We May Finally Be Able To Test One of Stephen Hawking's Most Far-Out Ideas (livescience.com) 87
New submitter GFS666 shares a report from Live Science: We may soon be able to test one of Stephen Hawking's most controversial theories, new research suggests. In the 1970s, Hawking proposed that dark matter, the invisible substance that makes up most matter in the cosmos, may be made of black holes formed in the earliest moments of the Big Bang. Now, three astronomers have developed a theory that explains not only the existence of dark matter, but also the appearance of the largest black holes in the universe. "What I find personally super exciting about this idea is how it elegantly unifies the two really challenging problems that I work on -- that of probing the nature of dark matter and the formation and growth of black holes -- and resolves them in one fell swoop," study co-author Priyamvada Natarajan, an astrophysicist at Yale University, said in a statement. What's more, several new instruments -- including the James Webb Space Telescope that just launched -- could produce data needed to finally assess Hawking's famous notion.
In the latest research, Natarajan, Nico Cappelluti at the University of Miami and Gunther Hasinger at the European Space Agency took a deep dive into the theory of primordial black holes, exploring how they might explain the dark matter and possibly resolve other cosmological challenges. To pass current observational tests, primordial black holes have to be within a certain mass range. In the new work, the researchers assumed that the primordial black holes had a mass of around 1.4 times the mass of the sun. They constructed a model of the universe that replaced all the dark matter with these fairly light black holes, and then they looked for observational clues that could validate (or rule out) the model.
The team found that primordial black holes could play a major role in the universe by seeding the first stars, the first galaxies and the first supermassive black holes (SMBHs). Observations indicate that stars, galaxies and SMBHs appear very quickly in cosmological history, perhaps too quickly to be accounted for by the processes of formation and growth that we observe in the present-day universe. "Primordial black holes, if they do exist, could well be the seeds from which all supermassive black holes form, including the one at the center of the Milky Way," Natarajan said. And the theory is simple and doesn't require a zoo of new particles to explain dark matter. "Our study shows that without introducing new particles or new physics, we can solve mysteries of modern cosmology from the nature of dark matter itself to the origin of supermassive black holes," Cappelluti said in the statement. The model could be tested relatively soon, the report says. "The James Webb Space Telescope, which launched Christmas Day after years of delays, is specifically designed to answer questions about the origins of stars and galaxies. And the next generation of gravitational wave detectors, especially the Laser Interferometer Space Antenna (LISA), is poised to reveal much more about black holes, including primordial ones if they exist."
In the latest research, Natarajan, Nico Cappelluti at the University of Miami and Gunther Hasinger at the European Space Agency took a deep dive into the theory of primordial black holes, exploring how they might explain the dark matter and possibly resolve other cosmological challenges. To pass current observational tests, primordial black holes have to be within a certain mass range. In the new work, the researchers assumed that the primordial black holes had a mass of around 1.4 times the mass of the sun. They constructed a model of the universe that replaced all the dark matter with these fairly light black holes, and then they looked for observational clues that could validate (or rule out) the model.
The team found that primordial black holes could play a major role in the universe by seeding the first stars, the first galaxies and the first supermassive black holes (SMBHs). Observations indicate that stars, galaxies and SMBHs appear very quickly in cosmological history, perhaps too quickly to be accounted for by the processes of formation and growth that we observe in the present-day universe. "Primordial black holes, if they do exist, could well be the seeds from which all supermassive black holes form, including the one at the center of the Milky Way," Natarajan said. And the theory is simple and doesn't require a zoo of new particles to explain dark matter. "Our study shows that without introducing new particles or new physics, we can solve mysteries of modern cosmology from the nature of dark matter itself to the origin of supermassive black holes," Cappelluti said in the statement. The model could be tested relatively soon, the report says. "The James Webb Space Telescope, which launched Christmas Day after years of delays, is specifically designed to answer questions about the origins of stars and galaxies. And the next generation of gravitational wave detectors, especially the Laser Interferometer Space Antenna (LISA), is poised to reveal much more about black holes, including primordial ones if they exist."
Re: If God wanted you to know this (Score:5, Insightful)
God did record it. You've been reading the wrong scriptures.
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Perhaps not the wrong scriptures, perhaps just misinterpreting religious teaching as science.
Re: If God wanted you to know this (Score:4, Interesting)
Religion is a sort of proto-science, it just isn't physics. It bears about the same relation to ethics or morality as alchemy bears to chemistry.
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He did, but Moses and Aaron ran out of tablets and had to condense stuff.
Lensing (Score:5, Informative)
If dark matter were black holes of approximately 1-Sol mass, they would be more common than stars. If they were so common, we would frequently see gravitational lensing events as the BHs pass in front of stars. We don't.
The number of lensing events observed indicates that BHs are less than 1% of the matter in the Milky Way. And all of the BHs observed are 3.3-Sol or more, which is the minimum size for a BH created by the collapse of a star. Any smaller, and they would form a neutron star or white dwarf.
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This sounds like a reasonable argument but do you know any place that gives these calculations a bit more thoroughly. Isn't it possible the lensing is so miniscule we don't statistically acknowledge it because the distance of the observed bodies?
Likewise, a quick search for primordial black holes reveals they could be as small as 10 ounces. So it seems the suggestion is the conditions such blackholes form in might be different considering this would occur in one of the earliest stages of cosmology. Maybe ex
Re:Lensing (Score:5, Informative)
do you know any place that gives these calculations a bit more thoroughly.
No. I have seen the argument made but never seen the math. There are two ways of detecting black holes:
1. Lensing events
2. BH-BH collisions
Lensing events would increase linearly with the number of BHs.
Collisions would increase in proportion to the square of the number of BHs.
We have observed both lensing events and collisions, and both predict that BHs are less than 1% of our galaxy's mass and that there are no BHs smaller than 3.3 Sol.
they could be as small as 10 ounces.
No way, Jose. A BH of 10 ounces would have a lifetime of 2.2e-37 sec [vttoth.com]. That is less time than it takes for light to move the diameter of a proton.
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Assuming that a microscopic black hole behaves the same as a back hole with at least the mass of a star. That is far from a given.
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Assuming that a microscopic black hole behaves the same as a back hole with at least the mass of a star. That is far from a given.
If the laws of physics are obeyed, then it is a given.
If the laws of physics are violated, then dark matter can be explained by purple elephants spontaneously materializing in space.
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If the laws of physics are violated, then dark matter can be explained by purple elephants spontaneously materializing in space.
I think you mean spherical purple elephants
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SPEs materializing to follow the turtles all the way down.
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Frictionless spherical purple elephants, at that.
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Assuming that a microscopic black hole behaves the same as a back hole with at least the mass of a star. That is far from a given.
If the laws of physics are obeyed, then it is a given.
If the laws of physics are violated, then dark matter can be explained by purple elephants spontaneously materializing in space.
What laws of physics? You mean we have a coherent, empirically tested quantum gravity theory that I didn't hear about? Because that's what you need to model the behaviour of BH this small, including Hawking radiation.
And even for non-quantum-sized BH the Hawking radiation effect has never been empirically confirmed, and is not quite a completely settled piece of science.
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I don't know anything about astrophysics. But whenever I hear about one of these new theories that 'elegantly unifies' etc it always reminds me of a bunch of guys in a pub trying to stop their table from wobbling by putting bits of beer mat under different table legs.
That's exactly the opposite. A unifying theory removes all beer mats under the table and either levels the floor or makes the table hover. Unification means getting rid of all special cases and weird constants.
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You're missing the OP's point, which is that all of these unifying theories are just bodges/hacks to make the maths work.
Re: Lensing (Score:3)
I did a quick ddg search for "primordial black hole mass constraint" and there were plenty of articles. Wikipedia also cites many studies.
Here's a Nature article (2019) claiming the established range is 10^-14 to 10^-9 solar masses. They then present their new results which constrain the upper bound to 10^-11. I guess the math is in there if you take a look, or at least references. So, way less than 1.3 solar masses.
Re: Lensing (Score:2)
Of course I forgot the actual link...
https://www.nature.com/article... [nature.com]
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A 1.4 solar mass black hole (which could only arise from primordial blackholes, regular star collapse needs a much higher mass) would not be miniscule. Further with smaller blackholes (Of the tiny scales you suggest) are going to interact with light in funky ways due to the wavelengths. I suspect you'll see a lot of Rayleigh scattering type interference which should in theory be detectable in optical telescopes.
One of the problems of all of this is, we arent seeing *anything*, no chromatic aberations, no le
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The idea of Dark Matter is that it does not merge with itself, as it has no way to dissipate the energy by means of electromagnetic waves. Thus Dark Matter is thought to form a halo around galaxies and not collect
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Because of how primordial black holes form, couldn't there possibly be an equal number of antimatter black holes? I'm not sure if that would make any practical impact on the scenario, though.
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a black hole is defined by only two numbers: its mass and its angular momentum.
Pedantic nitpick: Three numbers. A BH can also have an electric charge.
Charged black hole [wikipedia.org]
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couldn't there possibly be an equal number of antimatter black holes?
No. Everything we know about physics says that antimatter has positive mass.
AFAWK, there is no difference between a BH formed from matter and a BH formed from antimatter.
What happens when anti-matter falls into a black hole? [stackexchange.com]
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Primordial BHs predate stars, though, so can't form from them. They're from the inflationary phase rather than the stellar phase.
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ShanghaiBill opined:
If dark matter were black holes of approximately 1-Sol mass, they would be more common than stars. If they were so common, we would frequently see gravitational lensing events as the BHs pass in front of stars. We don't.
Well ... maybe.
Individual black holes are essentially point sources. It's their event horizons that produce the lensing effect. If dark matter exclusively consists of black holes of approximately 1 solar mass, your observation would perhaps point to a fatal flaw in the model under discussion. However, the thing about dark matter haloes around galaxies is that they appear to be mostly concentrated outside the visible part of those galaxies, in a ring much greater in diameter than the visi
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Are you sure that black hole evaporation is ever complete? My hand-wavy model says that when they get below a certain mass they'll stop being able to capture virtual particles, and so stop losing mass. If you know that this is wrong, I'd appreciate a link, as *I* sure can't do that kind of math.
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BTW - the reason I asked the question in the first place is because, prior to First Light , our universe was an insanely crowded place. Given that hyper-concentration of mass, it would be astonishing if anything less than a metric buttload of black holes was created during that era - and, in fact, it seems to me almost incredible that anything except black holes survived ...
I'm wondering if this also could be a solution for the matter antimatter difference, perhaps antimatter isn't as repulsive to itself as matter, so forms black holes a little easier. They would be so small that the likelihood of matter interacting with it would be small, and would therefore be unlikely to annihilate. It isn't like we have created enough antimatter to even study it well.
IANAP, so this is more wild guess than scientific conjecture, but that one as always bothered me as well, why is the unive
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There are probably dozens of types of galaxies, and Spiral is only one of them.
The hint that we have a "dark matter problem" is because the galaxies rotate too fast. Hence: the matter is inside of the galaxies and not spread out as a halo around them - well, probably both.
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angel'o'sphere lectured:
There are probably dozens of types of galaxies, and Spiral is only one of them.
I'm well aware of that, of course. However, as I mentioned in passing, most of the other types are clearly products of galactic mergers or near-misses warping what would otherwise be spiral galaxies out of shape. Globular ones are a special case that may be galaxies that are just forming, and that haven't shrunk far enough yet to start spinning out into spirals, or they may be galaxies that are too poor in "dark matter" to be able to rotate without flying apart. Or ... ?
The hint that we have a "dark matter problem" is because the galaxies rotate too fast. Hence: the matter is inside of the galaxies and not spread out as a halo around them - well, probably both.
That's one hi
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However, as I mentioned in passing, most of the other types are clearly products of galactic mergers or near-misses warping what would otherwise be spiral galaxies out of shape.
Yes you said that. And it is simply wrong.
There are dozens of galaxy types that emerge by itself. And those who emerged by mergers: usually have no type. They are just a bunch of stars not really knowing where to go and what shape to form.
Sorry, read a book a bout it.
But thank you for your lecture.
there are areas of gravity concentra
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FWIW, I postulate that the primordial black holes were formed at an even earlier period, and that they typically mass less than a typical asteroid.
OTOH, to make this work I've got to also postulate that there is a minimal size to a black hole, below which it is no longer able to capture virtual particles, so it stops emitting Hawking radiation. I know of no evidence against this, and not even any detailed theories...and *I* sure can't work out the math. But it makes sense in a hand-wavy kind of way. And
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But virtual particles pop up pretty much everywhere? Why would an extremely light mass black hole not exhibit hawking Radiation? That seems like a very big claim based on what exactly? Gravity is gravity.
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Because it's capture cross-section would be too small for any existing wave-form to enter. You can't eat a bite larger than your jaw spread.
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Individually, no. But we're talking about a helluva lot of low mass black holes in almost every galactic halo, including our own, so that raises the odds that the kinds of low mass black holes they're talking about ought to have some sort of a lensing event, not to mention collisions, which would, one thinks, give off gamma ray bursts, and would suggest if they are that common that their mass equals the dark matter needed, we should be spotting gamma ray bursts.
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The size range I'm thinking of would be too small to capture even a gamma wave. I'm not exactly thinking a mass of around a proton, but not too far from that. It would have needed to be created during the big bang, because any later time wouldn't be dense enough for fluctuations in mass to produce a black hole this small (though it could have started a bit larger and then evaporated as the environment became less dense).
Yes. you would need a tremendous number of them, but their gravitational fields as ind
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Do you actually understand why black holes evaporate. Regardless of size why would a very small black hole not grab one member of a virtual particle pair. You're making a claim with no justification that I can see
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IIUC, black holes evaporate because they repeatedly swallow half of a pair of virtual particle, each time losing the energy required to make the other half non-virtual. But this means they've got to have a capture cross-section large enough to capture the virtual particle. As they get smaller, the energy of the particles that they can swallow gets higher. This is described as an increase in the temperature, as the particles that get emitted get higher in energy state. But if this is true, then when they
Black matter = black holes (Score:2)
Already being tested (Score:4, Informative)
Re:black holes, unicorns, and other myths. (Score:5, Informative)
Black holes are theoretical people.
Hawking radiation is theoretical. Black holes are real. They have been observed.
GW150914 [wikipedia.org]
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The theory of Hawking radiation is compelling, and it does explain why the universe after the Big Bang is not frothing with micro black holes.
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Notably, it introduces the Blackhole Information Paradox, and also that it mixes two very much incompatible theories together to get its result.
The consequence is that the deduction relies on QM-invalid particles with sub-planck-length wavelengths. Sure, it's a mathematical artifact (You can't apply a quantized formula cleanly to a non-quantized spacetime curvature metric) but that's just more about it that
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Welll .. no. Signals that are generally interpreted as being emitted by black holes are real. It's possible that some other theory would explain the same evidence. And evidence is generally interpreted as showing that Hawking radiation happens is real.
Once you get away from directly sensed evicence you get away from the standard meaning of real, and even directly sensed evidence can be mistaken. See any stage magician, and most psychologists.
Even believing in the floor under your feet is a gamble. "Rea
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There are too many observations now that mean the idea that black holes don't exist is complete nonsense.
Now the idea that they have infinite density well I don't think any serious physicist/astronomer believes that for a moment. So while existing theories tend to an infinite density, the working assumption is there is some unknown state of matter of exceedingly high density that we have no theory for at this time. The observations for black holes we have don't actually require a singularity, putting the ma
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Quantum loop gravity avoids singularities entirely. String theory should, as nothing can be smaller than a string. Granular space again would.
Singularities assume smooth, continuous space and infinitely small particles. We can't have the former if QM is correct, and none of the candidates for quantum gravity permit infinitesimal particles.
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Singularities do assume smooth, continuous space, but there's also zero observational evidence that space isn't smooth and continuous.
Worse, there is observational evidence that if space is granular, it's granular at far below the planck scale.
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If space is smooth and continuous, then QM emerges from GR. Which is possible, there are models for it. However, there's no experimental evidence for that, either.
But there are only three options:
GR emerges from QM. Discrete spacetime.
QM emerges from GR. Continuous spacetime.
The universe is a badly written simulation where these were developed independently from an incomplete spec and aren't unifiable
There really aren't any other options. And of these three, the third is arguably the least likely.
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Einstein himself didn't like the idea of a singularity, but he also didn't like the idea of a non-static universe. The Singularity Theorums showed that they were unavoidable, and indeed- the beginning of the universe, so either GR is wrong, or they exist.
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But there is evidence that space is continuous- or more accurately, that its granularity is smaller than a planck length, which is a significant problem for theories of quantum gravity.
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The observations for black holes we have don't actually require a singularity, putting the mass of Sol in the volume of a proton would do just fine. Come up with an accepted theory to explain how to do that and a Nobel prize is all yours.
This is incorrect, as of the EHT observations.
Until you've got a theory of quantum gravity, you're using General Relativity, and as pointed out in the Singularity Theorums, you cannot have an event horizon without a singularity (according to General Relativity)
Therefor, if you put any amount of mass in any volume that results in an event horizon, you have a singularity.
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We don't need singularities in BHs. You're way out of date. QLG has been around a while. Even string theory makes a singularity impossible as nothing can be smaller than a string.
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We don't need singularities in BHs. You're way out of date. QLG has been around a while. Even string theory makes a singularity impossible as nothing can be smaller than a string.
Neither LQG or M-Theory can reproduce the predictions of General Relativity, so as it stands, for now, yes, we still need singularities.
We can start talking about a functioning theory of quantum gravity when one of them can reproduce GR in the classical limit.
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That the models as they stand are incomplete is inarguable. That they have not developed into a complete solution yet does not, however, mean we require singularities, just as quarks existed long before anyone realised that atoms were made of stuff. What it means is that we don't know precisely what the said stuff is, or how to represent it. We do know, however, that it's there.
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That they have not developed into a complete solution yet does not, however, mean we require singularities, just as quarks existed long before anyone realised that atoms were made of stuff.
How do you figure.
LQG and M-Theory are wrong, as they stand now.
With some work, one of them may end up not being so, but until they can reproduce GR, they certainly cannot be used to determine what's at the middle of a black hole.
Ergo, all science for black holes need the singularity- because there is no theory that currently exists and matches observations that describes the universe to any sort of accuracy that doesn't have them.
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Perhaps you should read up again what a Singularity is.
A singularity is a space/region inside our physics or math breaks down.
That is all.
It is bottom line nothing special and we do not know what actually a Singularity might be.
Beyond the Event Horizon of a big black hole comes - vacuum - a very damn big sphere of vacuum.
What we do not know is: is there something special in the center of the black hole which we can not describe yet? My bet is: it is just a gigantic neutron star.
In other words: no one "needs
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Perhaps you should read up again what a Singularity is. A singularity is a space/region inside our physics or math breaks down. That is all.
You are incorrect.
In General Relativity, what we call a "singularity" (popularized from the Penrose-Hawking theorums) is merely an area where spacetime ends. Where geodesics are incomplete.
We assume our math breaks down, because we don't like the fact that the Schwarzchild metric includes a division by zero.
It is bottom line nothing special and we do not know what actually a Singularity might be.
This is a silly way to look at it.
A better way to formulate that is, we don't know if General Relativity is correct, even though it is the most correct theory we've ever created.
According to GR, the
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You are incorrect.
In General Relativity, what we call a "singularity" (popularized from the Penrose-Hawking theorums) is merely an area where spacetime ends. Where geodesics are incomplete.
We assume our math breaks down, because we don't like the fact that the Schwarzchild metric includes a division by zero.
That is exactly what I said:
Perhaps you should read up again what a Singularity is. A singularity is a space/region inside our physics or math breaks down. That is all.
How we can both say the same thing
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Perhaps you should read up again what a Singularity is. A singularity is a space/region inside our physics or math breaks down. That is all.
You can say this until you're blue in the face, it doesn't make you more right.
I have already explained what a singularity is. It is a geometric area where geodesics are incomplete. It is a region where spacetime ends.
Whether or not this is a break down of physics or math, is a matter of interpretation and opinion. What you say is a matter of definitive truth, I point out (again) that it is not.
How we can both say the same thing and you claim my wording is "incorrect" is beyond me.
Your grasp of nuanced English truly is fucking terrible.
The Schwarzchild Radius can be computed as follows: I know how it is computed.
Perhaps you should check up how to calculate the "density" - as in matter density - of a black hole.
A big black hole has behind the Schwarzschild radius: mostly vacuum. You can travel there around as long as you can keep the speed up not to fall down into the center: what ever there is. Obviously you get ripped apart long before that.
This is another consequence of your poor English compreh
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You can say this until you're blue in the face, it doesn't make you more right.
Obviously it is, as you confirm here:
Yes, it does.
It is a point where geodesics are incomplete.
That means, it is literally a point where spacetime ends, as a geodesic will move infinitely as long as there is spacetime.
So no idea why you want to argue about stuff you barely grasp.
You are way out of your league here. You have made it clear in the past that you don't even have a secondary school physics education.
As I studied physi
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My next step is to simply link to all the stupid physics claims you've made in the past.
Hell, you literally said earlier that you think some form of matter made of neutrons- non-elementary particles- exists within a black hole.
That's precluded by quantum mechanics as much as General Relativity. The argument is what happens at a singularity. Stable non-elementary particles become impossible long before then.
You literally argued with me once about whether or not gravity was a force, or th
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Hell, you literally said earlier that you think some form of matter made of neutrons- non-elementary particles- exists within a black hole.
That was not a claim.
That was a speculation.
So no idea what your bollocks rants are about.
If you can not discuss physics like a normal person, then don't do it.
The idea that a singularity is non-physical, or is unknown as predicted by theory as a fact is one borne only of amateurs, or physicists talking to amateurs.
No idea what you want to talk about. The singularity is
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That was not a claim.
That was a speculation.
I didn't say it was a claim. I said you said it.
The implication was that your speculation was fucking ignorant.
The musings of someone with no knowledge on the topic.
So no idea what your bollocks rants are about.
My rant is about some dipshit with a grade school understanding trying to correct people who are discussing advanced topics.
If you can not discuss physics like a normal person, then don't do it.
If you don't know anything about a topic, then shut your fucking mouth about it.
The real question is, do you have some kind of personality deficit that compels you to try to chime in on things you know nothing about, or
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I didn't say it was a claim. I said you said it.
The implication was that your speculation was fucking ignorant.
The musings of someone with no knowledge on the topic.
You said claim. That is why I reacted to it.
And I muse about what ever I want regardless of my knowledge.
That is the damn point of musing.
the Universe arose from a literal singularity.
Nevertheless that singularity is just a mental construct. And not a physical one.
Sorry: absolutely no idea about what you want to nitpick.
No- as a mathematical so
How big is a Primordial Black Hole? (Score:2)
Gotta luv the inet - a calculator:
https://www.vttoth.com/CMS/phy... [vttoth.com]
Without actually checking what people theorize such a mass would be...
10000 metric tonnes gives a life time of 775.196 minutes.
We are some 13.8 billion years later now and all these primordials are still here? They must be well big!
Consequently, either Hawking Radiation is not a thing or this "swarm" of primordials is not a thing lest they were big.
The above 775.186min though does
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Primordial black holes aren't collapsed stars and may be too small to accrue much matter. If I understand correctly, they're created by inflationary effects. If that's the case, they'd really be a distinct class of objects rather than conventional black holes and may have different Hawking radiation properties.
They're 10^-19 solar masses, which is really, really small.
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If I understand correctly, they're created by inflationary effects. If that's the case, they'd really be a distinct class of objects rather than conventional black holes and may have different Hawking radiation properties.
No-Hair Theorum. No matter the size, a black hole is a black hole.
Hawking Radiation describes what happens to a black hole all the way down to the planck length- so includes these, and much, much smaller (which they'd have to be in order to evaporate away)
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Could there be, or,what if there were black holes the size of the known universe?
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I would not be surprised if our universe is just a black hole inside of a bigger universe, and all we see is the inside of it.
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Hawking Radiation isn't an effect of capturing matter, it's virtual particle-antiparticle pairs forming, one member of the pair being captured and the other escaping, and thus the black hole radiates, leading to its evaporation. According to Wikipedia, at least, micro black holes would in fact be extremely hot, and thus would evaporate quickly.
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1 solar mass is not 10,000 metric tones :D
From the nice link you gave: Indeed, any black hole with a mass greater than about 0.75% of the Earth's mass is colder than the cosmic background, and thus its mass increases for now.
Hawking's idea was right about at least one thing (Score:2)
Testable (Score:2)
It's nice to see that the idea is testable. Without this characteristic, it's just an idea.
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Well, it's not really testable. Only a specialized version that assumes black holes have a certain minimal mass is testable. (And I think that postulate is probably incorrect.)
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The idea of small mass (down to the presumed micro black holes formed shortly after the Big Bang) has been tested, since if there were sufficient numbers of low mass black holes in galactic halos to the sufficient quantity to explain the gravitational anomalies should lead to a numerous gravitational lensing events. Whatever dark matter is, it does not appear to alter the paths of photons in any significant way, which suggests that the individual particles of dark matter are themselves very low mass and do
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There is no demonstrated concept of "dark matter" at all, we have not found any observational evidence to date that such a thing exists. Dark matter is simply a word we give to the gap between what the calculations tell us we should see, and what we actually see. A possibility we must consider is that the underlying calculations are incorrect, and that we've missed something fundamental.
Any theory of why the discrepancy exists must be tested to be proven. Otherwise, it's merely a conjecture.
The real background (Score:2)
All of our theories about primordial black holes and formation of early stars/galaxies have been very rudely upended in the past couple years (not to mention many other astronomical models).
We're seeing monster black holes, for instance, at a time when they shouldn't have existed, and stars and galaxies forming much faster/earlier than predicted.
Also of note, white dwarfs behave differently than we assumed, able to burn for longer IIRC than ever thought possible. Since white dwarfs have been used as a scal