James Alexander Thom said this quote
“ Some writers don't believe they're ready to begin writing the story until they've finished all the research they can think of to do — until they're sure of everything. That's a logical approach, of course. The more factual knowledge, the less likelihood you'll have to throw out a lot of glorious prose when you find out that something you assumed to be true wasn't.But one problem with delaying your start until the research is all done is that the research is never all done. ”