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	~~Jayson Berryhill is how I~~'m known as and ~~my wife doesn~~'~~t like~~ it ~~at all~~. To perform ~~domino is something I truly appreciate performing~~. ~~Invoicing~~ is ~~my profession~~. ~~Kentucky is where I~~'~~ve always been residing~~.<br><br>~~Also visit my~~ web page [~~http~~://~~www~~.~~youronlinepublishers~~.~~com~~/~~authWiki~~/~~AdolphvhBladenqq psychics online~~]		The '''Hammar experiment''' was an experiment designed and conducted by [[Gustaf Wilhelm Hammar]] (1935) to test the [[aether drag hypothesis]]. Its negative result refuted some specific aether drag models, and confirmed [[special relativity]].

			==Overview==

			Experiments such as the [[Michelson–Morley experiment]] of 1887 (and later other experiments such as the [[Trouton-Noble experiment]] in 1903 or the [[Trouton-Rankine experiment]] in 1908), presented evidence against the theory of a medium for light propagation known as the [[Luminiferous aether]]; a theory that had been an established part of science for nearly one hundred years at the time. These results cast doubts on what was then a very central assumption of modern science, and later led to the development of [[special relativity]]. In an attempt to explain the results of the Michelson-Morley experiment in the context of the assumed medium, aether, many new hypotheses were examined. One of the proposals was that instead of passing through a static and unmoving aether, massive objects at the Earth's surface may drag some of the aether along with them, making it impossible to detect a "wind". [[Oliver Lodge]] (1893-1897) was one of the first to perform a test of this theory by using rotating and massive lead blocks in an experiment that attempted to cause an asymmetrical aether wind. His tests yielded no appreciable results differing from previous tests for the aether wind.<ref>{{Cite journal\|author=Lodge, Oliver J.\|title=Aberration Problems\|journal=[[Philosophical Transactions of the Royal Society A]]\|volume=184\|year=1893\|pages=727–804\|doi=10.1098/rsta.1893.0015\|url=http://gallica.bnf.fr/ark:/12148/bpt6k559898/f781\|bibcode = 1893RSPTA.184..727L }}</ref><ref>{{Cite journal\|author=Lodge, Oliver J.\|title=[[s:en:Experiments on the Absence of Mechanical Connexion between Ether and Matter\|Experiments on the Absence of Mechanical Connexion between Ether and Matter]]\|journal=[[Philosophical Transactions of the Royal Society A]]\|volume=189\|year=1897\|pages=149–166\|bibcode = 1897RSPTA.189..149L \|doi = 10.1098/rsta.1897.0006 }}</ref>

			In the 1920s, [[Dayton Miller]] conducted repetitions of the Michelson–Morley experiments, which allegedly gave a positive result. However, several experiments conducted afterwards by others gave negative results. Miller claimed that this is due to entrainment of the aether, because the other experiments used heavily enclosed equipment. To test Miller's assertion, Hammar conducted the following experiment using a [[common path interferometer]] in 1935.<ref name=ham>{{cite journal
			\| author= G. W. Hammar
			\| year= 1935
			\| title= The Velocity of Light Within a Massive Enclosure
			\| journal= [[Physical Review]]
			\| volume= 48
			\| issue= 5
			\| pages= 462–463
			\| doi= 10.1103/PhysRev.48.462.2
			\|bibcode = 1935PhRv...48..462H }}</ref><ref name=rob>{{cite book
			\| author= H. P. Robertson and Thomas W. Noonan
			\| year= 1968
			\| title= Relativity and Cosmology
			\| contribution=Hammar's experiment
			\| publisher= Saunders
			\| location= Philadelphia
			\| pages= 36–38}}</ref>

			==The experiment==
			[[File:Hammar experiment.svg\|center]]
			Using a half-silvered mirror A, he divided a ray of white light into two half-rays. One half-ray was sent in the transverse direction into a heavy walled steel pipe terminated with lead plugs. In this pipe, the ray was reflected by mirror D and sent into the longitudinal direction to another mirror C at the other end of the pipe. There it was reflected and sent in the transverse direction to a mirror B outside of the pipe. From B it traveled back to A in the longitudinal direction. The other half-ray traversed the same path in the opposite direction.

			The topology of the light path was that of a [[Common path interferometer#Sagnac\|Sagnac]] interferometer with an odd number of reflections. Sagnac interfometers offer excellent contrast and fringe stability,<ref name=Optics471ASagnac>{{cite web \|title=The Sagnac Interferometer \|url=http://www.optics.arizona.edu/opti471a/Sagnac/The%20Sagnac%20Interferometer.pdf \|publisher=University of Arizona College of Optical Sciences \|accessdate=30 March 2012}}{{dead link\|date=October 2013}}</ref> and the configuration with an odd number of reflections is only slightly less stable than the configuration with an even number of reflections. (With an odd number of reflections, the oppositely traveling beams are laterally inverted with respect to each other over most of the light path, so that the topology deviates slightly from strict common path.<ref name=Hariharan2007>{{cite book \|last=Hariharan \|first=P \|title=Basics of Interferometry, 2nd edition \|year=2007 \|publisher=Elsevier \|isbn=0-12-373589-0 \|page=19}}</ref>) The relative immunity of his apparatus to vibration, mechanical stress and temperature effects, allowed Hammar to detect fringe displacements as little as 1/10 of a fringe, despite using the interferometer outdoors in an open environment with no temperature control.

			Similar to Lodge's experiment, Hammar's apparatus should have caused an asymmetry in any proposed aether wind. Hammar's expectation of the results was that: With the apparatus aligned perpendicular to the aether wind, both long arms would be equally affected by aether [[entrainment (hydrodynamics)\|entrainment]]. With the apparatus aligned parallel to the aether wind, one arm would be more affected by aether entrainment than the other. The following expected propagation times for the counter-propagating rays were given by [[Howard Percy Robertson\|Robertson]]/Noonan:<ref name=rob />

			:<math>t_{1}=\frac{AB}{c+v}+\frac{BC+DA}{\sqrt{c^{2}-v^{2}}}+\frac{CD}{c-v+\Delta v} </math>

			:<math>t_{2}=\frac{AB}{c-v}+\frac{BC+DA}{\sqrt{c^{2}-v^{2}}}+\frac{CD}{c+v-\Delta v}</math>

			where <math>\Delta v</math> is the velocity of the entrained aether. This gives an expected time difference:

			:<math>\Delta t\simeq\frac{2l\Delta v}{c^{2}} </math>

			On September 1, 1934, Hammar set up the apparatus on top of a high hill two miles south of Moscow, Idaho, and made many observations with the apparatus turned in all directions of the azimuth during the daylight hours of September 1, 2, and 3. He saw no shift of the interference fringes, corresponding to an upper limit of <math>\Delta v<0.074</math> km/s.<ref name=ham/> These results are considered a proof against the aether drag hypothesis as it was proposed by Miller.<ref name=rob/>

			==Consequences for Aether drag hypothesis==
			{{Main\|Aether drag hypothesis}}
			Because differing ideas of "aether drag" existed, the interpretation of all aether drag experiments can be done in the context of each version of the hypothesis.

			# None or partial entrainment by any object with mass. This was discussed by scientists such as [[Augustin-Jean Fresnel]] and [[François Arago]]. It was refuted by the [[Michelson–Morley experiment]].
			# Complete entrainment within or in the vicinity of ''all'' masses. It was refuted by the [[Aberration of light]], [[Sagnac effect]], [[Oliver Lodge]]'s experiments, and Hammar's experiment.
			# Complete entrainment within or in the vicinity of only ''very large'' masses such as Earth. It was refuted by the [[Aberration of light]], [[Michelson–Gale–Pearson experiment]].

			==References==
			<references />

			{{Tests of special relativity}}

			{{DEFAULTSORT:Hammar Experiment}}
			[[Category:Physics experiments]]
			[[Category:Aether theories]]

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Jayson Berryhill is how I'm known as and my wife doesn't like it at all. To perform domino is something I truly appreciate performing. Invoicing is my profession. Kentucky is where I've always been residing.<br><br>Also visit my web page [http://www.youronlinepublishers.com/authWiki/AdolphvhBladenqq psychics online]

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