Nature

Nature: How do we know the shape of the Earth?

Answer: Watching what Earth's shadow looked like during multiple eclipses.

Patryk Kocielnik

Writing with the hope that a record of the random things people do around can save some duplication of effort -- except for fun.

More posts by Patryk Kocielnik.

12 Mar 2025 • 1 min read

Observing multiple lunar eclipses, ancient people realized the Earth cases a round shadow on the Moon.

If something casts a round shadow on something else from various angles, we know it must be a sphere.

Patryk Kocielnik