3 ms·

I had never heard of the two errors in Eratosthenes calculations I’ll have to look that up! Also farther down someone pointed out that coastal dwellers would al

• antognini 3y ago
  Eratosthenes's method basically relied on knowing the distance between two cities and the differ in the elevation of the Sun at those two cities. When he measured the change in elevation, he expressed it as "1/50th the circumference of a circle," which works out to be 7.2 degrees, whereas the true change in elevation is 7.5 degrees. He also assumed that the southern city (Smyrna) was exactly on the Tropic of Cancer. In fact it's a little north of it, but this assumption partially compensated for using too small a change in elevation. Then at another point he rounded up his answer to get a number that was divisible by 360 which further compensated for the original error and he ended up with a final result that was surprisingly good.