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Asked by renick to Colm, Eoin, Joseph, Lauren, Stephen on 12 Nov 2013. This question was also asked by amazeblaze123.
Question: How do black holes happen Please
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Eoin O Colgain answered on 12 Nov 2013:
A star is a balancing act between the nuclear fusion explosions, which tend to blow the star apart, and gravity which tries to crush the star.
When all the fuel is gone, the star will get smaller as gravity eventually wins. How far it collapses depends on how large the star was initially. If it is a large star, gravity is very strong, and there is no other remaining force that can counteract gravity and it crushes atoms, nuclei, etc.
Black holes have an event horizon from which no light is emitted. Although the Earth is not a star, we can calculate how small it would have to be to form a black hole and have an event horizon. All of the earth would have to fit inside a radius of 9 mm. So that is the entire mass of the earth in a sphere of radius 1 cm approx!
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Stephen Scully answered on 13 Nov 2013:
Large things, like the Earth and the Sun, cause light to bend as it passes by. The larger they are the more the light bends. If you have something with enough mass (large enough) then the light can be bent all the way around and travel in a circle. If you make it even larger then it can capture more light. If the light is captured then all you see is the blackness and this is a black hole.
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colm bracken answered on 14 Nov 2013:
Black holes are so dense that even light cannot escape due to the huge concentration of gravity. But they do not have be huge, or even very big. Its all about squashing matter into a really small space. In fact you could make a black hole from your lunch, but you would have to squash it into a space smaller than an atom! So some black holes are much larger than the sun, but some can be absolutely tiny!
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Comments
robyn commented on :
thankyou
Joseph commented on :
You’re very welcome 🙂