File this under don't try at home, but there is a safe and painless way to dip your hand into liquid nitrogen. The secret? The Leidenfrost effect, which briefly shields your hand from -320° temps with a layer of bubbles.
PopSci's extremely brave Theodore Gray trusts in science and tests the phenomenon with his own mitt, coming out unscathed. With his hand in the frigid vat for a split second, Gray says he "barely felt the cold at all." The principle that kept him from losing his hand is the same one you spot when water droplets fall onto a scalding hot skillet—rather than evaporating immediately, they bounce around on a thin layer of steam. And when you stick your hand into the sub-zero nitrogen—boom—another instant layer of protective gas. Just make sure to pull yourself out as quickly as you went in, because those bubbles don't last long, and frostbite is no fun.
Gray says the Leidenfrost effect (named after German doctor Johann Gottlob Leidenfrost) should, in theory, protect your hand from a vat of molten lead. But, yeah, we're not going to blame him for passing on that experiment. [PopSci]