Kuala Lampur, July 10 -- Not long ago, I was in the dentist waiting room at the Faculty of Dentistry, flipping through an old issue of Reader's Digest - the kind where the pages feel like they've passed through many hands. Somewhere in the middle, I came across a short piece on Planet Vulcan.

Not the Star Trek kind, mind you. This Vulcan was a theoretical planet once believed to orbit between Mercury and the Sun. In the 19th century, French astronomer Urbain Le Verrier noticed that Mercury's orbit didn't behave the way Newtonian physics said it should. The math didn't add up. So he hypothesised another planet - Vulcan - to explain the wobble.

For decades, astronomers looked for it. They believed it was there. Until 1915, when Einstein's...