The strangest objects we know of

The idea of black holes sounds so quintessentially modern and 20th-century that it may come as a surprise to learn that it originated over 200 years ago; John Michell, a natural philosopher and clergyman, used Newtonian physics to conceive of a star massive enough to prevent even light from escaping its gravitational pull.

Marcia Bartusiak’s lively and readable account of the history of black holes kicks off with an account of Michell’s 1784 paper. There’s a lull in the story after that, because a proper formulation of the physics had to wait until Einstein’s general theory of relativity in 1915. This date is significant; it’s the 100th anniversary of this theory in November, and Bartusiak is clear that the purpose of her book is to celebrate the theory’s most famous prediction. It should be said that there are many other popular accounts of general relativity, in particular Pedro Ferreira’s recent The Perfect Theory, which cover this material in greater depth.

However, Bartusiak’s stated aim is not to explain the detailed science (which is just as well, given the brevity of the book and the infamously complex mathematics involved), but to convey what she calls ‘the history of an idea’. The book succeeds best when she shows us how physicists repeatedly backed away from their own predictions of the theoretical possibility of black holes. Nowadays we may be fascinated by them, but to many scientists (and even Einstein himself), the idea was simply a monstrosity which Nature would somehow find a way to avoid.

Their problem was that a black hole was predicted to form when a massive star collapsed into a singularity; a point in space-time with infinite mass. The key sticking point was whether this singularity was physically real or simply an artefact of the convoluted maths.