One day the colonizers look back at Earth and all they see is a green light:
"It's so far away it's unbelievable. It's not here. You can't touch it. You can't even see it. All you see is a green light. Two billion people living on that light? Unbelievable! War? We don't hear the explosions."
It's simple for them to forget. They don't care what happens back there because they are here and now. It's a good lesson I think. All of those things that seem so important, seem like the only things that could ever be important...maybe they're not.
I don't know if I buy it though. Gatsby's green light was the key and it always made him think about Daisy. It was the essence of Daisy, that light.
"You always have a green light that burns all night at the end of your dock..."
Why did Bradbury make the light green? Why not blue if he didn't want me to think about Gatsby? That green light just has to be a Gatsby reference so why doesn't it make those colonizers want to just jump back on their rockets and go home?