Learn about the science of astronomy with iMinds insightful audio-knowledge series.

The human desire to know what we see when we look in the sky is so great that a branch of science has been dedicated to it: astronomy. Astronomy is the study of the material universe outside the earth's atmosphere. Astronomers research and make estimations about our universe and outer space in general.

Human beings have been gazing up at the sky since before written history began. Millennia ago, humans witnessed the setting of the sun, seasonal changes, and the phases of the moon. However, what human beings knew about this outer space region amounted to very little until relatively recently. The ancient philosopher Claudius Ptolemy wrote on astronomy in the second century. His main book is called Almagest, which translates as "great work". It was written in about 150 CE and outlines the common belief that the earth was the centrer of the universe. Ptolemy and his contemporaries believed the Earth did not move and did not spin on its axis because, if no movement can be felt, how could this be so? This same belief was held by most humans for the next 1,500 years, and was known as the Ptolemaic system.