$40 trillion. That's where the U.S. federal debt officially landed a few weeks ago. It's a number too large to picture, which is exactly what makes it feel alarming. So should you be alarmed? The honest answer: nobody knows where the line is, but people have predicted this catastrophe since the 1940s. In today's email: What the $40 trillion headline leaves out Why the doomsday predictions keep failing (and what would actually worry me) Why none of this should change how we invest As always,...