| The concept of the invisible ether or 'aether' is an old | | | | the aether in its many different abstractions. |
| concept dating to the time of the ancient Greeks. | | | | However the most important of these was |
| They considered the ether as that medium which | | | | conducted by american scientists Michelson and |
| permeated all of the universe and even believed the | | | | Morley. Their experiment considered another alleged |
| ether to be another element. Along with Earth, Wind, | | | | effect of a different aether theory which came to |
| Fire and Water Aristotle proposed that the ether | | | | be known as the aether wind. Since the aether |
| should be treated as the fifth element or | | | | permeated the entire universe, the earth would |
| quintessence; this term which literally means 'fifth | | | | move within the ether as it spun on its axis and |
| element' has even survived down to the present day | | | | moved within the solar system about the sun. This |
| to explain an exotic form of 'dark energy' which is | | | | movement of the earth with respect to the aether |
| crucial in some cosmological models. These ideas | | | | gave rise rise to the idea that it would be possible to |
| spread throughout the world until the advent of a | | | | detect an 'ether wind' which would be sensed |
| new springtime in scientific thought. The first person | | | | because of the aforementioned movement. Thus, |
| in the modern era to conceive of the idea of an | | | | their experiment was essentially an attempt to |
| underlying ether to support the movement of light | | | | detect the so-called ether wind. This mysterious |
| waves was seventeenth century dutch scientist | | | | zephyr would be nearly impossible to detect because |
| Christiaan Huygens.Many others followed in | | | | the aether only infinitesimally affected the |
| expressing their opinions on the ether concept. Whilst | | | | surrounding material world. Michelson first |
| Isaac Newton disagreed with Huygens wave theory | | | | experimented in 1881 with a primitive version of his |
| he also wrote about the 'aethereal medium' although | | | | interferometer; a mechanism designed to measure |
| he expressed his consternation in not knowing what | | | | the wave like properties of light. He would follow this |
| the aether was. Newton later renounced the ether | | | | by combining forces with Morley in the most famous |
| theory because in his mind the infinite stationary | | | | 'null' experiment of physics.In this investigation, |
| ether would interrupt the motions of the enormous | | | | Michelson utilized an improved version of his |
| masses (the stars and planets) as they moved in | | | | interferometer device. Michelson's apparatus would |
| space. This rejection was reinforced by some other | | | | help him win the Nobel prize for his optical precision |
| problematical wave properties which were not | | | | instruments and the investigations carried out with |
| explicable at the time; most notably, the production | | | | them. His most important study being what became |
| of a double image when light passes through certain | | | | known as the Michelson Morley experiment of 1887. |
| translucent materials. This property of matter known | | | | Michelson and Morley used a beam splitter made of a |
| as 'birefringence' was an important hurdle to be | | | | partially transparent mirror and two other mirrors |
| overcome for a proper understanding of the wave | | | | arranged horizontally and vertically from a light source. |
| nature of light.Some time later (1720) whilst working | | | | When a beam of light traveled from a source of |
| on other astronomical issues related to light and the | | | | coherent light to the half-silvered mirror (the |
| cosmos, English scientist James Bradley made | | | | semitransparent mirror) it is transmitted to either of |
| observations in hopes of quantifying a parallax. This | | | | the horizontal or vertical mirrors. When the light |
| effect is an apparent motion of foreground objects | | | | returned to the eyepiece of an observer the |
| in comparison to those in the background. Whilst he | | | | separately returning light waves would combine |
| was unable to discern this parallax effect he | | | | destructively or constructively. This phenomenon is |
| happened to reveal another effect which is prevalent | | | | known as the interference effect for light. It was |
| in cosmological observations; this other effect is | | | | hoped that a shifting of the interference fringes from |
| known as stellar aberration. Bradley was able to easily | | | | that which was normally predicted would be able to |
| describe this aberration in terms of Newton's particle | | | | ascertain the existence of the aether wind.To detect |
| theory of light. However, to do so in light of the | | | | this effect, the Michelson interferometer was |
| wave or undulatory theory was difficult at best since | | | | prepared in such a manner as to minimize any and all |
| to do so would have required a 'motionless' medium; | | | | extraneous sources of experimental error. It was |
| the static nature of this ether concept was of | | | | located in a lower level of a stone edifice to eliminate |
| course the property which had originally caused | | | | heat and oscillatory effects which might comprise the |
| Newton's denial of the idea.But Newton's acolytes | | | | experimental results. Additionally, the interferometer |
| would find themselves in a difficult position when it | | | | was mounted atop a marble slab that was floated in |
| was shown that birefringence could be explained | | | | a basin of mercury. This was so that the apparatus |
| through another interpretation of the nature of light. | | | | could be moved through a variety of positions with |
| If light was treated as being in a side to side action | | | | respect to the invisible ether. But despite their many |
| or 'transverse motion' then birefringence could be | | | | preparations the experiment did not yield the |
| attributed to a light wave rather than the particle or | | | | expected fringe patterns. Thus, Michelson and Morley |
| corpuscular theory of Newton. This along with the | | | | concluded that there was no evidence for the |
| detection of an interference effect for light by | | | | existence of the ether. Others would replicate the |
| Thomas Young in 1801 renewed the ascendancy of | | | | experiment in different incarnations which modified |
| the wave theory of light. These findings however | | | | the premise of the experiment. Each and every one |
| carried with them all of the preconceived notions | | | | returning a similar negative result. Modern theorists |
| prevalent in the scientific mind. Since it was assumed | | | | have taken these results and those of many other |
| that waves like water and sound waves required a | | | | experiments as being indicative of the non-existence |
| medium of propagation, it was similarly assumed that | | | | of the aether. However, even the negative result of |
| light still needed a medium or ether for its waves to | | | | Michelson Morley has come in to question as far back |
| be transmitted across the universe.However, further | | | | as 1933.In that year, Dayton Miller demonstrated the |
| problems would afflict the ether theory. Because of | | | | fact that even though the duo's experiment had not |
| the unique properties of a transverse wave it | | | | specifically found the expected range of interference |
| became apparent that this hypothetical explanation | | | | patterns, they had found an interesting little noticed |
| required the ether to be a solid. In response, Cauchy, | | | | effect. Miller then went on to suggest that Michelson |
| Green and Stokes contributed theoretical and | | | | Morley had found an experimental sine wave like set |
| mathematical observations to an 'entrainment' | | | | of data that correlated well with the predicted |
| hypothesis which later came to be known as the | | | | pattern of data. He also described how thermal and |
| 'ether drag' concept. But nothing would give more | | | | directional assumptions inherent in the experimental |
| impetus to these ideas than when James Clerk | | | | arrangement may have impacted badly on the fringe |
| Maxwell's equations (1870s) required the constancy | | | | interference data. Thus, the test may have been |
| of the speed of light (c). When the implications of | | | | performed in an imperfectly conceived experimental |
| Maxwell's equations are worked out by physicists, it | | | | setup and with a built in mathematical bias against the |
| was understood that as a result of the need for a | | | | detection of an appropriate outcome. Thus, in the |
| constant speed of light only one reference frame | | | | future the aether theory in some form or another |
| could meet this requirement under the teachings of | | | | may still be sustainable as a foundational theory of |
| Galilean Newtonian relativity. Therefore, scientists | | | | physics.Perhaps it is best to leave with these ideas as |
| expected that there existed a unique absolute | | | | expressed in 1920 by Einstein who stated that he |
| reference frame which would comply with this need; | | | | believed the ether theory to still be relevant to his |
| as a result, the ether would again be stationary.As a | | | | ideas on space and time:"More careful reflection |
| consequence, by the late nineteenth century the | | | | teaches us, however, that the special theory of |
| aether was assumed to be an immovable rigid | | | | relativity does not compel us to deny ether. We may |
| medium. However, earlier previous theories existed as | | | | assume the existence of an ether"he |
| to the nature of the aether. One of the most | | | | continued:"Recapitulating, we may say that according |
| famous of these is known as the 'aether drag' | | | | to the general theory of relativity space is endowed |
| hypothesis. In this concept, the aether is a special | | | | with physical qualities; in this sense, therefore, there |
| environment within which light moves. Also, this | | | | exists an ether"and finally:"According to the general |
| aether would be connected to all material objects | | | | theory of relativity space without ether is |
| and would move along with them. Measuring the | | | | unthinkable; for in such space there not only would |
| speed of light in such a system would render a | | | | be no propagation of light, but also no possibility of |
| constant velocity for light no matter where one | | | | existence for standards of space and time |
| tested for light's speed. This 'aether drag' idea | | | | (measuring-rods and clocks), nor therefore any |
| originated in the aftermath of Francois Arago's | | | | space-time intervals in the physical sense. But this |
| experiment which appeared to show the constancy | | | | ether may not be thought of as endowed with the |
| of the speed of light. Arago believed that refractive | | | | quality characteristic of ponderable media, as |
| indexes would change when measured at different | | | | consisting of parts which may be tracked through |
| times of the day or year as a result of stellar and | | | | time. The idea of motion may not be applied to |
| earthly motion. In spite of his efforts, he did not | | | | it."Michael Strauss is an engineer and author of |
| notice any change in the refractive indexes so | | | | Requiem for Relativity the Collapse of Special |
| measured.Many other experiments would follow; | | | | Relativity, a serious critique on the fallacies of Special |
| these were performed in order to find evidence of | | | | Relativity. |