👉 Light, or electromagnetic radiation, is composed of particles known as photons. The timeline of understanding light particles spans several centuries and key scientific milestones. In ancient times, philosophers like Aristotle debated the nature of light, but it wasn't until the 17th century that significant progress was made. Christiaan Huygens proposed the wave theory of light in 1678, suggesting that light travels as waves. However, Thomas Young's double-slit experiment in 1801 provided strong evidence for the wave theory by demonstrating interference patterns. The 19th century saw a pivotal shift with James Clerk Maxwell's equations, published in 1864, which unified electricity, magnetism, and optics into a single framework, predicting the existence of electromagnetic waves, including light. This laid the groundwork for Albert Einstein's explanation of the photoelectric effect in 1905, where he proposed that light also consists of discrete packets of energy, or photons. This dual nature of light—both wave-like and particle-like—was further solidified by experiments in the early 20th century, such as those conducted by Albert Michelson and Edward Morley, which reinforced the particle theory for high-energy photons. By the mid-20th century, the quantum theory of light became more accepted, with the development of quantum electrodynamics (QED) in the 1940s and 1950s, which provided a comprehensive framework for understanding light-matter interactions at the quantum level. Today, the particle nature of light is widely recognized, essential for technologies like lasers, fiber optics, and quantum computing.
