The Hunt for Vulcan

Thomas Levenson

Why I looked at this book

What do you do when your observations don't match your theory? If the theory is gravity, then postulating extra matter which hasn't been seen yet seems like a good idea. It worked in the case of Uranus and Neptune, and is the main reason for claiming the existence of dark matter today. Trying to come up with an alternative theory of gravity seems dubious in comparison. But in the case of the anomalous motion of Mercury, it was an alternative theory which was needed. I was impressed by Levenson's earlier book Newton and the counterfeiter. and I hope this will be equally impressive in telling about the planet which never existed.

First impressions

The book starts with a brief look at how Einstein's general theory of relativity explained the motion of Mercury, doing away with the need for Vulcan. We then go back to the work of Newton on developing his theory of gravity. Levenson emphasises the way science really proceeds. It's not so much that previous ideas (such as the planet Vulcan) were foolish mistakes - they made sense at the time. It's more that small problems arise for which revolutionary changes may be necessary.