Time up for atomic clocks

The Register ^ | 24 April 2006 | Chris Williams

[VRWCmember]

The Russians would probably still find a way to get two extra tries at the final three seconds of the basketball game in the Olympics if they needed it.

[LibWhacker]

Strontium clocks have now reached the point where their only point of reference for accuracy, the old-style Caesium clocks, can't compete.

Grrrr... exactly HOW MUCH better are they than cesium clocks anyhow? Basic information. Basic. I guess they don't have time to teach that crap in journalism schools anymore. Too busy teaching hatred of Bush.

[Turbopilot]

A meter is defined as the distance light will travel in some specific fraction of a second, and the modern definitions of all other units of length are some fraction or multiple of a meter. So I think it applies to all units of length.

[Publius6961]

Other than the light-year, to what does this apply?

Everything.
If time varies with speed, having a static reference is useless.

[Onelifetogive]

the Earth's rotation, which is relatively variable.

I was wondering if it was only me that was feeling it.....

[linear]

If they are super-accurate, you'd never be able to move one - it will get ever so slightly out of phase with the ones that remain stationary.

[Izzy Dunne]

A meter is defined as the distance light will travel in some specific fraction of a second

So it is - I didn't know that. Last I knew it was related to Krypton radiation, but I see that was replaced in 1983.

Shows how well I keep up. I'm really gonna have to work on that stack of magazines...

[Future Snake Eater]

How has it lasted that long? And how come they don't make 'em like they used to?

[Chuck54]

You are so right, they sure don't make 'em like they used to.

LIVERMORE'S

Facts

* Age: 104 years and counting (as of 2005)

* Installed: First installed at the fire department hose cart house in 1901. Then moved to fire station at First and McLeod, then to its present site in 1976 at the fire station, 4550 East Ave., Livermore, California

* Proof of Longevity: From local newspaper records; also GE engineers researched it. Was donated to the Fire Department in 1901 by Dennis Bernal who owned the Livermore Power and Light Co.

* Vital Statistics: Made by the Shelby Electric Company, a handblown bulb with carbon filament. Approximate wattage-4 watts. Left burning continuously in firehouse as a nightlight over the fire trucks.

* Recognition: Declared the oldest known working lightbulb by Guinness Book of World Records. Ripley's Believe-It-or-Not in 1972 researched it and declared it the oldest. Charles Kurault of the TV program "On the Road with Charles Kurault" visited the bulb in the 1970s and included it in his book as well.

* Closest Competitors: A bulb in a New York City hardware store had been working since 1912, but it is unknown if it still works today. Another bulb listed in the 1970 Guinness Book under the heading Most Durable says that "on 21 Sept 1908 a stagehand called Barry Burke at the Byers Opera House, Fort Worth, Texas screwed in a new light bulb and that it was still burning". The third was a bulb in a washroom at the Martin & Newby Electrical Shop in Ipswich, England was dated from 1930 and burned out in January 2001.

* Future Plans: The City of Livermore and the Livermore-Pleasanton Fire Department intend to keep the bulb burning as long as it will. They have no plans at present what to do with the bulb if or when it does burn out. Ripley's has requested it for their museum.

* Visiting: You can visit the bulb during normal office hours Monday through Friday from 8 to 5 p.m. at Fire Station #6, 4550 East Ave., Livermore, California. During the weekends, or evenings, is dependent on the availability of the Firemen on hand.

* Celebration: We commemorated its centennial on Friday, June 8, 2001 at the fire station. The celebration was from 5 to 8 p.m. with community BBQ and program. Three bands provided a variety of music, ranging from 1900 era, 1950s music, and a contemporary rock music group.

For more information contact the Lightbulb Centennial chairman Lynn Owens at (925) 447-9477 or email Bulb@lpfire.org

(Information provided by Livermore Lightbulb Centennial Committee 12/2005)

[ShadowAce]

You can visit the bulb during normal office hours Monday through Friday from 8 to 5 p.m.

Just don't try to smuggle in any contraband!

[jaydubya2]

http://tf.nist.gov/stations/wwv.html

NIST radio station WWV broadcasts time and frequency information 24 hours per day, 7 days per week to millions of listeners worldwide. WWV is located in Fort Collins, Colorado, about 100 kilometers north of Denver. The broadcast information includes time announcements, standard time intervals, standard frequencies, UT1 time corrections, a BCD time code, geophysical alerts, marine storm warnings, and Global Positioning System (GPS) status reports.

[Future Snake Eater]

Ah. 4-watt bulb. I didn't catch that when I read the website. I guess that's a big reason why it's lasted so long.

[steve86]

Just finished reading "About Time - Einstein's Unfinished Revolution" by Paul Davies. Terrific book.

[John Jorsett]

It would have been nice if the article had said what the accuracy of the new clocks is, relative to the Cesium ones.

[Redcloak]

You have to think about what "heat" really is. It's the measure of how much atoms are vibrating. The lasers push on the ion from opposite directions and hold it in place. This stops it from vibrating. No vibration, no heat. And for their purposes, no vibration means no Doppler shifts in the emitted light. All of the photons come from the same place and from something that isn't moving.

Light from a vibrating source is spectrally broadened by Doppler shifting. Imagine the old train-blowing-its-whistle-as-it-approaches analogy for Doppler shifting. Now imagine that the train isn't coming toward you; it's simply vibrating back and forth along the track. The whistle, rather than having a single, clear tone, will sound fuzzier as the tone smears out to different frequencies. The same thing happens with light. A laser should have a single wavelength; but, since the atoms inside the laser are hot, they vibrate and broaden the colors of the laser to other, nearby wavelengths (frequencies). Some are coming toward you and look "bluer" while some are going away and look "redder". If you are trying to use the light as a clock source, then the frequency is constantly changing. This clock avoids that by chilling the emitter.

[SlowBoat407]

Other than the light-year, to what does this apply?

It can apply to everything from laser and infrared ranging to a target, to fiber optic gyros, although the reference time still has to come from the strontium source, so there.

[Vermont Lt]

So, if I miss a few seconds over the next, say, 75 years or so...will I really miss it? Or is there something more meaningful here.

So a ship comes in off by a few feet. Is it THAT significant?

[Izzy Dunne]

So how does that define a basic unit of measurement, which was the question?
(It's been answered).

[CPOSharky]

basic units of length are defined by how far light travels in various time periods. ®

Other than the light-year, to what does this apply?

The speed of light in a vacuum is defined as 299,792,458 meters per second. That determines the meter as the distance light travels in 1/299,792,458 of a second. The more accurate the clock is, the more accurate distace measurement of distance will be.

That sounds like circular reasoning, but the speed of light in a vacuum (symbol lower case "c") is considered an unchanging universal constant.

[Izzy Dunne]

The speed of light in a vacuum is defined as 299,792,458 meters per second.

Right, but only since 1983. It takes a while to sink in to my brain.