The ancient Greeks called them ‘hairy stars’. In fact, they were seeing comets-heavenly bodies with long, streaming tails that travel endlessly around the sun. Before they were understood, comets were believed to foretell plagues, war and death. A comet was seen over Rome after the murder of Julius Caesar in 44 B.C. Another, Halley’s comet, appeared over Europe in 1066, the year the Normans invaded England. It caused great terror and a picture of it was embroidered on the Bayeux Tapestry.