Archimedes' Screw, a device used to raise water from one level to another. An Archimedes' screw consists of a helix, or spiral, fitted inside a cylinder that is open at both ends. In use, the lower end of the device is placed under water at a slant and a handle, attached to the helix, is turned. As the helix revolves, small amounts of water are slowly raised in wells formed by the side of the cylinder and the surfaces of the helix. The Archimedes' screw was developed in ancient Egypt and, it is believed, improved by Archimedes (287?-212 B.C.); it is still used occasionally in the Middle East. The device can also be used to lift loose materials, such as grains.
We're all exposed to tiny levels of radiation, but a blast of it can leave you in agony -- that is, if it doesn't kill you outright. What is it, what causes it and how can we treat it?
Atoms: the building blocks of life and the universe. We're all made of these microscopic bits of matter, but how many does it take to make a complete human being? And exactly what kinds of atoms do we have inside us?