HAVING OBTAINED A small but seaworthy vessel, with a scratch crew of professional physicists and curious amateurs, we set sail. The hold contains provisions, a mix of scientific equipment and a guitar. We have some theories to test, and we need data. We hope, like Darwin on the voyage of the Beagle, to find that we will be improved by a journey to distant countries.
We enter the mysterious seascape of the invisibly small from the west. On our map, the western fringes are objects at a human scale. As we sail eastwards we will shrink further, gazing from the bows of our boat into the heart of matter, mapping the otherwise invisible.
Most things are made of smaller things. Our boat is made of wood, metal, fibreglass. It doesn’t take much effort to see that these materials are themselves made of smaller stuff: splinters of wood, glass fibres, plastic. The glass fibre strands, the thickness of cotton thread, are made of silica. Each one of these strands is made of silicon atoms bound to oxygen atoms, with two atoms of oxygen for each of silicon – silicon dioxide. A silicon atom is a billion times smaller than the thickness of the thread. If each silicon atom were the size of one of the peas in the ship’s galley, the fibres would have a diameter close to that of the Earth.
Each atom consists of a nucleus surrounded by fourteen electrons, each with a negative electric charge. The nucleus has a positive electric charge of fourteen times that of the electron, which is why fourteen electrons are attracted to it. That is a familiar kind of configuration. The solar system has eight planets (and some rocks and rejects) in orbit around the central sun. It is tempting to picture the silicon atom as a tiny Solar System, with fourteen little electron-planets orbiting the nucleus. But as we will discover, electrons are not little planets, they are in reality something quite new and different.
As our boat sails east, and we shrink to ever-smaller size, the world around us changes. Most of the predictable laws governing the lands we travel turn out to be obeyed only on average, and electrons and the other objects we encounter are radically different from the features we are familiar with in the west.
For reasons connected with this, in ways which should become clearer during this voyage, the ability to see smaller and smaller pieces of matter requires particle beams – microscopes, effectively – of higher and higher energy. This means that the frontier of the very small also becomes the frontier of high-energy. The important point of high energy in particle physics is the concentration of the energy into a small space, or equivalently into a small number of particles. Because of this, a map of high energies and short distances also informs us about the physics of the very early universe: the hot, dense moments just after the Big Bang. In those first few moments, the energy in any given volume of space was so high that the smallest constituents of matter were laid bare.
To understand all of that, we first need to find out what inhabits this strange new world. What might we find inside an atom? For now, all we know is that the things we find will be very small, and that we need a lot of energy to access them. But where are we going? What strange seas are we sailing, and what laws, if any, apply? The place to start our first expedition is in the first relatively safe harbour we spot in the distance – Port Electron, on the strange shores of an unknown island.