Living in the deepest part of the Cosmos were some Supreme Beings. Feeling bored, one of these beings took up a hobby.
“I will become a collector,” said the Supreme Being. “I will collect everything that goes to make up the Universe. All the fundamental units that combine to construct every substance in existence. I will call these fundamental units –elements. Such a vast and impressive collection will take aeons to put together.”
And so it sifted through all the matter in the Universe and a short time later, it looked down upon its collection.
“Just ninety two elements! That’s all,” exclaimed the Supreme Being. “Just ninety two!”
But it was inescapable; just ninety-two elements made all the matter in the Universe. Baffled by its discovery, the Supreme Being looked closer. The first element in the collection was hydrogen. The Supreme Being looked deep into the atom of hydrogen and saw at the centre a positively charged proton and circling around it, a negatively charged electron. (Oddly, when it looked at how fast the electron was going, it couldn’t see its location and when it stared hard enough to see where the electron was, it couldn’t see how fast it was travelling.)
It shook the confusion out its Supreme mind and examined the nucleus of the second element in the collection – helium. There were two protons in this nucleus and circling around it were two electrons. Then it examined the third element, lithium, and lo, there were 3 protons and 3 electrons.
“Mmmm,” thought the Supreme Being. “Perhaps there’s a pattern emerging here.”
It then looked at the 92nd element in the collection–uranium – and, there were ninety-two protons and ninety-two electrons. Now bored with the stuff of the Universe, the Supreme Being gave away its collection to a friend and went travelling through a black hole (which took considerably longer than collecting all the elements in the Universe).
One day the new owner of the elements was peering into a hydrogen atom and saw something a little strange. Its friend had said the hydrogen atom comprised one positively charged proton and one negatively charged electron. But there in the nucleus of one of the hydrogen atoms there was something new; something without a charge, a neutron. The Supreme Being at once realised that within any one element there were different varieties, depending upon the number of protons and neutrons in the nucleus. So the Supreme Being sifted through all the hydrogen atoms and divided them into three piles. The first pile had one proton, the next pile had one proton and one neutron and the third pile had one proton and two neutrons. The nuclei of all hydrogen atoms contained one proton but there were three varieties, depending upon the number of neutrons in the nucleus. Those with one proton and no neutrons were by far the biggest pile and so the Supreme Being declared these were hydrogen atoms. Those with one proton and one neutron it named deuterium and those with one proton and two neutrons it named tritium. Rather than call them varieties, the Supreme Being called them isotopes.
No sooner had the Supreme Being discovered isotopes when a postcard arrived from his friend travelling through a black hole. It appeared time was standing still for his friend because the postcard was very long indeed. At last however, our Supreme Being finished reading it and returned to its collection. “Thief,” came a cry which was odd because Supreme Beings are perfect and there were no thieves at that time. “My tritium atoms have been stolen.”
Other Supreme Beings gathered around to see what the fuss was about. “Look,” said one bystander, “is that not them there,” mystically pointing.
“No,” said the owner of the elements, “those are not tritium atoms, those are helium…” The Supreme Being realised that the tritium atoms had not been stolen, they had changed into helium-3 (two protons and one neutron). With eternity available, the Supreme Being sat and observed its collection of tritium atoms. Now and again, a neutron flickered and vanished and in its place one proton, one electron and one anti-neutrino came into being. The tritium isotope that once had one proton and two neutrons, now had two protons and one neutron–it had become helium. As helium formed, an electron and an anti-neutrino sped out of the atom and vanished into the vacuum of space. The electron collided with an interstellar cloud and ionised some gas. The anti-neutrino arrogantly ignored everything around it and passed through clouds and planets alike as if they didn’t exist.
“Well,” thought the Supreme Being. “If anti-neutrinos are so ignorant, then I will ignore them and focus my interest on the electrons.” (Thus proving that even Supreme Beings can make mistakes as anti-neutrinos, and neutrinos, are very interesting to those who study them.) The Supreme Being then declared that the electrons speeding out of the tritium atom would henceforth be known as β-radiation – it had discovered radioactivity.
An advantage of being a Supreme Being is that time means nothing. Be it small amounts of time, a mere flicker of a fly’s wing, or immensely long periods of time where Universes wax and wane. And so our Supreme Being looked through its collection and realised that all the elements were subdivided into isotopes; and the radioisotopes were changing into other isotopes, some in an instant and some over aeons. A mystical, magical dance, the stuff of the Universe intertwining, changing, reacting, swirling, never ending! The Supreme Being could see little minute specks of matter flash out of existence only to become energy that radiated away from the disintegrating atom. The Supreme Being looked down on its collection and said, “wow”!
Uranium turned into thorium, then protactinium through radium and polonium and ending up as lead. From uranium to thorium the journey was long and slow and from polonium to lead it was but a blink of the Supreme Being’s eye (if it had eyes).
“How,” thought the Supreme Being, “can I distinguish between those isotopes that vanish quickly and those that seem to hang around for ever?”
“There are one million atoms in my tritium collection,” it thought. Then it started a cosmic stopwatch and waited until half of those tritium atoms had transmuted into helium; the stopwatch read 12.35 years. The Supreme Being kept looking at the pile of 500,000 tritium atoms that remained and when these had become half that number (250,000) another 12.35 years had passed.
“This,” thought the Supreme Being, “gives me a measure of the rate of atomic decay. Every 12.35 years my pile of tritium atoms reduces by half. Therefore, I will call 12.35 years the half-life of tritium.” (The Supreme Being then worked out all the mathematical equations for exponential atomic decay but it is not in the nature of mythical stories to convey such detail and so we will move on).
The Supreme being then catalogued all the isotopes in its collection. It counted 253 isotopes that were stable and the rest were radioactive. Of the radioisotopes, many had half-lives so short it was difficult to measure them (even Supreme Beings have some limitations). A total of 289 isotopes had half-lives of between one day and 10,000 years and 84 had half-lives greater than 10,000 years. Tellurium-128 had a half-life of 2,200,000,000,000,000,000,000,000 years. In fact this was so long that several Universes began and ended before The Supreme Being could figure out a value for the half-life of tellurium-128.
Just then, the Supreme Being’s friend came back from its holiday inside a black hole. Seeing that its collection had turned from a boring pile of atoms into a psychedelic, intertwining, choreography of interchanging isotopes, the returning Supreme Being demanded the return of its collection. The current owner of the isotope collection thought this a little unjust and refused. A little after this, the Supreme Beings invented war, and the Universe was never the same again. The study of the atom and radioactivity was therefore left to the inhabitants of a little blue-green planet called Earth. Ironically, the inhabitants of Earth often fought wars over which Supreme Being one side or another thought the most supreme – but that is a different story.