I read a fascinating story from the history of science. We’re all familiar with the conservation of energy – how it shifts between forms without being lost. But the story of its discovery is truly inspiring.

It began with mechanical energy. Consider a swing: potential energy converts to kinetic, and back again. Scientists, through experiments and calculations, found that the total energy remains constant.

Next came thermal energy. While people understood mass conservation, heat’s true nature was a mystery. One theory proposed heat as a kind of substance, massless yet capable of flowing between objects. This explained everyday observations, like mixing hot and cold water: the “heat substance” flowed, creating lukewarm water.

However, friction could generate seemingly endless heat, simply by rubbing things together. This “heat substance” appeared to materialize from nothing. This spurred investigation into the link between mechanical work and heat. Precise experiments and calculations of energy conversion finally led the scientific community to conclude that energy is conserved during mechanical-to-thermal conversions.

Around the same time, biologists suggested that animal heat and movement stemmed from food’s chemical energy. Chemists added to this, demonstrating energy conservation in chemical reactions.

Then came electromagnetism. Lenz, studying heat in current-carrying wires, found it depended on the current’s square, resistance, and time – Joule-Lenz’s law. Calculations revealed that electrical-to-thermal energy conversion is also conserved.

These discoveries occurred almost simultaneously. Different fields contributed their pieces, and when combined, revealed the true nature of energy. It was like magicians jointly casting a spell, opening a portal to a dazzling new world.