Episode four of A Further Five Numbers, the BBC radio series presented by Simon Singh.
Newton’s equation of gravity included a number G, which indicates the strength of gravitation. It took 100 years before the shy Englishman Henry Cavendish (he left notes for his maids because he was too shy to talk to women) measured G to be 6.67 x 10^-11 Nm²/Kg². It allowed him to weigh the Earth itself. There has been an ever-greater desire to measure this number with accuracy, which even implied an antigravity at times. How did we measure this tiny number and what does it mean for the universe? The Astronomer Royal Martin Rees explains that a large value for G would mean that stars would burn too quickly and a low value would mean that the stars would not form in the first place, so is G perfectly tuned for life? Is God a mathematician?