STEMvisions Blog

It’s been just over 110 years since Einstein published his groundbreaking papers in 1905 that revolutionized physics as we know it and ushered in the quantum age. Among these papers were his theories on special relativity (not to be confused with general relativity, which he published 10 years later in 1915). His theories on special relativity discussed such strange things as length contraction and time dilation when an observer moved at speeds approaching the speed of light (3 x 10⁸ meters per second, or c). While Einstein was a brilliant physicist, he by no means developed these theories in a vacuum. All great science comes from collaboration and parallel research. Results from an experiment from 1887 would go on to support Einstein’s theories of special relativity and help drive the quantum age alongside it. The experiment in question, the Michelson-Morley experiment, would become one of the most famous failed experiments in history. 

Image from quantum-reality.net

The idea behind the Michelson-Morley experiment can be simplified to the analogy of a person swimming in a river with a current. Depending on whether or not the person is swimming with or against the current, his or her relative velocity (the speed of travel) will change. For Albert Michelson and Edward Morley the river is a material (or medium) called “ether” and the person swimming is light. From ideas presented by physicist James Clerk Maxwell years earlier, Michelson and Morley knew that light was a wave. From daily experiences they had some preconceived notions about waves. For example, we can observe that in order to hear sound, the sound waves must move (or propagate) through something (e.g., air or water). Without a material to move through, there is no sound to be heard. If this is true for sound, thought Michelson and Morley, then surely it’s true for light as well. “Ether” was the name given to the hypothetical medium that surrounded all things that light propagated through (even the vacuum of space). 

Their experiment set out to measure different speeds of light depending on whether or not the light was “swimming” with or against the ether’s current. The results were… unexpected. Michelson and Morley saw that no matter which way the light “swam,” it maintained a constant velocity of c. If we look back to our river analogy that would mean that no matter how fast the current flowed against the swimmer, he or she would continue to swim at the same constant pace no matter what. But how? This goes against classical physics and our very intuitions about motion! What the results of this experiment meant for physics was that there was no absolute point of view (or reference frame) to measure events—that everything was relative. 

Michelson-Morley Experimental Setup Image from St. Lawrence University

Now, I must admit, Michelson is dear to my heart. At my school, Clark University, you’ll be hard pressed to take a physics course without hearing his name. This is not just because of his contributions to quantum theory but because he was the first head of our physics department in 1889! For his contributions to science, Michelson became the first American to be awarded the Nobel Prize in Physics in 1907. The Michelson-Morley experiment demonstrates many key aspects of the scientific process, most notably that when it comes to science there’s really no such thing as failure.  

References:

• Fowler, Michael. "The Michelson-Morley Experiment." The Michelson-Morley Experiment. University of Virginia Physics, 15 Sept. 2008. Web. 01 June 2016. 
• "Michelson and Morley." Michelson and Morley. American Physical Society, n.d. Web. 01 June 2016. 
• "The Michelson-Morley Experiment." Relativity. Nobel Media AB, n.d. Web. 01 June 2016.