History
In the fifth century BCE, Empedocles postulated that everything was composed of four elements; fire, air, earth and water. He believed that Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible. If this were true, then one could see during the night just as well as during the day, so Empedocles postulated an interaction between rays from the eyes and rays from a source such as the sun.
Around 400 BCE, emission theory was held by Plato.
In about 300 BCE, Euclid wrote Optica, in which he studied the properties of light. Euclid postulated that light travelled in straight lines and he described the laws of reflection and studied them mathematically. He questioned that sight is the result of a beam from the eye, for he asked how one sees the stars immediately, if one closes one's eyes, then opens them at night. Of course if the beam from the eye travels infinitely fast this is not a problem.
In 55 BCE, Lucretius, a Roman who carried on the ideas of earlier Greek atomists, wrote:
The light and heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove. – On the nature of the Universe
Despite being similar to later particle theories, Lucretius's views were not generally accepted and light was still theorized as emanating from the eye.
Ptolemy (c. 2nd century) wrote about the refraction of light, and developed a theory of vision that objects are seen by rays of light emanating from the eyes.
The dispute over the emission and Aristotelian intromission theories of vision began to settle during 11th century when the experiments of the Arabian physicist, Ibn al-Haytham (Alhazen, 965-1039) lent support to the intromissionist theory in his Book of Optics.
Read more about this topic: Emission Theory (vision)
Famous quotes containing the word history:
“The history of medicine is the history of the unusual.”
—Robert M. Fresco, and Jack Arnold. Prof. Gerald Deemer (Leo G. Carroll)
“Only the history of free peoples is worth our attention; the history of men under a despotism is merely a collection of anecdotes.”
—Sébastien-Roch Nicolas De Chamfort (1741–1794)
“In history the great moment is, when the savage is just ceasing to be a savage, with all his hairy Pelasgic strength directed on his opening sense of beauty;—and you have Pericles and Phidias,—and not yet passed over into the Corinthian civility. Everything good in nature and in the world is in that moment of transition, when the swarthy juices still flow plentifully from nature, but their astrigency or acridity is got out by ethics and humanity.”
—Ralph Waldo Emerson (1803–1882)