I've heard this so many times, and I still don't see how it's possible! Because of time dilation this merger will take infinite time.
No one has ever explained this satisfactorily to me. Why do people just seem to completely ignore relativity when dealing with black holes?
The problem with this argument is that there is no preferred global time coordinate with respect to which you declare that "the BH has formed". Rather, the spacetime events corresponding to "each dust particle crosses their mutual horizon" (i.e., "the formation of the BH"), along with the rest of the interior of the BH, comprise an additional spacetime region you can choose to attach to your manifold or not. This is a free choice because causality flows one-way across the boundary; no experiments outside the BH can be sensitive to whether the region "really" exists. There are multiple ways to extend the normal time coordinates (at infinity) into the interior of the BH, and a natural choice is the proper time of in-falling particles/observers. In that case, the BH definitely forms at a finite values of that time coordinate.
Merging two existing BHs doesn't introduce new fundamental issues. Quantum mechanics does introduce new fundamental issues, but formally the jury is still out on whether it resolves this question. The majority opinion is that the interior of the BH exists just as much as regions beyond your cosmological horizon (in an expanding cosmology) exist, from which you are likewise causally disconnected
I know. No one has ever explained how those can form either.
> From the outside, this is indistinguishable from a BH for all practical purposes
Except without the physics breaking properties of black holes. So not the same at all.
> The problem with this argument is that there is no preferred global time coordinate with respect to which you declare that "the BH has formed".
I don't need a global time, my own time frame is perfectly fine with me. If a black hole can never form, as viewed by me, then black holes don't exist.
> This is a free choice because causality flows one-way across the boundary
This presupposes the black hole exists already, but we have not gotten there yet. First it has to form, and it can not.
> and a natural choice is the proper time of in-falling particles/observers. In that case, the BH definitely forms at a finite values of that time coordinate.
It gets interesting here - what does happen from the POV of that particle? I suspect it never sees a black hole. This particle is moving exponentially close to the speed of light, relative to the center of mass of the forming black hole.
This means that time is stopped for the center of mass of the black hole from the POV of the particle, which means the center of mass can never form a black hole since it can never do anything at all (since time is stopped for it).
But they do -- the evidence is copious:
http://www.galacticcenter.astro.ucla.edu/animations.html
Arguing that, because the event horizon collapses the time dimension (from the perspective of a distant observer), therefore BHs aren't real, is like saying that sum(2^-n,(n,1,oo)) can't equal 1 because it's an infinite series and an infinity of additions takes too long.
Think of black holes as objects of great mass, that have very bright accretion disks, surrounding an event horizon that is perpetually almost forming a singularity but never quite completes it (from the perspective of someone far from the horizon).
> This means that time is stopped for the center of mass of the black hole ...
From the perspective of a distant observer, the time horizon is located at the event horizon.
The evidence is non-existent. The only evidence is for supermassive objects, not event horizons.
> Arguing that ... BHs aren't real, is like saying ... an infinite series and an infinity of additions takes too long.
That's a terrible argument. One is an actual physical process, the other is a mathematical abstraction. Do you not understand infinity? Infinity means you can't actually do it. It doesn't mean you can't calculate it.
> Think of black holes as objects of great mass, that have very bright accretion disks, surrounding an event horizon that is perpetually almost forming a singularity but never quite completes it (from the perspective of someone far from the horizon).
Eh? If it never forms a singularity, it has no event horizon. i.e. it has none of the physic breaking properties of black holes.
And accretion disks don't have to be bright BTW, as stuff falls in time dilation makes them much less bright (they "slow down", and emit photons less often).
> From the perspective of a distant observer, the time horizon is located at the event horizon.
When I say center of mass of the black hole I am naming the object I am talking about, not describing the location of the time horizon. Sorry if it was confusing.
> The evidence is non-existent.
If you're familiar with Occam's razor, you know that, for a given phenomenon, the simplest explanation is to be preferred. There certainly are massive objects at the center of most galaxies, and the most economical explanation is that they're black holes. No one is closing the book on these ideas -- that would be unscientific -- but there is strong evidence that these things are black holes.
That they exist is beyond question. That they have super-high masses confined to a small space is beyond question. General Relativity then fills in the blanks in our observations.
> That's a terrible argument. One is an actual physical process, the other is a mathematical abstraction.
So is General Relativity. But because nature follows the same rules, General Relativity accurately predicts many aspects of reality (certainly not all).
> And accretion disks don't have to be bright BTW ...
Well, yes, they do -- they're giving up a huge amount of gravitational potential energy, and that energy must be conserved -- it's converted to kinetic energy, it becomes heat and light.
Consider a satellite in an elliptical orbit. At the orbital apoapsis, potential energy is highest and kinetic energy is lowest. Not surprisingly, this is the point of smallest velocity. Now consider periapsis -- it's the reverse: lowest potential energy, highest kinetic energy, therefore highest velocity.
In a normal planetary elliptical orbit with no friction, even though the two kinds of energy are constantly changing, they sum to a constant at each point in the orbit, so there's no net dissipation of energy. But as matter falls into a black hole, in order for it to pass through the event horizon, it must give up most of its energy (both potential and kinetic). Most of that energy is converted into heat and light.
Most accretion disks preserve the rotational momentum of the infalling mass, so they're in the form of disks surrounding the event horizon. In theory, mass could fall directly into the BH without any rotation -- in that case, there would still be a huge energy conversion process and much radiated energy. Sp accretion disks are very bright.
Here's a graphic of the imagined BH from "Interstellar", thought to be fairly accurate as movie graphics go:
http://www.wired.com/2014/10/astrophysics-interstellar-black...
> Eh? If it never forms a singularity, it has no event horizon.
Yes, and by the same reasoning, because a Calculus limit expression never gets to its limit, therefore Calculus is bunk. My point? Just as (1+1/n)^n approaches e as n approaches infinity (http://www.wolframalpha.com/input/?i=limit+n+-%3E+inf%2C+%28...), a black hole approaches its final form as mass approaches it from the perspective of a distant observer.
You might as well have argued that, because this classic-physics gravitational equation:
f = (G m1 m2) / r^2
assumes that all the mass is a dimensionless point at the center of the central body, therefore if m1 and m2 occupy the same point in space, the result is infinite, therefore (because infinity isn't a number) Newtonian gravitation is bunk.
That is just not true. To be a black hole it must first be possible for black holes to exist, otherwise they are simply supermassive object - to us they would look EXACTLY the same!
A black hole is NOT the simplest explanation! It's the most complicated one. You are using your razor very incorrectly.
> That they exist is beyond question.
Absolutely not true. That massive objects exist? Sure. Are they black holes? Not so clear.
> That they have super-high masses confined to a small space is beyond question. General Relativity then fills in the blanks in our observations.
No, actually General Relativity does NOT fill in the blanks - it claims things are impossible. The math does the equivalent of divide by zero.
> So is General Relativity. [a mathematical abstraction]
Great, so since GR predicts it would take infinite time, I guess case closed. Since infinite time, by definition, can not actually happen, it means black holes can not form. Just because you can calculate what something will do doesn't mean it will actually do it.
> Well, yes, they do -- they're giving up a huge amount of gravitational potential energy, and that energy must be conserved -- it's converted to kinetic energy, it becomes heat and light.
Kinetic energy does not become heat and light. Kinetic energy is velocity. To make heat and light you need some other process. Have you never heard of conservation of momentum?
On top of that, the discs are dim because time is dilated to nothing not because there is no energy there.
> But as matter falls into a black hole, in order for it to pass through the event horizon, it must give up most of its energy (both potential and kinetic). .... in that case, there would still be a huge energy conversion process .... Most of that energy is converted into heat and light.
How in the world are you writing this stuff? You can't just "give up" velocity. You have to transfer that velocity to something else. You can't just wave your hands and say "magic". Friction might cause objects to equalize in velocity, but can not actually reduce velocity (only share it amongst the objects).
> a black hole approaches its final form as mass approaches it from the perspective of a distant observer.
And takes infinite time to do so, and since right now is not infinitely in the future, right now, today, black holes do not exist.
Infinite. Do you not understand that word? It means forever, it means it never actually does it, just gets closer and closer.
> therefore if m1 and m2 occupy the same point in space, the result is infinite, therefore (because infinity isn't a number) Newtonian gravitation is bunk.
Nice question, wrong conclusion. The actual conclusion is that since infinity is not actually seen in the real world (as opposed to math), there must be some method that prevents the two masses from ever occupying the same spot.
Your argument is entirely backward, you think that if infinity shows up in the math then it must show up in the real world. No. If infinity shows up in the math then your math is wrong, or incomplete. In this case there is something else that prevents r from hitting zero.
Maybe you should read this: https://en.wikipedia.org/wiki/Domain_of_a_function
> Kinetic energy does not become heat and light.
So have you told the LHC people that they're misguided for thinking they can produce the Higgs Boson by colliding protons together? I'm sure you can persuade them how wrong they are.
> Kinetic energy is velocity.
Yes, among many other things: http://physics.info/energy/ (see the table "Types of kinetic energy")
Electromagnetic energy (heat and light) is a kind of kinetic energy.
But you know what? I've decided not to try to correct all the errors you've made. If you actually understood physics, you wouldn't have objected to the things you have (you might have found a better reason to object).
> Friction might cause objects to equalize in velocity, but can not actually reduce velocity ...
Wow. Those fools in Europe are sure misguided to have spent so much money on a circular 17 mile pipe dream. if only they had consulted with you before building that monstrous contraption. They actually think their gadget can convert near-light-speed velocities into many other kinds of energy, including electromagnetic, and the creation of particles from energy and the reverse. Do them a favor -- set them straight, as you've set me straight.
The LHC collides TWO protons! The net velocity between them is zero.
You seem to know at least some physics, how can you possibly not know this?
But in your black hole scenario there are not two opposite velocities adding up at the horizon.
You can not just directly turn velocity into light, it's not possible, you need another object.
> Electromagnetic energy (heat and light) is a kind of kinetic energy.
Some people define only two kinds of energy: Potential and Kinetic, in that definition electromagnetic energy is a type of kinetic energy, and velocity is a type of kinetic energy.
But it does NOT follow that electromagnetic energy is the same as velocity energy!
It's like an apple is a fruit and an orange is a fruit, but an apple is not an orange.
> They actually think their gadget can convert near-light-speed velocities into many other kinds of energy, including electromagnetic, and the creation of particles from energy and the reverse.
I take it you've never heard of conservation of momentum? You can not just turn the velocity into other things, you have to react it with something else (which is what I said - go back and read it). In this case they react it with a proton going the other way.
They could also react it with the earth, or a slab of metal.
None of these apply to a black hole.
We have also gotten way off topic from time dilation.
Yes, but only because their original velocity has been converted into other forms of kinetic energy, like heat and light, among other things like Higgs bosons. Here is what you said:
> Kinetic energy does not become heat and light.
I proved your statement to be false. End of story. Now stop trolling.
You most certain did not.
Is this like some kind of contest to you to see if you win? Even if you win, you'll still be wrong.
Instead of focusing on that, why not actually learn something?
"To make heat and light you need some other process." For example, another proton to crash into. You can't just directly convert the velocity to energy, you need another object take the velocity from you.
> Kinetic energy does not become heat and light.
Now:
> "To make heat and light you need some other process."
Translation: "You were right." Apart from the fact that heat and light are kinetic energy.
Further reading: http://www.scientificamerican.com/article/gravitational-wave...
Quote from the above article: "LIGO's detectors, at their current sensitivity, could pick up only gravitational waves of frequencies well above 10 Hertz. So if they have picked up a signal, they would have captured the final stages of the drama, when the black holes circle more than 10 times per second, speeding up to several thousand times a second just before they merge. Simulations show that the resulting waves, if played as an audible sound, resemble a bird’s ‘chirp’ (http://www.ligo.org/science/GW-Inspiral.php) (http://www.ligo.org/science/GW-Overview/sounds/chirp40-1300H...)."
My original remark from yesterday, to which you ignorantly objected: "... eventually two black holes will merge, which will produce a completely fantastic observation consisting of a rapidly rising frequency (as the two BHs circle each other closer and closer, shedding their orbital energy as gravitational waves), followed by a very loud cosmological pop as the BHs finally collapse into each other."
I have said exactly the same thing the entire time, only you kept ignoring it. Or, to be charitable, maybe just not understanding it. Just because you don't understand the words I said, doesn't mean I didn't say it.
Do you need me to quote myself?
Also, I take it you did not ever study physics? If you did you would know this on your own without me telling you.
What I said, over and over, is you can not turn velocity into light directly, you have to transfer that velocity to something else. In an event horizon there is nothing to transfer the velocity to, since everything is moving more or less at the same speed.
I don't know why you can't seem to absorb this. I really don't. It's basic highschool physics, plus I've said it over and over and over and over. In as many different ways as I can think of.
> Apart from the fact that heat and light are kinetic energy.
Are you totally incapable of absorbing information? I know that sounds insulting, but I am serious. You keep saying the same wrong thing over and over despite being told different.
You are wrong. Period.
It's like you have a mental block stopping you from understanding this, I don't get it.
> ... eventually two black holes will merge, which will produce a completely fantastic observation consisting of a rapidly rising frequency (as the two BHs circle each other closer and closer, shedding their orbital energy as gravitational waves), followed by a very loud cosmological pop as the BHs finally collapse into each other."
Back to this, very nice. The problem is that they won't actually do this - time dilation means it will take infinite time for this to happen, so we'll never see this.
Not sure what the point of telling you this is though. If you can't understand Conservation of Momentum there is zero chance you'll understand relativity.
Try this - stop arguing with me. Clearly I'm not the teacher for you.
Go find some other people - show them this thread if you like. Then have them explain Conservation of Momentum to you. Also ask them to explain the difference between kinetic and electromagnetic energy.
Please do that before replying, otherwise we'll just be going in a circle.
This is a lie -- you keep changing your claim to keep up with the facts other people provide you with. Examples below.
> What I said, over and over, is you can not turn velocity into light directly, you have to transfer that velocity to something else.
That's not what you said originally, and you are now lying. You said that "Kinetic energy does not become heat and light. Kinetic energy is velocity." Both statements are false (velocity is one of many examples of kinetic energy but the reverse claim is an error of omission), and I provided the literature references, which you refused to read.
You earlier said:
> Friction might cause objects to equalize in velocity, but can not actually reduce velocity (only share it amongst the objects).
Totally false -- velocity is not conserved, energy is conserved. There's no conservation of velocity law. If you were a scientist, if you knew anything about physics and possessed intellectual integrity, you would drop a lump of clay, watch it abruptly stop at the floor as it efficiently converts velocity into heat. Or two billiard balls on a collision course, or two protons at the LHC, etc. etc..
> Clearly I'm not the teacher for you.
"The teacher?" You're utterly ignorant and a narcissist to boot. You're severely mentally ill, unfortunately there's no cure for malignant narcissism (https://en.wikipedia.org/wiki/Malignant_narcissism).
We're done -- you have to learn this on your own without embarrassing yourself further in this public forum. Have a nice day.
But there is, it's called Conservation of Momentum. It's velocity times mass. Go look it up - it will take just a few seconds on google. I'll wait.
> you would drop a lump of clay, watch it abruptly stop at the floor as it efficiently converts velocity into heat
No, it transferred its velocity to the entire planet.
> Or two billiard balls on a collision course
One has positive velocity, the other negative. They cancel out.
But go try making two billiard balls stop when they are both going the same way (as in your example about particles near the event horizon). You can't. Try it - maybe it will help. You have to transfer the velocity to something else.
> We're done -- you have to learn this on your own without embarrassing yourself further in this public forum. Have a nice day.
Oh, we were done ages ago.
One you do learn some physics you'll recall this conversion and cringe in embarrassment, not at your ignorance, but at your refusal to learn.
Your attempt at "diagnosing me" doesn't perturb me, because I know this stuff backward and forwards. Your obstinacy just amuses me. This stuff is so basic your comments are just laughable.
Just FYI, your conversational partner's website says:
"Paul Lutus has a wide background in science and technology. He designed spacecraft components for the NASA Space Shuttle and created a mathematical model of the solar system used by the Jet Propulsion Laboratory during the Viking Mars mission."
Are you sure it's the same person?
'How is it possible that someone with a "wide background in science" has not heard about conservation of momentum?'
It's probably not; but this comment thread (wading through the jibes, snipes, and nonsense) doesn't seem to demonstrate with much clarity that he hasn't.
Grab an intro GR textbook and work through it. There are free ones online.
> so it's often not possible to assign a sensible time that a particular event happens according to a clock held by an outside observer.
That's not completely accurate. The two can not assign the SAME time to some event happening - it might happen at different times for the two.
But it IS possible to say when the even will happen from ONE of their points of view. It just might not be the same time as what the other one sees.
That said, I doubt physicists would have overlooked this for 100 years when they pretty consistently say you'd fall into the hole unscathed and not even know you'd passed the horizon, so I'm sure this is wrong.
There would not be Hawking radiation since the black hole has not formed.
> That said, I doubt physicists would have overlooked this for 100 years
Other people have noticed this too: https://en.wikipedia.org/wiki/Eternally_collapsing_object
It doesn't seem to get as much attention, I think because there is less interesting math there to do research on.
> But it IS possible to say when the even will happen from ONE of their points of view. It just might not be the same time as what the other one sees
is again demonstrating that you don't understand how time coordinates work in GR. There is not a unique way to extent an observer's proper time to a time coordinate on an entire manifold, and different extensions are incompatible. Some of those extensions, as I said, give a finite time for BH formation.
I think you're more interested in axe-grinding that teaching or learning, so I'm going to call it quits on this one.
It's true that, at and below the event horizon, spacetime curvature is such that time hasn't its usual meaning, but this doesn't mean two BHs cannot orbit closer and closer and eventually merge. Such events take place primarily outside the event horizon. This video --
http://www.galacticcenter.astro.ucla.edu/animations.html
-- diagrams stars orbiting close to the BH said to be at the center of our galaxy (in fact these orbits give us an estimate of the BH's mass).
So if stars can orbit a BH, then a BH can orbit a BH, and the latter would orbit in normal spacetime, at least until the merger.
> Because of time dilation this merger will take infinite time.
Only from the perspective of the event horizon and below. Remember that "above" the event horizon, time still has its usual meaning, even though it's greatly modified compared to time on Earth's surface (which is also slightly dilated in GR).
> Remember that "above" the event horizon, time still has its usual meaning
The closer they get to that event horizon the slower time goes, so they will take longer and longer to orbit.
Yes, from the perspective of a distant observer. From the perspective of an observer falling into the BH, time will pass in the usual way, indeed it must.
> The closer they get to that event horizon the slower time goes, so they will take longer and longer to orbit.
Only from the perspective of a distant observer. This might explain why black holes last as long as they do, from the perspective of a distant observer. For all we know, they all blow up in short order from the perspective of an observer falling into one.
If, us, that distant observer, never see the black holes merge, then what does that mean for the gravity waves?
The black holes don't need to merge to create gravity waves, they only need to orbit each other. It turns out that all orbiting bodies create gravity waves, but in most cases the waves are too weak to detect. For black holes, because of their great mass and sometimes close separation, there is a good chance they will create detectable gravity waves.
The idea is, if there are no gravity waves, then two black holes could orbit forever with the same separation (no loss of energy). But if gravity waves are real, then the black holes will eventually merge, due to the loss of energy the waves represent.
There is already good indirect evidence for gravity waves:
https://en.wikipedia.org/wiki/Gravitational_wave
The idea here is that the period of orbiting pulsars will change due to the loss of energy represented by the gravity waves. In some cases we can see the change of orbital period, and it's consistent with the expected energy of the gravitational waves (which have not been directly observed).