Aristarchus of Samos

Over two millennia ago, without the aid of telescopes or modern instruments, a man attempted to measure the vast distances of our cosmos using only his eyes and geometry.

His name was Aristarchus of Samos, a Greek astronomer who lived around 310 to 230 BC.

Using a simple but brilliant method, he observed the Moon during its half-full phase. He measured the angle between the Sun and the Moon to calculate their relative distances from Earth.

From his observations, he wrote in his treatise "On the Sizes and Distances of the Sun and Moon" that the Sun was between 18 and 20 times farther away from us than the Moon. 🔭

While we know today the Sun is actually about 400 times farther, his logic was a revolutionary first step in measuring the heavens.

Based on this, he also correctly reasoned that since the Sun and Moon appear to be the same size in our sky, the Sun must be enormous. He estimated its diameter to be about six times that of Earth.

But his most startling idea was one that the world wouldn't be ready for until Copernicus nearly 2,000 years later.

Aristarchus proposed a heliocentric model—the idea that the Earth and other planets actually revolve around the Sun. 🌕 This challenged the accepted belief that everything revolved around the Earth.

His work wasn't forgotten, though. Later minds like Archimedes wrote about Aristarchus's theories, preserving them for history. His methods laid the groundwork for future generations of astronomers to build upon.

Sources: Aristarchus's treatise "On the Sizes and Distances," Archimedes’