I agree that this is a hard question.
General complaint: sometimes when I say that people should be doing a certain thing, someone responds that doing that thing requires answering hard questions. I don't know what bringing this point up is supposed to accomplish. Yes, many things worth doing require answering hard questions. That is not a compelling reason not to do them.
I do not ask it because I wanted to stop the discussion by asking a hard question. I ask it because I aspire to do research into physics and will someday need an answer to it. As such I have been very curious about different arguments to this question. By no means did I mean by asking this question that there are things that should not be research simply how to go about finding them?
Another monthly installment of the rationality quotes thread. The usual rules apply: