Historian David Bodanis subtitled his best seller E = mc2 "A Biography of the World's Most Famous Equation." Like most biographies, it includes stories of its subject's ancestors—in this case, innovative thinkers whose groundbreaking experiments shaped Einstein's understanding of mass, energy, and light. Their pioneering efforts helped make Einstein's great epiphany possible. With Bodanis's permission, we've adapted excerpts of E = mc2 to assemble snapshots of these ancestors.
"E" is for energy
The word energy is surprisingly new and can only be traced in its modern sense to the mid-1800s. It wasn't that people before then had not recognized that there were different powers around—the crackling of static electricity and the billowing gust of wind that snaps out a sail, for example. It's just that they were thought of as unrelated things. There was no overarching notion of "Energy" within which all these diverse events could fit.
One of the men who took a central role in changing this was Michael Faraday. Faraday's work showed a profound link between electricity and magnetism, and helped lead the scientific community to see that every other form of energy was connected. Scientists of the Victorian era came to believe that energy could change its form, but the total amount of energy would always remain precisely the same. The principle was called the law of conservation of energy.
This feature originally appeared on the site for the NOVA program Einstein's Big Idea.