A new photographic time machine,” when used with a high- speed camera, allows researchers to photograph events that occur before the camera’s shutter is opened. Called an image-preserving optical delay, the new device is an arrangement of optical components, including mirrors and a crystal shutter, that photographs an event “before it occurs after it happens,” says inventor Edward F. Kelley. Even though the camera is triggered after an event, its optical delay allows photographs to be taken of the processes leading up to the event. ‘Functionally, the optical delay is equivalent to forcing the image to travel an additional 120 meters before it gets to the camera,” says Kelley, a physicist at the National Institute of Standards and Technology. ‘Using a series of concave and planar mirrors, this path length is folded into about four meters.” The system is currently being used for processes lasting from 100 nanoseconds to 10...

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