ALFONSO the Wise, the 13th century King of Castile in what we now call Spain, had no false modest reticence about the qualities whereby he earned his name. "Had I been present at the Creation," he remarked on one occasion. "I would have given some useful hints for the better ordering of the universe.
But by the 18th century astronomers had reached the view that there was no real need for Alphonso's interference. They saw that there was a neatness in the universe, and it was a favourite pastime to try to uncover more and more examples of this heavenly precision.
In particular they explored a widespread notion that the planets and their orbits had a simple key.
In 1766 Johann Titius wash sure that he had solved the ultimate riddle of the cosmos. He pointed out that the sizes of the orbits of the planets could be set down as a series of numbers. The basic series he used was 3, 6, 12, 24 where each number is its predecessor multiplied by two. But to make the sequence fit the universe, Titius put a zero at the start, and added four to each - thus arriving at 4, 7, 10, 16, 28, 52, 100.
The pattern, he explained, reflected the proportionate distance of each of the seven known planets from the sun. If the nearest planet, Mercury, was regarded as being four units distant, then the series accurately predicted that Earth, number three, was 10 units away, and that the outermost planet, Saturn, was 100 units from the sun.
There was no known planet at distance 28, but otherwise the series was an excellent fit.
Titius did not publicise his great discovery: this was done by one Johann Bode, so the pattern - rather unfairly - came to be called "Bode's law". It is only recently that justice has been done, and the sequence re christined "Titius Bode".
Bode's Law was at first a mere mathematical curiosity. But then in 1781 William Herschel discovered the planet Uranus: the next number on the Titius scale was 196 - and Uranus was 190 "Titius units" from the sun! And to cement the rule, in 1801 a minor planet, Ceres, was discovered between Mars and Jupiter - which fitted 28.
The Titius Bode Law is still a mystery. Its magic faded when it failed to work for the two outer planets, Neptune and Pluto, the last to be discovered. But there is still argument and discussion as to why it should hold good for as many as it does.
By and large it is felt to be a mere coincidence: it is suggested that no matter what the arrangement of the planets in the solar system, it should be possible to find some orderly sequence of numbers to match their orbits closely.