Pytheas was an astronomer, navigator, and geographer raised in the third century B.C. in the Greek colony of Massalia (present-day Marseilles), a city on the southeastern coast of France.
At that time, the trade rivalry between the together in a “jelly-fish” kind of ice. Some scholars believe that Pytheas ran into an area of ice sludge and fog in the Arctic Ocean. After this, Pytheas finally returned south and wrote of his journeys in a volume titled On the Ocean, which has been lost.
In it Pytheas demonstrated his keen observation powers. He calculated the distance from north Britain to Marseilles at 1,050 miles, just short of the actual figure of 1,120 miles. He also theorized that the moon was responsible for the tides and noted that the North Star is not always above the North Pole.
No other ancient explorer is known to have followed his route, and at the time his accounts were dismissed as exaggerated stories.