I often get so caught up in the background research for stories that I can easily allow that research to eclipse the true task, which is to write. As I work on creating a believable landscape for my current story, I need to figure out weather patterns, seasons, agriculture and technology so that I don't inadvertently create an equatorial desert next to an arctic tundra. Whatever I make up, I want to be plausible. I just ordered this book in the hope that it is useful: World Building, by Stephen Gillett. World Building is part of Ben Bova's series called Science Fiction Writing.
*In this case, 4.5 billion years is 4.54 × 109 years ± 1%. An American billion is a thousand million, whereas a British billion is a million million. To quote Lone Star Ma, "Grrf."