Prehistory to 999 AD
The earliest human experiences with light and optics were of the natural world; sunlight, fire, and the reflective and refractive (light bending) properties of water, crystals, and other naturally occurring substances. Fire was one of the first tools utilized by ancestors of modern humans, perhaps as early as 1.4 million years ago, but it probably was not used for nighttime illumination until 500,000 years ago. By 15,000 years ago, people were burning fat and oil in lamps to illuminate the dark, the first artificial devices for creating light.
Archeological findings from early cultures, made by Austen Layard in the nineteenth century, indicate that by 3,000 BC people in the Middle East, Africa, and Asia were becoming increasingly aware of optical phenomena and were using them for a variety of purposes. Shadows were used for theatrical entertainment. Metals and crystals were modified and shaped to exploit their reflective and refractive properties for use as decoration and as jewelry. The invention of glass around this time was probably fueled by its remarkable optical properties. The oldest glass artifacts are glass beads that were obviously used as jewelry.
By 300 BC, Greek scholars had begun to study and contemplate optical phenomena in earnest, generating theories to explain vision, color, light, and astronomical phenomena. Many of those theories turned out to be wrong, but they did serve to inaugurate the science of optics. Plato is believed to be the first person to articulate the emission theory of vision. This theory, which prevailed until the second millennium AD, suggested that the eyes projected rays of light, like a flashlight, illuminating objects in front of them. When something blocked the "eye-rays," the result was darkness.
In the western world, Euclid of Alexandria made the first recorded observations concerning optics and light. He wrote an in-depth study of the phenomenon of visible light in his work Optica, where he defined the laws of reflection of light from smooth surfaces. Aristotle also studied the nature of vision, but disagreed with the theory that rays emanated from the eyes. Also during this time period, the great Sicilian mathematician Archimedes studied reflection and refraction, but his work was destroyed when the Romans sacked Syracuse.
The idea for the camera obscura, the ancestor of the camera, most likely originated in early Greece. It is essentially a pinhole camera in which light passes through a small hole and is projected in a darkened room or box, generally without the aid of a lens. For hundreds of years, scientists used the camera obscura to view solar eclipses without damaging their eyes, and it is still utilized for that purpose in modern times by amateur scientists and the general public.
The Romans did little to advance the science of optics, although Seneca, a tutor and favored friend of Roman Emperor Nero, noted the magnifying effects of liquids in transparent vessels. Nero is reported to have used a smooth emerald lens to better observe gladiators in combat.
During the second century AD, Ptolemy, a Greek astronomer based in Alexandria, Egypt, studied and wrote about many topics in science. Most notable was his development of the geocentric, or Earth-centered, theory of the solar system that would prevail for over a thousand years. He published five books about optics, but only one book has survived to the modern era. This series of works was dedicated to the study of color, reflection, refraction, and mirrors of various shapes. The establishment of theory by experiment, frequently supported by the construction of special apparatus, is the most striking feature of Ptolemy's Optics.
Few other advances were made in optics until after 1000 AD. However, the Arab scholar Alhazan, a.k.a. Abu Ali Hasan Ibn al-Haitham, conducted the first serious study of lenses in Basra (Iraq). He studied refraction in lenses, disproving Ptolemy's law of refraction, and also carried out research on reflections from spherical and parabolic mirrors. His writings were the first to explain vision correctly, as a phenomenon of light coming into the eye, rather than the eye emitting light rays.
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