How Does Light Actually Work?

The universe's early moments were filled with overwhelming heat and energy, creating a state of superheated plasma. Around 400,000 years later, this heat decreased enough to allow electrons to bond with protons, forming the first atoms and releasing photons, the first particles of light, allowing light to travel freely in the universe.

Light's journey through the universe began during the cosmic Dark Ages, devoid of stars or galaxies. Over time, stars and galaxies formed, and despite the universe's changing structure, light continued its journey. Finally, after nearly 14 billion years, a photon collided with a human-made telescope, marking the end of its ancient voyage.

While light existed from the universe's inception, it was initially blocked by particles until the universe became transparent. This allowed photons to travel unimpeded. As humans emerged, they explored the nature of light, leading to realizations about its external nature and triggering advancements in optics and the understanding of light's properties.

In the 1600s, Christian Huygens proposed that light is a wave, explaining phenomena such as refraction. This idea contrasted with Isaac Newton's view of light as particles—corpuscles. Huygens highlighted wave patterns through experiments, challenging existing theories and laying groundwork for wave-particle duality in understanding light's nature.

Newton opposed Huygens' wave theory, favoring a particle theory due to light's inability to diffract significantly, unlike sound waves. However, Thomas Young’s double-slit experiment in the 1800s provided strong evidence for the wave theory, showing how light could interfere and produce wave-like patterns, challenging the particle concept.

By Maxwell's time in the 19th century, light was understood as electromagnetic waves, a concept uniting electricity and magnetism. His equations described light as waves of oscillating electric and magnetic fields. This understanding spurred the exploration of radio waves and other wavelengths beyond visible light, transforming communication technologies.

Heinrich Hertz confirmed the existence of radio waves in the late 1800s, leading to wireless communication developments by Marconi. Maxwell's wave theory expanded to make sense of electromagnetic phenomena by showing light as a wave of fields rather than particles, but questions about its particle-like properties remained unsolved till the 20th century.

Einstein revisited the nature of light, proposing in 1905 that light exhibits packet-like properties known as photons, explaining the photoelectric effect where light seems to act as particles when interacting with metal surfaces. This discovery paved new paths for both quantum mechanics and our understanding of light as having dual wave-particle nature.

The early 20th century saw quantum mechanics evolve, complicating our perception of light as either wave or particle. The work of physicists like Louis de Broglie suggested that matter too exhibits wave-particle duality. Quantum field theory later emerged, portraying particles as excitations in fields, fundamentally altering physics' view on matter and light.