View Full Version : What would happen if two gravitational singularities meet
Mechapixel
07-10-09, 06:04 PM
If two black holes are in a reasonable distance from eachover in spae and exert the same force and energy, what would happen? I think maybe these two unstopable force can either collapse on eachover or cancel their effects out.
If two black holes are in a reasonable distance from eachover in spae and exert the same force and energy, what would happen? I think maybe these two unstopable force can either collapse on eachover or cancel their effects out.
Why would they "cancel out"?
What do you mean by "collapse"?
What's a "reasonable distance"?
If they're in each other's gravitational influence (and there's nothing else acting on them) then they'll move toward each other and merge.
mathman
07-10-09, 08:54 PM
Two black holes meeting would end up as one bigger black hole.
They wouldn't just get fresh with each other and have baby black holes then? :D
They might push each other as if they were magnets. So they can sail through the vacuum space without hitting each other.
The OP did state "black holes".
Black holes aren't (and can't be) magnets, they only have mass, charge and angular momentum.
I did not say they are magnets, I said "as if they were" magnets. You say they have mass, and charge, so what is the charge? Positive or Negative? If not, it is a gravitational charge and it must be pulling. But what do we really know about black holes, not so many things. We can just speculate anything and I speculate that they push each other.
I did not say they are magnets, I said "as if they were" magnets. You say they have mass, and charge, so what is the charge? Positive or Negative? If not, it is a gravitational charge and it must be pulling. But what do we really know about black holes, not so many things. We can just speculate anything and I speculate that they push each other.
Electrical charge.
Gravitational charge? :confused:
Nope, you can't "speculate anything", any speculation must be consistent with known physics and observations.
A reasonable start:
http://en.wikipedia.org/wiki/Black_hole
Your Wikipedia says this:
"In general relativity, a black hole is a region of space in which the gravitational field is so powerful that nothing, including light, can escape its pull."
This is another passage from your Wikipedia:
"The gravitational and electric fields of the black hole give very little information about what went in."
But it does not say anything about what two black holes behaves to each other. I think you should read it again...
But it does not say anything about what two black holes behaves to each other. I think you should read it again...
I didn't read it at all.
I gave YOU that link as a starter.
Look for "properties": you should find mass, charge and angular momentum (spin) listed as the ONLY properties a black hole may possess.
Since they both have mass (extremely so), and therefore a large gravitational pull (which works in only one direction - towards the centre), then there is no possibility of them repelling each other.
There is no other way that they can behave.
I hope you are not joking. Because under "properties" you can read this:
"For example, a charged black hole repels other like charges just like any other charged object, despite the fact that photons, the particles responsible for electric and magnetic forces, cannot escape from the interior region..."
I recommend you to google "Black Hole Repulsion", you'll be amazed...
I hope you are not joking. Because under "properties" you can read this:
"For example, a charged black hole repels other like charges just like any other charged object, despite the fact that photons, the particles responsible for electric and magnetic forces, cannot escape from the interior region..."
Correct.
Now think about the strength of that charge compared to the strength of the gravities involved...
I recommend you to google "Black Hole Repulsion", you'll be amazed...
I recommend you actually delve slightly further than simply looking at the titles that Google gives you.
For example, the first one listed (and many of the other links end up at the same place) gives a link to this (http://arxiv.org/PS_cache/gr-qc/pdf/0207/0207090v1.pdf) paper, which discusses the possible repulsive forces caused by interaction of the spins of the black hole. But nowhere in that paper does it state (or even suggest) that such force is capable of keeping the black holes apart, if indeed it exists. To quote from the paper:
This suggests that there may be a spin-spin force between the black holes that is attractive if the angular momentum have opposite directions and repulsive if they have the same direction. Presumably, in the second case the system expends energy in doing work against the spin repulsive force, and for this reason this energy is not available to be radiated via gravitational radiation.
Hawking’s argument only suggests that the spin interaction energy between black holes has in fact this sign dependence with respect to the spins. It is not a proof My italics, note them well.
Suggests, may be, if, not a proof...
Prove that your suggestion has a solid evidence other than some computer simulations depending on predictions derived from some mathematical possibilities. You are speculating, and I am speculating on what would happen. My difference is that I accept that I am speculating....
Prove that your suggestion has a solid evidence other than some computer simulations depending on predictions derived from some mathematical possibilities. You are speculating, and I am speculating on what would happen. My difference is that I accept that I am speculating....
Wrong again: "my suggestion"* is the result of physics and known properties.
Your suggestion is mere speculation based on... what?
If you want actual proof then you'll have to start by learning physics properly...
* It's not "mine" - the figures date back decades are are confirmed more every time we learn more about reality by more physicists and astrophysicists.
It's not a "suggestion", it's a prediction (in the scientific sense): based on known properties and behaviours.
You can not be scientific or "know your physics properly" if you can not show me an evidence, a source or anything this kind. You are just labelling your claims with words. I still see no concrete evidence.
You can not be scientific or "know your physics properly" if you can not show me an evidence, a source or anything this kind. You are just labelling your claims with words. I still see no concrete evidence.
I said that YOU should learn the physics: how much do you know to follow the reasoning?
How much of the paper I referenced can you follow?
It's not a question of what I know, it's a question of how much of what I tell you will you understand?
Start with Wheeler and work up... :rolleyes:
OK, this is my advice to you: You keep your "impossible to follow" reasoning to yourself. Don't give me a name of a particular experiment, just stuck to your "reasonings". I don't want to understand them, I saw enough evidence to believe that not all sophisticated reasonings do always work along with what is really going on. This is the process:
1- You start with a speculation (black holes merge each other)
2- You throw Wikipedia as a starting source for the topic
3- When I show the gravitational and electric charge issue, you refuse to read it, and say it proudly.
4- You refuse to look at other claims on internet without any reason.
5- You reject to give any reference or evidence with an excuse that your opponent would not understand it.
I think you either didn't actually understand what you are talking about or you are arguing for the sake of arguing; In each case I wish you good luck...
Betrayer0fHope
07-11-09, 07:17 AM
Your Wikipedia says this:
"In general relativity, a black hole is a region of space in which the gravitational field is so powerful that nothing, including light, can escape its pull."
This is another passage from your Wikipedia:
"The gravitational and electric fields of the black hole give very little information about what went in."
But it does not say anything about what two black holes behaves to each other. I think you should read it again...
Gravity only attracts. That's why black holes don't push each other away. :\
OK, this is my advice to you: You keep your "impossible to follow" reasoning to yourself. Don't give me a name of a particular experiment, just stuck to your "reasonings". I don't want to understand them, I saw enough evidence to believe that not all sophisticated reasonings do always work along with what is really going on. This is the process:
1- You start with a speculation (black holes merge each other)
2- You throw Wikipedia as a starting source for the topic
3- When I show the gravitational and electric charge issue, you refuse to read it, and say it proudly.
4- You refuse to look at other claims on internet without any reason.
5- You reject to give any reference or evidence with an excuse that your opponent would not understand it.
I think you either didn't actually understand what you are talking about or you are arguing for the sake of arguing; In each case I wish you good luck...
I'm not sure about 1, although that is intuitive.
2, because you're arguing against the current consensus, you must be misinformed because you have not shown that the consensus is wrong. So, you should read a wiki link.
3 Yeah I didn't read anything you wrote so I can't really help with this one.
4. Because they're on the internet. If the entire scientific community backs one idea, I'd assume that the internet doesn't hold the secret that black holes repel each other.
5. I didn't really read Oli's posts either, but come on dude, at least show logically why black holes would repel. Just because you've never heard of the evidence or proof doesn't mean it doesn't exist and need to be reproved by someone else.
If two black holes are in a reasonable distance from eachover in spae and exert the same force and energy, what would happen? I think maybe these two unstopable force can either collapse on eachover or cancel their effects out.
Yeah I don't really think so. To any of those. Actually I'm not sure what you mean by collapse (since it IS a supposed gravitational singularity, and I have no idea what that collapsing would mean). Why would they cancel out? If an object was in between them, it wouldn't be stationary. half would go to one and half of the object would be pulled to the other. I'd assume they'd crash and do what Oli said.
OK, this is my advice to you: You keep your "impossible to follow" reasoning to yourself.
Ah I see. You'd rather "speculate" groundlessly than learn science.
This is the process:
1- You start with a speculation (black holes merge each other)
As explained, this wasn't a speculation, it's based on reality.
2- You throw Wikipedia as a starting source for the topic
I didn't start with Wiki, I started with an education in physics: I offered Wiki as a starting point for YOU.
3- When I show the gravitational and electric charge issue, you refuse to read it, and say it proudly.
On the contrary, I answered that point in post #12. the sentence directly after the word "correct".
4- You refuse to look at other claims on internet without any reason.
Again, on the contrary, I not only looked at the offered "refutations" I read them, which is more than you seem to have done. Then I quoted one of them: showing that they didn't say what you "speculated" they said.
5- You reject to give any reference or evidence with an excuse that your opponent would not understand it.
Again, on the contrary, I ASKED what your knowledge of physics was. If I don't know how much you know then I can't tailor the explanation... :rolleyes:
I think you either didn't actually understand what you are talking about or you are arguing for the sake of arguing; In each case I wish you good luck...
Completely wrong on both counts, but I wish you well in your continuing wilful ignorance.
I recommend you to google "Black Hole Repulsion", you'll be amazed...
Given the language used in the original post, I seriously doubt you have the background to comprehend many results from this search.
Perhaps you should google "black hole merger".
Some other good search ideas, just to name a few:
NGC 6240
3C 75
Arp 220
NGC 4038/NGC 4039
Given the language used in the original post, I seriously doubt you have the background to comprehend many results from this search.
Perhaps you should google "black hole merger".
Some other good search ideas, just to name a few:
NGC 6240
3C 75
Arp 220
NGC 4038/NGC 4039
There are some lessons to learn from NGC 6240: Two black holes "push each other" for several millions of years and being nurseries for stars. And of course this will eventually merge into something new, if there is nothing, there is entropy principle. OK, but this does not require to reject the fact that these two black holes have been applying some physics and some forces to rotate around each other for hundreds of millions of years. They don't suddenly come accross and become one in the blink of an eye: It takes considerable amount of time. Those forces and relations do not care about the limits of our understanding about them. They reject to apply homemade gravity to vacuum each other; no, they use time and space differently.
What can I say for 3C 75: "Two supermassive black holes, once the centers of the progenitor galaxies, in a distance of 25 000 light-years now orbit each other." I stole this sentence from an astronomy site...
In the very beginning of my speculation, I said that maybe they are pushing each other. I said maybe a magnet like pushing. I never claimed anything about the spacetime geometry of this force, yet it works for long time.
Perhaps you should google "Black Hole Merger"...
eburacum45
07-12-09, 06:04 AM
When two black holes encounter each other, they will do one of three things;
1/ they may encounter each other head on, in which case they will simply merge, and most of their mass-energy wil be aborbed into a single black hole with almost the same mass as both holes combined. But head-on encounters would be rare.
2/ The two holes could swing past each other on hyperbolic curves, interacting somewhat but essentially remaining the same. If they lose any energy during the encounter they will be slightly smaller than before, but otherwise they will just carry on travelling through space, albeit on a slightly different path.
3/ The two holes could go into orbit around each other.
To go into orbit around each other the two holes need to lose some of their forward velocity; some mechanisms for this are discussed here
http://www.space.com/scienceastronomy/merging_backhole_021119.html
for two galactic black holes approaching each other (each with a halo of ordinary stars in orbit around it)
"Individual stars which approach the binary black hole closely are accelerated and finally ejected from the center of the galaxy," she said. "The energy is extracted from the orbital energy of the black hole binary."
The mechanism is the same slingshot effect NASA uses to sent spacecraft around a planet, robbing a tiny bit of the planet's energy to give the craft a speed boost and fling it a more distant planet.
Stellar mass black holes could do the same trick by transferring momentum to their accertion disks, if any.
Once the two holes are in orbit around each other they will lose energy by gravity radiation, and eventually get so close that their event horizons and/or ergospheres combine. They will continually lose energy via gravitational waves up to this point; and during the subsequent merger the two holes will lose more energy in this way. The end result of such a merger would be a single black hole, considerably smaller in mass than the combined masses of the two original holes. Remember that as seen from outside the event horizon, there is no difference between the energy and mass content of the hole(s), so any energy they lose in the process results in a drop in total mass.
There are some lessons to learn from NGC 6240: Two black holes "push each other"
No they don't.
Being in orbit has nothing to do with a "push", the forces are still attractive.
Perhaps you should google "Black Hole Merger"...
Perhaps you should learn some physics.
No they don't.
Being in orbit has nothing to do with a "push", the forces are still attractive.
...
Perhaps you should learn some physics.
For gravitational bodies:
Each gravity subject (That could be moon, planet, star, galaxies or black holes) in space has its own unique body, mass, totality, sum of energy, characteristic, position, movement. We can call sun’s gravity and earth’s gravity. We also know that they obey bigger gravitational body, Milky Way.
Each black hole must have a mass to occupy a place in the space. Their mass creates a collapsing horizon where even light can not escape from it. But they have limits and individual characteristics like any other space object. When they meet other masses, they interact according to their position and the position of other object’s speed, velocity, direction, mass and dynamics (whether it is a cold planet or burning star, or the centre of a galaxy). A dance starts for millions and billions of years. Each entity has its own internal mechanism. Sun will explode before the Milky Way and earth has nothing to do with it, because earth has its own gravity to deal with. Each and every dance has some characteristics because each partner brings different things to the action. If you are interested in what we do not know about gravitational waves, you can always visit Nasa. (“Dynamics of Super Massive Black Holes”http://lisa6.gsfc.nasa.gov/conf/lisa6/presentations/Tue_0940_Sigurdsson.pdf)
You are assuming that any twin entity (twin planets, twin stars, twin galaxies) will necessarily collapse to each other. Wrong. If they are not close enough they can be “separated” from each other, too. Each entity has its own mass and gravitational collapse, because it has its “separate” concentration in existence. This is why we call temporal situations as “this planet”, “that black hole”. If you accept that earth is falling down into sun’s gravity while moon is moving away from earth, you must accept that the role of the gravity depends on what is exercising it, and what is the relation to other entity.
Perhaps you should develop something that I really don't know what it is.
Perhaps you should go away for longer and learn something instead of simply cutting and pasting stuff that has no relevance.
This is my very first post in this thread:
If they're in each other's gravitational influence (and there's nothing else acting on them) then they'll move toward each other and merge.
Note the words "nothing else" - i.e. assuming they're not subject to any other forces: which would include tangential motion.
Also look at the wording of the OP: there is no suggestion that there's any forces or motion to be considered OTHER than those from the black holes themselves.
Or, to use your wording "If they are not close enough they can be “separated” from each other, too" which is correct, BUT that separation will only remain IF there is no other force/ motion/ condition to take into account. In the case of the Earth orbiting the Sun it's the Earth's speed AROUND the Sun that stops it being dragged in: remove that speed and the Earth is a cinder, remove gravity and the Earth disappears into the big dark bits...
Perhaps you should develop something that I really don't know what it is.
Perhaps you should resolve to REALLY know what you're talking about, because so far all you've done is demonstrate repeatedly that you don't know anything about this.
Perhaps you should resolve to REALLY know what you're talking about, because so far all you've done is demonstrate repeatedly that you don't know anything about this.
"If two black holes are in a reasonable distance from eachover in spae and exert the same force and energy, what would happen? I think maybe these two unstopable force can either collapse on eachover or cancel their effects out."
This is what OP asks for: “in a reasonable distance” from each other. And “same force and energy”, no one is including anything else, and you do not need to create hypothetical conversation like anyone introduced any extra force into the discussion; no, there is no such a thing. I gave you the examples of moon and earth just for the sake of giving an example to cosmologic diversity of the universe, not to include any other force into the equation. In this discussion, there is no other force, there are two black holes and nothing else. And the title of original post asks: “What would happen if two gravitational singularities meet?” In order to eliminate the possible confusion, it also states that “same force and energy”. Although it is utterly tough task to find such “equal” forces in real universe, we should accept this hypothetical situation for the sake of this discussion.
However, there is still no guarantee that two black holes would necessarily collapse, because we do not know what this “reasonable distance” is, depending upon their sizes and temporary positional agreement. We can deduce a mathematical formula which says “if these two have X amount of gravitational energy and they have Y distance between them, so merger will happen”. This is undeniable, and there are astrologic evidences that this math works in reality. But this is not the answer for the OP, because it asks for general possibilities in reality, where many different things happen, and each one can also be explained by matching mathematics. If two black holes meet at certain distance, which is not enough for a merge, they would not merge, simple as that. Without this “distance” concept, neither time and space, nor your physics make any sense.
Your claim “If they're in each other's gravitational influence (and there's nothing else acting on them) then they'll move toward each other and merge.” is a wrong assumption. Because they can also form twin galaxies at certain distance, which may be enough for twin formation (and not going for their own separate directions), but not enough to merge in the future. You are claiming that once “they're in each other's gravitational influence” so they will necessarily collapse to each other. Probably you would also claim that if there is a distance between them preventing from their merger, it is because there must be an involvement of another force in the scenery. These two gravitational forces, otherwise, must necessarily collapse to each other. So I ask, what is this force that prevent them collapsing to each other, if not their own relational and temporal agreement depending upon only their own gravitational body movements?
You can make sense in an isolated condition, not for the real possibilities and happenings in the universe.
This is what OP asks for: “in a reasonable distance” from each other.
And I asked that in my first post.
And “same force and energy”, no one is including anything else, and you do not need to create hypothetical conversation like anyone introduced any extra force into the discussion
Then if there are no other forces introduce the two will merge into one.
Note the thread title "if they MEET".
I gave you the examples of moon and earth just for the sake of giving an example to cosmologic diversity of the universe, not to include any other force into the equation.
Except that those examples DO have other forces/ motions etc to be taken into consideration.
In this discussion, there is no other force, there are two black holes and nothing else. And the title of original post asks: “What would happen if two gravitational singularities meet?” In order to eliminate the possible confusion, it also states that “same force and energy”. Although it is utterly tough task to find such “equal” forces in real universe, we should accept this hypothetical situation for the sake of this discussion.
In which case the two will merge and form a larger black hole.
However, there is still no guarantee that two black holes would necessarily collapse, because we do not know what this “reasonable distance” is, depending upon their sizes and temporary positional agreement.
As stated BY ME: if the reasonable distance means they are within each other's gravitational influence then they WILL meet and merge.
But this is not the answer for the OP, because it asks for general possibilities in reality, where many different things happen, and each one can also be explained by matching mathematics. If two black holes meet at certain distance, which is not enough for a merge, they would not merge, simple as that. Without this “distance” concept, neither time and space, nor your physics make any sense.
Actually it IS the answer to the OP.
Your claim “If they're in each other's gravitational influence (and there's nothing else acting on them) then they'll move toward each other and merge.” is a wrong assumption.
Incorrect.
Because they can also form twin galaxies at certain distance, which may be enough for twin formation (and not going for their own separate directions), but not enough to merge in the future.
The only reason that the black holes in your example don't meet and merge is because there ARE other forces acting on them.
You are claiming that once “they're in each other's gravitational influence” so they will necessarily collapse to each other.
That's true, I would claim it, because that's what would happen.
You can make sense in an isolated condition, not for the real possibilities and happenings in the universe.
You aren't making sense at all.
My first post clearly stated "no other forces" which you yourself have said is reasonable for the purposes of this discussion.
And as for "real possibilities and happenings in this universe" have you also just not written "we should accept this hypothetical situation for the sake of this discussion."
:rolleyes:
I repeat the question of "what is this extra force that create non-mergin twins?" Is it external to the gravitational forces of black holes? Is is dark matter, what is it? We accept hypothetical situation to understand what keeps two bodies separate, as much as to understand what makes them merge. You are still claiming that if there was not any other force, these two can not position themselves in certain distance without creating a single black whole. You can isolate every other forces and effects to analyse gravity in its pure sense in theory, but is there any real example in universe where gravitational force express itself without its mass representation? "The real possibilities and happenings" in the universe, this force, like others, comes with a package, rules, mass, and probably they would not express themselves without these packages. Yes we are ignoring other elements in order to understand gravity, and "when all other influences are ignored", two black holes would end each other's unique characteristics and become one. Why? Because gravity is the only force that pull, while others have opposite of their forces. But nowhere in the universe gravity behaves so freely to collapse all matter and make one single entity. Gravitational force is manipulated:
A) either by other unknown forces such as the ones the that can expand the universe.
B) or by the collection of different sizes and relations between gravitational bodies.
If we choose (A), we must find out what these forces are, and how they interact with gravity. If we choose (B), we must make sure that we know every possible situation that can be created by gravitational bodies in order to make an absolute statement. If we find correct statements in both (A) and (B), we can expect any kind of possibilities; mergings and separations.
You came to the point to accept the fact that there are "not merging" black holes in the universe, and now trying to enrich your original statement with extra forces. Let us know them as long as they are in this universe.
I repeat the question of "what is this extra force that create non-mergin twins?" Is it external to the gravitational forces of black holes?
How about the gravitational attraction of the rest of the stuff in the universe?
You are still claiming that if there was not any other force, these two can not position themselves in certain distance without creating a single black whole.
Correct, because gravity doesn't fade away, it merely gets weaker.
So if there's nothing else at all but two black holes they will eventually come together and merge.
But nowhere in the universe gravity behaves so freely to collapse all matter and make one single entity. Gravitational force is manipulated:
A) either by other unknown forces such as the ones the that can expand the universe.
B) or by the collection of different sizes and relations between gravitational bodies.
Exactly.
In the real universe there are other bodies that exert gravity on our two black holes and that may prevent them meeting.
If we choose (A), we must find out what these forces are, and how they interact with gravity.
That's being done.
If we choose (B), we must make sure that we know every possible situation that can be created by gravitational bodies in order to make an absolute statement.
That's impossible.
You came to the point to accept the fact that there are "not merging" black holes in the universe, and now trying to enrich your original statement with extra forces. Let us know them as long as they are in this universe.
Wrong: I have never disputed that black holes in the real universe may not meet. But that wasn't the OP.
If the OP meant in this universe then the answer depends upon far too many factors to give any definitive statement.
If the OP meant in this universe then the answer depends upon far too many factors to give any definitive statement.
OP did not ask for something out of this universe either. You take the one side of reality, you isolated all other factors, including
In the real universe there are other bodies that exert gravity on our two black holes and that may prevent them meeting.
Then you can make concrete assumptions on your isolated universe. "What would happen if two gravitational singularities meet?", you should have said, "there is no such a possibility, because there are other factors". Or, "one possibility is their merger" among others. No, you did not do that, instead, you ignored all "real universe" conditions to support your claim. Blame the language of OP, blame other forces, judge my physics knowledge. Why don't you blame twin galaxies for a difference...
OP did not ask for something out of this universe either.
Make your mind up.
You previously stated
In this discussion, there is no other force, there are two black holes and nothing else.
Then you can make concrete assumptions on your isolated universe. "What would happen if two gravitational singularities meet?", you should have said, "there is no such a possibility, because there are other factors".
But I stipulated "no other factors".
Or, "one possibility is their merger" among others. No, you did not do that, instead, you ignored all "real universe" conditions to support your claim. Blame the language of OP, blame other forces, judge my physics knowledge. Why don't you blame twin galaxies for a difference...
You really are dense aren't you?
I have stated categorically that given no other factors then a single black hole would result.
I have also stated that if the scenario is set in the real universe then other conditions would have to be specified and the result may prove to be incalculable.
Let's take it at its simplest: the thread title is -
"What would happen if if two gravitational singularities meet?"
Given that "meet" has a particular meaning in science and engineering (i.e. contact) then the answer can only be: they would merge into one.
As for the rest of your back-pedalling, I've already covered it, and dismissed your "repulsion".
As for the rest of your back-pedalling, I've already covered it, and dismissed your "repulsion".
You dismissed repulsion with what? With gravity.
How do you explain non-merging twin galaxies? With gravity.
Why things are collapsing into a black hole? Because of gravity.
How do some black holes form different combinations? Because of gravity.
I can do that. If this is what you call special meaning of meeting two astrophysical bodies in science and engineering jargon...
You dismissed repulsion with what? With gravity.
How do you explain non-merging twin galaxies? With gravity.
Why things are collapsing into a black hole? Because of gravity.
How do some black holes form different combinations? Because of gravity.
And your "point" would be?
I dismissed repulsion because the electrical charge repulsion is nowhere near strong enough not a factor, and the spin repulsion is simply an unproven possibility. But you didn't bother to read your own "sources" did you?
I can do that. If this is what you call special meaning of meeting two astrophysical bodies in science and engineering jargon...
meet 1 (mt)
v. met (mt), meet·ing, meets
v.tr.
1. To come upon by chance or arrangement.
2. To be present at the arrival of: met the train.
3. To be introduced to.
4. To come into conjunction with; join: where the sea meets the sky.
5. To come into the company or presence of, as for a conference.
6. To come to the notice of (the senses): There is more here than meets the eye.
7. To experience; undergo: met his fate with courage.
8. To deal with; oppose: "We have met the enemy and they are ours" (Oliver Hazard Perry).
9. To cope or contend effectively with: meet each problem as it arises.
10. To come into conformity with the views, wishes, or opinions of: The firm has done its best to meet us on that point.
11. To satisfy (a need, for example); fulfill: meet all the conditions in the contract. See Synonyms at satisfy.
12. To pay; settle: enough money to meet expenses.
Apart from the italicised one, which of the definitions above would apply to black holes?
No 5 could: and we've been through that, but that sort of meet would be expressed as something like "encounter".
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