ENERGY EXPLAINED
It’s one of the most basic concepts in physics, governing the behaviour of everything from subatomic particles to galaxies
WORDS
ANDREW MAY
Energy is a word that crops up all of the time in countless contexts. Sometimes we think of it as a kind of resource or commodity, like water or light, but it isn’t really a physical ‘thing’ like that at all. To a scientist, energy is an abstract property that’s possessed by actual ‘things’ – water, light, human beings, spaceships, stars and anything else you care to think of. As such, it’s one of the most important concepts in physics, and can help us understand how the universe works.
Energy manifests itself in amazingly diverse, constantly shifting forms and, perhaps for that reason, it took a long time for people to recognise its significance. It only really became an established part of physics in the 19th century, prior to which many great scientists were blissfully unaware of it. The turning point came when people started building machines like steam engines, which convert heat into motion, and needed to make them as efficient as possible. Though there’s no obvious connection between the two, both heat and motion are forms of energy, and like all other kinds of energy, they’re interchangeable.