Eratosthenes's only tools were sticks, eyes, feet, and brains; plus a zest for experiment. With those tools he correctly deduced the circumference of the Earth, to high precision, with an error of only a few percent. That's pretty good figuring for 2200 years ago.
Carl SaganIs it fair to be suspicious of an entire profession because of a few bad apples? There are at least two important differences, it seems to me. First, no one doubts that science actually works, whatever mistaken and fraudulent claim may from time to time be offered. But whether there are any miraculous cures from faith-healing, beyond the body's own ability to cure itself, is very much at issue. Secondly, the expose' of fraud and error in science is made almost exclusively by science. But the exposure of fraud and error in faith-healing is almost never done by other faith-healers.
Carl SaganThat we can now think of no mechanism for astrology is relevant but unconvincing. No mechanism was known, for example, for continental drift when it was proposed by Wegener. Nevertheless, we see that Wegener was right, and those who objected on the grounds of unavailable mechanism were wrong.
Carl Sagan