The Ancient Solar System...: Straight edges are a sign of something artificial… nature works in curves.... OK, that’s not entirely true – check out the Giant’s Causeway in Ireland - but when it comes to clouds it’s very nearly true. Seriously, you have got to check out the Giant's Causeway. I'm not being paid by the Irish tourist board. HonestPlanets are also very curvy, and they often have clouds. None of the above says ‘will form a huge spinning polygon’, not to my tiny brain anyway. So I wouldn’t expect the planet Saturn to have a ten thousand kilometre wide hexagon, made of clouds, spinning around it’s north pole. Which it does. This thing.The great Saturn hexagon is odd, in much the same way that elephants are plus sized. What is it? Well… the answer involves the weird physics of fluid flows, and a motorised bucket. First a bit of background: Like Jupiter, Saturn is all atmosphere, with the planet's air getting thicker with depth until it becomes a supercritical fluid (don’t ask)*. There’s nothing solid, at all, on the whole planet. So the huge hexagon, bizarrely, must be made of clouds, wind currents, and vapour. Incidentally, the idea that it’s a sign of ...