Clocks| Clocks |
In General > s.a. time.
* Atomic clocks: In general
they work by shooting microwaves into a sample of cooled Cs atoms and reading
out the microwave-absorption frequency
which corresponds to a specific quantum transition for electrons in the Cs
atoms.
The microwave frequency setting is used to define the "second."
* Most precise: 2002,
The NIST-F1, will have an accuracy of 1 part in 1015,
1 s in 30 Myr, used in the GPS; If one could cool the atoms to
lower
temperatures (thus reducing the blurring caused by their movement) or
observe
them for longer periods, the precision of the whole readout process
(and the
standardization of the second) would improve; NIST plans to have several
SPARC "space clocks" in orbit in the next few years; 2006,
The current accuracy of NIST-F1 is 1 s in 70 Myr, and is soon expected to reach
1
part
in
1016;
In the not-too-distant future, our ability to compare atomic frequency standards
and clocks at different laboratories will be limited by our knowledge of the
geoid; 2007, The current accuracy of the best NIST optical clock is 1
part
in
1017.
@ Precision: Bergquist et al PT(01)mar
[1 part in 1015]; news pw(08)mar
[1 part in 1017].
References > s.a. fine
structure constant [variation]; quantum
technology.
@ General: Aveni 89; Itano & Ramsey SA(93)jul; Hackman & Sullivan
AJP(95)RL;
Will gq/95;
Barnett 98 [r pw(98)nov];
Audoin & Guinot 01 [history]; Kleppner PT(06)mar.
@ Atomic clocks:
Jones 00
[I, r PT(01)oct];
Audoin & Guinot 01; Gibbs SA(02)sep; Gill & Margolis pw(05)may
[optical]; news pw(06)aug
[T effect]; Camparo PT(07)nov.
@ Clock paradox: Iorio FPL(05)
[in special and general relativity]; Jones & Wanex FPL(06)phy [static
homogeneous metric].
@ And quantum mechanics: Salecker & Wigner PR(58);
Frenkel qp/05;
> s.a. measurements [time], time
in
quantum mechanics, zeno
effect.
> And gravitation, spacetime
structure: see Chronogeometry; tests
of general relativity.
Synchronization
@ General references: AS(90)303 [with computers];
Bennett et al PRS(02)
[Huygens]; Rowlands FPL(06)
[and non-inertial observers].
@ In special relativity: Anderson et al PRP(98);
Russo NCB(06)
[conventionality].
@ In general relativity: Bahder gq/04-in
[near Earth].
@ In quantum theory: Yurtsever & Dowling PRA(02)qp/00;
Preskill qp/00;
Giovannetti et al Nat(01)qp, PRL(01)qp, PRA(02)qp/01, PRA(02)qp/01, PRA(04);
Boixo et al LP(06)qp [with
decoherence].
Related Topics
@ Calendars: Shimony 98 [fiction re Gregorian reform]; Richards 98 [history];
Aveni 02.
@ Timekeeping: Bartky 00 [XIX century America]; Andrewes SA(02)sep; in
Kleppner PT(06)mar
[leap seconds].
@ Dating methods: Turney 06; > s.a. elements [carbon dating].
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Send feedback and suggestions to bombelli at olemiss.edu – Modified
21 jun 2008