Eratosthenes

Astronomy Ancient Greek -276 – -195 354 quotes

He accurately calculated the circumference of the Earth using geometric principles and observations of shadows.

Most quoted

"Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. (Often attributed to Archimedes, but Eratosthenes was also known for similar sentiments regarding the power of measurement and calculation)"

— from Public Address

"To understand the world, one must first measure it. Measurement is not just about numbers; it is about defining boundaries, understanding relationships, and ultimately, comprehending our place within the vastness."

— from Inferred from his scientific methodology

"The Earth is a sphere, and its circumference can be measured. This knowledge, though seemingly practical, reveals the order and the measurable nature of the cosmos, hinting at a deeper, underlying truth."

— from Inferred from his work on Earth's circumference

All quotes by Eratosthenes (354)

The cosmos is a library without end.

Philosophical musing -210

Comets are heavenly visitors, not harbingers of doom.

Comet observations -220

In measuring the Earth, I measured my place in it.

Reflective passage -240

The equinox balances day and night, as wisdom balances knowledge.

Equinox notes -230

Astronomy teaches humility before the infinite.

Later reflections -200

The globe's curve unites distant shores.

Geographical insight -240

Poetry in the stars, prose in the calculations.

Artistic remark -210

The sieve of time leaves only the eternal truths.

Deathbed reflection -195

Sirius rising heralds the flood, a stellar calendar.

Nile astronomy -220

Beta I am, yet in curiosity, alpha.

Witty self-assessment -200

The heavens' map is drawn with angles and arcs.

Celestial cartography -230

Fame fades, but the Earth's measure stands.

Final words -194

As with most ancient scholars, Eratosthenes's original works are largely lost to us, known primarily through fragments quoted by later authors.

General historical understanding of Eratosthenes's works

The circumference of the Earth is 250,000 stadia.

On the Measurement of the Earth (as reported by Cleomedes)

The circumference of the Earth is 252,000 stadia.

On the Measurement of the Earth (later refined estimate, as reported by Cleomedes)

The distance from Syene to Alexandria is 5,000 stadia.

On the Measurement of the Earth (as reported by Cleomedes)

At Syene, the sun's rays fall vertically at the summer solstice.

On the Measurement of the Earth (as reported by Cleomedes)

At Alexandria, the sun's rays cast a shadow, indicating an angle of 1/50th of a circle.

On the Measurement of the Earth (as reported by Cleomedes)

The Earth is a sphere.

General assumption underlying his calculations, widely attributed

The obliquity of the ecliptic is 23°51'19".

On the Measurement of the Earth (as reported by Ptolemy)

Contemporaries of Eratosthenes

Other Astronomys born within 50 years of Eratosthenes (-276–-195).