In Mathematics, the early Greeks could accurately predict
the seasons, eclipses of the moon, the equinoxes
and even calculated the radius of the Earth correct to one per cent of what we believe today.
Euclid published a famous book called The Elements in 300 BC
which was still used as a geometry textbook in the 1960's
Another famous theorem which was to have severe consequences
on Greek thought was
Pythogoras' Theorem.