I watch a lot of Star Trek and it seems like they are frequently asking questions along the lines of "What planet are we on?" or "What planet are you from?" I can't remember the episodes well enough to remember if any of them ever respond with "wtf are you talking about?", but it got me thinking. Surely not all these cultures would have a concept of their home being a planet, because we haven't always had that concept. Sure, many of the early cultures had some knowledge of various heavenly bodies, but that's distinctly different from having the understanding that we are ON one. If we went back 100 years, would they understand that concept? 200 years? 500?

Does anyone know the history of our understanding of the Earth's relation to the universe?