Just Finished Reading: The Neptune File – Planet Detectives and the Discovery of Worlds Unseen by Tom Standage (FP: 2000)

The whole civilised world rejoiced in 1781 when, for the first time in centuries, a new planet in the heavens was discovered proving beyond doubt the mankind had truly entered the new Scientific Age. As astronomers all across the globe gazed upon the new planet and began to chart its movement joy gave way to puzzlement. The new world, named Uranus, was not behaving as predicted and, as more observations were made its aberrant behaviour only became worse. Checking back in the historical record sightings of Uranus (unknown at the time) didn’t help at all. In fact the more information astronomers had about the planet the less predictable its path through the Zodiac became. So the mystery remained for over 50 years – a puzzle without a solution indeed, as some saw it, without even a possible solution. But if there’s one thing that unites men across space and time is that they can’t resist a challenge no matter how seemingly intractable.

As with all good science any errors must be eliminated and the underlying theories examined for flaws. The observations of the orbit of Uranus were checked, confirmed and checked again. Errors were indeed discovered and eliminated but still the planet was not behaving as it should. Things became so desperate that the very framework of Celestial Mechanics itself – Newton’s Theory of Gravity – was examined for flaws and, with a great sigh of relief, found to be without error. Even ideas of some sort of substance only evident in the outer Solar system enforcing a drag on the new planet where put forward only to be dismissed when the accumulating facts found it wanting. There was only one theory that could account for the path of Uranus across the night sky. Something beyond its orbit must be influencing it. Another, yet undiscovered, body must be influencing its orbit but how could something like that be caught in even the world’s most powerful telescopes without any idea where to look in the vastness of space. To do that you would have to calculate the position of a planet effectively in reverse starting with the perturbation of another world and working backwards to identify what was causing the disturbance and where it was at any particular time. A task, many considered, simply beyond the capability of the human mind.

But in the first half of the 19th century two mathematicians, completely unknown to each other, put their minds to the problem of finding a planet without ever looking through a telescope. They would use mathematics alone to determine exactly where an invisible body was and then, when they were certain, announce it to the world and expect others to actually look for it themselves. The race was on between an unknown English mathematician John Crouch Adams and the famous French scientist and astronomer Urbain Jean-Joseph Le Verrier. Whoever got there first would become world famous and their name would become immortalised as the first man to find a planet by brain power alone.

This was a complete impulse buy from Amazon some months ago and there was a real danger that it would continue to gather dust far into the future without being read. Looking for something different to pass the time with I picked it up recently and was almost immediately hooked. Today we live in an age where new planets on far away stars are discovered on a weekly basis. So much so that new discoveries are rarely reported beyond the scientific press. After the amazing discovery of Uranus and the reality of an enlarged Solar system it must have come as quite a shock when yet another unknown world was discovered between the lines of pages of equations. Like all mysteries, even mathematical ones, the trick is to recognise the clues and to follow them to their conclusion – no matter the prejudices or preconceptions of the investigators. Theory after theory is put forward to explain the observed facts and each is demolished as the mysterious planet eventually named Neptune serenely smashes through them. This is science in action on a grand scale. Observations are made, theories are tested and found wanting, facts are checked and new theories built until, slowly and carefully, the new planet is tamed and becomes one of the family rather than a wayward son.

Of course that was not the end to things. Once the theory was in place and solidified into a useable technique the search for other planets began in earnest. Every slight ambiguity in the orbit of any planet was seen as a potential case of yet another world to be discovered. But over the years they each turned out to be false hopes. But over a century later similar techniques began to produce results and the first planets orbiting other stars emerged from the darkness of deep space. At least from a planetary perspective we were not alone. Well written and full of interesting characters (although not always the nicest or most professional) this is a must read for anyone interested in the history of planet hunting. Recommended.