Talk:Atomic clock

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Contents 1 WikiProject Time assessment rating comment 2 Discussion 3 Accurate compared to what? 4 Radioactivity? 5 Synchronization 6 Mercury Atomic Clock Keeps Time with Record Accuracy 7 picture of HP 5071A

[edit] WikiProject Time assessment rating comment

Needs more cites to be a B.

Want to help write or improve articles about Time? Join WikiProject Time or visit the Time Portal for a list of articles that need improving. -- Yamara 15:54, 17 January 2008 (UTC)

[edit] Discussion

"The most accurate time scales are moderated by precise astronomical measurements and the insertion or removal of leap seconds. " seems to be wrong since TAI is just as accurate as anything else, in fact, you could argue that it's more "accurate" than UTC since you can use a precise TAI time in the future and know how long from now that is. With UTC you can't.

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How did they set the first atomic clock? Did they use astronomical measurements or some other source?

--haavis 12:15, 5 Nov 2004 (UTC)

A: Using astronomical measurements. Does the last paragraph in caesium standard explain it well enough?

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--tdunc 8:29,10 May 2007

"When the electrons are attracted back closer by the opposite charge of the nucleus, the electrons wiggle before they settle down in their new location. This moving charge causes the light, which is a wave of alternating electricity and magnetism."

This explaination is unacceptable. The author either needs to elaborate or change it all together, why the electron jumps to a lower level. I have reason to believe it is not because of attraction due to charge (which would be constant), rather the electron emits a photon thus lowering its energy level, which could by coincidence mimick charge attraction but I dont feel its the same concept. If so it needs to work both ways, we cant for instance say a repeling charge is responsible for an electron going into a higher energy level. What is with the word "wiggle" anyway?

I have fixed the article to avoid this issue. The explanation is simply quantum mechanics. Chapter 9 of Griffith's undergraduate QM textbook has a cogent derivation. Amcfreely 07:01, 16 May 2006 (UTC)

[edit] Accurate compared to what?

"National standards agencies maintain an accuracy of 10^-9 seconds per day"

So I set up my brand new atomic clock, go away for 3 million years, and come back to find out it is off by one second. Compared to what? Another atomic clock? I don't see what else it could be if, by definition, an atomic clock is the standard. --Chauncey27 19:21, 24 December 2005 (UTC)

Compared to a theoretical ideal. Accuracy of one part in 10^-9 is because the clock can be off by as much as half a cycle per second without being noticed. --Carnildo 08:57, 26 December 2005 (UTC)

Great question, Chauncey27. The accuracy of an atomic clock is calculated indirectly from how wide an interval of time the device will indicate the same time. In the most accurate atomic clocks, the resonance peak is sharper than we can measure, and the accuracy is limited by how accurately the period of the microwave signal from the atoms can be measured by the apparatus. This is limited by how much time the atoms spend in the resonance chamber. The idea of the cesium 'fountain' clock is to get a ball of supercooled cesium atoms to spend as much time as possible (~1 sec) in free fall by tossing them up. The accuracy calculation looks something like this:

accuracy = (period of one oscillation) * (fraction of period electronics can measure) / (time atoms spend in apparatus)

For a cesium atomic fountain this is approximately:

accuracy

--Chetvorno^TALK 13:17, 26 May 2008 (UTC)

[edit] Radioactivity?

How radioactive are small atomic clocks? Is it safe to make handheld devices with them?

A small atomic clock is about as radioactive as any other similarly-sized piece of electronics: that is, slightly less radioactive than the average brick. --Carnildo 09:33, 10 May 2006 (UTC)

atomic clocks are not based on radioactivity or decay but on electromagnetic wave frequencies, and the materials used (such as cesium 133) are stable, otherwise the clock wouldn't work well.81.206.145.191 21:43, 13 May 2007 (UTC)

[edit] Synchronization

How are Atomic clocks synchronized across the world, or are they not? Do they have to be in the same place to be synchronized off each other sort of thing? Even then how do they set them with such prescison accuracy? —The preceding unsigned comment was added by 90.192.138.193 (talk) 21:02, 22 December 2006 (UTC).

they can be synched to each other 1: over a symmetric latency connection (such as radio waves), or 2: by using GPS as a reference. a location can tell how it's time compares to GPS, or a single GPS satellite, say 50 nanoseconds ahead. then another place can use that information.81.206.145.191 21:43, 13 May 2007 (UTC)

Or you can pop a portable atomic clock with a battery backup on a plane. Jim77742 01:25, 20 June 2007 (UTC)

Using airplanes would be unpractical, because Einstein learned us that clocks run slower the faster their speed and the higher their altitude (or the lesser the gravitational field). See [1] and [2] for explanation and experiment with cesium clocks at moderate altitude. Jaho 00:16, 5 July 2007 (UTC)

An answer to the synchronization issue can be found on http://tycho.usno.navy.mil/twstt.html. Jaho 00:29, 5 July 2007 (UTC)

[edit] Mercury Atomic Clock Keeps Time with Record Accuracy

www.nist.gov/public_affairs/releases/mercury_atomic_clock.htm —The preceding unsigned comment was added by 218.102.23.117 (talk) 14:30, 8 January 2007 (UTC).

[edit] picture of HP 5071A

i think the article about atomic clocks needs a picture of a HP/Agilent/Symmetricom 5071A, because it is the most common/famous atomic clock (caesium based primary frequency standard) in existence and it has most weight in maintaining UTC - every country's time keeping lab has them.81.206.145.191 21:43, 13 May 2007 (UTC)