But I don’t have any of that information! So you may think I’ve wasted my time by exchanging one question I can’t answer for four. Not so. What Fermi understood is that by breaking down the question, we can better separate the knowable and the unknowable. So guessing—pulling a number out of the black box—isn’t eliminated. But we have brought our guessing process out into the light of day where we can inspect it. And the net result tends to be a more accurate estimate than whatever number happened to pop out of the black box when we first read the question. Of course, all this means we have to
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