Night and Day
Can you identify which half of the Earth is experiencing day and which is experiencing night? Like the Earth, the North Pole of this model is oriented towards the North Star; that means that its axis is parallel to that of the Earth. Therefore the area of the globe that is in darkness is experiencing night and the area of the globe that is illuminated by the Sun's rays is experiencing day.
The first person to calculate the Earth's dimensions was Eratosthenes (a Greek scholar born in Cyrene [present-day Libya] more than 2,200 years ago), who did so by measuring the shadow cast by two obelisks located in two different cities: Alexandria and Syene, or modern-day Aswan.