Hafele–Keating experiment

Hafele–Keating experiment

The Hafele–Keating experiment was a test of the theory of relativity. In October of 1971, J. C. Hafele and Richard E. Keating took four caesium-beam atomic clocks aboard commercial airliners and flew twice around the world, first eastward, then westward, and compared the clocks against those of the United States Naval Observatory.

Overview

According to special relativity, the speed of a clock is greatest according to an observer who is not in motion with respect to the clock. In a frame of reference in which the clock is not at rest, the clock runs slower, and the effect is proportional to the square of the velocity. In a frame of reference at rest with respect to the center of the earth, the clock aboard the plane moving eastward, in the direction of the earth's rotation, is moving faster than a clock that remains on the ground, while the clock aboard the plane moving westward, against the earth's rotation, is moving slower.

According to general relativity, another effect comes into play: the slight increase in gravitational potential due to altitude that speeds the clocks back up. Since the aircraft are flying at roughly the same altitude in both directions, this effect is more "constant" between the two clocks, but nevertheless it causes a difference in comparison to the clock on the ground.

The results were published in "Science" in 1972: [cite journal | last=Hafele | first= J. | coauthors = Keating, R. | authorlink = | date= July 14 1972| title=Around the world atomic clocks:predicted relativistic time gains | journal=Science| volume = 177 | issue = 4044| pages=166–168| url= http://www.sciencemag.org/cgi/content/abstract/177/4044/166| doi = 10.1126/science.177.4044.166| accessdate= 2006-09-18| pmid=17779917] [cite journal | last=Hafele | first= J. | coauthors = Keating, R. | authorlink = | date= July 14 1972| title=Around the world atomic clocks:observed relativistic time gains | journal=Science| volume = 177 | issue = 4044| pages=168–170| url= http://www.sciencemag.org/cgi/content/abstract/177/4044/168 | doi = 10.1126/science.177.4044.168| accessdate=2006-09-18| pmid=17779918]

nanoseconds gained
predictedmeasured
gravitational
(general relativity)
kinematic
(special relativity)
total
eastward144±14−184 ± 18−40 ± 23−59 ± 10
westward179±1896±10275±21273±7

The published outcome of the experiment was consistent with special relativity, and the observed time gains and losses were reportedly different from zero to a high degree of confidence.

That result was contested by Dr. A. G. Kelly who examined the raw data: according to him, the final published outcome had to be averaged in a biased way in order to claim such a high precision. [A. G. Kelly,"Reliability of Relativistic Effect Tests on Airborne Clocks", Monograph No.3 Feb.1996, The Institution of Engineers of Ireland, ISBN 1-898012-22-9] Also, Louis Essen, the inventor of the atomic clock, published an article in which he discussed the (in his opinion) inadequate accuracy of the experiment. [Louis Essen, Electron. Wireless World 94 (1988) 238.] ; however, neither of these publications are in peer-reviewed sources.

One notable approximate repetition of the original experiment took place on the 25th anniversary of the original experiment, using more precise atomic clocks, and the results were verified to a higher degree of accuracy. [ [http://web.archive.org/web/20050411015134/http://www.npl.co.uk/publications/metromnia/issue18/ Metromnia Issue 18 - Spring 2005 ] ] . Nowadays such relativistic effects have been incorporated into the calculations used for the GPS system [Deines, "Uncompensated relativity effects for a ground-based GPSA receiver", Position Location and Navigation Symposium, 1992. Record. '500 Years After Columbus - Navigation Challenges of Tomorrow'. IEEE PLANS '92.] .

Equations

The equations and effects involved in the experiment are:

Total time dilation:Tau = Delta au_v + Delta au_g + Delta au_s

Velocity:Delta au_v = - frac{1}{2c^2} sum_{i=1}^{k}v_i^2 Delta au_i

Gravitation:Delta au_g = frac{g}{c^2} sum_{i=1}^{k} (h_i - h_0) Delta au_i

Sagnac effect:Delta au_s = - frac{omega}{c^2} sum_{i=1}^{k} R_i^2 cos^2 phi_i Deltalambda_i

Where h = height, v = velocity, omega = Earth's rotation and τ represents the duration/distance of a section of the flight. The effects are summed over the entire flight, since the parameters will change with time.

References

External links

* [http://www.cartesio-episteme.net/H&KPaper.htm Hafele & Keating Tests; Did They Prove Anything?] By A. G. Kelly PhD

ee also

* Twin paradox
* Time dilation
* GPS Time Dilation


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Hafele-Keating-Experiment — Das Hafele Keating Experiment war ein Test der aus der Relativitätstheorie folgenden Zeitdilatation. Joseph C. Hafele und Richard E. Keating brachten 1971 vier Cäsium Atomuhren an Bord eines kommerziellen Linienflugzeugs, und flogen zweimal rund… …   Deutsch Wikipedia

  • Hafele — ist der Name von Mathias Hafele (* 1983), österreichischer Skispringer Sonstiges Hafele Keating Experiment (J. C. Hafele Richard E. Keating 1971), siehe Maryland Experiment der Berg Hafelekarspitze in Tirol Siehe auch: Häfele …   Deutsch Wikipedia

  • Michelson–Morley experiment — Box plots based on data from the Michelson–Morley experiment The Michelson–Morley experiment was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University in Cleveland, Ohio. Its results are generally… …   Wikipedia

  • Michelson–Gale–Pearson experiment — The Michelson–Gale–Pearson experiment (1925) is a modified version of the Michelson Morley experiment and the Sagnac Interferometer. It measured the Sagnac effect due to Earth s rotation, and thus tests the theories of special relativity and… …   Wikipedia

  • Hughes–Drever experiment — Hughes–Drever experiments (also clock comparison , clock anisotropy , mass isotropy , or energy isotropy experiments) are testing the isotropy of mass and space. As in Michelson–Morley experiments, the existence of a preferred frame of reference …   Wikipedia

  • De Sitter double star experiment — This article is about observing binary stars. For precession of orbiting bodies, see de Sitter precession. de Sitter s double star argument The de Sitter effect was described by de Sitter in 1913 and used to support the special theory of… …   Wikipedia

  • Maryland-Experiment — Das Maryland Experiment war ein Versuch, der die allgemeine Relativitätstheorie überprüfte. Atomuhren, die längere Zeit in einem Flugzeug über der Chesapeake Bay (Maryland) kreisten, verglich man mit Uhren am Boden. Das Experiment bestätigte den… …   Deutsch Wikipedia

  • General relativity — For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. General relativity Introduction Mathematical formulation Resources …   Wikipedia

  • One-way speed of light — The one way speed of light from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. What can however be experimentally measured is the round trip speed (or… …   Wikipedia

  • Tests of general relativity — General relativity Introduction Mathematical formulation Resources Fundamental concepts …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”