Watch Clip

Energy Defined
2m 41s
What is energy and why are we on a never ending search for new energy sources?
NOVA brings you stories from the frontlines of science and engineering, answering the big questions of today and tomorrow, from how our ancestors lived, to whether parallel universes exist, to how technology will transform our lives. Visit the official website to watch full-length documentaries, or explore our world through short-form video, on our digital publication NOVA Next.
Video description: In 2011, the worst tornado season in decades left a trail of destruction across the U.S., killing more than 550 people. Why was there such an extreme outbreak? How do such outbreaks form? With modern warning systems, why did so many die? Is our weather getting more extreme - and if so how bad will it get?