Why black holes?arusse02 said:supermassive black holes
After the merger the newly formed black hole is deformed and will loose energy by radiating away gravitational waves until it is spherical symmetric.arusse02 said:T Where does all that energy go and how would it effect space time/what would the merger look like? What happens if they hit at a slight angle such that their event horizons would make contact but there isn't a direct hit.
PAllen said:Several cases of this are shown as movies in
https://www.black-holes.org/explore/movies
As to some of your questions:
Comparing head on collision of two BH of different relative velocity (but otherwise identical), the two with larger relative velocity would produce a larger resulting BH. The extra energy goes into the size of the BH.
If the horizons touch, they will merge. However, the details are extremely complex, and I do not personally know of a paper analyzing this case.
Clearly not. Those are simulations using general relativity, the very theory that predicts that the interior is vacuum. You'd need direct imaging of a real black hole merger that didn't look like the videos to provide evidence for your conclusion.arusse02 said:THe movies were very interesting. I find it odd that the black holes oscillate back and fourth after a direct collision. Almost like two blobs of water colliding in one of the international space station videos. Doesn't that suggest that the black hole isn't a singularity but has actual stuff with volume?
You aren't looking at simulations of the singularity (I've no idea how you'd even draw it in this kind of presentation), you are looking at simulations of the event horizon. The event horizon isn't a thing, it's a place - like "the altitude at which geosynchronous satellites orbit" is a place. It's the place where you can't get out of the black hole no matter how hard you try. What you are seeing is that point-of-no-return evolving as the black hole emits gravitational radiation and settles into its final form. There's no matter wobbling around here.arusse02 said:If it was just an infinitesimal singularity how could it oscillate like that according to the videos?
Right, I understand that the movies show only the event horizon. My confusion is that because the event horizon, like you said, is not even a thing, then how could it be oscillating? THe only thing I could think of with my admittedly limited understanding is that the event horizon shape is determined by the distribution of matter inside the black just like a gravitational field of a planet would be determined by the mass distribution of the material inside the planet. I realize this analogy is probably much too simplistic. However GR says there is no distribution of matter, it exists in a point.Ibix said:Clearly not. Those are simulations using general relativity, the very theory that predicts that the interior is vacuum. You'd need direct imaging of a real black hole merger that didn't look like the videos to provide evidence for your conclusion.
You aren't looking at simulations of the singularity (I've no idea how you'd even draw it in this kind of presentation), you are looking at simulations of the event horizon. The event horizon isn't a thing, it's a place - like "the altitude at which geosynchronous satellites orbit" is a place. It's the place where you can't get out of the black hole no matter how hard you try. What you are seeing is that point-of-no-return evolving as the black hole emits gravitational radiation and settles into its final form. There's no matter wobbling around here.
A boundary defined by the criteria that it is the boundary of where light can escape to infinity can easily oscillate. Your understanding is not just limited, it is simply wrong. In classical GR a BH more than a few days old is pure vacuum. The mass has left the universe, in some sense. However, the horizon remains, as does the interior excluding the singularity. The horizon is determined by the mass and energy that went into the BH in the past.arusse02 said:Right, I understand that the movies show only the event horizon. My confusion is that because the event horizon, like you said, is not even a thing, then how could it be oscillating? THe only thing I could think of with my admittedly limited understanding is that the event horizon shape is determined by the distribution of matter inside the black just like a gravitational field of a planet would be determined by the mass distribution of the material inside the planet. I realize this analogy is probably much too simplistic. However GR says there is no distribution of matter, it exists in a point.
If all the mass of a black hole is "located" in a singularity as described by GR, then it couldn't have a mass distribution in any sense of the word so I don't see how its possible to have oscillations from a point. Maybe you could explain how a merged singularity can produce an oscillating event horizon. It seems like once the black holes merge then the event horizon should be entirely spherical, not fluctuating between an ellipsoid and a sphere.
Consider a point such that the distance from your left hand, to the point, to your right hand is 2m. The set of all such points forms an ellipsoid around your hands. Clap your hands together; the ellipsoid collapses into a sphere. Now clap your hands repeatedly and the surface oscillates smoothly between a sphere and an ellipsoid. All I need to do is put together an animation showing that surface oscillating.arusse02 said:My confusion is that because the event horizon, like you said, is not even a thing, then how could it be oscillating?
The gravitational field depends on the stress-energy tensor, which includes mass, momentum, pressure, and angular momentum. And it doesn't only depend on what it is now ("now" is a slippery concept in GR), but on what it was elsewhere in the past. And the gravitational field affects the stress-energy distribution (loosely: matter moves due to gravity) which affects the gravitational field. It's the nature of that mutual interaction that makes GR maths hard.arusse02 said:THe only thing I could think of with my admittedly limited understanding is that the event horizon shape is determined by the distribution of matter inside the black just like a gravitational field of a planet would be determined by the mass distribution of the material inside the planet.
There are two spinning singularities merging. The surface can't go directly from two smooth featureless spheres to one smooth featureless sphere - you never see that kind of discontinuous behaviour. It takes a while for the surface to transition from one state, that's all. It isn't due to matter slopping around, it's due to the history of how the singularities came together (see my previous paragraph).arusse02 said:However GR says there is no distribution of matter, it exists in a point.
See above - it just takes a while for the two spheres to settle down into one.arusse02 said:Maybe you could explain how a merged singularity can produce an oscillating event horizon. It seems like once the black holes merge then the event horizon should be entirely spherical, not fluctuating between an ellipsoid and a sphere.
arusse02 said:It seems like once the black holes merge then the event horizon should be entirely spherical, not fluctuating between an ellipsoid and a sphere.
@arusse02 - note that Einstein published general relativity in 1915. Kerr published the solution describing a single isolated rotating black hole in 1963. We aren't joking about the time this stuff takes to work out.PeroK said:That's why you need mathematics. Physics isn't what might seem to be the case if you casually think about something for a minute of two. Physics is about having an evidence-based theory and working through the mathematics.
Some fraction of the kinetic energy becomes gravitational waves, rest collapses into a black hole.arusse02 said:The relative speed of two supermassive black holes moving directly towards each other is 0.999 c. What happens when the two black holes collide directly (so the black holes aren't orbiting each other) at such high velocity? Where does all that energy go and how would it effect space time/what would the merger look like? What happens if they hit at a slight angle such that their event horizons would make contact but there isn't a direct hit.
In short, a empty volume defined by a "shape" can oscillate.arusse02 said:My confusion is that because the event horizon, like you said, is not even a thing, then how could it be oscillating?
PeroK said:That's why you need mathematics. Physics isn't what might seem to be the case if you casually think about something for a minute of two. Physics is about having an evidence-based theory and working through the mathematics.
A black hole is a region in space where the gravitational pull is so strong that nothing, including light, can escape from it. This is caused by a large amount of mass being packed into a very small space.
Black holes can collide when two separate black holes are pulled together by gravity. This can happen when two galaxies merge or when two stars orbit each other and eventually collapse into black holes.
When black holes collide at such high speeds, a tremendous amount of energy is released in the form of gravitational waves. These waves can cause ripples in the fabric of space-time, similar to how a stone creates ripples in a pond.
The collision of black holes at 0.999c can be detected through the use of gravitational wave detectors, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO). These detectors measure tiny changes in the length of their arms caused by passing gravitational waves.
Studying the collision of black holes at 0.999c can help us better understand the properties of black holes and the nature of gravity. It can also provide insights into the formation and evolution of galaxies and the universe as a whole.