Light might seem like a simple concept. We wake up every morning, and sooner or later the Sun rises and things get "light." Or, we walk into a dark house and flick a switch and where there was once darkness, there is now light. But what exactly is light? Despite being 93 million miles from the Earth, the Sun delivers approximately 5 trillion giga-joules of energy to the Earth's surface every year. Credit: NASA/JSC Light is so much more than the “either/or” of illumination.