Dutch optics engineer Ralf Ottow created a 38-million-candlepower homemade flashlight he called the Maxblaster. It can shoot a lightbeam 4 miles long!
Powered by a pack of 54 batteries, the Maxablaster can put a bright spot of light on a cloud four miles high and illuminate a house from just as far. But Ottow doesn’t use it to spook his neighbors. “It’s not a torch you’d walk your dog with,” he says. “It would probably cook your dog.”
http://www.popsci.com/diy/article/2008-01/handheld-sunbeam - via GeekAlerts