The blades on a lawnmower aren't as sharp as the name would imply (although they will hurt you), and they don't use an opposing force like a knife on a cutting board or scissors, so how do they cut grass instead of just pushing it down? The answer may surprise you. Destin Sandlin of Smarter Every Day takes us underneath a mower with a high-speed camera so that we can understand what's going on. -via Geeks Are Sexy