Albert Einstein's development of the theory of special relativity, which includes the concept of a universal speed limit being the speed of light, came about through a combination of theoretical considerations and experimental evidence.
Einstein's exploration of the nature of light played a crucial role in his understanding of the universe's speed limit. In the late 19th century, the prevailing theory of light was based on Maxwell's equations, which described light as an electromagnetic wave traveling through a medium called the "luminiferous ether." The assumption was that light waves required a medium to propagate, much like how sound waves require air or water.
However, several experimental results challenged the existence of the luminiferous ether. The most famous of these was the Michelson-Morley experiment conducted in 1887, which aimed to detect the motion of the Earth through the ether. The experiment showed no evidence of ether drift, leading to the conclusion that the ether didn't exist or had properties that were not easily detectable.
Einstein built upon these experimental findings and developed a radical new framework to explain the behavior of light. He proposed that the speed of light in a vacuum is always constant, regardless of the motion of the source or the observer. This principle, known as the constancy of the speed of light, formed the basis of special relativity.
By assuming the constancy of the speed of light, Einstein derived a set of mathematical equations that described the transformation of space and time for observers moving relative to each other at constant velocities. These equations led to the discovery of time dilation, length contraction, and the equivalence of mass and energy (E=mc²).
Through the development of these concepts, Einstein realized that as an object with mass approaches the speed of light, its energy and momentum would increase without bound, requiring an infinite amount of energy to reach or exceed that speed. This insight led to the understanding that the speed of light is the universal speed limit.
In summary, Einstein's understanding of the speed limit of the universe being the speed of light was derived from a combination of experimental evidence, particularly the Michelson-Morley experiment, and his own theoretical work on the behavior of light and the nature of space and time.