Where International Standard Units Come From, Part Four: The Mole
Manufacturing Perfect Silicon To create pure and crystallographically perfect samples for this study, researchers used the float-zone method, manufacturing spheres of silicon crystals from the two bulges forming in the polycrystalline rod pictured here. Photo courtesy of B. Andreas, Y. Azuma, et alAll this week, the origin and continued preservation of five of our favorite standard units of measure This week, Sam Kean takes a look at some ridiculously precise standards -- the meter, the second, and other international standard units -- and the role that elements have played in defining, redefining, and re-redefining them over the ages. We all have an intuitive idea of what a meter or a second is, and even a candela seems pretty straightforward. The mole is different, probably the hardest metric standard to grasp at first. My high school teacher had a Velcro rodent she would dismember to help us visualize it-a "mole"...