What is the smallest measurable unit of time?
Nanoseconds–thousandths of a microsecond–are small, used often in discussions of computers, but things can get smaller still. How small? A: Basically, no one knows if there is a smallest unit of time, says Thomas O’Brian of the National Institute of Standards and Technology. By some theories, time is endlessly divisible, units getting as small as one wishes, though measuring them would be another matter. Other theories suggest that time and space are both “quantized,” with fundamentally indivisible units at the base. Below the nanosecond (10^-9, or 0.000000001 second) are the picosecond (10^-12) and femtosecond (10^-15), the current limit to our most accurate measurement of time, or about one second out of 30 million years. Then the attosecond (10^-18): Some present-day lasers can be pulsed at about the 100 attosecond level, and researchers keep making the pulses shorter, says O’Brian. Smaller yet are the zeptosecond (10^-21) and yoctosecond (10^-24, currently the second shortest int
