Welding a railroad with thermite

The process of laying down a fresh set of railroad tracks has come a long way over the last two centuries, but the welding process has basically stayed the same for the last 80 years. Since the mid 1930s, nearly every new rail is connected via thermite welding. Using an exothermic chemical reaction, welders don't need any external power or fuel source to supply heat or current. See the process in action with this neat video.