Black Holes

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Black holes warp the universe into a grotesque hall of mirrors

By Paul Sutter
livescience.com
22 July, 2021


Imagine a galaxy reflected in a fun house hall of mirrors. You'd see the galaxy, repeated again and again, with each image becoming more grotesque and distorted. That's how the universe looks near the event horizon of a black hole, one of the most warped places in the cosmos.

While physicists had some previous ideas about what such regions looked like, a new calculation has shown exactly what you would see around black holes, opening up potential new ways to test Einstein's theory of general relativity.

The area near a black hole is very strange indeed. Looking directly at the heavy object wouldn't give your eyes much to focus on; light rays get swallowed by the black hole's event horizon, the point at which nothing can ever escape its massive gravitational influence.

But if you were to place a galaxy behind the black hole and then look off to the side, you'd see a distorted image of the galaxy. That's because some light from the galaxy would barely graze the edges of the black hole, without falling in.

Because of the black hole's extreme gravity, such light would get bent toward your line of sight. Strangely, the galaxy would appear to be far away from the black hole, not directly behind it.

The gravity around black holes is so intense, and space-time is so incredibly warped, that at a certain distance, light itself can orbit the black holes. Some of the light from a background galaxy even gets trapped, looping forever.

However, the light would need to come the exact right distance from the black hole to get trapped in an orbit. It can also hit the black hole at an angle that allows it to make one (or many) loops before eventually escaping.

(...)

https://www.livescience.com/amp/black-hole-mirror-copies.html
 

WeeScottishLassie

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Black holes warp the universe into a grotesque hall of mirrors

By Paul Sutter
livescience.com
22 July, 2021


Imagine a galaxy reflected in a fun house hall of mirrors. You'd see the galaxy, repeated again and again, with each image becoming more grotesque and distorted. That's how the universe looks near the event horizon of a black hole, one of the most warped places in the cosmos.

While physicists had some previous ideas about what such regions looked like, a new calculation has shown exactly what you would see around black holes, opening up potential new ways to test Einstein's theory of general relativity.

The area near a black hole is very strange indeed. Looking directly at the heavy object wouldn't give your eyes much to focus on; light rays get swallowed by the black hole's event horizon, the point at which nothing can ever escape its massive gravitational influence.

But if you were to place a galaxy behind the black hole and then look off to the side, you'd see a distorted image of the galaxy. That's because some light from the galaxy would barely graze the edges of the black hole, without falling in.

Because of the black hole's extreme gravity, such light would get bent toward your line of sight. Strangely, the galaxy would appear to be far away from the black hole, not directly behind it.

The gravity around black holes is so intense, and space-time is so incredibly warped, that at a certain distance, light itself can orbit the black holes. Some of the light from a background galaxy even gets trapped, looping forever.

However, the light would need to come the exact right distance from the black hole to get trapped in an orbit. It can also hit the black hole at an angle that allows it to make one (or many) loops before eventually escaping.

(...)

https://www.livescience.com/amp/black-hole-mirror-copies.html
Mind blown!!
 

hunck

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Latest episode of Brian Cox’s Universe is about black holes

As usual you have to put up with him in various unnecessary locations but worth a watch.
 

Bad Bungle

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After an hour of explaining black-holes Prof Cox concluded the programme with saying nobody can explain black-holes, because in a larger reality there is no such thing as time and space. Thanks Brian.
 

oxo66

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As usual you have to put up with him in various unnecessary locations ...

that's because black holes are really like waterfalls where stuff moves faster than the speed of light.
Not one of Brian's clearer expositions, IMO
 

hunck

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After an hour of explaining black-holes Prof Cox concluded the programme with saying nobody can explain black-holes, because in a larger reality there is no such thing as time and space. Thanks Brian.
What did you expect? since nobody knows what goes on inside a black hole. It was just about what’s known so far. The space time weirdness & ‘deeper underlying structure’ implication is just too far out to grasp & hasn’t been generally accepted but [I think] is more theory based on maths, & maths doesn’t lie, but the history of our black hole was interesting, at least to me.
 

Bad Bungle

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What did you expect? since nobody knows what goes on inside a black hole. It was just about what’s known so far. The space time weirdness & ‘deeper underlying structure’ implication is just too far out to grasp & hasn’t been generally accepted but [I think] is more theory based on maths, & maths doesn’t lie, but the history of our black hole was interesting, at least to me.
I found it fascinating, even though me and Physics parted company when I was 12. I was just waiting for an idiot's guide to Hawkings Radiation so I could concile the notion of nothing escaping a black-hole with something escaping a black-hole.
 

hunck

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I found it fascinating, even though me and Physics parted company when I was 12. I was just waiting for an idiot's guide to Hawkings Radiation so I could concile the notion of nothing escaping a black-hole with something escaping a black-hole.
Emissions from black holes are one of the newer findings/theories. Before that it was thought nothing could escape a black hole. Don’t ask me anything about Hawkings Radiation though.

In the history part the theory is that a huge amount of matter was emitted from the black hole which spread to the outer reaches of the galaxy & slowed down star formation. So theory says it’s happened in the past, several billion years ago..
 

oxo66

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Emissions from black holes are one of the newer findings/theories. Before that it was thought nothing could escape a black hole. Don’t ask me anything about Hawkings Radiation though.

In the history part the theory is that a huge amount of matter was emitted from the black hole which spread to the outer reaches of the galaxy & slowed down star formation. So theory says it’s happened in the past, several billion years ago..

Hawking radiation is a quantum process: a particle pops into existence just outside the black hole's boundary and escapes: its a VERY slow process. The huge amounts of matter spread around the galaxy by the black hole comes from a halo of stuff orbiting the black hole at vast velocities: so not emitted from the black hole itself. I don't think Brian Cox made this clear.
 
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