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Astronomy The 2004 Perseid Meteor Shower Credits: Science@NASA In modern day astronomy, we know that the Moon orbits Earth while Earth orbits the Sun. This model is referred to as a heliocentric model of our solar system. We also know that the Sun is itself a star that is part of a huge galaxy that is only a tiny piece of a large, expanding universe. We have this knowledge from centuries of observation and studies. Today, we have the tools and technology that allow us to discover new things about the universe. The ancient Greek astronomers greatly influenced the astronomical thinking of today. The scientists of the Classic era in Greece, along with the Egyptians and Babylonians, have laid the foundations of modern astronomy. Check that you understand what these words mean in this document Heliocentric: revolving around the Sun. Universe: everything that exists in space. To lay the foundations: to put down the basic principles. For further reading visit: Space games