Did the Michelson-Morley Experiment Prove the Ether Does Not Exist? - The Constant Speed of Light and the Fall of Absolute Space | Sleepy Facts About the Universe

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For over two centuries, Newtonian mechanics provided a seemingly complete framework for understanding the universe, built upon the foundation of absolute space and a uniform flow of time. But the nineteenth-century unification of electricity and magnetism through Maxwell's equations revealed a troubling detail: light propagates at a fixed speed, regardless of the motion of its source. This single fact created a profound crisis in physics, challenging the intuitive rules that govern moving trains, thrown balls, and orbiting planets.

This episode examines how the scientific community responded to this contradiction. It explores the reasonable but ultimately incorrect hypothesis of the luminiferous ether, an invisible medium proposed to carry light waves through empty space. It also details the precise and sensitive interferometer built by Albert Michelson and Edward Morley in 1887, which famously failed to detect any motion of the Earth through this supposed ether, leaving the old framework in ruins.

While working on this episode, I kept returning to one question: how do you replace the stage on which all physical reality is built? I wanted to understand the conceptual leap required to abandon absolute time and space in favor of a unified spacetime. By tracing the path from the failed ether experiments to Albert Einstein's 1905 postulates, we explore how the constancy of light leads inevitably to relative simultaneity, length contraction, time dilation, and the equivalence of mass and energy.