Question

What are the scientific achievements of the classical age of greek civilization?

Answer 1

Observation was eventually undervalued by the Greeks in favour of the deductive process, where knowledge is built by means of pure thought. 
According to the Greek tradition , the process of replacing the notion of supernatural explanation with the concept of a universe that is governed by laws of nature begins in Ionia.
Anaximander, another Ionian argued that since human infants are helpless at birth, if the first human had somehow appeared on earth as an infant, it would not have survived. Anaximander reasoned that people must, therefore, have evolved from other animals whose young are hardier.
The Greek achievements in Mathematics and Astronomy were one of the finest in antiquity.