Stephen Hawking’s Legacy

The first real science book I ever read was Stephen Hawking’s A Brief History of Time. I was only 13, but I immediately fell in love with the world it opened for me. I spent the next four years working through every book he’d written, as well as a large variety of others, and I credit him with introducing me to the subject that I would later decide to devote my life to — physics.

Stephen Hawking has had this effect on many people. In the days following his death, I’ve talked to many people with stories similar to mine. He made a difficult and intimidating topic accessible and fun, and in a single book, he showed millions of people the beauty of the world around them. However, while everybody knows his book, many people don’t know the actual scientific contributions that made him famous.

His most famous theory was his discovery of Hawking radiation. Hawking radiation is a type of electromagnetic radiation that is emitted by a black hole, discovered by Hawking in 1974. This discovery was revolutionary first of all because it showed that black holes could shrink and even disappear, and that they emit heat. But even more than that, his discovery held deep symbolic importance. In order to formulate this theory, he had to use elements of the theory of relativity and quantum mechanics — and this showed that the “end goal” of physics, a grand unified theory, was possible.

The discovery itself had some beautiful math behind it. Basically, according to quantum mechanical theory, pairs of particles and antiparticles are always being randomly created and destroyed. These pairs usually quickly destroy each other, but at the event horizon of a black hole, it’s possible for one to fall into the hole. This particle has negative energy, so it subtracts from the energy of the hole and can make it smaller. The particle that escapes forms Hawking radiation.

The relationship between quantum mechanical theory and gravity is still largely a mystery to scientists, but unifying the two is generally seen as the final goal of modern physics. Nobody since Hawking has made such an incredible leap in our understanding of how the two work together.

Hawking had previously discovered that black holes carried increasing entropy and therefore adhered to the second law of thermodynamics, so he knew that they had to also have a temperature (if something has entropy, it has to also carry a measure of heat). His discovery of Hawking radiation accounted for that and unified quantum mechanics and relativity. It’s commonly known as his greatest discovery and the one that made him a household name.

However, this is not his greatest legacy. Stephen Hawking was an activist, an advocate for social change, and a pop culture icon. He made physics accessible and interesting to everyone, and captured the imagination of experienced physicists, young children, and everyone in between. His greatest legacy is not the books he wrote, or the theories he postulated, but the generation of scientists he inspired.