One attosecond - measuring time

"One attosecond [a billionth of a billionth of a second] - The most fleeting events that scientists can clock are measured in attoseconds. Researchers have created pulses of light lasting just 250 attoseconds using sophisticated high-speed lasers. Although the interval seems unimaginably brief, it is an aeon compared with Planck time - about 10 - 43 second- which is believed to be the shortest possible duration." A Matter of Time, Scientific American Special Edition