Ancient Greek Philosophers and the Spherical Earth Theory

12 Questions

What empirical evidence did Aristotle use to support his idea of a spherical Earth in 'On the Heavens'?

The observation of round Earth's shadow during lunar eclipses.

What did Aristotle conclude about the shape of the Earth based on his observations?

It is spherical.

How did Eratosthenes measure the Earth's circumference?

Using observations of the Sun's angle at different locations.

What was Eratosthenes' role at the Library of Alexandria?

Chief librarian

What did Eratosthenes compare to estimate the Earth's circumference?

The angle of the Sun's rays at noon on the summer solstice in two cities

How did ancient Greek philosophers contribute to understanding the Earth's shape?

By providing empirical evidence and mathematical reasoning to support their claims

Which ancient Greek philosopher proposed that the Earth was a sphere?

Pythagoras

Which ancient Greek philosopher is known for introducing the Pythagorean theorem?

Pythagoras

In Plato's dialogue 'Timaeus,' what shape does he describe the Earth to be?

Sphere

Which ancient Greek philosopher was a student of Socrates and the founder of the Academy in Athens?

Plato

Who among the ancient Greek philosophers influenced later thinkers with his ideas about a spherical Earth?

Heraclitus

Which ancient Greek philosopher studied the Earth's shape extensively as part of natural philosophy?

Aristotle

Study Notes

Ancient Greek Philosophers and the Spherical Earth

Pythagoras proposed the Earth was a sphere based on his observations of celestial phenomena, particularly during lunar eclipses.
He noted that the Earth's shadow on the Moon was always circular, regardless of the Moon's position in the sky.
This led him to conclude that the Earth itself must be spherical.

Plato's Contributions

Plato presented a cosmological framework in his dialogue "Timaeus" that includes the concept of a spherical Earth.
He discussed the Earth as a solid sphere at the center of the universe, surrounded by concentric celestial spheres carrying the stars and planets.

Aristotle's Observations

Aristotle observed that the Earth's shadow during lunar eclipses was always round, regardless of the Moon's position relative to the Sun.
He noted that as one traveled north or south, the positions of the stars in the night sky changed, indicating a curved surface.
These observations led Aristotle to conclude that the Earth was spherical.

Eratosthenes' Measurement

Eratosthenes calculated the Earth's circumference using simple geometry and observations of the Sun's angle at different locations.
He compared the angle of the Sun's rays at noon on the summer solstice in two cities (Alexandria and Syene) to estimate the Earth's circumference.
Eratosthenes' calculation was remarkably accurate, with an error of only a few percent of the actual value.