SO where, you might wonder, would you find the pot of gold? That's what the myth says you will find at the end of the rainbow. But sadly for treasure-hunters, this one has no end. This awesome sight in the skies over Malaysia this week was not really a rainbow at all but a rare optical illusion called a sundog. These appear when the sun is low and its rays catch the thin vapour formed of ice crystals that lies in the atmosphere six miles above the Earth's surface. The rays are refracted by the crystals, producing what looks like...