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Black Holes Explained – From Birth to Death
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CEFR 等级
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Black holes are one of the strangest things in existence.
They don't seem to make any sense at all.
Where do they come from...
...and what happens if you fall into one?
Stars are incredibly massive collections of mostly hydrogen atoms
that collapsed from enormous gas cloud under their own gravity.
In their core, nuclear fusion crushes hydrogen atoms into helium
releasing a tremendous amount of energy
This energy, in the form of radiation,
pushes against gravity,
maintaining a delicate balance between the two forces.
As long as there is fusion in the core,
a star remains stable enough.
But for stars with way more mass then our own sun
the heat and pressure at the core allow them to fuse heavier elements
until they reach iron.
Unlike all the elements that went before,
the fusion process that creates iron
doesn't generate any energy.
Iron builds up at the center of the star
until it reaches a critical amount
and the balance between radiation and gravity is suddenly broken.
The core collapses.
Within a fraction of a second,
the star implodes.
Moving at about the quarter of the speed of light,
feeding even more mass into the core.
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