Before revision: Pytheas is the first known person to describe the Midnight Sun,The theoretical existence of a Frigid Zone where the nights are very short in summer and the sun does not set at the summer solstice was already known.
After revision: Pytheas is the first known person to describe the Midnight Sun,The theoretical existence of a Frigid Zone where the nights are very short in summer and the Sun does not set at the summer solstice was already known.