Q&A: Seeing the Earth from Mars and More...

Another awesome video! Thank you so much. I wanted to know at what point in a planet's history is it actually deemed a planet? More specifically, when we say that the earth is ~ 4.5 billion years old, is that from some point in time where it had accumulated enough mass to be considered a planet or if not, at what stage in the solar system's development do we start counting the age of our home planet?

Tom, yes, that was also a very inspiring and moving image. Thanks for telling me. I forgot all about that one.

I liked the image that Carl Sagan showed of earth as one of the Voyager missions was at the other limits of our solar system. Really makes you feel small.