Yesterday, I posted a slo-mo  video of a Slinkeys, which, when dropped while their springs were completely distended, appeared to levitate momentarily, until their springs had time to re-compress, whereupon they began their expected downward trajectory. My pal Peter Barss (who is descended from a real pirate, kids) has a question "for anyone who remembers their physics better than I do." During most of the its fall, the bottom of the Slinky remains absolutely motionless, which, to my mind, means the gravitational force acting on the slinky pulling it down is exactly balanced by the force compressing the bottom of the...