PHYS 284 Lecture Notes - Lecture 1: Terrestrial Planet, Virgo Supercluster, Orbital Speed
When we look up in the sky, our eyes become scientific instruments and our minds interpreters. What we know about the size and structure of the universe is deducted from observation (mainly light) and our theories of physics. When you look at the night sky, careful observation reveals that objects circle the earth. We can conclude from this that the earth is the centre of billions of orbiting objects. Also born from experience, is that what we see is instantaneous in time, therefore; when we see a star we could believe we are seeing it at this instant. If we accept that light travels instantaneously, then our view of the universe would be much different. Today with scientific progress, we know that both of these two premises are incorrect. Earths role= the earth does not hold any privileged role in the universe. Speed of light= velocity of light is called the speed of light estimated at 300,000 kilometres per second.