What’s a nanosecond?

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A nanosecond is one billionth of a second and is commonly used in science and technology. Computer scientists use it to measure memory access speed, while in optics, nanosecond pulses of light are used to capture images of fast-moving phenomena. Other units of time, such as microseconds, picoseconds, and femtoseconds, are even smaller. Grace Hopper used a length of wire to demonstrate the distance light travels in a nanosecond during her lectures on computer science.

A nanosecond is 10-9 seconds, or one billionth of a second. That means there are a billion nanoseconds in one second; a billion is one followed by 9 zeros. Light takes a little more than a nanosecond to travel a single foot (0.3 meter); light travels at about 980 million feet per second (300 million meters per second). In science, a measurement involving nanoseconds is usually abbreviated to ns or nsec. While it’s simply too small a measurement to be useful in everyday life, the nanosecond has many important uses in chemistry and physics that both involve processes that occur in extremely short periods of time.

Computer scientists also make some measurements in nanoseconds as many processes in modern computing occur in very short time intervals. The speed a computer takes to access its memory, for example, is commonly expressed in nanoseconds. In this case, lower numbers are better: a computer that can access its memory in 10 ns is faster than a computer that takes 30 ns to access its memory. Both numbers, however, represent very, very high computational speeds. It is unlikely that an individual would be able to recognize the 20 ns time difference between the two processes.

Most uses of the nanosecond are in fields related to science and technology, such as electronics, optics, and communications. nanoseconds are often used to measure various aspects of electromagnetic waves such as frequency. In optics, very short nanosecond pulses of light or laser beams are used to collect precise images of fast-moving phenomena such as chemical reactions. When several such pulses occur in a very short period of time, a series of images is produced, allowing scientists to visualize the phenomenon at their leisure.

While the nanosecond is a very small measure of time, it’s certainly not the smallest. A microsecond is slightly larger than a nanosecond at 10-6 seconds. Picoseconds and femtoseconds measure 10-12 and 10-15 seconds, respectively, and tend to have similar uses. Femtoseconds, in particular, are commonly used in optics to measure the pulses used to acquire images in extremely small time intervals. None of these units have practical applications for most people, but physicists, chemists, and technicians often need such small units.

Grace Hopper, US naval officer and computer scientist, was known for her lectures on computer science. She is best known for developing the first compiler for a programming language. At her lectures, she was known to hand out lengths of wire just under 1 foot (0.3 meters) long to show the distance light traveled in a nanosecond; she did this to explain why satellite communication was not instantaneous.




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