How do you gain instant popularity in a room full of smart teenagers? Try solving a Rubik's Cube in 4.9 seconds.Lucas Etter, 14, completed a Rubik's Cube in 4.9 seconds Saturday at a competition at River Hill High School in Clarksville, Md. The World Cube Association and Guinness World Records have already recognized it as the fastest single solve ever.As soon as Lucas and the other teens realized what had happened, the room erupted in celebration. Lucas was instantly surrounded by well wishers and students snapping photos to capture the moment.Keaton Ellis had already broken the existing record earlier that day by solving a cube in 5.09 seconds, but he was no match for Lucas' "blink and you'll miss it" pace. Before then, the world record of 5.25 seconds had been set in April.