Johann Titius felt he had solved the ultimate riddle of the cosmos. In 1766 he pointed out that the orbits of the planets could be represented as a series of numbers.
The basic series he used was 3, 6, 12, 24 etc, 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.
This 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 4 units distant, then the series accurately predicted that Earth, number 3, 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's discovery was publicised by one Johann Bode, so the pattern, rather unfairly one might think, came to be called Bode's Law. And Bode's Law was a mere mathematical curiosity until, 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!
Astronomers were now wildly excited by the strange gap between the 4th and 5th planets, Mars and Jupiter. There must surely be a major heavenly body in between, and in 1800, after a gathering in the German town of Lilienthal, a group of enthusiasts formed a sort of heavenly neighbourhood watch.
Rather quaintly they called themselves "The Celestial Police" and they resolved not to leave a heavenly stone unturned until they found their missing body.
Unfortunately, however, while the police, under their leader Heinrich Olbers, were self-importantly making preparations for their search, an Italian astronomer called Giuseppe Piazzi discovered a new heavenly body quite by chance, right between Mars and Jupiter. Piazzi made his discovery on January 1st. 1801, and called it Ceres.
But Ceres was a disappointment; although it was in the right spot for the missing planet "28", it was very small indeed, smaller even than our own moon. The Celestial Police felt sure there must be more than Ceres in that tantalising gap, and continued their search for another 15 years.
In a way they were right. To date, some 1,600 bodies have been found in what we now call the "asteroid belt" between Mars and Jupiter, but a major planet to correspond to "28" on Bode's Scale was never found.