Nanosecond

Relations to other time units

A nanosecond is 1,000 picoseconds and one thousandth of a microsecond. In symbols: 1 ns = 1,000 ps, and 1,000 ns = 1 µs. For a focused note on the picosecond relationship consult picoseconds or the entry on microsecond at microsecond. Informally, a period of ten nanoseconds is sometimes called a "shake," a historical term used in nuclear physics.

Physical scales and examples

Nanoseconds are convenient for describing processes that are too fast for human perception but slow compared with atomic and subatomic events. Light in vacuum travels roughly 0.3 metres in one nanosecond — about 29.98 centimetres — which implies it takes a little over 3.33 nanoseconds to traverse one metre. See a basic reference on light speed at light.

• Many electronic and photonic events occur on nanosecond scales: switching, signal propagation, and some photoluminescence lifetimes.
• In particle and nuclear physics, certain reaction and decay times fall in the nanosecond range. Some fast neutron chain events can complete in on the order of ten nanoseconds; technical discussion appears under nuclear reaction.
• Certain mesons have lifetimes measured in nanoseconds. For example, charged kaons have characteristic lifetimes of about a dozen nanoseconds; see half-life and K meson notes for context.

Technology and measurement

Nanosecond timing matters in computing, telecommunications and instrumentation. A 1 GHz clock has a period of 1 ns, so processor cycle times and memory access latencies are often discussed in nanoseconds. High-speed digital electronics, radar pulses, and time-of-flight measurements commonly require instruments and oscilloscopes capable of resolving single-digit nanoseconds or better. Photonic systems and fiber links also use nanosecond-scale timing to characterize delays and synchronization.

History and terminology

The metric prefix "nano-" was standardized as part of the International System of Units (SI). The informal term "shake" originates from early nuclear-research vernacular and refers to a span of 10 ns (10^-8 s). Scientists use the nanosecond because it matches the natural timescale of many engineered and physical processes without resorting to overly large or small exponents.

Further reading

For concise technical entries and additional context see: unit definition, picoseconds, microseconds, speed of light, nuclear reaction times, decay and half-life, and kaon (K meson).