Light

Light (models)

In science, light is that portion of the electromagnetic radiation, of the electromagnetic spectrum, from about 380 to 780 nanometers in wavelength, visible to the human eye. [1]

History
The study of the nature and composition of light is probably one of the most intricate, involved, and as of yet unsolved subjects of modern science.

The finite velocity of light was measured in 1676 by Ole Romer. [1]

The first, supposedly, to seed the notion of light as a corpuscle, was Pierre Gassendi, who, building on the atomic theory work of life of Epicurus, in his circa 1649 work stated (check) that light is made up of small discrete particles called "corpuscles" (little particles) which travel in a straight line with a finite velocity and possess kinetic energy. [10]

The first dominate theory, however, was Isaac Newton's circa 1675 corpuscular theory of light, in which light was imagined to be a stream of minute particles or 'corpuscles' emitted by a light source, shooting through empty space like bullets in the form of light rays, detected by their impact on the retina. [3] The corpuscles, in Newton's theory, were argued to set up disturbances in the 'aether' of space. [1] From 1670 to 1672, Newton lectured on optics. During this period he investigated the refraction of light, demonstrating that a prism could decompose white light into a spectrum of colours, and that a lens and a second prism could recompose the multicoloured spectrum into white light. In his Hypothesis of Light of 1675, Newton posited the existence of the ether to transmit forces between particles.

In 1678, Dutch physicist-astronomer Christiaan Huygens published his undulatory theory of light, in which light was thought to be a wave spreading out in all directions from a light source, transmitted via a medium known as ether, and detected by the waves creation of sympathetic vibrations in the retina. [3]

In 1801, English physicist-physician Thomas Young invented the famous double slits experiment and thus re-discovered the phenomenon of the interference of light, showing that a wave theory was essential to the interpretation of light. [1]

In 1873, Scottish physicist James Maxwell published his famous A Treatise on Electricity and Magnetism, which introduced the world to the now-famous Maxwell equations, the four governing equations on the phenomenon of electricity and magnetism, with which Maxwell showed that these equations implicitly required the existence of electromagnetic waves traveling at the speed of light. [4]

In 1900, Max Planck postulated, based on the work of Ludwig Boltzmann, that the energy of black bodies could be quantized or divided into a discrete number of “energy elements”. In 1905, building on the Planck’s model, Albert Einstein proposed that light itself could be quantized. In his own words:

“According to the assumption to be contemplated here, when a light ray is spread from a point, the energy is not distributed continuously over ever-increasing spaces, but consists of a finite number of energy quanta that are localized in points in space, move without dividing, and can be absorbed or generated only as a whole.”

In the 1920s, the term "photon" was coined to describe Einstein's energy quanta. One reference claims it was American physicist Arthur Compton who coined the term photon in his 1923 work on the investigations showing that electromagnetic quanta behave like particles, exchanging both energy and momentum in collisions with electrons. [6] Most references, however, state that the term “photon” is a 1926 coinage of American physical chemist Gilbert Lewis to describe a “particle” of light. [7]

In modern particle physics terms, electromagnetic fields are described as being made up from photons, in which electric and magnetic forces are assumed to be due to the action of photons. In technical terms, photons of light are "on the mass shell", whereas photons of electric and magnetic fields are not. [8]

Chnopsology | Biology

One of the first to discuss the nature of light in thermodynamic terms, specifically in relation to biological mechanism, was Russian biogeologist Vladimir Vernadsky, who in his 1926 The Biosphere stated: [2]

“The important roles played by ultraviolet, infrared, and visible wavelengths are now well-recognized. We can also indentify the parts of the biosphere that transform these three systems of solar vibration, but the mechanism of this transformation presents a challenge which our minds have only begun to comprehend.”

Vernadsky goes on to state that the mechanism is disguised in an infinite variety of ways, e.g. natural colors, forms, and movements, of which we, ourselves, form an integral part. He continues:

“[Light] causes changes in electromagnetic fields, the decomposition of molecules, various ionization phenomena, and the creation of new molecules and compounds. Radiant energy is transformed, on the one hand, into various magnetic and electrical effects; and on the other, into remarkable chemical, molecular, and atomic processes.”

He continues “all forms of radiant solar energy outside of the four and one-half octaves that penetrate the biosphere are ‘retained’, i.e. transformed into new terrestrial phenomena.”

Human chemistry
In human chemistry, it is understood that light operates through the actions of activation energy, in working to trigger or setting off human chemical reactions, such as in the visual mechanism action (retinal molecule) of the reaction ensuing following the instance of love at first sight. [9]

See also
Blue sky problem

References
1. Daintith, John. (2005). Oxford Dictionary of Science. Oxford University Press.
2. Vernadsky, Vladimir I. (1926). The Biosphere (pg. 48). Copernicus.
3. Robinson, Andrew. (2006). The Last Man who Knew Everything: Thomas Young, the Anonymous Genius who Proves Newton Wrong and Deciphered the Rosetta Stone, among Other Feats (pg. 96-, etc.). Plume Books.
4. Maxwell, James C. (1873). A Treatise on Electricity and Magnetism (Volume One). New York: Dover.
5. Einstein, Albert. (1905). “On a Heuristic Point of View about the Creation and Conversion of Light”, Annalen der Physik March 18.
6. Schumm, Bruce. A. (2004). Things Down Deep – the Breathtaking Beauty of Particle Physics (pg. 33). Baltimore: The Johns Hopkins University Press.
7. (a) Ball, David W. (2001). The Basics of Spectroscopy (pg. 13). SPIE Press.
(b) Gribbin, John. (2000). Q is for Quantum – An Encyclopedia of Particle Physics. New York: Touchstone Books.
8. Veltman, Martinus. (2003). Facts and Mysteries in Elementary Particle Physics (pg.17). World Scientific.
9. (a) Thims, Libb. (2007). Human Chemistry (Volume One). Morrisville, NC: LuLu.
(b) Thims, Libb. (2007). Human Chemistry (Volume Two). Morrisville, NC: LuLu.
10. Corpuscular theory of light – Wikipedia.

External links
Light – Wikipedia.

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