3.
The
end of life on Earth?
Part 2
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Most scientists
agree that comets and asteroids pose the biggest natural threat to human
existence. It was probably a large asteroid or comet colliding with Earth which
wiped out the dinosaurs about 65 million years ago. An enormous object, 10 to
16km in diameter, struck the Yucatan region of Mexico with the force of 100
megatons.
That is
the equivalent of one Hiroshima bomb for every person alive on Earth today.
Many
scientists, including the late Stephen Hawking, say that any comet or asteroid
greater than 20km in diameter that hits Earth will result in the complete
destruction of complex life, including all animals and most plants. As we have
seen, even a much smaller asteroid can cause great damage.
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