PHYSICS - Radiation - Nuclear Fusion

At the start of the 20th century scientists had a good estimate of how old the Earth was. At least several billion years of age. This led to the tricky question as to how the Sun not only generated heat and light, but how it had done this for so long! Theories based on known science made no sense. It was impossible that the conventional chemical combustion of a fuel could be sustained for so long, and other ideas of gravitational shrinkage ran into similar time constraints. Best tutorial for nuclear fusion