QUANTUM THEORY

Towards the end of the 19th century, our understanding of the atom, combined with Newtonian gravity, led scientists to conclude that the understanding of the physical, inanimate world was complete. Such an understanding was to disappear in 1897 when JJ Thomson discovered the electron. The atom, it seemed, was not some solid indivisible entity, but something completely different, with tiny particles revolving around it.
Indeed, it was the escape of such electrons that caused what we know of as an electric current. And if the atom is partly composed of electrons, what else could it contain?
The answer came in 1911, when Ernest Rutherford discovered the nucleus. The age of nuclear physics was with us, with an atom described as a tiny nucleus orbited by electrons. The nucleus itself consisted of protons and neutrons (the latter discovered by James Chadwick in 1932), and it was the number of protons and neutrons in the nucleus that defined its charge, mass, and atomic number. However, the tiny world now discovered was to prove rather strange.
In 1900, Max Planck showed that energy did not radiate in a continuous way, but in packets of energy called quanta. This was the beginnings of quantum mechanics, and it hinted that the physical world was far more complicated than was thought. Indeed, by 1913, Niels Bohr proposed his orbiting electron theory, noting that you could never be absolutely sure where the electron was. Indeed, it seemed that an electron could be in any place it was probabilistic for it to be.
As a means of explanation, when two balls collide, one will shoot off in a specific direction as dictated by the first. In quantum mechanics, it seems, the electron can be said to shoot off in every direction possible. One means of explaining this was proposed by Erwin Schrodinger in 1926. Maybe the electron is not a particle at all, but a wave, thus allowing it to be in all positions. Yet, some definite position must be made for the universe to work.
Schrodinger attempted explanation of this by noting that the position of the particle only became clear when it was observed. Before observation, the quantum world was totally probabilistic. This confusion was made official in 1927 with Werner Heisenberg’s ‘uncertainty principle.’ The problem seemed to be that, in order to observe the quantum world, you had to shine light upon it. Yet light was also made up of particles. Hence, what was actually observed was a crash of particles. The natural conclusion was, therefore, that we cannot see the reality of the quantum world. We can only see the result of our observation; and it was that observation that created a definite from the probabilistic.
The physical world had become very strange indeed. At a fundamental level, the hard universe disintegrated into an electronic fuzz, which could not be observed. Today, explanations are more philosophical than scientific. Such concepts as superstrings are aired, enfolded in eleven dimensions, held together only by mathematics. However, such theorising did lead to practical application when it was realised that if an atom could be split, different elements could be produced. And not only this, the massive forces required to keep the nucleus together could be released.
If such a release could be controlled, the world could have unlimited nuclear energy. If released fast, a massive explosion could be the result. By 1939, Otto Hahn had created such nuclear fission, leading Enrico Fermi to produce a controlled chain reaction in 1942. The nuclear world was with us.

(c) Anthony North, July 2006