Most of us have not only seen a black hole but been inside one—courtesy of Christopher Nolan’s film
Interstellar. True, physicists don’t expect to find a time-travelling matrix in there, although Nolan’s scientific advisor Kip Thorne of the California Institute of Technology holds up the possibility of spacetime wormholes, the science fiction staple for making shortcuts to other parts of the universe.
Marcia Bartusiak’s thorough, lucid biography of black holes shows how Albert Einstein’s theory of general relativity posited how gravity produces these bizarre astrophysical objects. A gravitational force so strong that even light can’t escape, it was an acknowledged possibility in the 18th century; but no one took the idea seriously until Einstein’s theory seemed to make it inevitable that old stars, depleted of nuclear fuel and thereby of the “radiation pressure” that keeps them swollen, could collapse under their own gravity to extreme densities. If they are big enough, nothing seems able to curb them: the theory says that all the star’s matter is crushed into an infinitely small point, and all that remains is the light-swallowing gravity.
The greatest modern physicists, from John Wheeler to Stephen Hawking, have grappled with the consequences for astronomy and cosmic evolution. The job isn’t done yet, awaiting a union of general relativity and quantum theory before we know what truly lies in a black hole’s dark heart.
