For the planets to be truly indistinguishable, they must have precisely the same density and composition at every point within, and this represents a truly colossal amount of information.īut black holes, on the other hand, are surprisingly simple. Take planets, for instance: no two planets are the same, because each has a vast number of properties. What is black hole hair?Īlmost every macroscopic object you know is incredibly complex. If you waited long enough, the cliff would eventually smooth into a gentle slope, and there would no longer be a frightening drop into the unknown. This is a very slow process, analogous to the gradual erosion of the cliff underneath the waterfall. They evaporate, shrinking away until there is only empty space. As black holes slowly heat their surroundings, they give up energy (and therefore lose mass according to E=mc 2) until there is nothing left. In 1974, Hawking showed that black holes can emit heat. Much like how nothing flows back up from a waterfall, we know absolutely nothing about what lies inside a black hole, as nothing ever gets emitted. In this river, a black hole is like a large, steep waterfall, where the current gets so incredibly strong that even light cannot escape. Gravitational forces can be thought of as currents in a river, pulling objects along in certain directions. As we will see, if we want to predict the future of our universe, we need to understand how black holes work. Yet their very existence poses a profound challenge to our fundamental principles on how our world evolves. Once a theoretical construct, direct detection on Septem(see our recent blog post about the LIGO discovery) finally proved their existence. This recent work of Hawking, Perry and Strominger has some profound implications for how we understand not only black holes, but all cosmological objects, and can be neatly summarized in the following theorem: “Black holes have soft hair.” What are black holes?īlack holes are among the most extreme objects in our universe, places where gravitational effects get so strong that our current physical theories begin to break down. Professors Hawking and Malcolm Perry of Cambridge University have been working closely with Harvard’s own Professor Andy Strominger in order to explain some of the deepest mysteries surrounding black holes and the ultimate fate of information in the universe. That is, at least, according to Stephen Hawking, who visited Harvard in April this year to give a sold-out lecture in Sanders Theatre. This strange question has been debated by physicists for at least forty years, and today it seems we may be approaching an even stranger answer: You’ll never guess how Google autocompletes: Figures by Shannon McArdel and Michael Gerhardt
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