The Michelson-Morley experiment, not Mickelson-Molly, was actually conducted to detect the presence of the luminiferous ether, which was believed to be the medium through which light waves propagate. The experiment aimed to measure the change in the speed of light as the Earth moved through this hypothetical ether. However, the experiment yielded a null result, indicating that the speed of light remained constant regardless of the Earth's motion.
Although the Michelson-Morley experiment didn't directly provide evidence for light being a wave, it played a crucial role in the development of the theory of special relativity, proposed by Albert Einstein in 1905. Special relativity reconciled the constant speed of light with the laws of physics by suggesting that the speed of light is a fundamental constant and is independent of the observer's motion. According to special relativity, the speed of light in a vacuum is the same for all observers, regardless of their relative motion.
The wave-like nature of light was known prior to the Michelson-Morley experiment through various other experiments and phenomena, such as interference, diffraction, and the wave nature of electromagnetic radiation. These phenomena were successfully described by James Clerk Maxwell's electromagnetic wave theory, developed in the 19th century. Maxwell's equations mathematically described the behavior of electromagnetic waves, including light.
The Michelson-Morley experiment, along with subsequent experiments and the development of special relativity, led to a better understanding of the nature of light as an electromagnetic wave. It demonstrated that the speed of light is constant, independent of the motion of the source or observer, and that light waves propagate through space without the need for a medium like the luminiferous ether.