Discovering that Black Hole Evaporate

Black holes were understood as cosmic vacuum cleaners, endlessly sucking in matter and energy from their surroundings. That was before Stephen Hawking introduced a groundbreaking idea: black holes are not just takers, they are also givers. His proposal that black holes could emit radiation would be one of the most important physics discoveries of the 20th century.

Hawking dedicated much of his scientific career to studying black holes, whose gravitational pull is so strong that not even light can escape. His insight came from imagining what would happen at the edge of a black hole, the event horizon. Hawking considered how particle-antiparticle pairs, which continuously pop into and out of existence, might behave at this boundary. He theorized that if one particle fell into the black hole while its partner escaped, it could lead to radiation emitted from the black hole, which we now call Hawking radiation.

He proceeded to back up his theory with rigorous mathematical calculations. By applying quantum field theory in the curved space-time around a black hole, he demonstrated that black holes could indeed emit radiation. This work was pivotal because it began to bridge the gap between quantum mechanics, which governs the smallest particles in the universe, and general relativity, Einstein’s theory of gravity and the large-scale structure of the cosmos.

However, Hawking’s theory also opened a Pandora’s box of new questions, particularly about the ultimate fate of black holes and the information they absorb. If black holes can evaporate over time, what happens to all the matter and information they have swallowed? As black holes slowly disappear, the information they contain seems to vanish as well, posing a profound dilemma for the laws of physics, which state that information can never be completely destroyed. Go deeper: Black Holes Evaporate—Now Physicists Think Everything Else Does, Too - Scientific American

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