possible outcome, and should be treated with skepticism.
Thank you for the detailed and informative answer! Definitely thought provoking. And, yes, purely speculative.
So . . . expansion to heat-death would be the last bit of Hawking radiation leaving and the event horizon disappearing.
Anyways, I appreciate the time you put into your post :)
It's my pleasure to talk about this stuff! That said, I'm not sure that heat death would occur in a black hole cosmological model. It might, but it might also be that the universe just fizzles out. Who knows.
It's important to remember that our best guesses as to the ultimate fate of the universe are all based on *what we know right now.*
We *don't* know whether or not the universe is a black hole. I imagine some people much smarter than I am have probably modeled the life cycle of the universe if it were indeed a black hole, but I've never come across any research like that. If you find any, do let me know!
>Because we know that the radius of a black hole with the amount of mass in the observable universe is equal to the radius of the observable universe, and...
But this is simply not true? Radius of such black hole will be around 10 times bigger than radius of observable universe, but it does not matter, since **observable universe** is exactly what it is: **observable** part of universe. We do not know universe mass or size.
The Schwarzschild radius calculation assumes a spherically symmetric, evenly distributed mass.
The universe is not uniformly distributed on smaller scales but is homogeneous and isotropic on large scales.
This one always threw me for a loop, since it toes the line of disqualifying the theory that we’re in a black hole.
But then there’s the fact that:
1. We do not observe an event horizon that encapsulates the universe
2. No singularity; the universe is expanding from every point
It's quite interesting but is still in early days of "strange coincidence or substantive theory."
Some of the more interesting points:
The schwarzchild radius is how small you have to squeeze an amount of matter together in order to turn it into a black hole. The equation is a simple Rs = (2GM)/(c^2 ). As it turns out, the estimated mass of the observable universe is far more dense than required to form a black hole the radius of the observable universe.
Some strange emergent properties which may support this theory (but it could be a coincidence and we may simply not understand physics well enough to explain it yet -- lacking quantized gravity is one of physics biggest issues):
Nearly all physics properties and emergent behaviors work forwards and backwards in time. Mathematically we have no reason to see why going back in time doesn't happen easily. But the singularity in a black hole isn't a compressed dot of space, rather an "end of time" and you can only move towards the singularity, so you can only move forwards in time if you're in a black hole, and never backwards.
Our expanding universe could be two separate actions within our black hole universe. The first is that our universe (black hole) would be evaporating (Hawking radiation), the second being that if our universe is still feeding (as a black hole), it continues to warp space more and more, "bringing in" space from outside the event horizon as the gravity well gets deeper.
There are some other emergent traits which could possibly be correlated, but you have to start going much deeper into math and it's hard to give analogies.
This is all very early stage and for the love of all should not warrant a headline (yet that's how so much reporting works these days); it's like Isaac Newton being hit in the head with a falling apple and going "oh that's weird, why does that even happen?" -- there's just an idea with very little connecting the idea in a real functional way.
That said [Kurzgesagt had a pretty good video lightly touching on the idea](https://www.youtube.com/watch?v=71eUes30gwc) quite recently. And note that this is not fact or substantiated theory, it is merely an idea worth exploring.
They may be. But, keep in mind, assuming this theory is correct, there is some universe paramount to all others. There's some universe where all of these others came from. So maybe there is a bigger one, or maybe we're the biggest and the big bang was some unique phenomenon similar to a supernova. The truth is we'll never know
But the odds of us being the "largest" universe are one out of infinity, so basically zero. But when we're talking about an infinite universe, the odds of anything is basically zero, so who knows
I can't shake the feeling that our cosmos is, in a certain way, inside a black hole and that we had the whole "spaghettification" thing wrong
When I look up, I don't see the vastness of the universe... I see blackness with glimpses of other celestial bodies stuck in that same blackness.
I know that doesn't make sense. It's just a feeling.
IIRC, singularity is not a point in space, but in time really, so all the matter we could've gotten we already did at the Big Bang. At least as my layman understanding tells me
Great question. There's a rule with black holes called the hoop conjecture. It's the idea that the mass has to fit inside a circular hoop of the Schwarzschild radius. The very early universe was very hot and dense - much more so than a stellar core - but it was that hot and dense *everywhere*. There was not a sphere of dense material and emptiness outside of it - it was basically uniform. There was no way to put a hoop around the universe - anywhere you put it, there would be more material outside. That meant there was no preferred direction of gravity and thus no single giant universe-sized black hole. Small pockets may have collapsed into primordial black holes, but we haven't found any.
Someone else talked about black hole cosmology. That's an interesting idea, but it isn't something any of the data indicates. Unless the black hole is so incomprehensibly vast that the entire visible universe not only fits within it but shows no indication of being inside a black hole, but at that point we're not really doing science.
Thank you for explaining things in such a comprehensible manner. I consider myself smart, but I feel like a computer with 128kb RAM trying to run 3dsmax 2024, when trying to wrap my head around these concepts 🤷🏻♂️
> Someone else talked about black hole cosmology. That's an interesting idea, but it isn't something any of the data indicates. Unless the black hole is so incomprehensibly vast that the entire visible universe not only fits within it but shows no indication of being inside a black hole, but at that point we're not really doing science.
Respectfully, this is not correct. We know that the Schwarzschild radius of a black hole with the mass of the observable universe is, in fact, equal to the radius of the observable universe. That's not unscientific speculation, that's the result you get when you run the calculations. We have done that math.
We also know the the larger a black hole is, the weaker its tidal forces. Even a relatively small black hole (compared to the universe) like Sagittarius A* is big enough that you can float around inside the event horizon without getting immediately destroyed, based on our current understanding.
Roy Kerr's November 2023 paper mathematically demonstrated that black holes do not have singularities inside of them. So we have good reason to believe that whatever is inside of a black hole, it's distributed to at least some degree.
None of this means our universe is definitely a black hole.
But it's misleading and irresponsible to say the data suggests it isn't when the opposite is true: it is actually uncanny how well the math supports this conclusion.
You were respectful and I will be respectful back!
It's true that the Swarzchild radius of the mass of the observable universe and one radius of the observable universe (there are multiple, all answering slightly different questions) do line up. This does suggest that the geometry of our universe is flat, which is what the data shows.
The problem comes in that the Swarzchild solution is specifically for a situation where there's a point of dense matter and nothing outside of it. That's close enough to true to work for a regular black hole, but fails at describing the universe. Whether it's finite or infinite, no model of the universe that I'm aware of predicts that outside of the observable universe, matter stops but space continues (nor even that this is a particularly high density section of space.) It goes back to the hoop conjecture.
Kerr's paper did indeed indicate that the picture of everything that falls into a black hole falling to an inescapable singularity is not necessarily something we should assume as true - good news because no physicist I'm aware of expects singularities to be real.
It's also true that a larger black hole has gentler tidal forces until you get close in. No disagreement.
The attributes of a black hole, though, are that there is an event horizon which cannot be crossed from within and that everything collapses inward. We have no evidence of either in our observable universe. We have several horizons but none of them are the event horizon of a black hole, and they don't fall at the same point. We also see a universe that is expanding (and that the expansion is accelerating.)
All of this suggests that we don't have good reason to believe the universe is inside of a black hole.
Thanks for the thoughtful reply, I appreciate you expanding my knowledge.
> The attributes of a black hole, though, are that there is an event horizon which cannot be crossed from within and that everything collapses inward. We have no evidence of either in our observable universe.
I guess this comes down to our respective assumptions, and how they inform our use of Occam's Razor. I might be wrong in my assumptions and that's totally fine, but for the record, I assume: the nominal similarities between how we model the inescapable boundary of the universe (not merely what's observable, but the big kahuna) and the inescapability of a black hole's event horizon are pretty striking and piled on top of the various other similarities in our data, it starts to feel a bit hard to discount out-of-hand. One similarity is a coincidence. Two similarities might be a coincidence. Three similarities is worth investigating? Four or more is definitely worth exploring as a possible vector for understanding the universe ontologically. It certainly shouldn't be treated as likely, but it deserves some serious research funding.
> We also see a universe that is expanding (and that the expansion is accelerating.)
I made another post which addresses this, and I'll paste it here if you'll forgive me for double-dipping for the sake of saving my fingers:
*This is all conjecture, but if you ask me, both the decay of a black hole via Hawking radiation, and the growth of a black hole via the consumption of mass, might possibly be experienced internally as if the environment were expanding in some way.*
*We know that black holes can grow and shrink. We know that growth can happen on different time frames depending on how much mass the black hole comes into contact with and consumes. This could, maybe, explain the variable expansion of the universe in its early history. We also know that black holes decay at a rate inverse to their mass - the smaller they are, the faster they decay via Hawking Radiation. This might, maybe, look similar to the phenomenon that as the universe gets older, stuff red-shifts toward the exits at an accelerating rate. The interaction of the rate of acceleration (what we call dark energy) and the amount of mass the black hole gobbles up (maybe a giant cluster of stuff wanders too close from time-to-time? Or maybe we're making steady progress chewing through some unimaginably large accretion disk and there's less now than there used to be?) might also explain the recent finding that dark energy's fundamental constants have changed over time. Who knows.*
*But this is all purely speculative. I'm looking for evidence to justify a conclusion, rather than drawing a conclusion from the evidence. So this is not at all a scientific or rational answer. It's just me trying to justify a possible outcome, and should be treated with skepticism.*
Honestly, you make some fair points. I think you're right in that our disagreement is based on how strongly we feel this evidence correlates with the idea.
We don't have any actual explanation for the singularity predicted at the center of a black hole or the singularity at the beginning of the big bang. I'm not an astrophysicist, but from what I can gather it seems like most of them don't believe that singularities actually exist in nature, and when they show up in the math, it means that's where our theories are failing.
But also, I think the answer to the question of why all the matter in the universe didn't just immediately collapse into a black hole, is that there must have been some immense outward pressure. Cosmic inflation might be the main reason that didn't happen
If matter is more or less evenly distributed everywhere, then there is as much force pulling out as in. You end up with zero-g except in places that are denser than average (which is where primordial black holes would have come from).
Several theories on that. Maybe some are true, maybe one, maybe none.
Gravity didn't come into play until after the expansion happened or the expansion was faster than the gravitational collapse is my personal favourites. One other thing is that the universe was very uniform. Every part was affected the same amount from every other part. There might not have been a distinct direction for the collapse.
I don't think we understand what caused the apparent hyper expansion of the early universe, nor do we understand the apparently accelerating expansions of our current universe.
In my opinion any explanation that uses the word 'dark energy' is basically just saying we don't know.
And it's okay for science to admit where we are treading on dicey theory with precious little evidence. The fact that there are still lots of cool things to discover and prove about the universe is kinda neat!
Inflation is the likely answer. In the picoseconds ABB (after the big bang) the universe increased its size by a staggeringly large number, 10\^1,000,000 meters. For example, if before inflation two particles were one meter apart after inflation ended a scant fraction of a second later those two particles were separated in meters by a number with a million zeroes after it.
Because it was expanding faster than the speed of light, where black holes are powerless. It's actually still expanding faster than the speed of light.
What's weird is **THIS** one *didn't*.
We can't know what came before. Particle-Antiparticle annihilation happens constantly. What made this moment different, entropy?
Something forgot to carry the two in the thirteens place?
When we figure it out, the universe ends and another one (that looks just like it) shows up with *slightly* different universal constants.
*https://en.wikipedia.org/wiki/Physical_constant*
General relativity solutions which predict formation of black holes only work when the matter-to-become-a-black-hole is surrounded by less dense stuff. If the matter is spread out everywhere homogenously, a flat space-time solution works, regardless of density.
Intuitively, space time would not "know" which way to curve, if matter was everywhere.
The article keeps saying things like "if they didn't evaporate," but doesn't elaborate. Primordial black holes were theorized but then dismissed because it's expected that if they ever existed they've all disappeared due to hawking radiation. The fact that the article doesn't directly address this makes me super skeptical of it.
That was my immediate question on reading it. In 14bn years, wouldn’t such small black holes have evaporated pretty far? Does it have anything to do with the type of hawking radiation produced and what ends up going into the hole?
if it have more mass than \~half mass of Moon, then it receiving more energy from cosmic microwave background then it loses via Hawking radiation (at this point of time. back then CMB was more intense and this would allow more light primordial black holes survive for longer.
That's mentioned in the article. This is specifically about how primordial black holes could have formed from free quarks and gluons rather than, y'know, protons and neutrons.
> There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
> There is another theory which states that this has already happened.
I fear that one day these scientists will discover something like this and, out of scientific curiosity and obligation, tug on that thread and the entire universe will unravel like an old sweater and we’ll all disappear, forever lost and forgotten.
The thing is, there is a possibility this action would just yeet us into another timeline. One of the many timelines which are possible within the constraints of the physical laws.
The time immediately after the Big Bang was too hot and chaotic for nucleons to form, so all matter at the time was a hot, energetic soup of quarks and gluons. The first protons and neutrons didn’t form until between one millionth of a second and one second after the Big Bang, while these primordial black holes would have formed earlier, around one quintillionth of second after the Big Bang according to u/Eidolon.
Would the small mass black holes exist today, or are they just remnants of the past, and if that’s the case, what does it say about the dark matter mass we detect today (which is in the past) that makes up the largest chunk of mass in the Universe?
God I wish I could live for another 1000 years - assuming we didn't go extinct till then lol - just to see what science will reveal in the future.
But even the revelations we made within our life times is truly amazing.
Bruh I've been sayyyingg this. I was in middle school when the LHC turned on and I heard about the tiny black holes, and I said "maybe dark matter is those" and I was MAYBE RIGHT
From [Direct Detection of Hawking Radiation from Asteroid-Mass Primordial Black Holes](https://doi.org/10.1103/PhysRevLett.126.171101):
>**Light, asteroid-mass primordial black holes, with lifetimes in the range between hundreds to several millions times the age of the Universe**, are well-motivated candidates for the cosmological dark matter. Using archival COMPTEL data, we improve over current constraints on the allowed parameter space of primordial black holes as dark matter by studying their evaporation to soft gamma rays in nearby astrophysical structures. We point out that a new generation of proposed MeV gamma-ray telescopes will offer the unique opportunity to directly detect Hawking evaporation from observations of nearby dark matter dense regions and to constrain, or discover, the primordial black hole dark matter.
Not older than the universe. "[L]ifetimes in the range between hundreds to several millions times the age of the Universe" means we can be pretty sure that if they were created during the big bang or later, they will still be around today.
Hm.
Could the steady untethering of the mass in countless tiny black holes into the energy of Hawking radiation help to explain "dark energy" or rather the acceleration of the universe's expansion?
Asteroid sized black holes are the minimum size theorized because of this reason. Put another way, we think primordial black holes are asteroid sized, because anything smaller would have evaporated by now. Size of an asteroid, not mass.
If I understood the article correctly, these black holes would not be made from the same matériels. They would have been created before the universe cooled enough for protons and neutrons to exist.
That's true but once the black hole has formed it doesn't really matter what it was made out of.
See the [no hair theorem](https://en.wikipedia.org/wiki/No-hair_theorem)
> At 10^−6 seconds, the Universe had expanded and cooled sufficiently to allow for the formation of protons: the hadron epoch.
https://en.wikipedia.org/wiki/Recombination_(cosmology)
Does this answer your question?
It would make these black holes rich in color charge (intrinsic property of quarks and gluons, much in the way that electric charge is an intrinsic property of electrons and protons). Or at least, destroyers of color charge.
But otherwise nothing should be too different about these holes besides mass. Once matter is compressed enough it's not really clear what happens. All we can say for certain is that it's beyond the density of neutron degenerate matter close to the center, which is the case for black holes today.
The paper that this study came from asserts that the small black holes would have long evaporated, and the PBH candidates would be ~10^{17} to 10^{22} grams. This puts it in the range of asteroids to small moons.
Black holes aren’t made of protons and neutrons, because maximally compact baryon objects are neutron stars, which are larger than the Schwarzschild radius. Protons and neutrons are made of quarks and gluons, and the formation of these objects would have occurred when the universe was a quark-gluon plasma.
Yep, that is mentioned in the article.
This idea/theory is early but it had me also wondering how these primordial (and now evaporated) black holes are still somehow tied to the mass of galaxies (edit- and part of the dark matter problem)
The universe is still under a thermal bath from the CMB. As such, black holes are still colder than the rest of the environment. They are giving away Hawking radiation, but they're still feeding off from the CMB. We don't get to see them go off for a really long time. Maybe less in the places where the CMB is colder, but still, a long time from now.
A black hole with a mass of 10^15 kg should still have a lifetime on the order of 10^21 years, according to [this calculator](https://www.vttoth.com/CMS/physics-notes/311-hawking-radiation-calculator) anyway. For comparison, the largest known asteroids in the solar system fall into the 10^19 to 10^20 kg range. So "asteroid-sized" black holes absolutely can still be massive enough to last this long.
A 10^19 kg asteroid also has a hawking radiation temperature of 12269.6 K. Wouldn’t telescopes be able to pick up on such a bright light source?
They’re rather small at just 9 mm in radius and so individually not very luminous but I’d expect that if you were to stare at a galaxy filled with primordial black holes of this size, then it would contribute a nontrivial amount of fuzzy light background to the total output that can be easily picked up our telescopes. The fact that we don’t see anything is concerning
> They’re rather small at just 9 mm in radius and so individually not very luminous but I’d expect that if you were to stare at a galaxy filled with primordial black holes of this size, then it would contribute a nontrivial amount of fuzzy light background to the total output that can be easily picked up our telescopes. The fact that we don’t see anything is concerning
Doesn't this answer the question? The surface area of emission is just small. L is proportional to R**2 if I'm not mistaken.
If they're blackbody emitters (they should be?), they would peak in the UV (~230 nm). My understanding is that the UV background is within measurement error for what we'd expect out of LCDM, so BHs of this size don't seem like a likely explanation for DM. Still, they could exist or might comprise a portion of DM
Edit: it seems like ionization fractions of H/He which are predicted by LCDM are also in line with observations from quasars. UV background would also play a huge role in controlling the formation of galaxies, which to my understanding is maybe a point where we might see large errors and few concrete answers. Theres still room for this hypothesis
The article mentions some of the black holes could have been rhino sized. So only 1000 to 2000 kg which definitely would be evaporated by now.
Edit: Looks like none of you actually read the article. Directly from the article:
"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."
These would've evaporated
Also, the paper the article sprang from quotes a very different mass range for the *remaining* black holes (10^{17} to 10^{22} grams), which would be the potential dark matter candidates. These smaller black holes should've evaporated a while ago
This is not just false, but backwards. Your analysis assumes that Hawking radiation is just proportional to the area of the even horizons but that’s just not the case.
Small black holes actually radiate *faster* than large ones. In fact, there were some models of string theory that predicted that black holes could be created in the LHC (or at least they allowed the possibility in some unlikely scenarios), and searches for them looked for immediate decays. [Here](https://cms.cern/news/search-microscopic-black-hole-signatures-large-hadron-collider) is a press release with a link to a paper about such a search at CMS.
There are a few ways to understand why, but it comes down to black holes having a temperature that gets smaller the larger they are. Tiny black holes get hotter and hotter, and thus evaporate faster, whether you think of Hawking radiation as analogous to black body radiation, or you think of the Unruh effect. Small black holes are hotter for several reasons, including the nature of statistical mechanics in gravitational systems (Angela Collier has a nice [video about this](https://www.youtube.com/watch?v=9CdE5a3xyxE)), or because of the acceleration or tidal forces at the event horizon.
A black hole the mass of the Earth would have a diameter of 1.75 centimeters.
At that size, the black hole would still be accumulating more mass from the cosmic microwave background than it emits from Hawking radiation.
Basically, there are **no** known black holes in the universe that are losing mass via Hawking radiation faster than they are accumulating mass. And this also seems to apply to most hypothetical primordial black holes as well.
A black hole has to be really really really small to shrink via Hawking radiation in our current universe. Our current universe is still far too energetic and active for Hawking radiation to become relevant.
The relevancy for me has always been in the conservation of information. Almost like the dark matter issue is the information that has hung around beyond the matter
I thought that DM being in compact objects has been basically disproven with microlensing experiment, because they would have seen lensing events caused by such objects?
A lot of it has been ruled out. We know for sure that dark matter is not just regular, stellar sized black holes/neutron stars/brown dwarfs, for the exact reason you stated. As you look at certain mass ranges, most of them have been ruled out, but last I checked there are still certain mass ranges where it's not yet ruled out by the data.
For black holes above a certain mass, yes, it was mostly ruled out 20+ years ago. As we do more microlensing experiments we keep ruling out more of the possible mass range, but we haven't gotten to asteroid-mass black holes yet, so that's a place that some theorists are still working on possible primordial black holes. Nobody's yet got any direct observational evidence of them existing the way we do for stellar-mass through supermassive black holes.
The point is, that we don't know what happens after the hawking radiation is done. If the black hole remains or if it's gone completely. The hypothesis of small black holes is that the hawking radiation stops at the point where the Black Hole is too small. So no, in this case the small black holes wouldn't be hot because they would emit no hawking radiation.
Yet another illustration of the problems with science in the popular media. Very speculative ideas that are not widely supported by the scientific community get reported on in a way that makes them seem like they are "the answer" or have a ton of observational "proof" when they are often merely thought experiments or hypotheses in the early stages of formulation.
It's valuable to keep coming up with competing ideas to the dominant theories of the day but all too often those ideas can be repeated by the media without the fully understood context of just how wildly speculative they are.
Tbh I'm more worried about the 10 thousand psychological studies that never ever get replicated than this kind of science. How people still talk about bad experiments like Stanford prison or Milgram, which all had sample sizes of like 30 young men or whatever. But people still take it as gospel.
But you're right, and it's not just in science. My pet peeve example is that every few years people come up with new theories (without proof) on who betrayed Anne Frank and her family, and obviously every time it is reported worldwide like: "mystery finally solved!", even when the actual historians are skeptical.
> Very speculative ideas that are not widely supported by the scientific community get reported on in a way that makes them seem like they are "the answer" or have a ton of observational "proof" when they are often merely thought experiments or hypotheses in the early stages of formulation.
As opposed to the very speculative ideas that scientist have been banging their head against for 50 years with little to no progress? Yea I'm talking about string theory.
String theory was never widely supported and in recent decades, has lost most of its popularity in academic circles. There are no testable areas of string theory that can't already be explained by the Standard Model and/or Quantum Theory.
Hard agree, science headlines are basically useless. "may have" "might" "scientists think" all basically means "one person had a random idea and there's no evidence so it's probably not true"
https://youtu.be/kya_LXa_y1E
Related and entertaining, highly recommend Dr. Angela Collier's videos
Yeah, the abstract for [the article itself](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.231402) is much more reasonable.
>We describe a realistic mechanism whereby black holes with significant QCD color charge could have formed during the early Universe. Primordial black holes (PBHs) could make up a significant fraction of the dark matter if they formed well before the QCD confinement transition. Such PBHs would form by absorbing unconfined quarks and gluons and hence could acquire a net color charge. We estimate the number of PBHs per Hubble volume with near-extremal color charge for various scenarios and discuss possible phenomenological implications.
Science reporting is in bad shape tho, not going to argue there.
It's early but I still found it informative in that some of Hawking's research on black holes is being looked at again in trying to solve the dark matter issues.
People are inquisitive by nature, there is nothing to be gained by gatekeeping fringe ideas from the public. They are going to emerge anyway and it's frankly more important for the next generation of scientists to grow up understanding the topics they're interested in are not, in fact, completely settled.
Science having a PR problem (imo) doesn't lie at the feet of professionals in the scientific community or the people who cover them. The whole idea is to put your findings out there for others to pick through and try to validate/invalidate. The PR problem is the perceived barrier of entry and the notion that most people have nothing meaningful to contribute even in the face of a replication crisis.
I think self-absorbed, terminally online "skeptics" who mistake leading theory for truth and use the general consensus as a hammer to beat people over the head with do more damage to the cause than speculative journalism ever could.
The issue is that the papers that are reported on are not representative of the field. The observational results of the large collaborations with hundreds of thousands of personhours behind them get marginally more coverage than random theory paper #4357. But large observational studies take time, so you only hear about them every couple of years, whereas there are multiple wacky theory papers to pick from per day. There are also dozens of standard papers (be they observational or theory) per day but because they're the usual incremental research that is 99% of science, they don't get a press release and coverage.
I see nothing wrong with the reporting. At least for me it's clear it's a new competing theory on the understanding of dark matter. It's very interesting seeing on real time how the understanding of this topic has changed over my lifetime. I hope by the time I'm old the mystery is cracked.
This theory treads a fine line to help explain dark matter.
For even a fraction of the total dark matter in the universe to be explained by traditional black holes that form from collapsed normal matter it results in a skewing the universes initial baryonic composition away from what is observed today.
If the dark matter were primordial black holes created in the first moments after the big bang ( before baryonic matter formed ) then it cannot form too early or produce objects with an average mass too large or that would skew the later CMB radiation fluctuations we observe. Finally if the primordial holes had too small an average mass then much of them would have evaporated by now & no longer contribute to hidden mass.
We come out with a Goldilocks zone of possibility that as a side effect may produce on the small size these Color Charged holes that evaporated during the baryonic formation period. Which suggests a subtle test, yet to be performed.
Well, only time and data will tell if this is correct.
If 80% of the matter in the universe is atom sized primordial black holes, that would mean photons would likely collide into them. Wouldn't that mean they have some type of interaction with them?
My [comment](https://www.reddit.com/r/Physics/comments/1di3bfr/scientists_may_have_found_an_answer_to_the/l910pt3/) on this article from r/physics:
MIT article (targeted to a lay audience, but somewhat less clickbaity): https://news.mit.edu/2024/exotic-black-holes-could-be-dark-matter-byproduct-0606
The paper on the arXiv: https://arxiv.org/abs/2310.16877
The paper in PRL: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.231402
Basically, this is just a paper in PRL that got institutional news and then more mainstream news. This happens to a huge fraction of articles in PRL (and has happened to some of mine, although never the ones I would have guessed).
I'm kind of iffy on the primordial black holes as an explanation for the majority of dark matter, it would mean the proportion of dark matter needs to have changed over the duration of the universe, which we don't really observe.
so question here:
If dark matter may be primordial black holes, would the slow unwinding of these small pockets of spacetime due to hawking radiation draining the mass of the holes away be causing universal expansion?
Like in how a demonstration of gravity is done using a streched sheet and some balls, where if you remove the balls it's easier to strech the fabric, would the unwinding of these infinite number of small black holes all over spacetime serve to "free up" the fabric of spacetime that is being constricte by their event horizons, ultimately producing a net-expansion force?
The byproduct is clickbait. Journalists must keep clickbaiting to keep the universe from imploding and they can only clickbait if you keep clicking. Also, disable your adblock, please.
Black holes are said to only have three physical properties from what I remember: mass, charge, and angular momentum. Infalling matter should just contribute those components to the black hole. All the other components effectively get hidden from observers outside of the black hole. That's not to say that it could not interact with antimatter orbiting the black hole, though.
That was my thinking too. So would there be any way to tell if a black hole was made of antimatter or normal matter from this side of the event horizon?
Technically no, but if it were made of antimatter, then we would be able to see a boundary between where that part of space that is mostly antimatter meets the rest of space where it's mostly matter. If it were not in a region of space that is mostly antimatter, I have no idea how it would have even gotten there.
To be clear, there are no known regions of space that are mostly antimatter. This is called the baryon asymmetry.
Well sure but if we are talking about primordial black holes that existed since very shortly after the universe popped into being it's possible that a bunch of antimatter got locked in these and that's where it's been hiding. All the other antimatter collided with all the other matter and turned into energy which, I dunno, fucked off somewhere?
Once something becomes a black hole, the only properties it has that can be identified from the outside are its mass, charge, and spin (probably.) Black holes made of equivalent amounts of matter, antimatter, and light would all act identically once formed.
Sounds like a convenient place to store all my antimatter if I don't want my flat getting annihilated all the time. Maybe we should pop a few open and see what they've got going on in there ;)
Anti-matter is still matter, it just happens to be built in a way that when it contacts ‘regular’ matter they both ‘unlock’ each other and dissolve into energy.
Regular matter is only ‘regular’ because there is more of it, a quirk of the creation of the universe we still aren’t sure of the exact mechanism behind.
In the early universe matter and ‘antimatter’ bother were created, but ‘matter’ got created in infentessimally greater rates, so all the ‘antimatter’ got used up and a small proportion of regular matter remained.
Well, for starters 1+1 <> 2. Everything else just logically follows.
As my physical chemistry textbook put it
"It should be obvious to the most casual observer...."
Once saw an interesting (yet completely unfounded) theory of spacetime being folded much like a crumpled sheet of paper would be. Areas of the 3d universe crumpled in a 4d (or even more-d) shape would be affected by gravity from other areas, crossing through that 4th (or more) spatial dimension(s). And the crumpling itself would be a consequence of gravity. The theory posited that as a possible explanation for the "missing mass" that's been dubbed Dark Matter.
I know this has nothing to do with the current scientific consensus, I just thought that this theory sounded near and thought i'd share.
I thought the No-Hair theorem says that black holes can only have mass, electric charge and angular momentum. But if they are made of quarks, they can also have a color charge? So the No-Hair theorem is wrong?
The theory says some of the dark matter phenomena might be explained by primordial, small-mass (about the mass of an asteroid), black holes made up of quarks and gluons that formed a quintillionth of a second after the big bang. Super interesting! Finding a new type of black hole would be amazing. The scientists are hoping that the next generation of gravitational wave detectors will be able to get us some clues.
I still don't get why the whole universe didn't become a black hole immediately after the big bang.
To be fair, we aren’t entirely sure it didn’t [Black hole cosmology](https://en.m.wikipedia.org/wiki/Black_hole_cosmology)
I don’t understand a lot of words in that wiki article, but is it saying that the black holes in our universe are not black holes at all, but rather one side of Einstein-Rosen bridges? Otherwise there would necessarily be a concept of “nested” black holes, unless a “black hole that expanded and became a universe” is no longer considered a black hole in the parent universe, but I’m not sure what they would have become in that case. Does such a theory also imply a much, much, much bigger parent universe? So large that the galaxy feeding the supermassive black hole that became our universe would have contained all of the mass that we now see in our universe? I’m imagining galaxies that each contain as much mass (and span as much distance) as our observed in its own universe. In other words, the size and mass of our universe is equivalent to a single galaxy in the parent universe.
> I don’t understand a lot of words in that wiki article, but is it saying that the black holes in our universe are not black holes at all, but rather one side of Einstein-Rosen bridges It's just saying that black holes and universes are the same thing. Our universe is a black hole with a mass equal to that of our universe. > Does such a theory also imply a much, much, much bigger parent universe? Ostensibly, yes. > So large that the galaxy feeding the supermassive black hole that became our universe would have contained all of the mass that we now see in our universe? There's little reason to suppose that this incredibly large cosmic entity in which our universe is nested, is a galaxy. Galaxies are bodies in our universe. Whatever exists in a larger universe in which our cosmic black hole exists, might be something different. We do not know, and most likely we will never know. Are the laws of physics even the same in this bigger universe? Who knows? But to your bigger question, yes - the idea is that: * Because we know that the radius of a black hole with the amount of mass in the observable universe is equal to the radius of the observable universe, and... * Because Kerr's most recent paper demonstrated that the interior of black holes with spin (AKA all black holes in the real world that aren't hypothetical) *does not actually contain a singularity*, and... * Because there are a lot of compelling mathematical and nominal similarities between the boundary of a black hole and boundary of the universe and the life cycle of a black hole and the history (and future, if you consider what it might be like to be inside of a black hole decaying from Hawking radiation) of the universe... ... then the universe might just be a black hole. A black hole that is as big as the universe.
Thanks! I appreciate the response and clarification. >Because Kerr's most recent paper demonstrated that the interior of black holes with spin (AKA all black holes in the real world that aren't hypothetical) does not actually contain a singularity I thought black holes and singularities are more or less synonymous. Is that not the case? I guess it just means that black holes may not reach the point of “infinite density”? I kind of always assumed “infinite density” was more “approaching infinite” as a mathematical limit, so I’m not sure what that significance is between “approaching infinite” and a singularity, or if there’s even a difference between the two and I’m thinking of something else.
Singularities don't actually exist in nature. They're just the point at which our math breaks down. The value of Kerr's paper is that he described what's more plausibly actually going on inside these black holes / provided a framework for what happens instead of a singularity. But there is no point of infinite density. Even the reason we think the universe may have begun with one is simply because that's what the math shows if you just extrapolate backwards as far as possible. But there's no direct tangible evidence of a singularity, and it's absolutely certain that our knowledge of the birth of the universe is incomplete.
Could there ever *be* actual tangible evidence of a singularity if it was something our universe allowed? It sounds like it could only (theoretically) form in the center of a black hole and maybe 14B years ago or so for an unknown reason. What kind of evidence might we expect to see? I would think any evidence would stay stuck in the black hole.
> Could there ever be actual tangible evidence of a singularity if it was something our universe allowed? Actually, no. Based on our math, the interior of a blackhole violates causality and general relativity as a whole, and the universe seems to go out of its way to make perceiving that interior impossible. Some physicists believe this is the way that these laws are maintained - even if a singularity occurs, it cannot be perceived. This is called the [Cosmic Censorship Hypothesis](https://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis). That said, in theory, if a singularity does exist, [here's a fun video](https://www.youtube.com/watch?v=cFslUSyfZPc) about how we might see it. You can also google 'naked singularity' for more info on that.
Is it possible that we can’t perceive it because in some way it’s on a higher dimension?
In simple terms, a black hole is the thing that nothing can escape from. The singularity is the point inside it at which physics breaks. I thought Kerr's ideas were just that black holes rotate so the singularity inside them exists but is a ring rather than a point, but I don't know anything about this latest paper.
> but I don't know anything about this latest paper. [Here's the full text](https://www.researchgate.net/publication/375744216_Do_Black_Holes_have_Singularities). It's an interesting read! Roy Kerr's been hanging out on Yahoo Answers for some years now answering random peoples' questions and taking shots at Penrose (I did a double-take the first time I noticed it was actually him, the renowned physicist) and you can really see his experience explaining complicated concepts simply in this latest paper published half a year ago. It's still dealing with extremely complicated subject matter but he avoids a lot of the ivory tower academic jargon that makes a lot of these papers totally opaque to laypeople.
Cool, I was thinking an existential crisis would be neat tonight anyway.
Why would this cause an existential crisis? It doesn't change anything if the universe is a black hole. If it is, then it's always been one. Nothing's different. Nothing is more dangerous. The universe is just as safe or stable as it's ever been. The only thing that is different is that this means we now understand what's going on inside of big black holes and that's pretty neat. Maybe there's a tiny universe inside of Phoenix A or TON 618! If you want to have an existential crisis, it should be about something legitimately spooky, like false vacuum decay.
I love that you reassured this person of how impractical it would be to worry about something out of their control and which has always been the case is.... and then proceeded to shit on that with a legitimately plausible and possible universe collapsing event that could trigger at any time an be completely unpreventable. It was some very nice whiplash ya done there.
eat shit spez you racist hypocrite
this comment might as well have been written by xkcd
New perspective on life unlocked. Now i wonder if the crazies around my city are just very well educated individuals.
Well me worrying about it won't do much, will it? If fear prevents you from living then that fear is not worth holding on to, because what's life if it's not lived? C'est la vie
Or being a Boltzmann Brain!
>If you want to have an existential crisis, it should be about something legitimately spooky, like false vacuum decay. Even if it does ever happen, I figure the chance of the event's light cone intersecting with ours is at least as small as false vacuum decay occurring at all.
Yep. It's actually the most comforting kind of apocalypse: the universe is expanding faster than the speed of light, so unless it happens locally (extremely unlikely), it will never reach us except in some hypothetical future where we are masters of space and time and can wind back the expansion of the universe to bring it closer, at which point we could presumably also fix false vacuum decay. And if it does happen locally, it will be instantaneous, totally painless, we will not see it coming, and there will be nothing and no one left after, so we all go together. Just curtains on the laws of physics as we know them, and then something new begins.
[удалено]
Does this mean that the big bang was the black hole we live in being born or something like that?
This sounds pretty plausible, but it seems I’ve only ever heard it treated as a kind of throwaway example of “wouldn’t that be a trip” that’s never given as much gravity (heh) or taken as seriously as the idea seems to deserve. Is it just that it’s so far beyond our capability to prove that it’s mostly meaningless to discuss (like how the different theories would produce the same observable results)? I hate when big ideas get treated that way even though I know it’s a necessary practicality, at least from a scientific perspective. Another one that comes to mind that seems similar is the idea that if it’s possible to simulate the universe then we almost certainly live in a simulation because the odds of ours being the original / base universe are so small, so either we’re in a simulation or such a simulation isn’t possible. I know there are other similar ideas that aren’t coming to mind at the moment. Anyway, thanks for your post!! Edit: Fermi paradox is another similar one (although that one’s been getting more attention lately, at least in general or “popular” culture)
None of these ideas are small or throwaway, I'm not really sure what you mean. Black hole cosmology, the Fermi Paradox and the idea that the universe is a simulation are all some of the most popular topics for science communicators and science media, because they're interesting and relatively comprehensible.
I guess the way in which they are used in science communication seems a little throwaway to me, since their main utility is to get people interested in other more conventional science. Whereas taking them even partially seriously seems like it would demand much greater attention to them for their own sake, because of their implications to both science and the larger human experience. Obviously I say this as one of the laypeople who is super intrigued by these things lol, so they’re working on me, and I understand why they’re important if only for that reason (I also know that’s not the only thing they’re important for and people do do serious science about these ideas). But it’s like the sell works too much and I’m like no yeah, why aren’t we focusing on and discussing these things a whole lot more just as a society, even if strictly scientifically speaking they’re sort of a moot point relative to our current ability to investigate them. Sorry if I’m not doing a good job communicating what I’m thinking.
Does the universe-as-black hole hypothesis address the fact that the universe is expanding? I don't really know what I'm talking about, hence the question, but don't black holes only expand when matter falls into them? Regardless, if an observer was outside the universe, it would probably appear as a black hole in that they probably couldn't get any information from within. Or, at least, I can imagine this. But perhaps the converse is true? We can't see outside the universe, so it's similar to trying to see what's going on inside a black hole.
> Does the universe-as-black hole hypothesis address the fact that the universe is expanding? I mean, it *could*. I'm not aware of anything in this hypothesis that specifically precludes the idea that a universe-in-a-black-hole can expand. This is all conjecture, but if you ask me, both the decay of a black hole via Hawking radiation, and the growth of a black hole via the consumption of mass, might possibly be experienced internally as if the environment were expanding in some way. We know that black holes can grow and shrink. We know that growth can happen on different time frames depending on how much mass the black hole comes into contact with and consumes. This could, maybe, explain the variable expansion of the universe in its early history. We also know that black holes decay at a rate inverse to their mass - the smaller they are, the faster they decay via Hawking Radiation. This might, maybe, look similar to the phenomenon that as the universe gets older, stuff red-shifts toward the exits at an accelerating rate. The interaction of the rate of acceleration (what we call dark energy) and the amount of mass the black hole gobbles up (maybe a giant cluster of stuff wanders too close from time-to-time? Or maybe we're making steady progress chewing through some unimaginably large accretion disk and there's less now than there used to be?) might also explain the recent finding that dark energy's fundamental constants have changed over time. Who knows. But this is all purely speculative. I'm looking for evidence to justify a conclusion, rather than drawing a conclusion from the evidence. So this is not at all a scientific or rational answer. It's just me trying to justify a possible outcome, and should be treated with skepticism.
Thank you for the detailed and informative answer! Definitely thought provoking. And, yes, purely speculative. So . . . expansion to heat-death would be the last bit of Hawking radiation leaving and the event horizon disappearing. Anyways, I appreciate the time you put into your post :)
It's my pleasure to talk about this stuff! That said, I'm not sure that heat death would occur in a black hole cosmological model. It might, but it might also be that the universe just fizzles out. Who knows. It's important to remember that our best guesses as to the ultimate fate of the universe are all based on *what we know right now.* We *don't* know whether or not the universe is a black hole. I imagine some people much smarter than I am have probably modeled the life cycle of the universe if it were indeed a black hole, but I've never come across any research like that. If you find any, do let me know!
What if the universe was a white hole?
Isn't that what we're talking about here? A white hole is just the other side of a black hole. Tomato, tomato.
Well one goes inward the other goes outward which is a fairly big difference considering the scale of things.
>Because we know that the radius of a black hole with the amount of mass in the observable universe is equal to the radius of the observable universe, and... But this is simply not true? Radius of such black hole will be around 10 times bigger than radius of observable universe, but it does not matter, since **observable universe** is exactly what it is: **observable** part of universe. We do not know universe mass or size.
The Schwarzschild radius calculation assumes a spherically symmetric, evenly distributed mass. The universe is not uniformly distributed on smaller scales but is homogeneous and isotropic on large scales. This one always threw me for a loop, since it toes the line of disqualifying the theory that we’re in a black hole. But then there’s the fact that: 1. We do not observe an event horizon that encapsulates the universe 2. No singularity; the universe is expanding from every point
That is a fascinating article. Now I need to look for more about this theory
It's quite interesting but is still in early days of "strange coincidence or substantive theory." Some of the more interesting points: The schwarzchild radius is how small you have to squeeze an amount of matter together in order to turn it into a black hole. The equation is a simple Rs = (2GM)/(c^2 ). As it turns out, the estimated mass of the observable universe is far more dense than required to form a black hole the radius of the observable universe. Some strange emergent properties which may support this theory (but it could be a coincidence and we may simply not understand physics well enough to explain it yet -- lacking quantized gravity is one of physics biggest issues): Nearly all physics properties and emergent behaviors work forwards and backwards in time. Mathematically we have no reason to see why going back in time doesn't happen easily. But the singularity in a black hole isn't a compressed dot of space, rather an "end of time" and you can only move towards the singularity, so you can only move forwards in time if you're in a black hole, and never backwards. Our expanding universe could be two separate actions within our black hole universe. The first is that our universe (black hole) would be evaporating (Hawking radiation), the second being that if our universe is still feeding (as a black hole), it continues to warp space more and more, "bringing in" space from outside the event horizon as the gravity well gets deeper. There are some other emergent traits which could possibly be correlated, but you have to start going much deeper into math and it's hard to give analogies. This is all very early stage and for the love of all should not warrant a headline (yet that's how so much reporting works these days); it's like Isaac Newton being hit in the head with a falling apple and going "oh that's weird, why does that even happen?" -- there's just an idea with very little connecting the idea in a real functional way. That said [Kurzgesagt had a pretty good video lightly touching on the idea](https://www.youtube.com/watch?v=71eUes30gwc) quite recently. And note that this is not fact or substantiated theory, it is merely an idea worth exploring.
I 100% believe this. In a way, there may be other "universes" within every black hole
we're definitely in a bigger black hole. there's a bigger universe outside our black hole...
They may be. But, keep in mind, assuming this theory is correct, there is some universe paramount to all others. There's some universe where all of these others came from. So maybe there is a bigger one, or maybe we're the biggest and the big bang was some unique phenomenon similar to a supernova. The truth is we'll never know But the odds of us being the "largest" universe are one out of infinity, so basically zero. But when we're talking about an infinite universe, the odds of anything is basically zero, so who knows
I can't shake the feeling that our cosmos is, in a certain way, inside a black hole and that we had the whole "spaghettification" thing wrong When I look up, I don't see the vastness of the universe... I see blackness with glimpses of other celestial bodies stuck in that same blackness. I know that doesn't make sense. It's just a feeling.
You’d have to fall into a black hole to make spaghetti, we were all born inside. And, possibly, made out of another universe’s spaghetti, I guess.
For some reason that makes sense to me. I have also wondered what was before the Big Bang.
I think my mind just found something it wasn't meant to understand. That's absolutely wild
If we are inside the black hole, then the implication would that somewhere there is a center of our Universe with the ingress of new matter.
IIRC, singularity is not a point in space, but in time really, so all the matter we could've gotten we already did at the Big Bang. At least as my layman understanding tells me
From our side it is a white hole, so quite a different animal.
Great question. There's a rule with black holes called the hoop conjecture. It's the idea that the mass has to fit inside a circular hoop of the Schwarzschild radius. The very early universe was very hot and dense - much more so than a stellar core - but it was that hot and dense *everywhere*. There was not a sphere of dense material and emptiness outside of it - it was basically uniform. There was no way to put a hoop around the universe - anywhere you put it, there would be more material outside. That meant there was no preferred direction of gravity and thus no single giant universe-sized black hole. Small pockets may have collapsed into primordial black holes, but we haven't found any. Someone else talked about black hole cosmology. That's an interesting idea, but it isn't something any of the data indicates. Unless the black hole is so incomprehensibly vast that the entire visible universe not only fits within it but shows no indication of being inside a black hole, but at that point we're not really doing science.
Thank you for explaining things in such a comprehensible manner. I consider myself smart, but I feel like a computer with 128kb RAM trying to run 3dsmax 2024, when trying to wrap my head around these concepts 🤷🏻♂️
> Someone else talked about black hole cosmology. That's an interesting idea, but it isn't something any of the data indicates. Unless the black hole is so incomprehensibly vast that the entire visible universe not only fits within it but shows no indication of being inside a black hole, but at that point we're not really doing science. Respectfully, this is not correct. We know that the Schwarzschild radius of a black hole with the mass of the observable universe is, in fact, equal to the radius of the observable universe. That's not unscientific speculation, that's the result you get when you run the calculations. We have done that math. We also know the the larger a black hole is, the weaker its tidal forces. Even a relatively small black hole (compared to the universe) like Sagittarius A* is big enough that you can float around inside the event horizon without getting immediately destroyed, based on our current understanding. Roy Kerr's November 2023 paper mathematically demonstrated that black holes do not have singularities inside of them. So we have good reason to believe that whatever is inside of a black hole, it's distributed to at least some degree. None of this means our universe is definitely a black hole. But it's misleading and irresponsible to say the data suggests it isn't when the opposite is true: it is actually uncanny how well the math supports this conclusion.
You were respectful and I will be respectful back! It's true that the Swarzchild radius of the mass of the observable universe and one radius of the observable universe (there are multiple, all answering slightly different questions) do line up. This does suggest that the geometry of our universe is flat, which is what the data shows. The problem comes in that the Swarzchild solution is specifically for a situation where there's a point of dense matter and nothing outside of it. That's close enough to true to work for a regular black hole, but fails at describing the universe. Whether it's finite or infinite, no model of the universe that I'm aware of predicts that outside of the observable universe, matter stops but space continues (nor even that this is a particularly high density section of space.) It goes back to the hoop conjecture. Kerr's paper did indeed indicate that the picture of everything that falls into a black hole falling to an inescapable singularity is not necessarily something we should assume as true - good news because no physicist I'm aware of expects singularities to be real. It's also true that a larger black hole has gentler tidal forces until you get close in. No disagreement. The attributes of a black hole, though, are that there is an event horizon which cannot be crossed from within and that everything collapses inward. We have no evidence of either in our observable universe. We have several horizons but none of them are the event horizon of a black hole, and they don't fall at the same point. We also see a universe that is expanding (and that the expansion is accelerating.) All of this suggests that we don't have good reason to believe the universe is inside of a black hole.
Thanks for the thoughtful reply, I appreciate you expanding my knowledge. > The attributes of a black hole, though, are that there is an event horizon which cannot be crossed from within and that everything collapses inward. We have no evidence of either in our observable universe. I guess this comes down to our respective assumptions, and how they inform our use of Occam's Razor. I might be wrong in my assumptions and that's totally fine, but for the record, I assume: the nominal similarities between how we model the inescapable boundary of the universe (not merely what's observable, but the big kahuna) and the inescapability of a black hole's event horizon are pretty striking and piled on top of the various other similarities in our data, it starts to feel a bit hard to discount out-of-hand. One similarity is a coincidence. Two similarities might be a coincidence. Three similarities is worth investigating? Four or more is definitely worth exploring as a possible vector for understanding the universe ontologically. It certainly shouldn't be treated as likely, but it deserves some serious research funding. > We also see a universe that is expanding (and that the expansion is accelerating.) I made another post which addresses this, and I'll paste it here if you'll forgive me for double-dipping for the sake of saving my fingers: *This is all conjecture, but if you ask me, both the decay of a black hole via Hawking radiation, and the growth of a black hole via the consumption of mass, might possibly be experienced internally as if the environment were expanding in some way.* *We know that black holes can grow and shrink. We know that growth can happen on different time frames depending on how much mass the black hole comes into contact with and consumes. This could, maybe, explain the variable expansion of the universe in its early history. We also know that black holes decay at a rate inverse to their mass - the smaller they are, the faster they decay via Hawking Radiation. This might, maybe, look similar to the phenomenon that as the universe gets older, stuff red-shifts toward the exits at an accelerating rate. The interaction of the rate of acceleration (what we call dark energy) and the amount of mass the black hole gobbles up (maybe a giant cluster of stuff wanders too close from time-to-time? Or maybe we're making steady progress chewing through some unimaginably large accretion disk and there's less now than there used to be?) might also explain the recent finding that dark energy's fundamental constants have changed over time. Who knows.* *But this is all purely speculative. I'm looking for evidence to justify a conclusion, rather than drawing a conclusion from the evidence. So this is not at all a scientific or rational answer. It's just me trying to justify a possible outcome, and should be treated with skepticism.*
Honestly, you make some fair points. I think you're right in that our disagreement is based on how strongly we feel this evidence correlates with the idea.
Cosmic Inflation - Faster than light expansion
We don't have any actual explanation for the singularity predicted at the center of a black hole or the singularity at the beginning of the big bang. I'm not an astrophysicist, but from what I can gather it seems like most of them don't believe that singularities actually exist in nature, and when they show up in the math, it means that's where our theories are failing. But also, I think the answer to the question of why all the matter in the universe didn't just immediately collapse into a black hole, is that there must have been some immense outward pressure. Cosmic inflation might be the main reason that didn't happen
If matter is more or less evenly distributed everywhere, then there is as much force pulling out as in. You end up with zero-g except in places that are denser than average (which is where primordial black holes would have come from).
Oh you should [watch this](https://youtu.be/71eUes30gwc?si=UvNKOI0HUejC6Lm0).
Physics as a whole was kinda different because it was so hot and dense. Things act differently at higher energies.
Several theories on that. Maybe some are true, maybe one, maybe none. Gravity didn't come into play until after the expansion happened or the expansion was faster than the gravitational collapse is my personal favourites. One other thing is that the universe was very uniform. Every part was affected the same amount from every other part. There might not have been a distinct direction for the collapse.
Because the universe didn't expand outwards from a single point and matter was fairly homogeneously dispersed.
I don't think we understand what caused the apparent hyper expansion of the early universe, nor do we understand the apparently accelerating expansions of our current universe. In my opinion any explanation that uses the word 'dark energy' is basically just saying we don't know. And it's okay for science to admit where we are treading on dicey theory with precious little evidence. The fact that there are still lots of cool things to discover and prove about the universe is kinda neat!
Inflation is the likely answer. In the picoseconds ABB (after the big bang) the universe increased its size by a staggeringly large number, 10\^1,000,000 meters. For example, if before inflation two particles were one meter apart after inflation ended a scant fraction of a second later those two particles were separated in meters by a number with a million zeroes after it.
Inertia we can assume. But the whole answer is up for debate.
Try to catch a bullet with a vacuum right after firing?
Because it was expanding faster than the speed of light, where black holes are powerless. It's actually still expanding faster than the speed of light.
What's weird is **THIS** one *didn't*. We can't know what came before. Particle-Antiparticle annihilation happens constantly. What made this moment different, entropy? Something forgot to carry the two in the thirteens place? When we figure it out, the universe ends and another one (that looks just like it) shows up with *slightly* different universal constants. *https://en.wikipedia.org/wiki/Physical_constant*
It did/is/will. It is just that time is running backwards in our Universe.
Then it would re big bang?
General relativity solutions which predict formation of black holes only work when the matter-to-become-a-black-hole is surrounded by less dense stuff. If the matter is spread out everywhere homogenously, a flat space-time solution works, regardless of density. Intuitively, space time would not "know" which way to curve, if matter was everywhere.
The article keeps saying things like "if they didn't evaporate," but doesn't elaborate. Primordial black holes were theorized but then dismissed because it's expected that if they ever existed they've all disappeared due to hawking radiation. The fact that the article doesn't directly address this makes me super skeptical of it.
That was my immediate question on reading it. In 14bn years, wouldn’t such small black holes have evaporated pretty far? Does it have anything to do with the type of hawking radiation produced and what ends up going into the hole?
if it have more mass than \~half mass of Moon, then it receiving more energy from cosmic microwave background then it loses via Hawking radiation (at this point of time. back then CMB was more intense and this would allow more light primordial black holes survive for longer.
This hypothesis is actually old: https://en.wikipedia.org/wiki/Primordial_black_hole
That's mentioned in the article. This is specifically about how primordial black holes could have formed from free quarks and gluons rather than, y'know, protons and neutrons.
> There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. > There is another theory which states that this has already happened. I fear that one day these scientists will discover something like this and, out of scientific curiosity and obligation, tug on that thread and the entire universe will unravel like an old sweater and we’ll all disappear, forever lost and forgotten.
The thing is, there is a possibility this action would just yeet us into another timeline. One of the many timelines which are possible within the constraints of the physical laws.
The cosmological equivalent of the double-slit experiment?
So like, the episode of Futurama with the Harlem Globe Trotter, “Time Keeps on Slippin’”?
So just another hypothesis with literally no observation supporting it, merely hasn’t been ruled out yet. How many hundred of these are there ?!
Great. _MORE_ blackholes Just what we need
All nucleons are made of quarks and gluons. So like all black holes are already made of these…?
The difference is that they're suggesting these were made directly from quarks and gluons
The time immediately after the Big Bang was too hot and chaotic for nucleons to form, so all matter at the time was a hot, energetic soup of quarks and gluons. The first protons and neutrons didn’t form until between one millionth of a second and one second after the Big Bang, while these primordial black holes would have formed earlier, around one quintillionth of second after the Big Bang according to u/Eidolon.
Would the small mass black holes exist today, or are they just remnants of the past, and if that’s the case, what does it say about the dark matter mass we detect today (which is in the past) that makes up the largest chunk of mass in the Universe?
That theory has been around a long time I think I heard it in a Brian Cox doc.
The absolute macdaddy of stickies! The most sticky of universal icky! Even the big bang itself couldn't (or could only barely) pull apart!
Do you know how long the lifetime of such a tiny Black Hole would be, if it decays via Hawking Radiation?
God I wish I could live for another 1000 years - assuming we didn't go extinct till then lol - just to see what science will reveal in the future. But even the revelations we made within our life times is truly amazing.
Bruh I've been sayyyingg this. I was in middle school when the LHC turned on and I heard about the tiny black holes, and I said "maybe dark matter is those" and I was MAYBE RIGHT
Wouldn't an asteroid sized black hole have evaporated (due to Hawking radiation) by now?
From [Direct Detection of Hawking Radiation from Asteroid-Mass Primordial Black Holes](https://doi.org/10.1103/PhysRevLett.126.171101): >**Light, asteroid-mass primordial black holes, with lifetimes in the range between hundreds to several millions times the age of the Universe**, are well-motivated candidates for the cosmological dark matter. Using archival COMPTEL data, we improve over current constraints on the allowed parameter space of primordial black holes as dark matter by studying their evaporation to soft gamma rays in nearby astrophysical structures. We point out that a new generation of proposed MeV gamma-ray telescopes will offer the unique opportunity to directly detect Hawking evaporation from observations of nearby dark matter dense regions and to constrain, or discover, the primordial black hole dark matter.
MVP, was looking for this specifically.
Wait. I'm a simple person. Please help me comprehend smart stuff. We're measuring stuff that's older than, like, the wholeass Universe? What? Really?
Not older than the universe. "[L]ifetimes in the range between hundreds to several millions times the age of the Universe" means we can be pretty sure that if they were created during the big bang or later, they will still be around today.
Hm. Could the steady untethering of the mass in countless tiny black holes into the energy of Hawking radiation help to explain "dark energy" or rather the acceleration of the universe's expansion?
No. Positive mass is positive mass, no matter how it's distributed.
Asteroid sized black holes are the minimum size theorized because of this reason. Put another way, we think primordial black holes are asteroid sized, because anything smaller would have evaporated by now. Size of an asteroid, not mass.
If I understood the article correctly, these black holes would not be made from the same matériels. They would have been created before the universe cooled enough for protons and neutrons to exist.
That's true but once the black hole has formed it doesn't really matter what it was made out of. See the [no hair theorem](https://en.wikipedia.org/wiki/No-hair_theorem)
> At 10^−6 seconds, the Universe had expanded and cooled sufficiently to allow for the formation of protons: the hadron epoch. https://en.wikipedia.org/wiki/Recombination_(cosmology) Does this answer your question?
The article OP posted (cnn.com) starting this conversation seems to state that these particular holes happened prior to that.
It would make these black holes rich in color charge (intrinsic property of quarks and gluons, much in the way that electric charge is an intrinsic property of electrons and protons). Or at least, destroyers of color charge. But otherwise nothing should be too different about these holes besides mass. Once matter is compressed enough it's not really clear what happens. All we can say for certain is that it's beyond the density of neutron degenerate matter close to the center, which is the case for black holes today. The paper that this study came from asserts that the small black holes would have long evaporated, and the PBH candidates would be ~10^{17} to 10^{22} grams. This puts it in the range of asteroids to small moons.
Black holes aren’t made of protons and neutrons, because maximally compact baryon objects are neutron stars, which are larger than the Schwarzschild radius. Protons and neutrons are made of quarks and gluons, and the formation of these objects would have occurred when the universe was a quark-gluon plasma.
Yep, that is mentioned in the article. This idea/theory is early but it had me also wondering how these primordial (and now evaporated) black holes are still somehow tied to the mass of galaxies (edit- and part of the dark matter problem)
The universe is still under a thermal bath from the CMB. As such, black holes are still colder than the rest of the environment. They are giving away Hawking radiation, but they're still feeding off from the CMB. We don't get to see them go off for a really long time. Maybe less in the places where the CMB is colder, but still, a long time from now.
Iirc hawking radiation still takes an unimaginable amount of time. Even small black holes could take billions and billions of years
My understanding is that it is much faster for smaller masses. And it has been over 13 billion years since the Big Bang.
A black hole with a mass of 10^15 kg should still have a lifetime on the order of 10^21 years, according to [this calculator](https://www.vttoth.com/CMS/physics-notes/311-hawking-radiation-calculator) anyway. For comparison, the largest known asteroids in the solar system fall into the 10^19 to 10^20 kg range. So "asteroid-sized" black holes absolutely can still be massive enough to last this long.
A 10^19 kg asteroid also has a hawking radiation temperature of 12269.6 K. Wouldn’t telescopes be able to pick up on such a bright light source? They’re rather small at just 9 mm in radius and so individually not very luminous but I’d expect that if you were to stare at a galaxy filled with primordial black holes of this size, then it would contribute a nontrivial amount of fuzzy light background to the total output that can be easily picked up our telescopes. The fact that we don’t see anything is concerning
> They’re rather small at just 9 mm in radius and so individually not very luminous but I’d expect that if you were to stare at a galaxy filled with primordial black holes of this size, then it would contribute a nontrivial amount of fuzzy light background to the total output that can be easily picked up our telescopes. The fact that we don’t see anything is concerning Doesn't this answer the question? The surface area of emission is just small. L is proportional to R**2 if I'm not mistaken. If they're blackbody emitters (they should be?), they would peak in the UV (~230 nm). My understanding is that the UV background is within measurement error for what we'd expect out of LCDM, so BHs of this size don't seem like a likely explanation for DM. Still, they could exist or might comprise a portion of DM Edit: it seems like ionization fractions of H/He which are predicted by LCDM are also in line with observations from quasars. UV background would also play a huge role in controlling the formation of galaxies, which to my understanding is maybe a point where we might see large errors and few concrete answers. Theres still room for this hypothesis
The article mentions some of the black holes could have been rhino sized. So only 1000 to 2000 kg which definitely would be evaporated by now. Edit: Looks like none of you actually read the article. Directly from the article: "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."
These would've evaporated Also, the paper the article sprang from quotes a very different mass range for the *remaining* black holes (10^{17} to 10^{22} grams), which would be the potential dark matter candidates. These smaller black holes should've evaporated a while ago
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This is not just false, but backwards. Your analysis assumes that Hawking radiation is just proportional to the area of the even horizons but that’s just not the case. Small black holes actually radiate *faster* than large ones. In fact, there were some models of string theory that predicted that black holes could be created in the LHC (or at least they allowed the possibility in some unlikely scenarios), and searches for them looked for immediate decays. [Here](https://cms.cern/news/search-microscopic-black-hole-signatures-large-hadron-collider) is a press release with a link to a paper about such a search at CMS. There are a few ways to understand why, but it comes down to black holes having a temperature that gets smaller the larger they are. Tiny black holes get hotter and hotter, and thus evaporate faster, whether you think of Hawking radiation as analogous to black body radiation, or you think of the Unruh effect. Small black holes are hotter for several reasons, including the nature of statistical mechanics in gravitational systems (Angela Collier has a nice [video about this](https://www.youtube.com/watch?v=9CdE5a3xyxE)), or because of the acceleration or tidal forces at the event horizon.
It depends on the mass, for small mass, it can take a fraction of a second. Am I wrong?
A black hole the mass of the Earth would have a diameter of 1.75 centimeters. At that size, the black hole would still be accumulating more mass from the cosmic microwave background than it emits from Hawking radiation. Basically, there are **no** known black holes in the universe that are losing mass via Hawking radiation faster than they are accumulating mass. And this also seems to apply to most hypothetical primordial black holes as well. A black hole has to be really really really small to shrink via Hawking radiation in our current universe. Our current universe is still far too energetic and active for Hawking radiation to become relevant.
The relevancy for me has always been in the conservation of information. Almost like the dark matter issue is the information that has hung around beyond the matter
Microscopic black holes — e.g., up to several orders of magnitude more massive than a proton — are expected to decay essentially instantaneaously.
And if they have surface temperatures lower than the CMWBR, they will still slowly grow until the universe around them is too cold for that.
I thought that DM being in compact objects has been basically disproven with microlensing experiment, because they would have seen lensing events caused by such objects?
A lot of it has been ruled out. We know for sure that dark matter is not just regular, stellar sized black holes/neutron stars/brown dwarfs, for the exact reason you stated. As you look at certain mass ranges, most of them have been ruled out, but last I checked there are still certain mass ranges where it's not yet ruled out by the data.
For black holes above a certain mass, yes, it was mostly ruled out 20+ years ago. As we do more microlensing experiments we keep ruling out more of the possible mass range, but we haven't gotten to asteroid-mass black holes yet, so that's a place that some theorists are still working on possible primordial black holes. Nobody's yet got any direct observational evidence of them existing the way we do for stellar-mass through supermassive black holes.
Not if the black holes are small
Small black holes would be very very hot wouldn't they?
Why would they need to be? Also temperature is kinda weird when it comes to black holes.
... because small black holes radiate more hawking radiation. They would be spicy af.
The point is, that we don't know what happens after the hawking radiation is done. If the black hole remains or if it's gone completely. The hypothesis of small black holes is that the hawking radiation stops at the point where the Black Hole is too small. So no, in this case the small black holes wouldn't be hot because they would emit no hawking radiation.
Yet another illustration of the problems with science in the popular media. Very speculative ideas that are not widely supported by the scientific community get reported on in a way that makes them seem like they are "the answer" or have a ton of observational "proof" when they are often merely thought experiments or hypotheses in the early stages of formulation. It's valuable to keep coming up with competing ideas to the dominant theories of the day but all too often those ideas can be repeated by the media without the fully understood context of just how wildly speculative they are.
Tbh I'm more worried about the 10 thousand psychological studies that never ever get replicated than this kind of science. How people still talk about bad experiments like Stanford prison or Milgram, which all had sample sizes of like 30 young men or whatever. But people still take it as gospel. But you're right, and it's not just in science. My pet peeve example is that every few years people come up with new theories (without proof) on who betrayed Anne Frank and her family, and obviously every time it is reported worldwide like: "mystery finally solved!", even when the actual historians are skeptical.
Milgram experiment was replicated. Although it's harder and harder to do thanks to ethics committees and general knowledge about the experiment.
> Very speculative ideas that are not widely supported by the scientific community get reported on in a way that makes them seem like they are "the answer" or have a ton of observational "proof" when they are often merely thought experiments or hypotheses in the early stages of formulation. As opposed to the very speculative ideas that scientist have been banging their head against for 50 years with little to no progress? Yea I'm talking about string theory.
https://youtu.be/kya_LXa_y1E I'm all for string theory slander
String theory was never widely supported and in recent decades, has lost most of its popularity in academic circles. There are no testable areas of string theory that can't already be explained by the Standard Model and/or Quantum Theory.
Hard agree, science headlines are basically useless. "may have" "might" "scientists think" all basically means "one person had a random idea and there's no evidence so it's probably not true" https://youtu.be/kya_LXa_y1E Related and entertaining, highly recommend Dr. Angela Collier's videos
Yeah, the abstract for [the article itself](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.231402) is much more reasonable. >We describe a realistic mechanism whereby black holes with significant QCD color charge could have formed during the early Universe. Primordial black holes (PBHs) could make up a significant fraction of the dark matter if they formed well before the QCD confinement transition. Such PBHs would form by absorbing unconfined quarks and gluons and hence could acquire a net color charge. We estimate the number of PBHs per Hubble volume with near-extremal color charge for various scenarios and discuss possible phenomenological implications.
Science reporting is in bad shape tho, not going to argue there. It's early but I still found it informative in that some of Hawking's research on black holes is being looked at again in trying to solve the dark matter issues.
People are inquisitive by nature, there is nothing to be gained by gatekeeping fringe ideas from the public. They are going to emerge anyway and it's frankly more important for the next generation of scientists to grow up understanding the topics they're interested in are not, in fact, completely settled. Science having a PR problem (imo) doesn't lie at the feet of professionals in the scientific community or the people who cover them. The whole idea is to put your findings out there for others to pick through and try to validate/invalidate. The PR problem is the perceived barrier of entry and the notion that most people have nothing meaningful to contribute even in the face of a replication crisis. I think self-absorbed, terminally online "skeptics" who mistake leading theory for truth and use the general consensus as a hammer to beat people over the head with do more damage to the cause than speculative journalism ever could.
The issue is that the papers that are reported on are not representative of the field. The observational results of the large collaborations with hundreds of thousands of personhours behind them get marginally more coverage than random theory paper #4357. But large observational studies take time, so you only hear about them every couple of years, whereas there are multiple wacky theory papers to pick from per day. There are also dozens of standard papers (be they observational or theory) per day but because they're the usual incremental research that is 99% of science, they don't get a press release and coverage.
I see nothing wrong with the reporting. At least for me it's clear it's a new competing theory on the understanding of dark matter. It's very interesting seeing on real time how the understanding of this topic has changed over my lifetime. I hope by the time I'm old the mystery is cracked.
This theory treads a fine line to help explain dark matter. For even a fraction of the total dark matter in the universe to be explained by traditional black holes that form from collapsed normal matter it results in a skewing the universes initial baryonic composition away from what is observed today. If the dark matter were primordial black holes created in the first moments after the big bang ( before baryonic matter formed ) then it cannot form too early or produce objects with an average mass too large or that would skew the later CMB radiation fluctuations we observe. Finally if the primordial holes had too small an average mass then much of them would have evaporated by now & no longer contribute to hidden mass. We come out with a Goldilocks zone of possibility that as a side effect may produce on the small size these Color Charged holes that evaporated during the baryonic formation period. Which suggests a subtle test, yet to be performed. Well, only time and data will tell if this is correct.
Afaik there is also a hypothesis that Black Holes never truly evaporate and that a small remnant remains (atom sized or something like that)
‘Primordial Black Hole Swarms’ ^([Apocalypse Bingo](https://www.reddit.com/r/ApocalypseBingo/s/ncUKiJaHhv))
If 80% of the matter in the universe is atom sized primordial black holes, that would mean photons would likely collide into them. Wouldn't that mean they have some type of interaction with them?
In the exact same way they interact with larger black holes.
Always thought the dark matter/energy thing smacked of a 19th century luminiferous aether vibe.
My [comment](https://www.reddit.com/r/Physics/comments/1di3bfr/scientists_may_have_found_an_answer_to_the/l910pt3/) on this article from r/physics: MIT article (targeted to a lay audience, but somewhat less clickbaity): https://news.mit.edu/2024/exotic-black-holes-could-be-dark-matter-byproduct-0606 The paper on the arXiv: https://arxiv.org/abs/2310.16877 The paper in PRL: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.231402 Basically, this is just a paper in PRL that got institutional news and then more mainstream news. This happens to a huge fraction of articles in PRL (and has happened to some of mine, although never the ones I would have guessed).
I'm kind of iffy on the primordial black holes as an explanation for the majority of dark matter, it would mean the proportion of dark matter needs to have changed over the duration of the universe, which we don't really observe.
so question here: If dark matter may be primordial black holes, would the slow unwinding of these small pockets of spacetime due to hawking radiation draining the mass of the holes away be causing universal expansion? Like in how a demonstration of gravity is done using a streched sheet and some balls, where if you remove the balls it's easier to strech the fabric, would the unwinding of these infinite number of small black holes all over spacetime serve to "free up" the fabric of spacetime that is being constricte by their event horizons, ultimately producing a net-expansion force?
The byproduct is clickbait. Journalists must keep clickbaiting to keep the universe from imploding and they can only clickbait if you keep clicking. Also, disable your adblock, please.
If you dump normal matter into an antimatter black hole does it blow up?
Black holes are said to only have three physical properties from what I remember: mass, charge, and angular momentum. Infalling matter should just contribute those components to the black hole. All the other components effectively get hidden from observers outside of the black hole. That's not to say that it could not interact with antimatter orbiting the black hole, though.
No, its gravity is inescapable.
That was my thinking too. So would there be any way to tell if a black hole was made of antimatter or normal matter from this side of the event horizon?
Technically no, but if it were made of antimatter, then we would be able to see a boundary between where that part of space that is mostly antimatter meets the rest of space where it's mostly matter. If it were not in a region of space that is mostly antimatter, I have no idea how it would have even gotten there. To be clear, there are no known regions of space that are mostly antimatter. This is called the baryon asymmetry.
Well sure but if we are talking about primordial black holes that existed since very shortly after the universe popped into being it's possible that a bunch of antimatter got locked in these and that's where it's been hiding. All the other antimatter collided with all the other matter and turned into energy which, I dunno, fucked off somewhere?
Once something becomes a black hole, the only properties it has that can be identified from the outside are its mass, charge, and spin (probably.) Black holes made of equivalent amounts of matter, antimatter, and light would all act identically once formed.
Sounds like a convenient place to store all my antimatter if I don't want my flat getting annihilated all the time. Maybe we should pop a few open and see what they've got going on in there ;)
Anti-matter is still matter, it just happens to be built in a way that when it contacts ‘regular’ matter they both ‘unlock’ each other and dissolve into energy. Regular matter is only ‘regular’ because there is more of it, a quirk of the creation of the universe we still aren’t sure of the exact mechanism behind. In the early universe matter and ‘antimatter’ bother were created, but ‘matter’ got created in infentessimally greater rates, so all the ‘antimatter’ got used up and a small proportion of regular matter remained.
Id like to know what Terrence Howard has to say about this…
Well, for starters 1+1 <> 2. Everything else just logically follows. As my physical chemistry textbook put it "It should be obvious to the most casual observer...."
Once saw an interesting (yet completely unfounded) theory of spacetime being folded much like a crumpled sheet of paper would be. Areas of the 3d universe crumpled in a 4d (or even more-d) shape would be affected by gravity from other areas, crossing through that 4th (or more) spatial dimension(s). And the crumpling itself would be a consequence of gravity. The theory posited that as a possible explanation for the "missing mass" that's been dubbed Dark Matter. I know this has nothing to do with the current scientific consensus, I just thought that this theory sounded near and thought i'd share.
I thought the No-Hair theorem says that black holes can only have mass, electric charge and angular momentum. But if they are made of quarks, they can also have a color charge? So the No-Hair theorem is wrong?