Can someone explain how is it possible for black holes to even collide? Wasn't the usual expanation that time goes faster (for you, slower for outside observer) as you approach the black hole singularity and that it stops exactly as you "get there"? If this is true the black holes never actually collide. They just endlessly spin closer and closer. For the outside observer it taking infinite time before they actually "touch"?
Or do we just call it a collision if they simply get as close to each other as to be within the event horizon of the other?
If the former and we see these true collisions, how is it not a proof the age of the universe is infinite ? If we see events that are supposed to take infinitely long to occur?
Black holes' radius is linear in proportional to their mass, they are not constant density, larger ones are less dense. Therefore, when a 5 solar mass BH merges with another 5 solar mass, the radius doubles, surface area quadruples, and volume goes up 8x. If they "never actually merge", SMBHs would not exist.
An observer falling into the black hole would not observe any distortion in time. They would simply fall in, under the influence of gravity. From the perspective of a far-away observer it would look as if time is slowing down as the photons would take increasingly longer to escape. At the event horizon the photons would effectively be held in place. Eventually though, the last photon will have escaped and you will just observe a slightly larger black hole.
So the merger definitely happens from the point of view of the black holes. We might observe odd artifacts but they would eventually fade away.
They can merge event horizons on a finite timescale from the outside and still take an infinite amount of time to merge singularities or whatever it is that singularities do when they meet up in the privacy of an event horizon.
I don't get it. There are black holes that have millions of sun masses. The current theory is that these were formed by many consecutive mergers.
What then makes this 225 sun mass merger so large that it shouldn't exist?
Large mass stars are very, very few in number, and have short lifetimes, so collapse into black holes (if it happens), and then mergers are vanishingly small. 225 solar masses black holes are in the realms of unlikely if only had that information.
"Such a high mass may place it into a proposed category of stupendously large black holes (SLABs), black holes that may have been seeded by primordial black holes with masses that may reach 100 billion M or more, larger than the upper maximum limit for at least luminous accreting black holes hosted by disc galaxies of about 50 billion M[12]"
(which comes from a paper from one of my old lecturers).
If we accept that primordial black holes do indeed exist (the evidence against, is, I believe that they should be evaporating about now, but are as yet unobserved), there must therefore be a weight distribution of those, which means there are probably other 'solar mass' 'seeded' black holes lurking, that were never created by stellar collapse.
To make a stupendously large black hole, you only need a stupendously large amount of mass in the galactic core, no need for primordial black holes. Coincidentally Phoenix galaxy is stupendously heavy.
Just guessing, but maybe the common situation is that one ever growing black hole absorbes small ones? But that two of these large ones merging "should not happen"?
After digging around, the masses of these Black Holes are in the forbidden zone, where there shouldn't really be Black Holes of that size because of how they are formed.
They are usually either bigger or smaller depending on their origin. They could be second or third generation Black Holes, which would be unlikely due to the probability of them forming in close neighborhood. So what their reason for existing there are questions that should lead to some interesting answers if we ever get to the bottom of it.
Greg Egan's Diáspora starts with the merger of two neutron stars, and that causes a lot of trouble in this side of the galaxy, don't want to imagine what would it be with 2 massive blackholes for the nearby galaxies.
It wouldn't do anything special actually. A black hole from a distance does nothing a sun can't do.
Black holes only become destructive/powerful when you are very close to them.
To elaborate: A black hole is mass, a sun is mass. From a distance there's no difference. The only difference is up close - you can get a lot closer to a black hole dramatically increasing the gravitational force.
In a shrinking univers, they absolutely would. (But neither of these things would necessarily have already happened.)
In an expanding universe, some things will eventually so far away from black holes that they won't get "eaten". Also, they won't see them anymore, nor most of the rest of the universe.
That third option is, to our best knowledge, the one we live in.
An interesting implication is that, if intelligent life evolves several billion years from now in any given galaxy, it's galaxy might be so far away from its nearest neighbors that light from them will never reach it. That civilization's Hubble will never be able to test their crazy theory that "there could be more than one galaxy in the universe".
inconsequential for the most part, gravity doesn't interact directly with matter (which I understand, might be still quite counterintuitive to many).
I do wonder though if it would be possible for the "ripple" to deorbit us (or any other body).
It’s impressive how LIGO and Virgo keep pushing the limits of what we thought was possible. Each new event seems to open more questions than it answers.
225 solar masses… that's just wild. We keep building these models that tell us mergers like this shouldn't happen, and the universe keeps dunking on them
The models are constrained by what is known at the time they are built - those that clash with existing observations are discarded while those that don't, get published.
The article fails to explain why this event challenges our understanding of black holes. Did we expect such big masses to spiral for much longer or something? Why was this collision supposed to stay unstable?
There just isn't a way to make black holes that big from the collapse of stars when they go supernova.
So maybe both of these black holes formed from earlier mergers of smaller black holes. Or maybe there are other ways to make larger black holes we don't know about. They are in a range of mass we don't really expect to see theoretically.
The numbers in the article suggest a violation of conservation of mass:
> Today, the LIGO Collaboration announced the detection of the most colossal black hole merger known to date, the final product of which appears to be a gigantic black hole more than 225 times the mass of the Sun.
> GW231123, first observed on November 23, 2023, seems to be an unprecedented beast of a black hole merger. Two enormous black holes—137 and 103 times the mass of the Sun—managed to keep it together despite their immense combined mass
Is the explanation here "225 is a nice round number, and 240 is technically 'more than' that", or "a lot of mass evaporates into other forms of energy when black holes merge", or "during a merge, it becomes possible for matter to escape an event horizon", or what?
I suppose nothing but gravitational waves can escape the even horizon — or, rather, gravitational waves are born near / around it, because the black holes bend the space enormously.
OTOH whatever else may be outside the black holes near the merger and count towards their mass for astronomical purposes, such as accretion discs, should be much lighter weight than what's inside the event horizon.
Gravity does action at a distance. That's its thing.
The reason these waves are not generated from inside the black hole is that, to us, time stops there. For example these black hole mergers aren't actually merging, they are getting closer, and then they time dilate out of existence.
It would be difficult for two warships to collide without some of the material in one warship touching some of the material in the other one.
But there is no matter at an event horizon. That's just an imaginary line in space. It's opaque, but not solid.
If the black holes were moving fast enough, it should be possible for their event horizons to cross and then uncross, although that would immediately raise the question of what would happen to matter in the zone of overlap. Perhaps "fast enough" would exceed the speed of light?
All you really need to know for the moment is that the universe is a lot more complicated than you might think, even if you start from a position of thinking it’s pretty damn complicated in the first place.
Title needs an edit (maybe the clickbait algo): Astronomers Detect a Black Hole Merger That’s So Massive It Shouldn’t Exist - although, it's not a great title.
Our understanding of this universe constantly changes. We all know those - Earth is flat or it is center of universe, on and on.
The black hole is happening. So it exists. So either the observations are wrong or the undeying assumptions are wrong or math / physics we are using to make sense of the event is wrong.
Click-bait articles serve no purpose in advancing science.
Or do we just call it a collision if they simply get as close to each other as to be within the event horizon of the other?
If the former and we see these true collisions, how is it not a proof the age of the universe is infinite ? If we see events that are supposed to take infinitely long to occur?
So the merger definitely happens from the point of view of the black holes. We might observe odd artifacts but they would eventually fade away.
Photons travel at the speed of light always, that's what Einstein told us.
So rather, the observed energy (frequency) of the photons decreases, and it takes longer between each photon.
At least that's my understanding.
https://en.wikipedia.org/wiki/List_of_most_massive_stars
Then again, the universe is really big and to paraphrase Pratchett, million-to-one chances happen nine times out of ten.
https://en.wikipedia.org/wiki/Phoenix_Cluster#Supermassive_b...
"Such a high mass may place it into a proposed category of stupendously large black holes (SLABs), black holes that may have been seeded by primordial black holes with masses that may reach 100 billion M or more, larger than the upper maximum limit for at least luminous accreting black holes hosted by disc galaxies of about 50 billion M[12]"
(which comes from a paper from one of my old lecturers).
If we accept that primordial black holes do indeed exist (the evidence against, is, I believe that they should be evaporating about now, but are as yet unobserved), there must therefore be a weight distribution of those, which means there are probably other 'solar mass' 'seeded' black holes lurking, that were never created by stellar collapse.
After digging around, the masses of these Black Holes are in the forbidden zone, where there shouldn't really be Black Holes of that size because of how they are formed.
They are usually either bigger or smaller depending on their origin. They could be second or third generation Black Holes, which would be unlikely due to the probability of them forming in close neighborhood. So what their reason for existing there are questions that should lead to some interesting answers if we ever get to the bottom of it.
Black holes only become destructive/powerful when you are very close to them.
To elaborate: A black hole is mass, a sun is mass. From a distance there's no difference. The only difference is up close - you can get a lot closer to a black hole dramatically increasing the gravitational force.
But from a distance? Nothing special.
These jets can kill from a long distance.
In a shrinking univers, they absolutely would. (But neither of these things would necessarily have already happened.)
In an expanding universe, some things will eventually so far away from black holes that they won't get "eaten". Also, they won't see them anymore, nor most of the rest of the universe.
That third option is, to our best knowledge, the one we live in.
An interesting implication is that, if intelligent life evolves several billion years from now in any given galaxy, it's galaxy might be so far away from its nearest neighbors that light from them will never reach it. That civilization's Hubble will never be able to test their crazy theory that "there could be more than one galaxy in the universe".
So maybe both of these black holes formed from earlier mergers of smaller black holes. Or maybe there are other ways to make larger black holes we don't know about. They are in a range of mass we don't really expect to see theoretically.
The numbers in the article suggest a violation of conservation of mass:
> Today, the LIGO Collaboration announced the detection of the most colossal black hole merger known to date, the final product of which appears to be a gigantic black hole more than 225 times the mass of the Sun.
> GW231123, first observed on November 23, 2023, seems to be an unprecedented beast of a black hole merger. Two enormous black holes—137 and 103 times the mass of the Sun—managed to keep it together despite their immense combined mass
Is the explanation here "225 is a nice round number, and 240 is technically 'more than' that", or "a lot of mass evaporates into other forms of energy when black holes merge", or "during a merge, it becomes possible for matter to escape an event horizon", or what?
OTOH whatever else may be outside the black holes near the merger and count towards their mass for astronomical purposes, such as accretion discs, should be much lighter weight than what's inside the event horizon.
The waves are actually made just to the outside of the event horizon.
Was my understanding wrong all along?
How do we feel about this vis-a-vis action-at-a-distance?
The reason these waves are not generated from inside the black hole is that, to us, time stops there. For example these black hole mergers aren't actually merging, they are getting closer, and then they time dilate out of existence.
https://en.wikipedia.org/wiki/List_of_most_massive_stars lists only 2 stars more massive than that
https://www.popularmechanics.com/space/deep-space/a65038572/...
These aren't points; they are (literally) opaque volumes of space, and once their outer limits broach, they have collided.
By analogy, two warships can collide, even though their centers of mass don't.
But there is no matter at an event horizon. That's just an imaginary line in space. It's opaque, but not solid.
If the black holes were moving fast enough, it should be possible for their event horizons to cross and then uncross, although that would immediately raise the question of what would happen to matter in the zone of overlap. Perhaps "fast enough" would exceed the speed of light?
No, that is not possible.
... and give it a go: "Yo mama is so big she can't even collide with a black hole" (or something ...)
Black hole merger challenges our understanding of black hole formation
The black hole is happening. So it exists. So either the observations are wrong or the undeying assumptions are wrong or math / physics we are using to make sense of the event is wrong.
Click-bait articles serve no purpose in advancing science.