When Albert Einstein stated that "light has no real existence," he was referring to the nature of light as described by the theory of relativity, specifically in the context of the theory's postulates and implications.
In the theory of relativity, Einstein proposed that the speed of light in a vacuum is constant and is the same for all observers, regardless of their relative motion. This principle, known as the "constancy of the speed of light," is a fundamental postulate of the theory. It has been experimentally confirmed and has significant implications for our understanding of space, time, and the behavior of light itself.
By saying that light has no real existence, Einstein meant that light does not behave like classical particles or objects that have a well-defined position and velocity. Instead, according to the theory of relativity, light is described as a disturbance or oscillation of electromagnetic fields. It exhibits wave-particle duality, behaving both as a wave and as discrete particles called photons.
Einstein's statement highlights the departure of our understanding of light from classical intuitions. In classical physics, light was often described solely in terms of particles (corpuscular theory) or solely as waves (wave theory). However, the theory of relativity showed that light's behavior cannot be explained by either description alone and requires a more nuanced understanding.
Einstein's work on relativity revolutionized our understanding of light and laid the foundation for modern physics. It led to the development of quantum mechanics, which further deepened our understanding of the dual nature of light and the quantum behavior of particles.