By about 1000 B.C.E. Greece had inherited knowledge about astronomy from Egypt and Babylon. At this time religion and science were one in the same, as the Gods were responsible for all natural phenomena.
Around 700 B.C.E. the Greeks became the first intellectuals to separate from religion and look at the world from a naturalist point of view.
This point in time is considered the birth of science as we know it, and many aspects of our lives today can be dated back to ancient Greece philosophers challenging the truths that they had previously known.
"The momentous leap from 'mythos' to 'logos'." (Burkert, 1999)
Scientists and philosophers alike were now free to ponder the universe in a completely unrestricted way. The origin of the universe was often a topic of study, though even today we still do not know for sure how everything came to be. Some thought that matter has to have always existed, based off the idea that matter cannot come from nothing. Others believe that the creation of matter marked the creation of the universe. Pythagoras, a pupil of Thales, took an avid liking to the study of geometry. He claimed that all relations in the natural world could be reduced to numbers, and often studied music in this way as well as science. Pythagoras was extremely influential then and even now his ideas and theories, such as the Pythagorean theorem, are taught in classrooms worldwide. He claimed that "geometry is the architecture of the universe", and so far nothing has been found to disprove this multiple thousand year old idea proposed by someone who had no tools other than his mind and paper to write on (Fernández-Armesto, 5.2.3).
The spread of Hellenism
Once Hellenism, this naturalist way of looking at the world, took hold in Greece it was only a matter of time before surrounding areas caught on. Trade was extremely prevalent in the ancient world and allowed the great societies of the time to become what they did. It also nurtured the spread of ideas and culture. Hellenism became advanced very quick and the societies along the edge of the Mediterranean that Greece often traded with (Afroeurasia) saw the potential of this new way of thinking and it did not take very long for ideas to spread throughout a multitude of cultures.