Building a Better Clock: The Adoption of the NIST-F2 Atomic Clock

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Why bother with an outdated atomic clock whose accuracy is limited to an embarrassing few tens of quadrillionths of a second when you could have the NIST-F2, the United States’ new atomic clock that is three times as accurate as its predecessors. Officially launched on April 3rd by the National Institute of Standards and Technology, the NIST-F2 has been in the works for more than a decade. In 300 million years, the NIST-F2 will not lose or gain a single second. To add to its prestige, the clock was also recently named the most accurate time standard in the world by the International Bureau of Weights and Measures. Read on to learn how the clock works and what makes it superior to previous models.

What Makes Atomic Clocks Tick

Image via Flickr by Steven Depolo

The NIST-F2 and its predecessor are cesium-based atomic fountain clocks, which means they measure the vibration inside a cesium atom to determine the length of a second. Inside the clock, lasers force a ball of ten million cesium atoms together and cool them to help minimize noise. The ball is then passed through a microwave beam as it is pushed up a three-foot chamber. The beam jolts some of the atoms into a higher energy state in which they give off light.

The ball travels up and down the chamber multiple times, with the wavelength of the microwave beam changing a little each time. The purpose of this is for engineers to determine the correct frequency. At the right frequency, the atoms will emit the most light. This number, known as the natural resonance frequency of cesium, defines a second’s length in today’s world.

Why the NIST-F2 Is Superior

Although the NIST-F2 still uses the cesium-atom method, one major improvement sets it apart from previous models. The NIST-F1 runs at room temperature, which means the walls of the clock’s chamber get warm and thus emit a tiny amount of radiation. The radiation tampers with the atoms, resulting in a slight shift in their energy states. To correct this, engineers cooled the NIST-F2 with liquid nitrogen, causing it to operate at a temperature of -316 degrees.

The Implications of Accurate Time-Telling

You might be thinking, “We have a really, really accurate clock now.  So what?” Well, precise timekeeping is the keystone of a lot of modern technology. For example, GPS requires accurate time to a billionth of a second to navigate you correctly. GPS is also the basis of digital network synchronization, such as with cell phones and NTP servers that are the foundation of the Internet.

Next time you glance at your cell phone to check the time, know that it wouldn’t be possible without the precision of the NIST-F2 atomic clock. Your phone might not tell you the time to the sixteenth decimal like the NIST-F2, but it still very much relies on the standards of the NIST clocks. What’s exciting is that all the present applications of atomic clocks were not obvious when they first came about, so the future technology of more accurate timekeeping is anyone’s guess.


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