Fotoni - valon kvantti

Fotonin aalto 4-vektorin mahdolliset arvot
vihreä ja indigo kartio edustavat vasemman ja oikean suuntaista polarisoitnia
kuva wikimedia

Teologiaa
יהי אור 
Raamatun alussa ovat Israelin Jumalan majesteettiset sanat JEHI OR "Tulkoon valo!" Gen 1:3

Miten tämä Luojan käskysana on ymmärretty ja ymmäretään ihmiskunnan parissa on jokseenkin pitkä kertomus.

Tässä blogissa kiinnitän huomiota siihen, että Raamatun alussa oleva aihe - valo - on osoittautunut modernin tieteen kannalta ratkaisevan tärkeäksi aiheeksi. Juuri valon tutkimuksen kautta ihmiskunta on oppinut tuntemaan kosmoksen syntyä ja rakennetta, päässyt määrittelemään linnunratojen pyörimisnopeutta, tutustunut tähtien kemiallisiin ominaisuuksiin niiden säteilemän valon spektrin huolellisella tutkimuksella ja onnistunut mittaamaan etäisyyksiä laajenevan maailmankaikkeuden ääriin.

Valo ei siis ole laisinkaan hassumpi teema Raamatun alkulehdelle, joka kertoo kaiken alusta. Aiheen syvällisyyttä ihminen on alkanut hieman ymmärtää vasta näinä viimeisinä aikoina. Jumalan ilmiotus on ihmeellistä ja se avautuu eri tavoin erilaisissa tilanteissa oleville ihmisille. Sääli, että niin monet sen ylenkatsovat, universumin Luojan oman raportin.

Modernia tiedettähän vanha heprealainen kirjoitus ei hetkauta, eihän se anna juuri mitään tietoa valosta. Se kertoo silti ratkaisevan tärkeän asian, jota tiede ei pysty tutkimaan Jumala väittää Sanassaan, että Hän on luonut valon.


Fotoni - valon kvantti

In 1900, Maxwell's theoretical model of light as oscillating electric and magnetic fields seemed complete. However, several observations could not be explained by any wave model of electromagnetic radiation, leading to the idea that light-energy was packaged into quanta described by E=hν. Later experiments showed that these light-quanta also carry momentum and, thus, can be considered particles: the photon concept was born, leading to a deeper understanding of the electric and magnetic fields themselves.
kuva ja teksti wikipedia

Wikipedia johdattelee asiantuntevasti valon, maailmankaikkeuden tärkeimpiin tutkimuskohteisiin kuuluvan aiheen pariin. Kopsaan tähän ainoastaan perusteellisen artikkelin johdannon ja koetan tehdä siitä helpommin hahmotettavan muutamin muokkauksin koskematta itse tekstin sisältöön.

[suomalainen versio artikkelista on wikipedia.fi mutta kuten tavallista, se on sisällöltään englantilaista aika lailla kevyempi]

A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation, and the force carrier for the electromagnetic force, even when static via virtual photons.

The effects of this force are easily observable at both the microscopic and macroscopic level, because the photon has zero rest mass; this allows long distance interactions.

Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, exhibiting properties of both waves and particles. For example, a single photon may be refracted by a lens or exhibit wave interference with itself, but also act as a particle giving a definite result when its position is measured.

The modern photon concept was developed gradually by Albert Einstein to explain experimental observations that did not fit the classical wave model of light.

• In particular, the photon model accounted for the frequency dependence of light's energy, 
• and explained the ability of matter and radiation to be in thermal equilibrium. 

It also accounted for anomalous observations, including the properties of black-body radiation, that other physicists, most notably Max Planck, had sought to explain using semiclassical models, in which light is still described by Maxwell's equations, but the material objects that emit and absorb light do so in amounts of energy that are quantized (i.e., they change energy only by certain particular discrete amounts and cannot change energy in any arbitrary way).

Although these semiclassical models contributed to the development of quantum mechanics, many further experiments starting with Compton scattering of single photons by electrons, first observed in 1923, validated Einstein's hypothesis that light itself is quantized.

In 1926 the optical physicist Frithiof Wolfers and the chemist Gilbert N. Lewis coined the name photon for these particles, and after 1927, when Arthur H. Compton won the Nobel Prize for his scattering studies, most scientists accepted the validity that quanta of light have an independent existence, and the term photon for light quanta was accepted.

In the Standard Model of particle physics, photons are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this gauge symmetry. 

• The photon concept has led to momentous advances in experimental and theoretical physics, such as lasers, 
• Bose–Einstein condensation, 
• quantum field theory, and 
• the probabilistic interpretation of quantum mechanics. 

It has been applied to

• photochemistry, 
• high-resolution microscopy, and 
• measurements of molecular distances. 

Recently, photons have been studied as elements of quantum computers and for sophisticated applications in optical communication such as quantum cryptography.
lue koko artikkeli wikipediasta

Siis mistä ensimmäiset fotonit, nuo itsenäiset hiukkaset, valon kvantit?