When did humans first learn the size of the Earth? Or, for that matter, when did it become clear that the Earth was a sphere?
To those not attuned to science history, it may come as a surprise to learn that the Earth’s size and shape were settled 2,200 years ago, and by the same person. In what was one of the great intellectual feats of antiquity, the Greek Eratosthenes took the measure of the Earth using only simple tools and mathematics, together with his creative mind. This post recounts how Eratosthenes did it.Read the rest of this entry »