For all the talk about the menagerie of particles locked inside the nuclei of atoms, the universe we directly experience is generated almost entirely though the play of electrons and photons, a dance whose steps are laid out in one of the supreme accomplishments of twentieth-century science in a theory called QED. The theory ignores gravity and stops short of the nuclear frontier, but it is stunning how much is still encompassed within its grasp.
To be sure, we are electromagnetic creatures in an electromagnetic world, existing at the intersection between light and electricity. Moonlight reflecting off a lake becomes, in the language of QED, solar photons bounced by the electron shells of silicon and oxygen atoms in lunar rock and bounced again by the electrons in the hydrogen and oxygen atoms that clap together to make water. And the photons ricocheting from the water interact with electrons again -- the charged haze surrounding the carboniferous chains of protein molecules in our retinas. Almost everything we experience comes to us as reflected light, and so QED give us a theory of how we may know the world.
But electromagnetism is more than a carrier of signals, or a beacon to illuminate matter. Even for creatures that have no eyes, light and the way it plays with electrons is as fundamental as anything can be; it is the very reason atoms stick together to form matter, and they do so according to the rulebook of QED. Therefore, in the way twentieth-century physics has carved up the world, quantum electrodynamics lies at the foundation of chemistry. Whenever two atoms pull together or push apart, the force arises from photons bouncing back and forth between their electron shells. Most of these interactions are invisible, but sometimes a chemical reaction will shed such an excess of photons that they light up the night: oxygen rapidly binds with carbon to make a forest fire; a firefly phosphoresces with a dull green glow.
But even when the light is too weak or vibrates at frequencies our nerves cannot register, it is there providing the medium through which atoms become objects and objects disintegrate into atoms again. Indeed, with every step we take, it is electrons exchanging photons that generates the repulsive force that stops our feet from going through the sidewalk, that creates the illusion of solidity in the world that, we have come to believe, is mostly the empty space inside electron shells. Hence, in this world where we find ourselves, it is QED that provides the best rules of the game.
B. L. Nelson