Your son is almost right. There really aren't any brand new , recently discovered inventions. Everything we have is the result of previous improvements. in our knowledge base. Even when you think of Edison, he didn't work in untested fields. He improved on what went before him. There always was a body of fact to improve upon. Granted Edison had unique solutions to problems, but those "problems" were always based on previous 'discoveries'. Nobody works entirely in a vacuum. So there aren't any "discoveries", which aren't based on previous 'discoveries'.