Tiny black holes may cascade through the universe. Created in the Big Bang, they're smaller than an atom, but as massive as a mountain. They could zip through the heart of a star -- or even our own planet -- without hurting a thing. And they may even account for some of the mysterious "dark matter" that fills the universe -- matter that produces no detectable energy, but that exerts a gravitational pull on the visible matter around it.
Today, a black hole forms when the heart of a massive star collapses. The core becomes so dense that its gravity prevents anything from escaping -- including light. These black holes are a few times as massive as the Sun, but only a few miles across.
Primordial black holes are far tinier. They formed shortly after the Big Bang, when the universe was a dense, hot mixture of matter and energy. It was so dense, in fact, that a passing ripple could squeeze a pocket of matter or energy tightly enough to form a black hole.
Some models predict that countless primordial black holes were formed. Many of them quickly evaporated. But others were massive enough to stick around -- and may still exist today. Despite their mass, they're so tiny that they could pass through a star or planet without harm.
That small size makes them hard to detect. But scientists are working on a few techniques for finding them -- a discovery that would tell us a great deal about the early universe. More about that tomorrow.
Script by Damond Benningfield, Copyright 2009
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