The Michelson-Morley experiment, conducted in 1887 by Albert A. Michelson and Edward W. Morley, aimed to detect the presence of the luminiferous ether—a medium through which light was once believed to travel. The results of this experiment played a crucial role in the development of the theory of relativity, challenging the existing notions of space and time. Below are three diverse, practical examples of the Michelson-Morley experiment that illustrate its foundational impact on modern physics.
The original experiment utilized an interferometer to measure the speed of light in perpendicular directions, assuming that the Earth moved through the ether.
In this context, the experiment was designed to compare the travel times of light beams moving along two different paths—a horizontal arm aligned with the motion of the Earth and a vertical arm perpendicular to that motion. The expectation was that light should travel faster in the direction of motion compared to the perpendicular direction.
The apparatus consisted of a beam splitter, two mirrors, and a viewing telescope. Light from a single source was split into two beams at the beam splitter, directed along the two arms. After reflecting off the mirrors, the beams returned to the beam splitter and recombined, creating an interference pattern visible through the telescope.
If the ether existed, changes in the interference pattern would be observed as the Earth moved through it. However, the experiment revealed no significant shift in the interference pattern, suggesting that the speed of light is constant irrespective of the motion of the observer.
In contemporary physics labs, adaptations of the Michelson-Morley experiment have been conducted using laser technology to improve precision.
In this setup, a laser beam replaces the original light source, and a modern interferometer is used to enhance the measurement accuracy. The experiment is conducted in a controlled environment to minimize external factors such as vibrations or air currents that could affect the results.
The use of lasers allows for clearer interference patterns due to the monochromatic nature of laser light. The beams are again split and directed down the two arms before returning to the beam splitter. Observations are made with high-resolution detectors that can measure minute changes in the interference pattern.
Despite the advancements in technology, the results continue to reinforce the original findings: no evidence of ether was detected, supporting the idea of a constant speed of light as articulated in Einstein’s theory of relativity.
Many educational institutions conduct simplified versions of the Michelson-Morley experiment to teach students about the principles of light and interference.
In a typical classroom setup, a simple interferometer can be constructed using a laser pointer, beam splitter, mirrors, and a screen or wall to observe the interference pattern. Students can adjust the length of the arms and observe how the interference changes—or remains stable—regardless of their orientation.
Such demonstrations serve to visually illustrate the concept of light behaving consistently irrespective of the relative motion between the source and observer. This hands-on approach helps students grasp the significance of the experiment in the context of modern physics and relativity.