When Black Holes Collide

EricTheGreen writes "CNN.com reports on a pair of black holes in a mating dance that can only end badly for both of them. Fortunately they've still got several million years for the emotional rush to wear off and realize what a terrible mistake they're both making..."

Comments

And new rings around uranus!

[Anonymous Coward]

First Post bitches!

Why?

[JordanL]

Why did this remind me of that Family Guy episode?

"President Douchebag: I just got a call from my challenger.
Crowd: Boooo!
President Douchebag: Now now, Mr. Daterape ran a fine campaign."

Re:Why?

[mnemonic_]

Probably because you don't know how to punctuate quotations properly.

yup...

[3.14159265]

gravity sucks...

Oh boy

[Klowner]

First blue rings around uranus, now we've got black holes colliding.. This place is really getting to disgusting for me.

Re:Oh boy

[cnflctd]

Only if you speak both Russian and English. When a Russian says "YourAnus", he won't get the joke. Black hole on the other hand is russian slang for, well, your anus.

Re:Oh boy

[Anonymous Coward]

Were you aware that Uranus is a large blue gas giant which is flattened at the poles and surrounded by a cloud of methane?

Re:Oh boy

[fbjon]

I propose a name change to be rid of these ridiculous jokes: Urectum, and Brown Holes.

Re:Oh boy

[chrismcdirty]

I propose we call them star holes, since they're in space and they suck up stars, among other things.

Re:Oh boy

[shotfeel]

Unfortunately, after reading your comment I read this page.

Where I learned that blue rings were associated with small moons. And "The outer ring of Saturn is blue and has Enceladus right smack at its brightest spot, and Uranus is strikingly similar, with its blue ring right on top of Mab's orbit,".

Re:Oh boy

[butterwise]

By that logic they should be called "stars-and-other-things holes." Brilliant!

Re:Oh boy

[freak132]

More like stellar vaccum cleaners, I can't wait until the central blackhole in our galaxy gets named 'The Great Hoover'

Re:Oh boy

[hazah]

Mal'chik, vin' is popi' pal'chik.

Re:Oh boy

[middlemen]

"star holes"!!! ?? Might as well call them Paris Hilton then...

LISA

[alta]

Neat, a new telescope thing called LISA will be able to detect the merger. If they can keep the power on for a few million years.

Re:LISA

[Stormwatch]

The LISA telescope won't last that much: it'll soon be replaced by the MACINTOSH telescope.

Re:LISA

[Gattman01]

Yeah, but then someone will take the MACINTOSH telescope, clone its lens, and release the clones with added security holes.

Re:LISA

[mgabrys_sf]

At the same time the origonal team leader of the LISA telescope will be snubbed and storm off to create an overdesigned and exensive telescope called NEXT - which will be coveted by high-end astronomers, but will be panned by everyone else until it's core tech is purchased by members of the MACINTOSH telescope in which case it will usher in the 10th iteration of tech design.

There! Try to keep this lame thread going NOW.

Re:LISA

[Gattman01]

Eventually an astronomy student will create his own lens after being told he can not modify a telescope built by someone else. Then other astronomers will add more parts to this lens, and the LINUX telescope will be completed. These enthusiasts will then proclaim their telescope the best every created, and some will claim that is impervious to space dust that plagues the popular telescopes. This telescope will battle other popular telescopes with its main claim that it makes astronomy cheaper to do.

There! Try to keep this lame thread going NOW.

How is that?

Re:LISA

[mgabrys_sf]

Naw - you fell off the apple tree. Good try though. If you were to get away from Apple jokes then you'd have to add Atari, Commodore, Sol, the Altair, IBM Microsoft and all the rest.

Oh noes!

[voice_of_all_reason]

Teh galaxies are dividing by zero!!!!oneone

ATTENTION /. MODS: DO NOT MOD THIS COMMENT DOWN!!!

[Anonymous Coward]

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Sooner than you think

[Skevin]

> Fortunately they've still got several million years

Umm, how many light years away is this? Sure, it might take million years for the *light* from the spectacle of them merging to reach us, but if they're millions of light years away (center of the galaxy?), they may have already merged.

I've always speculated as whether gravity travels like light. Would "gravity waves" from the merge be felt here on earth the instant it happened, or would it take the same amount of time as light/electromagnetic radiation to reach us?

Re:Sooner than you think

[osgeek]

The effects of gravity don't travel any faster than light can.

Re:Sooner than you think

[thePig]

No Information can travel at the speed more than that of light.
Even if (just a hypothesis) gravity waves reaches here at the instant it happened, it means that it is not detectable, since if we can detect it, it means information travelled at more than the speed of light.

Anyways, einstein proved that the concept of 'same instant (instantaneous)' is not there anymore.
So that q itslef is not valid.

Re:Sooner than you think

[BlewScreen]

I've always speculated as whether gravity travels like light. Would "gravity waves" from the merge be felt here on earth the instant it happened, or would it take the same amount of time as light/electromagnetic radiation to reach us?

If you take a look at this book, you'll find that there is a way to measure the "speed of gravity" (according to the author) and that it is indeed faster than the (current) speed of light.

I'm not going to agree or disagree with what he puts forth, but if you're interested in questions such as the one you propose above, you'll probably find the book interesting. The supposition is that the speed of light and the speed of gravity were, at the time of the big bang, equal, and that the speed of light has gradually slowed over time.

I think the answer the author would give to your question is that the "gravity waves" you mention would arrive before the light would, but it would not be instant.

-bs

Re:Sooner than you think

[HolyCrapSCOsux]

Will it really matter? Their respective gravity wells are already in (relative) proximity. when they converge There shouldnt be a huge gravity spike or anything should there?

Re:Sooner than you think

[HolyCrapSCOsux]

never mind.. I just RTFA.

Re:Sooner than you think

[Luyseyal]

Scientists measured the speed of gravity a few years ago... short answer: it travels at the speed of light as predicted by Einstein's equations.

Cheers,
-l

Re:Sooner than you think

[penguin-collective]

That is plausible, but there is at best one experiment that purports to show that (and even that one is in dispute).

Re:Sooner than you think

[xtieburn]

According to this http://www.space.com/scienceastronomy/gravity_spee d_030107.html Gravity travels at light speed.

However, it was immediately attacked http://www.space.com/scienceastronomy/gravity_spee d_030116.html

Contrary to some of the other posts there is no current reason to exclude the idea that gravity is faster than the speed of light. Some experiments have shown that it is possible. ( http://physics.about.com/cs/gravity/a/speedofgravi ty_2.htm ) We do not know what gravity is, exactly, so its impossible to simple compare it to your average particle physics and the like.

As I said there is equal amounts of arguments against these experiments and there conclusions so we simply dont know for sure. It is very likely that it does travel at exactly the same speed as light (Just as Einstein predicted) but you should never rule out other possibilities until you are sure.

Re:Sooner than you think

[HTH NE1]

Consider that the speed of light really is just the maximum speed at which causality can propogate and you'll understand why gravitational effects cannot propogate faster.

Now whether gravity can propogate slower than light would be an interesting question.

Re:Sooner than you think

[chrisatoremus]

gravity is a force. it produces acceleration. Using

F=ma,

where the mass of earth is 5.9742 × 10^24 kilograms, in order to get an acceleration of 1 meter per second squared toward these black holes (now this black hole), they would need to exert a gravitational pull of

5.97 x 10^24 meters per second squared, or very roughly 10^24 times earth's gravity.

This rough calculation does not include the (small amount of) friction present in space, or opposite gravitational pulls from other objects. Plus, when referring to a wave of gravity, the article would be referring to a temporary gravitational pull resulting from this merger, so chances are the force wouldn't ever get the Earth to move at all. If it did, we'd probably never notice it.

Re:Sooner than you think

[Anonymous Coward]

As long as you ignore that the equations used in the calculations already included, as an assumption, that the speed of gravity is the same as the speed of light.

Nice try, though.

Re:Sooner than you think

[ComaVN]

Even if (just a hypothesis) gravity waves reaches here at the instant it happened, it means that it is not detectable, since if we can detect it, it means information travelled at more than the speed of light.

Alternatively, it could mean that no information can travel at more than the speed of light, except in the form of gravity waves.

I mean, shouldn't "No Information can travel at the speed more than that of light" really be "There's no known mechanism by which information can travel at a speed more than that of light"?

Re:Sooner than you think

[Anonymous Coward]

yeah right. .95c with error margin of .25c. that creates a range of .7-1.2c. all i would say is good innovative way to measure something but need more accuracy. a LOT more in this case.

Re:Sooner than you think

[pclminion]

Umm, how many light years away is this? Sure, it might take million years for the *light* from the spectacle of them merging to reach us, but if they're millions of light years away (center of the galaxy?), they may have already merged.

Time is all relative. The idea of "simultaneity" gets more and more ambiguous as distances increase. Does the fact that something is happening "now" even matter, if the effects of that occurrence can't reach us in less than millions of years? The entire concept of "now" loses its power.

Basically, you can't really talk about what is happening "now" at some location that is millions or billions of light years away.

Re:Sooner than you think

[LiquidCoooled]

If you consider that the Earth/Moon gravitational playground affects the very earth we stand on.
It is strong enough to move the oceans, and thats just a tiny moon around a tiny star at the outer edge of a smallish galaxy.
Imagine how the tidal forces of these two monsters would be playing and distorting and twisting their surroundings.
Hurling entire star systems great distances at a time, suddenly one system comes out from behind the shadow of another system and is thrown into the path of an oncoming blackhole.

I would imagine it would be immense super traumatic twister and if that doesn't cause gravitational waves, then I don't know what will.

Re:Sooner than you think

[xtieburn]

'Mod parent down: -1 nonsense.'

Err thanks.

'The article to which you link mentions a paper by Kopeiken that has been discredited.'

Really? How'd you work that out? Was it from the second link I posted discrediting him perhaps...

'Measurements of binary pulsars, the canonical example of which is PSR B1534+12, have demonstrated that the speed of gravity is equivalent to the speed of light to within +/-1.5%.'

Yes and the study I posted, while less accurate, said more or less the same thing.

'Quite apart from these results, gravity most certainly does not (as some here have suggested) propagate at infinite speed. The fact that we observe gravitational damping of binary pulsar systems such as PSR 1913+16 conclusively demonstrates that gravity has a finite propagation speed.'

A moot point. I never said gravity works at instantaneous speeds. If others did respond to them with your self superior crap.

As far as I am aware gravitational damping is evidence that gravity moves at a speed around that of light. At no point did I dispute that, in fact, as ive said already the site I posted says more or less the same.

As I also pointed out in my post there are arguments for and against all the tests for gravitational speed they all remain inconclusive and unless you can actually post some evidence, there is no study that proves for certain gravity works at light speed.

Its exceptionally likely that it does, there is torrents of indirect evidence and theory backing that fact up. Something I also said in my apparently nonsensical post...

Re:Sooner than you think

[kestasjk]

It's worth bearing in mind that the varying speed of light (VSL as the author puts it) is still considered a crackpot theory, and the book is written by the same person who put it forth. I'm not saying it wasn't an interesting read though.

Re:Sooner than you think

[Chowderbags]

Wha? The word "gravity" by itself isn't a force. It's a concept. The "force of gravity" is the force felt by two objects pulling on eachother, which you could calculate using (G(m1)(m2))/(r^2). Since we can calculate the mass of the black holes based on the speed of the dust orbiting a particular distance from the center, we could find the real force that the black holes exert on the earth (which, yes, would be small, since the objects are so far away). The problem, though, is that since the black holes are merging, it's going into crazy Einsteinian physics. Two rips in spacetime are coming together, with unknown consequences, one of which could be noticible (to instruments, probably not to the man on the street) gravitational effects which could show the true nature of gravity.

Re:Sooner than you think

[Feanturi]

Gravity used to go the same speed as light, but then it pissed off Chuck Norris and has to go faster now to get away.

Re:Sooner than you think

[Anonymous Coward]

"Mod parent down: -1 nonsense. "

That's part of what the overrated mod is used for. When they're not flaming or trolling or being offtopic but happen to be wrong.

Re:Sooner than you think

[Anonymous Coward]

Ummm..

The assumption was used generate equations in order to predict the effect that jupiters gravity waves would have when occluding a quasar. If the assumption that the gravity waves traveled at the speed of light was wrong then it should be a poor predictor of what physically happens. The margin of error was huge (0.25) but the result was well withing what one would expect if the assumption were correct (0.95).

But thanks for playing.

Re:Sooner than you think

[4D6963]

The way I humbly understood it, gravity is a deformation of space-time, and thus doesn't really travel and is instataneous, or something like that. Anyways, with that quantum thing about two particles changing of state at the same time, isn't it possible to transmit information instantaneously?

Re:Sooner than you think

[Anonymous Coward]

Well; one could argue that neither is E.M. If you go Kaluza-Klein-ey, E.M. is "just" more general relativity in a curled up extra dimension. If gravity isn't a force, neither should e.m. or strong or weak be, for consistency :-).

Re:Sooner than you think

[thePig]

Two ways to look at it -
First way -
Every force is believed to be set up by a particle as per current theories -
and gravitational force is caused by gravitons. And gravitons can move at the speed of light and no faster.*
The second way -
When black holes merge, the merging will cause a different sort of deformation of space-time. Now, for that effect to reach out to some other particle, it has to travel, and that wave travels at the speed of light and no faster*

Also, for the second point you mentioned, there is no transfer of information in that case, and so is void.

Re:Sooner than you think

[xtieburn]

No, my first claim was that there were studies proving gravity moves around light speed.
My second claim was that there are also studies proving these are flawed.
My third claim was that there is no reason to exlude the idea that it moves faster than light.
My fourth claim was that we just werent entirely sure.

and not one of them is inacurate. There _are_ studies proving and attacking all of our current methods of measuring its speed. There _isnt_ as far, as I am aware, hard evidence that it moves at the speed of light. Which means that you _can not_ exclude the possibility it doesnt, and we are in fact unsure.

'strongly suggests' is a reason to doubt gravity moves at anything other than light speed. Not believe that it is a certainty and can now exclude all other possibilities.

Which is what my 'central' claim was. An attack on the absolute accuracy of its speed shown by other posters. Given that I have always stressed throughout all of this that it is highly likely that it does move at light speed I do not understand the problem here. You appear to be on a mission to discredit my posts by bringing up facts and theories that I have never disputed, or which attack things that I have never even claimed.

Re:Sooner than you think

[4D6963]

ight, when it comes to relativity, i get it all wrong :-). anyways, how do we know that there is such a particle as gravitons?

Re:Sooner than you think

[Darby]

Gravity used to go the same speed as light, but then it pissed off Chuck Norris and has to go faster now to get away.

Heresy!
You're claiming something managed to get away from Chuck Norris?!?
No, my friend, it pissed off Chuck Norris who roundhouse kicked it past the speed of light.

Re:Sooner than you think

[Fulcrum of Evil]

Gravity is not a force.

Oh sure, like you know. Nobody has yet provided a satisfying answer to what exactly Gravity is.

What...Goatse Guy met Tubgirl?

[R2.0]

Come on - tell me no one else thought of that?

Re:What...Goatse Guy met Tubgirl?

[Cheapy]

No one thought of that.

Re:What...Goatse Guy met Tubgirl?

[MindStalker]

Damn you.. Damn you to all enternity. I had never heard nor seen tubgirl until just now. Damn you all.

Re:What...Goatse Guy met Tubgirl?

[Zoolander]

Welcome... to the real world.

Re:What...Goatse Guy met Tubgirl?

[lbmouse]

"Come on - tell me no one else thought of that?"

No, I was thinking new show on Fox.

Re:What...Goatse Guy met Tubgirl?

[MindStalker]

Trust me I got enough of the real world seeing goatse guy years ago. I wanted nothing more to do with this "real world" after that point in time.

Re:What...Goatse Guy met Tubgirl?

[Zoolander]

Yeah... the experience is somewhat overrated.

"When Black Holes Collide..."

[PenguinBoyDave]

That could also be a good title for a porn flick!

Hope they signed a prenup...

[YU Nicks NE Way]

How else are they going to figure out what to do with the stuff which is left over after their pairing collapses?

Comment removed

[account_deleted]

Comment removed based on user account deletion

Stop!

[Hikaru79]

Fortunately they've still got several million years for the emotional rush to wear off and realize what a terrible mistake they're both making...

Black holes hate it when you anthropomorphise them!

Re:Stop!

[Anonymous Coward]

No no. The better phrasing it, "Black holes hate being anthropomorphised!" It's more effective. "it when you" and ending with "them" makes it weaker.

Re:Stop!

[Anonymous Coward]

Why is that? Does it make it weaker to everyone, or just the common denominator? Does it make it harder to understand to you or someone else? I'm not saying you're wrong, I just want to understand your reasoning for saying that.

Re:Stop!

[normal_guy]

It's a grammatical turn of phrase. Here are some examples and exercises. I'm not the parent poster, just an interested party.

Re:Stop!

[Anonymous Coward]

No, it doesn't make it harder to understand. It was a purely stylistic objection, related to the active/passive issue that normalguy raised. So, yes, it's subjective, but I do think the vast majority of people would say that my version has more punch. (Well, it's not my version--I read it that was in someone's sig here on slashdot a few months ago. I assume the grandparent did too, and remembered it wrong.) The grandparent's version is diluted unnecessary filler words, and it even ends on one of them.

Re:Stop!

[Anonymous Coward]

Crap. I mean to say, "The grandparent's version is diluted by unnecessary filler words, and it even ends on one of them."

Re:ATTENTION /. MODS: DO NOT MOD THIS COMMENT DOWN

[Anonymous Coward]

WTF does that say in english?

Re:ATTENTION /. MODS: DO NOT MOD THIS COMMENT DOWN

[Hoho19]

I recognize it from Apple's iWeb tempates...but beyond that you got me...

something I always wondered

[F�an�ro]

Something I always wondered:
When two black holes are close together, then something that has exactly the same distance to each of them should not fall into either one.

What happens when they are so close that their event horizons overlap?

Shouldn't there always be some flat zone between them that is not part of either event horizon?

So how can they merge?

Re:something I always wondered

[Scott Lockwood]

I'm just speculating here, but I'm betting you have a RAZOR thin 'line' between the two. You're still squished into spaghetti at that line, and once they 'touch' event horizons, it's only a (short?) matter of time before their center's merge and form one, larger black hole, whith one, larger event horizon. It's not like there is any force that will cause them to repell one another, so they likely arc together in an ever tightening vortex until they merge. The closer they get, the faster they go, as well.

Re:something I always wondered

[F�an�ro]

Well, at the "line", they would cancel each other out exactly, but close to the line they would still almost cancel each other out, so a small object might be able to hold together there. It would be an instable position, but a small spaceship might be able to maintain that position?

What if they don't collide exactly head-on, but just circle each other? They would circle closer and closer, whithout ever actually coliding, so would this "line" stay?

Re:something I always wondered

[afex2win]

when two black holes are close to each other they become surrounded by a common horizon and for all practical purposes they look like a distorted black hole

Re:something I always wondered

[Bob3141592]

Something I always wondered: When two black holes are close together, then something that has exactly the same distance to each of them should not fall into either one. What happens when they are so close that their event horizons overlap? Shouldn't there always be some flat zone between them that is not part of either event horizon? So how can they merge?

There's a difference between the strength of a gravitational field and a gravitational gradient. It's like at the center of the Earth. The gravitational gradient there (relative to the Earth's field) is zero, but the force of all that overhanging rock is pretty high. You wouldn't float there comfortably with no force acting on you. You'd be squished.

And that's in a conventional, Nwtonian view of gravity, which is where most people are comfortable thinking about these things. In the relativistic world things get a bit more complicated. The gravitational field itself has energy, and energy at sufficiently high densities has an appreciable mass equivalence and so itself gravitates. At high enough values, like at the event horizon of a black hole, this kind of positive resonance causes the equations describing the system to diverge and the solutions go to infinity, and this divergence is called a singularity.

The event horizon isn't a physical thing, it's the point where the divergence is assured. You can't really think of a black hole as a single hard little ball agt the center of a black hole surrounded by black empty space up to the event horizon, though I believe that's now most people think of it. All spatial and temporal points within the event horizon are indistinguishable - but it's be somewhat misleading to say that they're all the same point either, because the equations that describe those points can't be solved rationally since they contain infinities and it's like asking how infinity +1 is different from infinity + 2.

If you were able to maneuver in space such that you were always equidistant from two black holes of identical mass, you would float around comfortably as long as the bh's were sufficiently far from you. As they approached, you'd feel significant tidal stretching. As the bh's got closer, you would be stretched further, and smaller regions even closer to that exact midpoint would feel increased stretching. At the point where they merged, even the infinitestimal point at the exact center would be stretched to infinity (that one zero volume point could not resist the force that was stretching it out to fill the volume of the whole universe). Of course, this is a somewhat poetic way to describe events that cannot really be described because the physical equations contain infinities and have no meaningful interpretations.

At times like that, poetry is all you can do. It's hard to resist making analogies with this scenario and the creation of the universe, but such analogies, like any other analogy what talk about on or inside the event horizon of a black hole, are meaningless here. But it's still fun.

Re:something I always wondered

[cnflctd]

See wikipedia on black holes. Any spinning black hole has a ring-shaped singularity. Anything that sits on the line thru the center will never hit the singularity, but everything else will. *cue twilight zone theme*

Re:something I always wondered

[vertinox]

It would be an instable position, but a small spaceship might be able to maintain that position?

I'd have to give a big resounding no. IANAAP (I Am Not An Astrophysist), but it would be generally assumed that since we are 3 dimensional, some of our atoms would fall on one black hole's event horizon and then some on the other resulting in the space craft and those inside of it to be ripped into two bits sans the atoms that fall along the razor edge.

However, if you were a 2d entity, you might be able to pull this off... But I'm not sure how a 2d entity can survive in a 3d world much less transport itself between two black holes.

Lastly it could be possible that the two black holes could be uneven in strength so that the even horizon is contantly shifting towards the lesser gravity as the larger consumes it so that the razors edge on the EH would be constantly being dragged towards the black hole.

I could be wrong about this though...

Re:something I always wondered

[drsquare]

Well, at the "line", they would cancel each other out exactly, but close to the line they would still almost cancel each other out, so a small object might be able to hold together there. It would be an instable position, but a small spaceship might be able to maintain that position?

You'd be ripped in half.

Re:something I always wondered

[PieSquared]

There is nothing magic about the event horizon of the black hole. When two things pass an equal distance from any two objects that are big enough that they would normaly fall toward one thing or the other, the net force is zero. This is not to say that the force on the object is zero however, and if something passed between two black holes that were close to each other, they would be ripped in half. Due to the massive forces involved, however, people invariably talk of a slice of atoms that are in the exact center that would go to neither one. This only happens because of an incorrect train of thought. Remember that any spaceship or body is made of atoms (as far as *we* know...). Each of these atoms is incredibly small, and only an atom that was exactly in the center where net force was zero would stay put. Also remember that the majority of the mass of an atom is in the nucleus and this only take a tiny fraction of the total volume, making it highly improbable that any given atom through which the line passes isn't closer to one black hole then the other. In the fraction of those atoms in the center plane who ARE exactly blanced, which no longer make up a sheet but instead scattered atoms, that these atoms are moving, some translational movement from when they arived, all rotational or at least electron movement. As such, they will eventually tend one way or another and pass into a black hole.

As for the black holes themselves merging, remember that the event horizon isn't magic. It only means that something, even light, that passes into it won't get out without passing light speed due to the amount of gravity involved. Now recall that this is only true because the NET force is such that a speed faster then light is needed to get out. With two black holes near each other, the net force at any point between them will be less, causing the event horizon to shrink away from the black holes. My only uncertainty comes when the actual masses come close to each other, and then only to wonder what happens to light that passes between them.... can light itself be ripped with 2 black holes a few miles apart?

In anwser, I think the event horizons should shrink as the black holes get to the point where they should touch, doing unplesent things to anything that passes between them, but allowing the black holes to accelerate toward each other in perdictable patterns until they touch and become one larger black hole.

I think that it would be interesting to plot the event horizons of two black holes near each other: if my thinking is correct, there would be a conical section from the point between the holes outward missing from the event horizon: in which light could travel and be observed if said system of black holes passed between a sun and us. (assuming it doesn't somehow get torn apart by the forces involved, and that we have telescopes that can see it with all that plasma and such flying about).

Re:something I always wondered

[shotfeel]

However, if you were a 2d entity, you might be able to pull this off... But I'm not sure how a 2d entity can survive in a 3d world much less transport itself between two black holes.

Wasn't that covered in a ST:TNG episode?

Re:something I always wondered

[Anonymous Coward]

The event horizon of a black hole can be thought of as the surface from which no information (particles, energy, whatever) can escape. It's the event horizon because it's where observable events (time) ends; you can't see what happens inside a black hole.

Now, merging black holes. If you're in the exact center (or maybe not the very exact center, since black holes drag space-time around them and other funky effects), then maybe you don't get "pulled" into either black hole before the merger. But you still can't escape the combined system, which is the point where the event horizon swallows you up.

To think of it another way, if the system were Newtonian, and consisted of point masses, then you could balance perfectly between the two. But at some point, the field becomes so strong that you can't escape that balance point; if you try to leave, no matter how powerful your engines, both black holes will act to pull you back. (Similar to what happens at the L1 Lagrange point.) At this point, that balance point has been enveloped by the event horizon.

The event horizon is a surface that encloses a volume that simply describes a region of space-time where events (which, as far as we know, are limited by the speed of light) can no longer observed. As such, it's not really a physical boundary, but a mathematical one. An object crossing the event horizon wouldn't notice until it tried to get out. Otherwise, there's nothing special about it.

Of course, this all assumes continuity, and we know the actual universe is quantum, and once you add quantum in, you get funky effects like Hawking radiation. But we haven't solved the quantum gravity problem yet, and Einstein's theory is the best we've got for now.

Re:something I always wondered

[rabel]

Wow. After that explanation I think I need a cigarette.

Re:something I always wondered

[Odin_Tiger]

In a perfect, hypothetical universe of infinite size which contained only those two black holes, and if both were far enough apart that you and your ship could be centered between them without being close enough to either black hole for the gravity to tear you / your ship apart, yes, maybe you could maintain a central position. Given those two, there's the third problem of movement...The two black holes will be in motion, and it while you may be able to calculate where the 'safe spot' will be at a given instant, you probably will not be able to get there, calculate the next safe spot, get there, etc.
Unfortunately, the first 'if' fails immediately. You would not only have to center yourself on the two gravitational pulls from the black holes, but also on the gravitational pull of every other entity in the universe, because they will all tug on you a little bit. The second 'if' is a matter of random chance, but considering the size of the universe, might be considered probable. The third issue, movement, is a certainty, and it's just a question of 'how much?', but any way you look at it, it complicates things far too much.

Re:something I always wondered

[shotfeel]

In the fraction of those atoms in the center plane who ARE exactly blanced

Then you hit a problem when the electron moves to a different position, throwing off the balance. Or maybe in this position, the electron gets ripped off in one direction and the nucleus goes another -or part of the nucleus goes one way and part goes the other...

Re:something I always wondered

[BinaryOpty]

There's a difference between the strength of a gravitational field and a gravitational gradient. It's like at the center of the Earth. The gravitational gradient there (relative to the Earth's field) is zero, but the force of all that overhanging rock is pretty high. You wouldn't float there comfortably with no force acting on you. You'd be squished.

Doesn't Newton's shell theory state that when within a large spherical body of mass you can treat the mass as a shell of radius to where you are within it because the mass that's further out than you ends up cancelling out? As such, if the center of the earth was somehow hollow and you somehow got transported there or something, then you would float because by the shell theory all of the mass above you is cancelling out all the mass below you and thus you have a net gravitational force of 0 pulling on you. The "overhanging" rock wouldn't squish you because you'd have "underhanging" rock to counteract its pull (even though those terms mean nothing if you're at the center of the planet where essentially every direction is up).

Re:something I always wondered

[ScriptedReplay]

There's a difference between the strength of a gravitational field and a gravitational gradient. It's like at the center of the Earth. The gravitational gradient there (relative to the Earth's field) is zero, but the force of all that overhanging rock is pretty high. You wouldn't float there comfortably with no force acting on you. You'd be squished.

ouch! no. At least, not if you assume spherical symmetry. Baby analytical mech. example: the uniform sphere. Gravitational force is linear inside, going to zero.

You'd be squashed, alright, but not by gravity. It's the pressure in all that rock around you that you have to watch for. But if you manage to stabilize the hole you supposedly dug in the center of the Earth against the surrounding pressure, then you'd be floating quite comfortably.

Re:something I always wondered

[pboulang]

What do you mean by a "small" spaceship? Compared to what?

Re:something I always wondered

[Tzarius]

Nope, the gravitational attraction of all the Earth's mass points in one direction: down. When you are at "down", you've got 5.972e19kg of rock trying to get to where you are. It wouldn't be pretty. (Although the strength of the gravitional field does drop as you approach "down", at no point does it reverse, let alone strongly enough to counteract weight of the outer mass). A hollow earth isn't stable, either. Especially for a mostly-liquid mantle. As soon as the center of the hollow sphere (the "bubble") diverges from the gravitational center, more material will pile up on one side, further accelerating the "rise" of the bubble.

Re:something I always wondered

[Anonymous Coward]

When two black holes are close together, then something that has exactly the same distance to each of them should not fall into either one.

Wrong, I think. The beginning of the event horizon is the distance at which the force pulling you into to black hole and the centrifugal force cancel each other out. Which means in order to not be pulled in, you'd have to circle around one black hole at quite some speed.

Now the two holes are not sitting there minding their own business. They are circling around each other at high speed, otherwise they would crush together instantly.

I think getting into the "eye" where you are sitting still while two singularities circle around you is quite.. non-easy in the first place.

Re:something I always wondered

[Artifakt]

To paraphrase the above: If the center of the Earth was hollow, then there wouldn't be any rocks there, so there wouldn't be any rocks to squish you.

(but it's not hollow, so there are rocks there, so they would.)

And this is currently up to +3 Insightful how?

There is no "mass canceling out" involved. Even though in a hollow shell, the gravetational attractions for rocks in the shell on you at the center all cancel, the gravitational attractions of those rocks on each other don't, so big hollow shells of rock collapse into planets. All the rock trying to get to the lowest spot is what squishes things, not the pull that rock exerts on you.
      In the same way, if you were in the asteroid belt, and you got between two floating rocks coming together at a thousand miles an hour, they would squish you quite thoroughly even though they were both too small to have significant gravity. It doesn't matter one little bit whether they are drawn together by their own gravity, by your gravity as well (if you are big enough to matter), or brought together by some other means, like attacked rockets or just starting out with the right vectors.

Re:something I always wondered

[amRadioHed]

The area where they "almost" cancel each other out wouldn't be large enough to worry about as the tidal forces are extremely intense near a black hole. In fact, they are strong enough that you would be torn apart by just falling into a single black hole, you don't need the tug of another singularity to do the damage.

Betting line

[dyslexicbunny]

Anyone running odds on which one eats the other? Or what happens post eating?

Re:Betting line

[Anonymous Coward]

you have two event horizon surfaces, then you'll have only one. As far as this side of it is concerned all you have is the surface anyway.

What I'm more interested is whether this will prove to be a detectable source of gravitational waves.

Re:Betting line

[nizo]

I will bet anyone any amount they want as long as I get to hold the money until we discover the outcome in a few million years.

Why am I reminded of the video for...

[idontgno]

that '80s classic, Mondern English's I Melt With You? A pair of dancers whirling together in the darkness...

Meh, I must be getting sentimental in my old age.

Party?

[Jugalator]

CNN.com reports on a pair of black holes in a mating dance

Sounds like there's a party at the Goatse guy. :-S

lorem ipsum

[mnemonic_]

It's the standard filler text for page layout, see lipsum.com. It's a garbled version of a latin speech by Cicero.

Conglomeration

[RealGrouchy]

I dunno, but here on Earth, mergers of Supermassive companies usually end up in additional service charges.

- RG>

Re:ATTENTION /. MODS: DO NOT MOD THIS COMMENT DOWN

[RandomPrecision]

Lorem ipsums are Latin filler texts. The origanl Lorem Ipsum was from some famous work, way back in the day.

An excerpt translation from Wikipedia: "H. Rackham's 1914 translation: "Nor again is there anyone who loves or pursues or desires to obtain pain of itself, because it is pain, but because occasionally circumstances occur in which toil and pain can procure him some great pleasure. To take a trivial example, which of us ever undertakes laborious physical exercise, except to obtain some advantage from it? But who has any right to find fault with a man who chooses to enjoy a pleasure that has no annoying consequences, or one who avoids a pain that produces no resultant pleasure?"

The poster probably used a Lorem Ipsum generator like this one.

If I was sufficiently advanced

[cnflctd]

Two supermassive black holes are spiraling closer and closer, leading to an inevitable merger.

But is it really inevitable, I ask myself? What would it take to pry them apart? Welcome to einstein's tractor pull!

Imaging the black holes 1 and 2 falling straight towards each other. (Trying to do this with them spinning makes my head hurt). You take a third supermassive BH, call it 3, and give it a large velocity relative to the other two. Send it thru the system at a slight angle.

As it hurtles by the hole 1, it drags it along -- has to come real close, but not too, noam sayin?

As 1 and 3 zip by 2, 1 gets slowed down some, but still has excape velocity from 2. See? No sweat. Now if DARPA will give me a grant, I'd hire a math major to solve orbiting BH case.

Re:If I was sufficiently advanced

[gstoddart]

But is it really inevitable, I ask myself? What would it take to pry them apart? Welcome to einstein's tractor pull!

Imaging the black holes 1 and 2 falling straight towards each other. (Trying to do this with them spinning makes my head hurt). You take a third supermassive BH, call it 3, and give it a large velocity relative to the other two.

Man, I always hated word problems. So ... which one is leaving Chicago again?

Re:ATTENTION /. MODS: DO NOT MOD THIS COMMENT DOWN

[Anonymous Coward]

It's just nonsense. Yes, it looks like Latin. It's supposed to. Apparently someone back in the day created this bunch of text as a useful "placeholder" for real text in the printing business, since it has similar distributions and letter frequency of (and looks like) an average block of text. That's why you'll find it in Apple's iLife templates for text blocks. And why the troll could be successful in getting modded back up, simply because some people get mod points and then proceed to listen to the subject line...

"Can only end badly"?

[ElMiguel]

They are black holes. How much worse can it get?

Re:"Can only end badly"?

[otis wildflower]

They could get stabbed...

Re:"Can only end badly"?

[Zoolander]

Thank you for making me giggle uncontrollably! :)

Re:"Can only end badly"?

[Anonymous Coward]

Centurion: Stabbed? How is that worse than being crucified?

Prisoner: Well at least your out in the fresh air.

Centurion: Your wierd.

Re:ATTENTION /. MODS: DO NOT MOD THIS COMMENT DOWN

[Anonymous Coward]

Why do you insist this is trolling? It's just a speech by Cicero that has nothing to do with anything. That's certainly offtopic, but I don't see how it's trolling.

star gate

[Joe123456]

Thay are a black hole and a supergate next to each other and the ori are coming.

Speed of gravity

[Anonymous Coward]

Replying in one place regarding several responses.

First, the speed of gravity was measured decades ago, inferred by the rate at which the orbits of two neutron stars in a binary pair decayed. The rate of decay agreed exactly with what general relativity predicts due to energy loss via gravitational radiation traveling at the speed of light. The 1993 Nobel Prize was awarded for this work. See this FAQ.

Some poster mentioned Magueijo's work; it is, to put it politely, not well accepted. In point of fact, there is little evidence that the speed of light has changed (although there are some controversial studies), and very little evidence that the speed of light differs from the speed of gravity.

Someone else noted Kopeikin's Jupiter paper, but noted that it was immediately attacked. Well, that's true, and if you read the followup papers, you will see that it is now agreed by pretty much everbody but Kopeikin and co. that what they actually measured was the speed of light. And one of the linked articles noted that while this measurement found 1.06c for the speed of gravity, the error bars were +/- 0.2c, so it means nothing; no measurement of the speed of gravity (or light, or anything else) will give exactly c, what matters is whether the error bars exclude c. Anyway, the "measurement" of the speed of gravity discussed by New Scientist really wasn't a measurement of the speed of gravity.

There has as yet been no direct measurement of the speed of light (although the binary star experiment is regarded as a conclusive indirect experiment); that will have to wait until gravitational waves are detected directly by LIGO or a similar experiment.

It is also worth noting that quantum field theory predicts that gravity and light have to travel at the same speed since they're both mediated by massless particles (photons and gravitons); the same goes for extensions beyond QFT such as string theory. Actually, it's true even classically in any field theory compatible with special relativity.

P.S. In case anyone wants to bring up Tom van Flandern and metaresearch.com, he's a famous Usenet crank; see the above FAQ as well as Steve Carlip's paper on the gr-qc arXiv.org for an explanation.

I really wish you hadn't thought of that.

[dpbsmith]

(Enough said)

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Re:ATTENTION /. MODS: DO NOT MOD THIS COMMENT DOWN

[g0bshiTe]

jello

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Re:ATTENTION /. MODS: DO NOT MOD THIS COMMENT DOWN

[Anonymous Coward]

Ipso fatso!!

Sincerely,
Archie Bunker ;)

Tonight on FOX - When Black Holes Collide

[murderlegendre]

"The funny part, was when the Black Holes collided."

Its perfectly natural for two young singularities

[mentrial]

Let it bee let it beee let it beee oh let it beeeee -aslongasitdoesntdestroythewholeuniverse- let it beeeeeee eeee

Like a vacuum store

[Anonymous Coward]

This sucks.

Black Hole Collision Simulations

[dcartoon]

My astrophysics professor actually does work simulating black hole collisions. There are some cool images and movies of galaxies containing black holes colliding at http://web.phys.cmu.edu/~tiziana/BHGrow/

Haven't you been though grade school?

[Anonymous Coward]

Clearly infinity +2 beats infinity +1

... which one is leaving Chicago again?

[Anonymous Coward]

Jesus just left Chicago and he's bound for New Orleans.

Re: ... which one is leaving Chicago again?

[pboulang]

Now that's obviously a hypothetical, you using imaginary cities like that. . .

its all about time

[lazy genes]

Gravity and time are products of the shape of space-time.The movment of the hands on a clock passing through a bh would increase in speed untill it reached the center ,and then decrease as it passes out the other side.Space-time will not rip it only bends.Thus,the amount of time expired on the clock cannot exeed the age of the universe.

Re:its all about time

[lazy genes]

I should say it was only a prediction.I have spent the last few days thinking it over .I can only add to my original comment by saying that a stationary clock inside a BH would run slower than one outside the BH.But a clock in motion moving through a BH would act as i mentioned earlier. It seems strange that we cant agree on this,because my prediction concerning the structure of space-time is very simular to a cone structure like you mentioned earlier.I was very happy to see that comment and would like to know how they came up with that idea. My -1 rating does not relate to my true visual mag.

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Vacuum cleaners?

[Anonymous Coward]

So, for us here at home.. it would be like being stuck between two vacuum cleaners.. each with infinite energy and power?

Geez. That would suck.

Russian Frozen Stars

[NuShrike]

This is why they're first called a "frozen star" in Russian, and then it got renamed to Black Holes by some American.