This was how physicists hypothesized the sun and other stars work in the late 19th and early 20th century, before the discovery of nuclear fusion. It presented

This was how physicists hypothesized the sun and other stars work in the late 19th and early 20th century, before the discovery of nuclear fusion. It presented a conundrum because calculations showed that the sun could only sustain the observed rate of energy release for a few million years – whereas the contemporary geological evidence was indicating that the Earth must be billions of years old.