Why do colors fade in sunlight?

Question

Why do colors fade in sunlight?

Answer 1

the member "Trismes" gave a very wrong and very misleading answer about quark "color" causing visible color changes.   I'm assuming he/she is just joking, but it can be very misleading and rude to somebody who is not familiar with physics.  Photons of visible light do not knock quarks off atoms, and quark "color" has nothing to do with real color. And to say that photons are grey because they are bosons is completely wrong in terms of human perception of color.  Photos ARE light, and they are what create the appearance of color, so this is, of course, carefully crafted nonsense.  Quark "color" has nothing to do with visible color.  it's just an analogy used by physicists.  Just like my bitter attitude has nothing to do with me tasting bad.  

So what causes fading of color?  Most colors that fade in sunlight are organic dyes.  This is different than mineral pigments, which do not fade in the sun (like red rocks do not turn white in the sun).  Organic compounds that have long alternating series of double and single bonds between the carbons have what is called a "conjugated system", where the series of bonds acts as one giant electron orbital.  It just so happens that the energy levels of these conjugated orbitals correspond with the energy levels of visible photons.  They end up absorbing certain colors from white light, leaving behind colored light (white light is just all colors of light mixed together--not caused by "gray photons"!).  

The double bonds of conjugated organic systems are susceptible to many oxidizing reactions, such as caused by bleach.  Ultraviolet light from sunlight can also break those double bonds, breaking the conjugated system, and rendering the compound colorless.  It's kind of like taking a guitar string, that has  a specific frequency (color) and cutting it in half--it will no longer vibrate at the correct frequency.  So, if you leave organic dyes in sunlight for too long, the UV light breaks their bonds that make the colors.  

Visible and ultraviolet light can interact with and break chemical bonds, not nuclear or subatomic bonds.  Color is caused on the chemical or electron orbital level, not on the atomic nucleus level.  Photons created at the atomic nucleus level are in the gamma ray energy levels.  Sorry, I feel like I have to keep explaining why Trismes is so wrong.

Answer 2

Well it depends on the object, and what it's made from.  Fabrics fade in the sunlight because they cannot hold as much color, so they run out quicker.  Plastics and paint can hold more color charge so they retain their color for longer.

A brief explanation of the physics behind light and color may help.  In quantum chromodynamics, all quarks have something called "color charge" (there are 6 kinds of quarks, 2 for each color (R,G,B)).  When a photon (a particle of light) strikes an atom, one of two things will happen:  if the atom's nucleus has a net color charge, the photon will knock the extra quark out of the nucleus, rendering the atom color neutral.  When these color-charged quarks strike your eyes your perceive that as color.  Over time, the number of color-charged atoms decreases, as the number of color-neutral atoms increases, which is why the colors appear to fade.  If a photon strikes a color-neutral atom, it will either be absorbed (as heat) or reflected.  Since photons are bosons and hence have no color charge, they are perceived as gray.

The chemicals that make up certain materials have fewer excess quarks, and thus they run out of color quicker.

Answer 3

a more simpler one is because of ultraviolet rays that the sun emits

Answer 4

Dear Zhong L,

Its some elemental substance that plays a vital role to carry itself of being potently charged to ensue its valent discharges at a subatomic : quantum levels as an interminable process between the two given entities [ Sunlight & Colour as an Entity ]  to renders itself into a transmutated EFFECTs, which is been  noticed later as an Objective change... and this we happen to address & call as what you have quoted "Colours... FADE"

The Charge from the Sunlight, may being the same at a given time & place, but the EFFECTs witnessed in different entities are ought to be different... being the inter'weaven format of / for / by the "Quantum World Constituents" ...  who are indeed the makers and builders of these constituted Quarks & Gluons...  as building blocks for the sub-atomic world...

These Quantum World Constituents are being extrapolated as the "Thermal-Valuity", as an Par' Entity or Para' Being extrapolated to be named as TITHONS....  by a student to an esoteric subject of arcane prudence to the theory of ASTRAL SCIENCE...  whislt lucubrating his heuristic approach through the realms of Para'Physics [ relation between Mind & Matter ], Omnijectivism [ relation between Mind & Reality ], Piezo'Photonics [ Cause & Effect Continuum : World of / for / by the Colours at a Quantum-Levels : Beyond Quantum Chromo'Dynamics ]...  an astral'scientist & gnosiologist : Mr. Charanjeet Singh Lamba

An Illustrated but a laconic explication to depict an inculcation to each mind...  LIGHT is a Composite of Colours ;  COLOUR is nothing but the Composing Entities as Photon belts in term of Rays that in-forms the Constituents of Light.

"Quantum Chromo'dynamics" establishingly spells through its presentational studies that Quark & Gluons are productives of varried & allied Colours at a quantum-levels in term of genesis of hue... creator of  colour charge called PHOTONS.

To understand "Why do colur fade in sunlight"... kindly epitomise the hereaftersaid with the ordinary painting job we do at a given page on Computer by playing the ratio of mixing of & in between the given hues of colours... how we opt to dull, bright, chose & apply to create 'the admixtures'.  

In parity to same...  the playful game in between the Cosmos in context to Quantum Energy and Nature in term of any given entity...  when a particular photonic charge of a potent 'sparticle of light' strikes an atom of any given entity, the role valency takes place to exercise its discharge to the one who is acceptable and receptor as a weak charge...  creating an interminable excitational and assimilational interactions amongst the Quantum-world between the two... and this reactional objectivity been seen and witnessed over time, is what we justify by saying that the Colour FADE in sunlight.

This Effects what we happen to call & address as 'Fade' is again nothing, but a Chemical Reaction at a sub'atomic or quantum level of a given substance/entity.

The Chemical Reaction at these levels of sub'atomic or quantum world is what has been extrapolated as TITHONICITY...

So, the Fading of Colour [entity] in sunlight is the Cause & Effect of a particular process called scientifically as "Tithonic-Effects" on a given Colour [entity]