HAVING PREPARED OURSELVES for the fact that the objects we encounter will be a strange amalgam of wave and particle, we approach the shore of Atom Land with confidence and excitement, eager and, we think, well prepared to explore the interior. We disembark and head off on foot.
An atom is the smallest indivisible fragment of a chemical element. Think back to the fibreglass of our boat, and the silicon the fibres are made of. We already peered briefly inside the silicon atom, observing the nucleus and especially the electrons around it. If we were to break up an atom of silicon, what we would get might be interesting,fn1 but it would no longer be silicon. Everyday materials consist of different chemical elements, each one of which is a different kind of atom, sometimes bound together as molecules.
The idea that there are indivisible building blocks to matter may date back to the ancient Greeks, but the knowledge that atoms are real was the result of careful exploration over the last two centuries. Much of that exploration was not done directly with high-resolution instruments probing tiny structures: it was done by observing the properties of different materials, identifying how they combine and react with one another, and weighing them precisely. Most of the elements were discovered between 1745 and 1869, by many different explorers using a wide variety of inventive techniques, including tasting, smelling, weighing or simply observing the properties of various materials and the products of various reactions between them.
For example, several scientists working independently in the 1760s worked out that air contains two major components, one of which would allow flames to burn, and make mice more active and healthy, while the other would put out flames and suffocate mice. In the 1770s the mouse-friendly gas – which was also produced by heating mercury oxide – was identified as the element oxygen. A Scottish student, Daniel Rutherford, guessed that the mouse-killing gas was another element, nitrogen, in his 1772 doctoral thesis.
Astronomy was also employed, being responsible for the observation that there was a new element present in the Sun, not previously known on Earth but identified by the distinctive frequencies of light it emitted. It was named helium, after Helios, the Greek god of the Sun, and was later identified in gases emitted by Mount Vesuvius. In 1895, Swedish chemists Per Teodor Cleve and Nils Abraham Langer noted that the same gas was produced by dissolving certain minerals in acid, and managed to isolate enough of it that they could measure its atomic mass.
John Dalton, a chemist, physicist and meteorologist working in the nineteenth century in Manchester, conducted a series of enormously careful experimentsfn2 – combining, reacting and weighing various gases and other substances – and established that some materials involved in various chemical reactions always combined in fixed ratios. He hypothesised that this was due to the fact that the reaction was actually taking place between tiny fractions of each material. These tiny building blocks possessed, he believed, certain well-defined ways of combining and recombining to make new stable building blocks of a new material. Carbon dioxide, for example, could be made from combining two parts oxygen with one part carbon. Water could be made by combining two parts hydrogen with one part oxygen. If you get the ratio right, all the initial materials will turn into the final product. If you get it wrong, you will find that you have something left over.
In 1869, the Russian chemist Dmitri Mendeleev arranged the known elements, according to their chemical properties, into the Periodic Table. This is more than just a neat way of arranging things. Grouping the elements by their reactivity and masses in the way that Mendeleev did reveals a pattern which reflects the internal structure of the atoms, and which had predictive power. Gaps in his original table suggested ‘missing’ elements, all of which have since been discovered. It is the ‘Standard Model’ of chemistry, in a sense, and it points rather directly towards the beginnings of the Standard Model of particle physics.
Our exploration of Atom Land has shown us a complex and beautiful array of features, the building blocks of everyday materials. They exhibit some fas cinating behaviour, which we would like to understand better. But everywhere we go in Atom Land, everyone we ask tells us that to understand the economy and ecology of the place, grasp how its denizens really interact with each other, we must return to Port Electron.