On the origin of the cosmic elements and the nuclear history of the universe

The quest for the energy source of stars, capable of maintaining their long-lasting brightness, has puzzled physicists during centuries. Early suggestions, due to Julius R. von Mayer, John James Waterson, Hermann von Helmholtz, and William Thomson (Lord Kelvin), among others, relied on the conversion of gravitational potential energy into heat. However, the age of the Sun inferred in this framework was only a few million years, a value clearly at odds with estimates based on geological records.