4 ms·

Likely familiar to this crowd, but Carl Sagan's explanation on Cosmos of Eratosthenes' discovery is great: https://www.youtube.com/watch?v=G8cbIWMv0rI&ab_chann

• rugina 4y ago
  That explanation irks me a lot because it implies Eratosthenes knew the Sun was so far away, the rays reaching the earth are practically parallel. And while it might sound a like a detail, the whole calculation depends on it. If you presume the Earth is flat and the Sun not that far away, Eratosthenes was calculating the distance to the Sun.
  • zardo 4y ago
    Wouldn't observing that shadows at noon do not change as you travel east-west rule that out?