Find yourself adrift at sea, surrounded by undrinkable water, and you will parch to death. Find yourself lost in a desert and you will meet the same fate, also surrounded by water, also undrinkable. That’s because, even in the driest of lands, the air is loaded with water molecules—they just won’t do you any good. Devices exist that can pull that water out of the air and convert it into liquid, but they are bulky and use a lot of energy.