India, July 5 -- Summer is over and floods are in the air. But still, let's talk about heat.

Why? Because while India's summer heatwaves may be over, the planet's heat continues to speak through many tongues.

Let's start at the source. The Sun is made up largely of hydrogen, and a little helium. Deep in its core, where temperatures reach 15 million degrees Celsius and pressures are immense, hydrogen nuclei fuse into helium. This helium nucleus has slightly less mass than the four hydrogen nuclei that formed it, and the difference in mass is released as energy.

In just one second, the sun releases enough energy to meet humanity's needs for 612,900 years. Only a fraction of that energy reaches the top of the atmosphere above Earth. Then,...