We are made of star stuff — and here is the proof

Carl Sagan began writing Cosmos as a companion to a PBS television series, but the book quickly became something of its own — a sustained argument that science is not a dry accumulation of facts but a way of being in the world. Published in 1980, it remains one of the best-selling science books ever written.

Sagan's organizing idea is what he called the cosmic perspective: the recognition that the same physical laws govern a star and an atom, and that the elements in your body were forged inside ancient suns that exploded long before the Earth existed. We are not separate from the universe looking at it — we are the universe looking at itself.

The book weaves science with history, following the rise and fall of ancient libraries, the lives of astronomers who were mocked or imprisoned for their findings, and the slow accumulation of methods that allowed humanity to figure out the size, age and structure of the cosmos. Sagan treats the history of science as a drama, full of false starts and hard-won insight.

Running beneath all of this is a worry. Sagan wrote at the height of the nuclear arms race, and Cosmos ends with a plea for the survival of our species — a species that, as he put it, has only recently acquired the means to destroy itself along with much of the rest of life on Earth. The grandeur of the cosmos, he suggests, is also a measure of what we stand to lose.