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NIST F2 Clock Video Description for the Visually Impaired

News ReleaseBackgrounder | Video on YouTube

Visual: NIST rolling cube intro

Narrator: Time is the most measured quantity in the world.

Visual: A full moon on a cloudy night. A field of clocks and gears.

Narrator: We use it to plan our lives, find our way, and make our fortunes.

Visual: Looking out the front window of a car as it speeds down the highway. Overhead view of a pile of bundled $50 bills.

Narrator: Because so much depends on accurate timekeeping, the National Institute of Standards and Technology, or NIST, is constantly working to build better clocks.

Visual: Cityscape at night with a transparent field of analog clocks superimposed over it. Background switches to a view of NIST's lab in Boulder, Colo. NIST'S new atomic time standard, the F-2 fountain clock, is the most accurate clock of its kind in the world. If NIST-F2 ran continuously for 300 million years, it would not stray from perfect time by one second.

Visual: Inside NIST Boulder labs, we see the NIST F-2. NIST's Steve Jefferts enters, kneels, and makes some adjustments to the apparatus.

Jefferts: "In some very real sense, the job of NIST is to recognize and bring forward the best standards you can have for certainly the basic quantities of length and mass and time and things like that. And presumably you end up pushing as hard as you can to build the best standard you can. And when you can do something better than the Earth gives you naturally and its rotation, well, you go ahead and you start down that road. And then people keep making it better, and when you make it better, somebody starts having a use for it, and so you have to make a better one, and this process continues to this day."

Visual: Steve Jefferts speaking in front of a background of flying mathematical formulas and shifting sine waves.

Narrator: The new clock is three times more accurate than the previous NIST standard, NIST-F1.

Visual: NIST physicists at a laser table making adjustments.

Narrator: Several improvements were made in NIST-F2, the most important being to nearly eliminate small errors caused by background radiation.

Visual: NIST physicists at a laser table making adjustments.

Narrator: First, lasers slow and cool the atoms to just a fraction of a millionth of a degree above absolute zero.

Visual: Computer animation of the clock in operation. A transparent cylinder at the base has many small colored spheres representing cesium atoms moving randomly around. Above that is the microwave chamber and another cylinder. Lasers inside the lowermost chamber activate and push the cesium atoms together.

Narrator: A laser then lofts the ultracold atoms into a tube inside a liquid nitrogen-cooled chamber. The cold chamber reduces errors caused by thermal radiation, which slightly alters the "ticking rate" of the atoms.

Visual: The ball of atoms is lofted upwards through the microwave emitter ring and into the refrigerated chamber. As the atoms descend they pass through the microwave chamber again and are energized by a laser. Light escapes the atoms and hits a sensor. The camera pans to a computer screen that plots how much light the atoms have emmited on a graph. The first group of atoms have not emitted much light.

Narrator: Within the clock, the cesium atoms make two passes through a microwave chamber. If the frequency of the microwaves matches the atoms' ticking rate perfectly, their outermost electrons flip over and enter an excited state.

Visual: Another ball of atoms is lofted up through the microwave emitter ring and into the cooled chamber above. The atoms fall back through the microwave emitter where they are again struck by a laser and emit light. This time much more light is released, as shown by the graph on the computer screen.

Narrator: When a laser beam hits the atoms, only those in the excited state respond by absorbing and re-emitting the light. Scientists know they have found the right microwave frequency when they see the atoms re-emit the most light. "That frequency is defined, it's the only defined frequency we have, okay? So all other frequencies you measure with respect to that frequency, and that frequency is, as I said, it's 9 billion times a second. Well, if I count 9,192,631,770 cycles of the radiation that makes the electron flip over, then that's one second, and now I count another 9 billion I've got another second and so on, and so you simply keep counting."

Visual: Steve Jefferts speaking. An animation of a cesium atom's electron appears as a glowing white sphere with a blue arrow pointing downwards. Wavelengths of microwave radiation hit the electron from the right side. The number 9,192,631,770 Hz appears below the radiation. The arrow inside the election turns from blue to red and points upwards.

Narrator: NIST scientists use that second to recalibrate their commercial atomic clocks, which run more reliably, but aren't nearly as accurate as a cesium fountain.

Visual: Camera pan past a bank of atomic clocks, a digital readout of the time, and the new atomic clock.

Narrator: We need ultra-accurate time for a host of applications, including the global positioning system, telecommunications, and the Internet.

Visual: A computer screen showing a view of the Earth. Tracked satellites move across the screen.  

Narrator: But do we really need time accurate to within 1/300,000,000th of a second per year?

Visual: People hurriedly walking through a train station with dozens of clocks. 

Narrator: "So the short answer is that there is probably no relevance to the best clock that we can build today in everybody's life tomorrow, but that clock is going to be the progenitor for something that really is important 10 years from now, I would predict. The fact of the matter is the commercial atomic clocks you go buy today, and, look, there are companies in business selling these things, and if there wasn't a market there wouldn't be. The clocks they sell are as good as the clocks we could possibly build in the laboratory 20 years ago and they're being used all over the place. And so we have to stay out in front of that if for no other reason than we have to be able to calibrate them. So we have to be that much better than they are in order to measure them."

Visual: Steve Jefferts speaking.

Visual: Screen fades to black.


For more information
inquiries [at] (inquiries[at]nist[dot]gov)

Animation of F2 clock created by:
Trent Schindler

Videography by:
Breck Larson

Animation of F2 clock created by:
Jake Dean
Aloe Design Studios, LLC

Video footage and stills provided with permission by:
NIST Production Staff

Producer/Editor: Leon Gerskovic
Narrator/Scriptwriter: Mark Esser
Additional Footage and Stills: Jim Burrus

The production team wishes to thank the staff of the NIST Boulder Labs for their help in the making of this video.

The display of products and services in this program is for demonstration purposes only and does not imply an endorsement by NIST.

National Institute of Standards and Technology
Public Affairs Office
March 2014

Created April 3, 2014, Updated January 4, 2017