Michelson-Morley Experiment

The Michelson–Morley experiment was an experiment that was first performed in 1887 by Albert A. Michelson and Edward W. Morley. Unfortunately, a number of writers on this topic tend to gloss over, or sometimes mischaracterize, what this experiment demonstrated, its significance, and how it was a turning point in science which necessitated the adoption of a radically different and alternative model of space.

The goal of the Michelson–Morley experiment was to compare the speed of light in perpendicular horizontal directions at various times of the day, in an attempt to detect the relative motion of matter through the stationary luminiferous aether by using the rotation of the earth and its motion around the sun to create interference bands of light for the study. Morley wrote to his father that the purpose of the experiment was “to see if light travels with the same velocity in all directions.”1

The shocking result of this experiment is that the earth did not measurably move around the sun at all, in contradiction to all expectations and the accepted astronomical model. Michelson and Morley found that a light beam discharged in the direction of the Earth’s assumed motion showed virtually no difference in speed from a light beam discharged north to south or south to north. In other words, the experiment failed to detect the Earth moving in or against space, of whatever space was understood to consist.

After the famous Michelson-Morley experiment of 1887, one of Albert Einstein's biographers, Ronald W. Clark, describes what came next:

Michelson and Morley and later scientists repeated the experiment many times, and in many different horizontal axial positions and configurations, at different times of the day, all with a null result. The earth was seen to be motionless. The experiment has been referred to as "the moving-off point for the theoretical aspects of the Second Scientific Revolution"3 and directly influenced the creation of Albert Einstein's Theory of Relativity.

The Theory of Relativity subsequently found favor among scientific circles because its model, where the velocity of light is constant to all observers, was designed to seemingly explain the motionless earth result of the Michelson-Morley experiment. This fundamental change to the nature of space and time allowed the theory of the earth's motion around the sun to survive direct contradicting experimental evidence and encouraged, perhaps forced, its adoption as the accepted model of space for Copernicanism.

G.J. Whitrow, a British mathematician, cosmologist, and science historian, characterized the Michaelson-Morley experiment from a historical perspective:

1 Letter dated April 17, 1887, in the Edward W. Morley Papers, Library of Congress, as cited  in  Dorothy  Michelson Livingston’s Master of Light: A Biography of Albert Michelson, New York, Charles Scribner, 1973, p.126. 2 Einstein: The  Life  and  Times,  Avon  Book,  New  York,  NY,  1984,  p.  109-110. 3 Hoover, Earl R. (1977). Cradle of greatness : national and world achievements of Ohio's Western Reserve 4 G. J. Whitrow, The Structure and Evolution of the Universe, New York, Harper and Brothers Publishers, 1959, p. 79.

http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/mmhist.html (Archive)

=Description and Result=

Material from a York University course by Prof. Byron E. Wall provides a good summary of the Michelson-Morley experiment and its result. Below are slides that tell the story. Interested readers should feel free to go through the entire slide deck.

Course Description (Archive) Full Slideshow (.ppt Archive)



=Peer Reviews and Repetitions=

Since 1887 the Michelson-Morley experiment has been repeated and verified on many occasions, with several different methodologies. The Michelson-Morley Wikipedia article (Archive) maintains a list of subsequent experiments.

A 2009 repetition of the experiment is described below:

2009 Repetition in Germany
https://physicsworld.com/a/michelson-morley-experiment-is-best-yet/ (Archive)

Michelson–Morley experiment is best yet

=Influence of the MiMo Experiment on Relativity=

In a lecture titled How I Created the Theory of Relativity (Archive) Albert Einstein points this experiment out as a basis on developing Special Relativity:

Einstein also mentions in regards to SR: "I also started to work on the problem of Fizeau’s experiment and tried to account for it," which is another light velocity experiment.

Historical Marker
In Cleveland, Ohio, there is a Michelson-Morley Historical Marker located just outside the science building on the Case Western Reserve University campus which provides the following:

The marker describes that, when science was confronted with direct evidence of an earth without motion around the sun, an entirely new model of space and time was required to explain it.

Why Relativity Was Accepted
Why Was Relativity Accepted? By Stephen G. Brush

Full Text: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.535.1670&rep=rep1&type=pdf (Archive)

An interesting analysis on why Relativity was accepted in science. The author concludes that much of why it was accepted is because it was a world-model which purported to explain the Michelson-Morley experimental result of a motionless non-rotating earth. Another top reason was because of an underlying desire for a unified, elegant physical theory.

The author provides quotes by the scientists of the day, identifying the Michelson-Morely null result as a primary factor.

Statistical Tables
The author provides three statistical analysis tables for why Relativity was accepted, focusing on Empirical reasons, Social-Psychological reasons, and Aesthetic-Mathematical reasons.



Abbreviation Reference

Empirical MiMo — negative result of Michelson-Morley experiment EtDr — failure of ether drift experiments ElMa — variation of electron mass with velocity ElCh — variation of electron charge with velocity VeLi — velocity of light from terrestrial and celestial sources is the same BoOr — correction of orbits and energy levels in Bohr model of atom LiBe — light-bending observations MePe — Advance of Mercury Perihelion GrRe — Gravitational redshift of spectral lines

Social-Psychological NSTh — rejection of absolute space and time is consistent with neoscholastic theology MoSc — association with ‘‘modern’’ science PoSt — relativism of political structures, attractive to anit-democratic ideologues CoIC — acquire prestige for comprehending the incomprehensible GePh — respect for authority of German physics

Aesthetic-Mathematical Math — mathematical aspects of the theory Unif — desire for a unified, elegant physical theory EMWV — connection with electromagnetic worldview NEGe — connection with Lobachevskii’s non-Euclidean geometry

The reader should note that the Michelson-Morley Experiments are a subset of the "failure of the ether drift experiments," which are a larger collection of experiments which have failed to detect earth's motion through space. The Michelson-Morley Experiment is the most known and famous experiment of the collection.