Patrick Moore
Tuesday, September 7th, 2010 |
There are some scientists who are remembered mainly not for what they accomplished, but for less worthy reasons. For my column this month I thought 1 would say something about three of these – one of whom I knew well.
I will begin with Percival Lowell, an American asLronomer whom I never met; he died in 1916, six years before 1 was born. He was noL trained as a professional astronomer, hut made his name as a diplomat (he came from a well-to-do family). His reputation established, he turned to astronomy, and in particular he was fascinated by Mars. In 1877 the Italian astronomer Giovanni Schiaparelli had drawn maps showing straight lines crossing the red Martian plains, and referred to them as canali (channels). Inevitably this was translated as ‘canals’, and Lowell became convinced that they were artiOcial waterways, making up a planet- wide irrigation system. He financed and seL up a major observatory at Flagstaff in Arizona, where the major telescope was – and is – a 24-inch Clark refractor, one of the largest and best in the world. Here Lowell and his assistants went on with their work, most of them drawing canals.
Well, we now know that Lowell’s canals do not exist. They were nothing more than tricks of the eye, and it is only too easy to ’see’ what one half- expects to see. Lowell was simply wrong – and it is for this that he is best remembered today, regardless of his sterling work in other fields of astronomy, notably in connection with the magnetic field of the Sun. He accomplished a great deal; he was a major mathematician, an educator and a benefactor, while the Lowell Observatory is still one of the most important tn the world. So when Percival Lowell is mentioned, do not think only of the canals of Mars.
My second candidate is also a man whom I never actually met, though our lives overlapped. The Dutch astronomer Adriaan van Maanen was born in 1884 and died on 26 January 1946. I wish 1 had met him, because from all accounts he was an exceptionally pleasant person – gregarious, friendly, generous and fond of parties – apparently he was an excellent cook! After graduating from Utrecht University in 1911 he went to America and joined the staff of Mount Wilson ObservaLory, where he spent the rest of his career.
Van Maanen was concerned mainly with the nature of the objects then known generally as spiral nebulae, of which the best-known example is M31 in Andromeda; not far from it in the sky is another spiral, M33 in Triangulum, Were the spirals simply members of our Galaxy, or were they separate star systems, immensely remote? Harlow Shapley, one of America’s leading astronomers and who was respected all over the world – believed that they were reasonably local – that is to say, no more than a few tens of hundreds or at most tens of thousands of lightyears away. He pointed out that if M31 were not part of the Milky Way its distance would have to be of the order of 100,000,000 lightyears, greater than Shapley and his supporters could accept. There was also S Andromedae, a nova that flared up inside M31 in 1885 and reached the fringe of naked eye visibility. If it were millions of lightyears away it would have to be unbelievably luminous. We now know, of course, that it was not a normal nova. It was a supernova, but supernovae had not even been suggested in 1885.
Van Maanen was one of Shapley’s followers, and he believed that he could provide proof. He used the best available photographs to measure the positions of some of the spirals, and found definite cases of stars that shifted slightly over periods of years – for example, the Triangulum Spiral appeared to be rotating. If it lay beyond the Milky Way, and Van Maanen’s measurements were correct, the stars would have to be moving at a speed greater than that of light, which was clearly out of the question.
But were the apparent shifts real? One sceptic was Edwin Hubble, a comparative latecomer to Mount Wilson. Using the new 100-inch reflector, he made measurements which did not confirm Van Maanen’s. Hubble, whom I did meet, was generally believed to be somewhat austere and remote, and was never particularly popular (though to me, a young British amateur lunar observer, he was always courteous – possibly because I always wear my RAF tie – and Hubble had served briefly in the post-war US Army, and always liked to be referred to as ‘Major Hubble’). Eventually Hubble found Cepheid variables in the Andromeda Spiral. These convenient stars give away their distances by the way they behave – and the arguments were over. The Cepheids, and hence their host spirals, lay far beyond our Galaxy.
Van Maanen’s measurements were wrong. He had made a completely honest mistake, probably because he had not taken account of optical effects in his photographs; the stars were very slightly ’smeared’ differently on plates taken at different times. This caused systematic errors resulting in apparent movements that were not real.
Van Maanen promptly and very generously accepted Hubble’s results, and it is unfair to remember him today chiefly because of his one major mistake.
Finally, a man whom I knew very well: Fred Hoyle. There is absolutely no doubt that he was one of the greatest of modern astrophysicists, and the fact that he was never awarded a Nobel Prize was frankly scandalous. Some people tend to forget this, and turn back to the prolonged debate about the origin of the Universe. Was the Universe created suddenly, in what Hoyle scornfully referred to as the ‘Big Bang’, or has it always existed and is now in a ’steady state’, so that it will exist forever? Hoyle supported the steady state picture, and made desperate efforts to rescue it in some form or other, even after observational results had disproved it. He never changed his mind, and later in his life he supported some theories which can only be described as weird. But it is time to ignore these, and remember Fred Hoyle as one of the greatest astrophysicists of all time.
These are only three of many similar cases. But I am confident that future historians will ensure that justice is done. ©
