Heather Couper presents a narrative history of astronomy.

In 1933, Fritz Zwicky realised that a huge cluster of galaxies is being held together by something more powerful than the gravitational pull of the visible matter. In the 1960s, Vera Rubin was coming to the same conclusion from studying the rotation of stars within individual galaxies. The conclusion was inescapable; all the visible stars and gas comprise a mere fraction of the total matter in the universe. Dark matter exists, although nobody knows what it is.

The question remains unanswered, though now there are many theories. It is hoped that elaborate experiments in particle accelerators may cast some light on the subject.

Readers are Timothy West, Robin Sebastian, Julian Rhind-Tutt and John Palmer. Show less