Gravity turned all the way up
What Is a Black Hole?
Squeeze enough stuff into a small enough space and even light cannot climb out.
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Step 1 of 5
To leave anything, you need escape speed.
Throw a ball up and it falls back. Throw it at 11 km per second and it never comes back — that is Earth's escape speed. Heavier objects demand more.
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Step 2 of 5
Squeezing something makes its pull fiercer.
Gravity gets stronger the closer you can get to the middle. Crush Earth down to the size of a marble and its surface gravity becomes monstrous — same mass, much closer in.
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Step 3 of 5
A black hole is squeezed past the limit.
When a giant star runs out of fuel it collapses under its own weight. If it is heavy enough, nothing can stop the squeeze, and escape speed passes the speed of light.
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Step 4 of 5
The black part is where light stops getting out.
The edge is called the event horizon. It is not a surface you could touch — it is the line past which any light heading outward still ends up falling in.
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Step 5 of 5
From far away, it behaves like anything else.
If the Sun became a black hole of the same mass, Earth's orbit would not change one bit. It would just get very dark. Black holes only devour things that come very close.
We photographed one in 2019 — not the hole, but the glowing ring of gas circling its edge.
The short version
A black hole is stuff packed so tight that escaping would need to be faster than light — and nothing is.
Try it yourself
Roll a marble across a stretched blanket with a heavy ball in the middle. The steeper the dip, the harder it is to get back out.
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