Modern time is maintained by atomic clocks that monitor the vibrations of cesium atoms. For most of us, we get this time secondhand, radioed from GPS satellites or relayed through digital networks. But a select few will be able to keep their own atomic time—losing only 1.5 seconds every thousand years—thanks to the Hoptroff No. 10, a pocket watch with a built-in cesium gas oven. The No. 10 is technically a marine chronometer, and with a sextant, it can be used to navigate across oceans. The London-based watchmaker Hoptroff will make only 12 of these timepieces. Customers will have to pass a security check before taking delivery next year, lest the precision timing technology be reverse engineered for things such as missile guidance. Pricing is on request but will be in the high five figures (U.S. dollars).
From Wikipedia:
The Q of a cesium fountain is about 10^10, or about 100 times higher than a traditional cesium beam. Although the resonance frequency is the same, the resonance width is much narrower (< 1 Hz), due to the longer observation times made possible by the combination of laser cooling and the fountain design. The combined frequency uncertainty of NIST-F1 is estimated as less than 5 x 10-16.
The Q of a rubidium oscillator is about 10^7. Undesirable shifts in the resonance frequency are due mainly to collisions of the rubidium atoms with other gas molecules and aging effects in the lamp system. These shifts limit the long-term stability. Stability is typically 1 x 10-11, and about 1 x 10-12 at one day. The frequency offset of a rubidium oscillator ranges from 5 x 10-10 to 5 x 10-12 after a warm-up period of a few minutes or hours, so they meet the accuracy requirements of most applications without adjustment.
Microwaves are non-ionising radiation and completely shielded by metal foil. Caesium-133 (the only form relevant to a frequency reference) is not radioactive.
[quote author=Coding Badly link=topic=202994.msg1496289#msg1496289 date=1386298285]
A quote from the Navy website...
A caesium clock operates by exposing caesium atoms to microwaves...
Would you want microwaves near your you-know-what?
Microwaves are non-ionising radiation and completely shielded by metal foil. Caesium-133 (the only form relevant to a frequency reference) is not radioactive.[/quote]
Paul__B:
Microwaves are non-ionising radiation and completely shielded by metal foil.
Speaking of phones in pants pockets... Is that why cans of nuts always have foil freshness seals? To keep them safe from spurious non-ionizing radiation? Sounds like a good model to follow, if not a bit awkward and susceptible to heat retention.
Hi, I will be kept awake tonight , wondering which standard we are using, rubidium or caesium, and if it will make me 0.0001 of a second late or early for work, if early will I get payed that 0.003cents more. (Just a guess didn't use calculator.)
If the 0.0001Sec discrepancy will help me avoid or put me in the way of a dangerous accident.
My alarm clock, LEGO Shadow Trooper Digital Clock, called Kevin. He is tune with the force......
