This article was first published on Forskning.no
Black holes don’t act like an always-on vacuum cleaner. Nor like a drain in a bathtub or a voracious hole in the ground.
But we resort to comparisons with something we know when we think about and explain black holes.
Space is beyond our imagination, so understanding something as complex and compact as a black hole can be a challenge.
But that doesn’t mean we shouldn’t try. Therefore, videnskab.dk reader Henning has written to us in the hope of finding out if black holes really are insatiable.
“Can a black hole continue to attract material? Will it not be filled up in the end or where will the material end up?” he writes in an email.
To investigate what happens to everything that a black hole attracts, we have spoken to Albert Sneppen, PhD student at the Niels Bohr Institute at the University of Copenhagen.
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He has previously solved one of astrophysics’ biggest riddles about black holes.
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Here, an artist has visualized a black hole more like a sphere than a hole. Photo: XMM Newton/ESA/NASA
A black … bullet?
First, we must correct a misunderstanding. A black hole is not a hole, but rather shaped like a sphere.
The name of the phenomenon probably arose because what ends up in a black hole cannot escape again.
But the question is whether a black hole can really continue to attract material without any limits.
– Yes, it can, is the short version of the answer from Albert Sneppen.
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– If you pour cement into a hole, you will eventually fill it, but a black hole can always attract more material, he explains.
The black hole will gain more and more mass, more gravity and grow even bigger.
A bit like a drain
If a material is captured by a black hole, the first stop is the so-called accretion disk. Imagine a rotating disc around the black hole, which is spherical.
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When the material is in the accretion disk, many collisions occur. The material then heats up and starts to glow.
– Matter on its way into a black hole glows brightly, and that light can slow down the process, explains Sneppen.
Does your mind start to get a little fuzzy when you try to visualize it? Fortunately, Sneppen has a metaphor that can help.
– The concept may be a bit complicated, but it’s really just about if all of this ends up in the drain in a bathtub, it will be pressed very tightly together and then it will be very bright. And that makes it difficult for other material to come down at the same time, he explains.
A hole in physics
But what happens to everything that ends up in a black hole?
The short answer is that we don’t really know.
– It is almost more of a philosophical question, because there is an idea that when something falls into a black hole, we lose all contact with the world it falls into, says Sneppen.
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As soon as the material passes what is called the event horizon, the boundary between the black hole and the outside world, we have no idea what happens to it.
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You may have heard that everything in a black hole is squeezed together due to gravity? It may be so, but the researchers do not know.
Because gravity is so strong that not even light can escape, we will never be able to see or measure what is going on in there.
Even if we sacrificed ourselves and went on a one-way trip into a black hole, we wouldn’t be able to see it, because there is no way to send information back out.
However, physicists have modeled what such a scenario might look like. They do this by taking physical laws that we know from Earth and adapting them to space.
For example, Einstein’s gravitation equations. If they apply to black holes, it would mean that material there would forever fall towards an infinitesimally small point.
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Albert Sneppen does not want to guess:
– What happens when you take us, suns, stars and mass and put them together in an infinitesimally small place, is in itself quite undefined and incomprehensible, he says and takes what is by definition a question that cannot be answered.
© Videnskab.dk. Translated by Lars Nygaard for forskning.no. Read the original story on videnskab.dk here.
2023-08-19 07:26:23
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