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Time & frequency

Time may be our most measured quantity — and unquestionably one of the most important. We use time to organize our lives, to communicate, to run global industries and to navigate our world. To keep time today, we use atoms — nature’s perfect clocks. Atoms themselves don’t tell time; rather, they absorb and emit specific frequencies of light waves. By building clocks that count those waves with exquisite accuracy, scientists can precisely measure and define the second — the fundamental unit of time — and share time with the world.

The quest to accurately measure time and frequency has pushed the frontiers of science and opened up a host of technological applications. Some technologies, like GPS, are mature and used daily by billions of people. Others are still being developed, such as next-generation gravity and mass sensors and spectrometers for measuring chemicals in the air and signals from space.

NIST, in coordination with the U.S. Naval Observatory, provides official time for the United States. NIST builds and operates the country’s most accurate atomic clocks, which help set the global time scale known as Coordinated Universal Time. Through its own time scale, NIST provides time to the nation and the world via the internet and radio. NIST develops chip-scale atomic clocks and calibrates clocks for customers such as stock exchanges. NIST researchers are working with international colleagues to redefine the second — the fundamental unit of time — using next-generation optical clocks.

NIST has built a broad research program in time and frequency measurement. NIST scientists are using optical atomic clocks to push limits of accuracy and precision and test theories of fundamental physics; they are also building compact atomic and microfabricated optical devices for real-world applications. By controlling atoms with unprecedented precision, NIST researchers are advancing quantum computing, sensing and networking. NIST scientists are also developing state-of-the-art frequency sensors to measure greenhouse gases in the atmosphere and habitable planets outside of the solar system.

The Research

Projects & Programs

Compact Cold Atom Instruments

Ongoing
Chip-scale laser cooling This project develops technologies to achieve chip-scale laser cooling, beyond direct miniaturization of existing laboratory techniques. This includes development of the vacuum technology for realizing low power, passively pumped ultra-high vacuum chambers [1,2] and novel

Time Measurement and Analysis Service (TMAS)

Ongoing
The TMAS meets the requirements of any facility or organization that needs to maintain a high accuracy time standard. TMAS customers include calibration and metrology laboratories, telecommunication providers, instrumentation manufacturers, military installations, defense contractors, government

Frequency Comb Spectroscopy

Ongoing
Erbium mode-locked fiber lasers are a mature technology that provide a means to build robust optical frequency combs centered near 1550 nm. One research focus of our group is to extend the optical bandwidth of Er fiber-based combs into the near- to mid-infrared wavelength region of 1000 to 5000 nm

Additional Resources Links

What Is Time?

Philosophically, what is "time"? Even if we don’t completely understand what time is, we can precisely measure what time it is, thanks to the atomic clock, humankind’s most accurate measurement device. Atomic clocks have revolutionized navigation. Only time will tell us its future applications.

What is time?
What is time?

News

Keeping Time at NIST

Einstein is reported to have once said that time is what a clock measures. Some say that what we experience as time is really our experience of the phenomenon of entropy, the second law of thermodynamics. Entropy, loosely explained, is the tendency for things to become disorganized. Hot coffee always goes cold. It never reheats itself. Eggs don’t unscramble themselves. Your room gets messy and you

Major Leap for Nuclear Clock Paves Way for Ultraprecise Timekeeping

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What Time Is It on the Moon?