(Image: Richard Kail/SPL)
IT WAS while serving in the German army on the Russian front that, in the winter of 1915-1916, the physicist Karl Schwarzschild sent Albert Einstein some papers. He had solved Einstein’s equations of general relativity for the first time, and shown what happens to space-time inside and outside a massive object – in this case, a perfectly spherical, non-spinning star. Einstein was thrilled.
He wouldn’t be so thrilled with a prediction that eventually emerged from Schwarzschild’s work. Make a star compact enough and it could develop a gravitational pull so great, and warp space-time so much, that even light would not escape.
Just months after his exchange with Einstein, Schwarzschild was dead. It was left to others to work through the details of these curious compact objects, the surfaces of which became known as Schwarzschild singularities.
Chief among them was a young Indian physicist named Subrahmanyan Chandrasekhar. In 1930 he boarded a steamer from India to the UK, where he was to take up a scholarship at the University of Cambridge. Whiling away the 18-day voyage, he worked on the properties of highly compact white-dwarf stars. He found that if they had more than 1.4 times the sun’s mass, they would implode under their own gravity, forming a Schwarzschild singularity.
This did not go down well. At a meeting of the Royal Astronomical Society in 1935, the eminent astrophysicist Arthur Eddington declared that “there should be a law of nature to prevent a star from behaving in this absurd way”. In 1939, Einstein himself published a paper to explain why Schwarzschild singularities could not exist outside the minds …
