Light.

MIT professor Ramesh Raskar starts his talk by showing the classic Doc Edgerton photograph of an apple being shot by a bullet. It demonstrated an exposure of a millionth of a second. Wonderful, right? he asks us, to wide agreement. Only now, 50 years later, technology advances mean we can photograph a million times faster than this. “Now we can see the world at a trillion frames per second,” he says. “I present to you femto-photography, a new imaging technique so fast that it can create slow-motion videos of light in motion.”

What does this mean? Well, it means that now Raskar and co can create cameras that look around corners. “We can challenge what we mean by camera,” he says.

Read and watch the rest at TED.