The Invisible Ether and Michelson Morley

The concept of the invisible ether or 'ether' is an old concept dating to the time of the ancient Greeks. They considered the ether as the medium which permeated the entire universe and even believed the ether to be another element. Along with Earth, Wind, Fire and Water Aristotle proposed that the ether should be treated as the fifth element or quintessence; this term, which literally means 'fifth element' has even survived down to today to explain an exotic form of 'dark energy' which is crucial in some cosmological models. These ideas spread throughout the world until the advent of a new spring in scientific thinking. The first person in the modern era to conceive the idea of an underlying ether to support the movement of light waves was seventeenth century Dutch scientist Christiaan Huygens.

Many others followed in expressing their views on the ether concept. Although Isaac Newton disagreed with Huygens 'wave theory, he also wrote about "aethereal medium', although he expressed his dismay at not knowing what they were ethereal. Newton later renounced ether theory, because in his mind it infinite stationary ether would interrupt the movement of huge masses (the stars and planets) as they moved in space. This rejection was reinforced by some other problematic wave properties, which were not explicable at the time, especially the production of a double image when light passes through certain translucent materials. This property of matter known as 'birefringence' was an important hurdle to overcome for a proper understanding of the wave character of light.

Some time later (1720) while working on other astronomical issues related to light and the cosmos, made English scientist James Bradley messages in hopes of quantifying a parallax. This effect is an apparent motion of foreground objects relative to those in the background. While he was able to distinguish this parallax him to reveal a second effect which is predominant in cosmological observations, this second effect is known as stellar aberration. Bradley was able to easily describe this aberration in the form of Newton's particle theory of light. But to do so in light of the wave or undulatory theory was difficult at best, as this would have required a 'quiet' medium; the static nature of the ether concept was of course the property which had originally caused Newton's denial of the idea.

But Newton's acolytes would find themselves in a difficult position, because it was shown that birefringence could be explained by a different interpretation of the nature of light. If light was treated as being in a side to side action or 'lateral movement' then birefringence could be attributed to a light wave rather than particle or corpuscular theory of Newton. This, together with the detection of an interference effect for light by Thomas Young in 1801 re-entry in the wave theory of light. These findings, however, carried with them all the prejudices prevalent in the scientific mind. Since it was assumed that waves like water and sound waves required a medium for dissemination, it was also assumed that light still need a medium or ether for the waves to be transmitted across the universe.

However, further problems plaguing ether theory. Because of the unique properties of a transverse wave, it was clear that this hypothetical explanation required ether to be a solid. In response, contributed Cauchy, Green and Stokes theoretical and mathematical observations to an 'entrainment' hypothesis which later became known as "ether drag 'concept. But nothing would give greater impetus to these ideas than when James Clerk Maxwell's equations (1870' s) required constancy of the speed of light (c). When the implications of Maxwell's equations developed by physicists, it became clear that because of the need for a constant speed of light is only a reference to the demands of learning Galilean Newtonian relativity. Therefore, researchers expected that there existed a unique absolute frame of reference that would meet this need, as a result, the airwaves would be quiet again.

As a result, by the late nineteenth century, ether was assumed to be an immovable rigid medium. However, previous theories previously existed regarding the nature of the air. One of the most famous of these is known as "ether drag 'hypothesis. In this concept, the ether a special environment in which light moves. Also, it would ether be connected to all physical objects would move with them. Measurement the speed of light in such a system would make a constant speed of light, no matter where you are tested for speed of light. This 'ether drag' concept arose in the wake of François Arago's experiment which appeared to show the constancy of the speed of light. Arago thought that refractive index would change when measured at different times of day or year as a result of heavenly and earthly movement. Despite his efforts, he had not notice any change in the refractive index as measured.

Many other experiments will follow, which were performed in order to find evidence of ether in its many different abstractions. But the most important of these was conducted by American scientists Michelson and Morley. Their experiment was a second alleged effect of a second ether theory, which came to be known as the ethereal wind. Since ether permeated the entire universe, the earth would move within the ether as it spun on its axis and moved within the solar system on the sun. This movement of the earth with respect to ether gave rise rise to the idea that it would be possible to detect an "ether wind 'which would be sensed because of the aforementioned motion. Thus, their experiment was essentially an attempt to uncover the so-called ether wind. This mysterious Zephyr will be almost impossible to detect because they are essential only negligibly affected the surrounding material world. Michelson first experimented in 1881 with a primitive version of his interferometer, a mechanism to measure the wave-like properties of light. He would follow that by joining forces with Morley in the most famous 'null' experiment of physics.

In this study, Michelson used an improved version of his interferometer unit. Michelson's apparatus would help him win the Nobel prize for his optical precision instruments and the investigations carried out with them. His main study, which became known as the Michelson Morley experiment in 1887. Michelson and Morley used a beam splitter made of a partially transparent mirror and two other mirrors arranged horizontally and vertically from one source. When a beam of light traveled from a source of coherent light to the half-silvered mirror (the semitransparent mirror) are sent to either horizontal or vertical mirrors. When the light back to the eyepiece of an observer separate back light waves would combine destructively or constructively. This phenomenon is known as interference effect of light. It was hoped that the relocation of the interference fringes from that which was normally predicted would be able to establish the existence of the ether wind.

To detect this effect Michelson interferometer was prepared in such a way as to minimize any and all extraneous sources of experimental error. It was located at a lower level of a stone edifice to remove heat Oscillatory and effects which can include the experimental results. In addition, the interferometer was mounted on a marble plate, which was floated in a pool of mercury. It was then that the apparatus can be moved through a number of different approaches to the invisible ether. But despite their many preparations the experiment did not yield the expected fringe patterns. In conclusion Michelson and Morley that there was no evidence for the existence of ether. Others will repeat the experiment in different incarnations as amended condition of the experiment. Each and every one returned a similar negative result. Modern theorists have taken these results and the many other trials, which are indicative of the non-existence in the air. However, even the negative result of Michelson Morley comment on issues as far back as 1933.

In that year, Dayton Miller demonstrated the fact that even though the duo's trial had not specifically found the expected types of interference patterns that they had found an interesting little rated power. Miller then to suggest that Michelson Morley had found an experimental sine wave like set of data, which correlated well with the expected pattern of data. He also described how thermal and directional assumptions inherent in the experimental arrangement can be affected badly on the fringe interference data. Thus can have the test performed in a poorly designed experimental setup and with a built-in mathematical bias against detection of an appropriate outcome. Thus, in future, ether theory in one form or another may still be sustainable as a foundational theory of physics.

Perhaps it is best to leave these ideas as expressed in 1920 by Einstein who stated that he thought the ether theory still be relevant to his ideas about space and time:

"More careful reflection teaches us, however, that the special theory of relativity does not compel us to deny ether. We can presume the existence of an ethereal"

He continued:

"Recapitulating, we can say that according to general relativity space is equipped with physical qualities, and in that sense, therefore, that there exists an ether"

and finally:

"According to general relativity space without ether is inconceivable; in these spaces are not only there would be no dispersion of light, but no opportunity to talk about standards of space and time (measuring-rods and clocks), nor therefore any space - time intervals in the physical sense. But this ether may not be perceived as endowed with the quality characteristic of measurable media, which consists of several parts, which can be traced through time. The idea of the proposal can not be applied to it. "