Students in Greece will revive Eratosthenes' calculation of the Earth’s radius and circumference, a remarkable experiment in ...

I don't know where he got this idea (surely not from the internet), but Eratosthenes estimated the radius of the Earth by looking at two shadows at two different locations on the Earth. This diagram ...

More than 2,000 years ago, pretty much every educated human knew the Earth was round. There are some pretty obvious clues, after all. If you travel south, you see stars and constellations you’ve never ...