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Amazing image of black holes

Detroit City said:
how can two black holes "crash" into each other? they are made out of nothing
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Uh, no, they're not. Black holes are what you get when there is a sufficient concentration of mass in one place to produce a gravitational force whose escape velocity is that of the speed of light.

We don't know what they're made of, because no information can ever leave them to tell us.
 
Detroit City said:
how can two black holes "crash" into each other? they are made out of nothing
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No space is nothing, or rather a vacuum that can be made more of a vacuum. A black hole is a black hole because its like a hoover so intense not even a photon of light has sufficient energy to mass ratio to escape its suction..
The centre of a black hole contains stuff packed so densely that you couldn't lift cruet set spoon of it
 
stavros said:
Can you have an image of a black hole, or just an image of where a black hole is?
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The effect that a black hole has on its local environment tends to produce phenomena that indicate where the black hole is. But, by definition, the black hole emits no light, so there is nothing to see if you look directly at it.

One interesting phenomenon that black holes can produce, due to their intense gravitational field, is "gravitational lensing". As telescopes have become more accurate, and with better image analysis, we can find duplicate objects in the sky that correspond to the light from them having been bent both ways around a gravitational lens - in essence, a piece of spacetime so profoundly warped that it is able to bend light over significant distances.
 
existentialist said:
The effect that a black hole has on its local environment tends to produce phenomena that indicate where the black hole is. But, by definition, the black hole emits no light, so there is nothing to see if you look directly at it.
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how would you know if you're looking directly at it if there is nothing to see??
 
existentialist said:
The effect that a black hole has on its local environment tends to produce phenomena that indicate where the black hole is. But, by definition, the black hole emits no light, so there is nothing to see if you look directly at it.
Click to expand...

This part may not actually be true.

Black holes are strongly suspected to emit Hawking radiation. Of course it's hard to tell through observation, because the equations predict that stellar-mass black holes will emit only the tiniest trickle of black-body radiation, with a peak intensity in the far infra-red. It is by mass loss through Hawking radiation that black holes are predicted to eventually evaporate. The larger the black hole, the slower it evaporates. The gravitational monstrosity lurking lurking in the heart of the Milky Way will be among the last familiar objects to ever exist, taking about 1.67906e87 or 16,790,600,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 years to finally disappear. Although at this point in cosmological history, the amount of cosmic background radiation is such that the largest supermassive black holes at the centres of galaxies are radiating away less mass-energy than they are absorbing, so it will take a bit longer than that.

Detroit City said:
how would you know if you're looking directly at it if there is nothing to see??
Click to expand...

The same way that I can infer that the invisible man lying on my bed is a weighty bastard.
 
NoXion said:
This part may not actually be true.

Black holes are strongly suspected to emit Hawking radiation. Of course it's hard to tell through observation, because the equations predict that stellar-mass black holes will emit only the tiniest trickle of black-body radiation, with a peak intensity in the far infra-red. It is by mass loss through Hawking radiation that black holes are predicted to eventually evaporate. The larger the black hole, the slower it evaporates. The gravitational monstrosity lurking lurking in the heart of the Milky Way will be among the last familiar objects to ever exist, taking about 1.67906e87 or 16,790,600,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 years to finally disappear. Although at this point in cosmological history, the amount of cosmic background radiation is such that the largest supermassive black holes at the centres of galaxies are radiating away less mass-energy than they are absorbing, so it will take a bit longer than that.



The same way that I can infer that the invisible man lying on my bed is a weighty bastard.
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I thought Hawking radiation (and the whole black holes have hair/rotating frames of reference thing) might be a bit more than Mr City was ready for quite yet... :)
 
existentialist said:
Uh, no, they're not. Black holes are what you get when there is a sufficient concentration of mass in one place to produce a gravitational force whose escape velocity is that of the speed of light.
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They're the most something you can possibly get in one place in fact. And they may well contain a type of matter which, if it ever escaped, could unravel the entire fabric of reality.
 
SpookyFrank said:
They're the most something you can possibly get in one place in fact. And they may well contain a type of matter which, if it ever escaped, could unravel the entire fabric of reality.
Click to expand...

Well, calling whatever is inside a black hole's event horizon anything like matter is understating the concept a bit much. Relativity predicts the presence of a gravitational singularity, a point of zero volume and infinite density. It's more likely to be a ring, since any naturally-formed black hole is going to conserve any angular momentum it had in a previous life. Some of the mathematical implications of rotating black holes are most curious; a traveler winding around the ring singularity could time travel, while one heading through the centre of the ring singularity could end up in another universe. When you cross that event horizon, you ain't in Kansas no more.

Just today, PBS Space Time released a video about dissolving a black hole's event horizon, and how physics might work against any attempt:



Naked singularities haven't been entirely ruled out yet, Cosmic Censorship Hypothesis notwithstanding. What a naked singularity is actually going to be like will be the subject of a future video, since they like to keep their videos less than 20 minutes, and it takes longer to explain an intensely mathematical subject in a non-mathematical way.

Space Time have recently done a number of videos on the physics of spinning black holes. I think this one is my favourite so far:




Detroit City said:
i wonder what it's like being spaghettified
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Like being stretched. If you are positioned so that the soles of your feet are pointing at the centre of the black hole, the stretching sensation will become increasingly intense the closer you get to the singularity. From there it will become uncomfortable, then painful, then excruciating, then lethal. Extreme spacetime curvature can be nasty like that.
 
Hopefully the Event Horizon Telescope (EHT-VLBI) will be able to observe some more black holes in the region. We still have a lot to learn.
 
ska invita said:
I don't understand what you're trying to say by posting that wiki link

I'm saying it looks to me that the "amazing image of black holes" in the thread title is an artists impression knocked up on a computer
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It is
 
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