Eli5: How do blackholes form and exist?
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Mass warps space/time.
Gather enough mass and the warping of space/time becomes so great and so pervasive that nothing, not even light can escape.
So, the singularity itself can’t be observed, but many of them have what’s called an accretion disk that surrounds the black hole and marks the boundary where its gravity becomes so strong that nothing can escape. This disk usually glows with the heat and energy of the falling matter being torn apart.
Most black holes form from the collapse of very large stars.
Stars exist in a state of balance. The energy they’re producing in their core is streaming outward, which tends to push the star apart, while the pull of gravity tends to push the star’s material together into a more compact form.
At the end of a star’s life, this energy production drops low enough that gravity can start compressing the star into a smaller and smaller area. In some cases, the increased pressure at the center ignites new forms of nuclear reaction, which produce more energy and stop the collapse, but this can only go on for so long.
When the star’s energy production finally fails completely, there are three (well, technically a bit more than this, but I’m simplifying a bit for ELI5 purposes) possibilities:
* If the star is small enough, then the core of the star is compressed until (to simplify a bit) the very electrons and protons are pushed up right against one another. Compressing the star further requires a lot of energy, which the gravity of a small star can’t provide. In this case, the star stops collapsing, the core becomes very rigid, and the outer layers of the star “bounce off” the core and puff off into space, leaving a white dwarf.
* If the star is a bit larger, this compression can go further. The protons and electrons are squeezed so much that (unlike under normal circumstances) it actually produces energy for them to combine into neutrons to “save space”. But eventually the neutrons themselves are pushed up against one another, and if the star isn’t too large, no further compression is possible. As in the previous case, the outer layers bounce off (more violently this time – this is a supernova) and a neutron star (a ball of almost pure neutrons) is left from the core.
* But if the star is big enough, even neutrons being pressed right up against one another isn’t enough to resist the force of its gravity. Instead, the force continues to force the core into ever-more-exotic states of matter (the details are not well understood) and, as far as we know, none of those states is rigid enough to stop the collapse. Gravity wins out, and the core compresses down to a single point whose properties are not known. The compressed core becomes so small and dense that its gravity prevents anything from escaping from the area around it – in other words, it becomes a black hole.
We don’t know how they form and we don’t know why they exist. We can only make observations and educated guesses about them.
All objects with mass have gravity. Gravity appears to us as a force of attraction between objects which increases as distance decreases, and because this is ELI5 let’s leave it at that. Stars, especially the really big ones, exert a huge gravitational force on everything around them, including their own atoms. Usually they’re undergoing fusion reactions which release the heat required to keep atoms apart, but when these fusion reactions run out of fuel and the star dies, there is no longer anything to keep the gravitational attraction in check. Atoms begin squeezing together, as they near eachother gravitational forces become stronger, until every atom of that star occupies an infinitely small space.
This gigantic mass has been compressed so far that near its center, the gravitational pull is so intense not even light can escape. The exact distance to the center where the orbital velocity equals the speed of light is called the event horizon, and anything going beyond that limit can’t escape.
They exist because nothing stops them from existing and something causes them to exist.
Black holes are regions of spacetime where, according to Einstein’s field equations, the density of matter in a region of space is so great that not even light can escape.
Scientists in the 1930s predicted that once bodies of matter reached a certain mass, the gravitational pull would overcome any of the forces stopping it from collapsing into a singularity. Stars that were large enough could form these conditions when they died in a supernova.
Since then, even really big and heavy black holes have been found. These are assumed to have formed early on in the universe – so called primordial black holes, and they could merge and combine into supermassive black holes that we observe at the centre of galaxies.
I’ll let some other people answer this one.
“ a star collapsing … eventually shrinks to zero size.”
(p. 49) 23 S. Hawking, A brief history of time, Bantam (1988)
“The matter that forms a black hole is crushed out of existence.”
Prof. Cole Miller of U Maryland.
“the matter of the object is crushed out of existence.”
Prof. David Harrison or U Toronto.
“The star eventually collapses to the point of zero volume…”
NASA on Imagine the Universe, Black Holes.
So as you can see they form by being crushed out of existence.
Lets say we have a star. This star produces heat through a process called nuclear fusion, in which two smaller nuclei come together to form a more dense nucleus. This process creates a force that pushes outwards. This force will also push outwards with the exact same force as gravity pushes in on the star with. Since these two forces are equal, they cancel each other out and the star remains at a constant size. However, when the star dies, the fusion process slows down before stopping, and the gravitational force that pushes inwards is able to compresses the star. If the star is big enough, this will compress it to an incomprehensibly small point, where it becomes a black hole.
I still hate this notion of time being warped by observer. Some dude reaches speed of light and time for him and observer are different. Age differently. It annoys me, the movie buzz lightyear touched on the theory.
Anywho
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