How did Ancient Greek Philosophers Know the Earth was Round?

The video explores the historical understanding of Earth's spherical shape, starting with early philosophers like Pythagoras and Plato. Aristotle provided evidence through lunar eclipses and constellations. Later, Ptolemy and others added observations about ships and horizons. Eratosthenes calculated Earth's circumference using shadows and geometry, achieving remarkable accuracy despite uncertainties in measurement units.

Who was the first philosopher credited with the idea of a spherical Earth?

• Aristotle

• Pythagoras

• Plato

• Eratosthenes

What observation did Aristotle use to argue that the Earth was spherical?

• The flight patterns of birds

• The changing tides of the ocean

• The movement of the sun across the sky

• The shape of the Earth's shadow on the moon

What did Claudius Ptolemy observe that supported the idea of a round Earth?

• The changing seasons

• The migration of birds

• The disappearance of ships hull-first over the horizon

• The phases of the moon

What was the key observation Eratosthenes used to calculate the Earth's circumference?

• The length of the Nile River

• The distance between Athens and Sparta

• The angle of the sun's rays in two different cities

• The height of the pyramids

What assumption did Eratosthenes make about the sun's rays?

• They are perpendicular

• They are parallel

• They are curved

• They are divergent