Pytheas

Pytheas of Massalia, born around 350 BC and active roughly between 320 and 306 BC, was a Greek geographer, explorer and astronomer from the Greek colony of Massalia, the city now known as Marseille in southern France. Around 325 BC he made a voyage of exploration to northern Europe that was widely known in antiquity, though his own written account of it has not survived and is known today only through the quotations and summaries of later ancient authors. On that voyage he circumnavigated and visited a considerable part of the British Isles, becoming the first known Greek to see and describe the Arctic, polar ice, and the Celtic and Germanic peoples he encountered, and he is also the first person on record to describe the midnight sun. Pytheas introduced the concept of a distant northern land called Thule into the Greek geographic imagination, and his surviving account of the tides is the earliest one known to propose that the moon causes them, an insight well ahead of most ancient explanations for tidal behavior.