So it's official – Ernest Rutherford is the top New Zealand history maker. Prime's recent TV series on New Zealand's top 100 history makers had him at number one, as voted for by both a scientist-free panel of "experts" and also the New Zealand public. And who am I to disagree? By any measure, Rutherford was an extraordinary human being and the fact that one of mankind's greatest minds received his formative education here in New Zealand is something that should make all New Zealanders very proud. But yet it seems that some of us don't appreciate just what it was that made Rutherford so great – David McPhail, writing in the Sunday Star Times on November 20^th, would have apparently rather seen Hudson and Halls as our greatest history maker(s), and described Rutherford as "the man who discovered the way to drop a bomb on Hiroshima". Such staggering ignorance cannot be allowed to go unanswered, and so, in this final column of the International Year of Physics, it is appropriate that we revisit Rutherford's genius.

 

But why mention Physics in a Chemistry column? Precisely because Rutherford did in fact see himself as a Physicist – when he was awarded the Nobel Prize in Chemistry in 1908, he noted that the fastest transformation he knew of was his own from a physicist to a chemist. And yet it was in Chemistry that he made his greatest contributions, three of which stand out. And, in my opinion, each of the three was worth a Nobel Prize by itself. The first, for which he actually did win the Nobel Prize, was his theory of radioactivity. It is hard for us today to imagine a time only a little over one hundred years ago, when radioactivity hadn't even been discovered, and we can't even begin to appreciate the enormous impact it had on science at the time. Rutherford, in collaboration with his student, Frederick Soddy (who himself won a Nobel Prize in Chemistry in 1921) was the first to explain radioactivity, through his disintegration theory, which contended that radioactivity was an atomic phenomenon in which the atom itself underwent a transformation to another type of atom – a quite extraordinary proposal, given that the structure of the atom was at that time unknown.

 

Which brings us to his second great discovery, the structure of the atom. Every high school student now knows that the atom contains a central positively-charged nucleus which contains most of the mass, and surrounding this are tiny negatively-charged electrons, but again, at the time, nothing of this was known. Around 1909, Rutherford devised his famous gold-foil experiment, where he took an incredibly thin sheet of gold (only a few atoms thick) and bombarded it with positively-charged alpha particles. Most of the particles went straight through the foil essentially undisturbed, but about 1 in 8000 was deflected almost straight back towards the source. Of this amazing observation, Rutherford said "It was almost as incredible as if you had fired a fifteen-inch shell at a piece of tissue-paper and it came back and hit you". It took Rutherford another two years to conclude that this result was consistent with the atom being mostly empty space, and that most of the mass was concentrated in a nucleus which was positively charged. In so doing, he developed the first truly modern model of the atom.

 

And it is again to the atom that we turn for his third great discovery. The phrase that is synonymous with Rutherford is "he split the atom". But that's not really true. What he did do was something that mankind had been trying to do since its infancy – he turned one element into another, thus becoming history's first successful alchemist. In 1917 he carried out experiments in which he bombarded nitrogen with alpha particles to give production of oxygen and hydrogen. In fact, this was the opposite of splitting the atom – he essentially managed to glue a nitrogen atom to part of an alpha particle to give an oxygen atom, an utterly astonishing achievement.

 

I don't have space to outline the rest of Rutherford's discoveries. He did early work on radio, he discovered the gas Radon, he developed the Geiger counter, he discovered the alpha and beta particles, he was the first to date planet Earth to a high degree of accuracy and eight of his students went on to win Nobel Prizes. It was not for nothing that no less a scientist than Einstein called Rutherford "a second Newton", and it is indeed fitting that the majority of New Zealanders (Mr McPhail excepted) view him as our top history maker. We can only hope that we see his like again.