[grant2171 (OP)]

It seems that most things have an opposite either in existence or in theory such as Matter and anti-matter.  Does this extend to Light.  Rather than just dark or the absence of light is there such a thing as "Dark-Light"?

[alancalverd]

Symmetry is not universal. There is no antigravity, so why should there be antilight? 

[evan_au]

Matter and anti-matter.  Does this extend to Light.  ...is there such a thing as "Dark-Light"?

Light is its own anti-particle. When a gamma-ray photon strikes another gamma-ray photon, both can disappear, and the energy is released as matter (eg an electron and positron).
This process plays a major role in the Big Bang theory.
See: http://en.wikipedia.org/wiki/Matter_creation

For a particle to be its own antiparticle, the particle must be electrically neutral (like a photon), or it would have the opposite charge to its antiparticle.

For some particles like the ghostly neutrino, it is still not established if its antiparticle is the same or different.
See: http://en.wikipedia.org/wiki/Majorana_fermion

[Colin2B]

It seems that most things have an opposite either in existence or in theory

Many things don't have an opposite, just an absence. We can have a sound or no sound, water in the sink or no water, rain or no rain.
I suspect that because in early history people did not understand the nature of light and absence of light a specific name, darkness, was coined.

[Alohascope]

It seems that most things have an opposite either in existence or in theory such as Matter and anti-matter.  Does this extend to Light.  Rather than just dark or the absence of light is there such a thing as "Dark-Light"?

I've had the same thought .. an 'anti light' particle.  No reason why not. 

[Alohascope]

Matter and anti-matter.  Does this extend to Light.  ...is there such a thing as "Dark-Light"?

Light is its own anti-particle. When a gamma-ray photon strikes another gamma-ray photon, both can disappear, and the energy is released as matter (eg an electron and positron).
This process plays a major role in the Big Bang theory.
See: http://en.wikipedia.org/wiki/Matter_creation

For a particle to be its own antiparticle, the particle must be electrically neutral (like a photon), or it would have the opposite charge to its antiparticle.

For some particles like the ghostly neutrino, it is still not established if its antiparticle is the same or different.
See: http://en.wikipedia.org/wiki/Majorana_fermion

The Big Bang is suddenly missing an esential element .. the Cosmic Microwave Background Radiation has been found to be, simply, heat from dust. http://physics.aps.org/articles/v8/21 while Rapid Inflation itself always was an 'add on' to 'explain' why data of age of stars and the universe were widely divergent.

[Alohascope]

It seems that most things have an opposite either in existence or in theory

Many things don't have an opposite, just an absence. We can have a sound or no sound, water in the sink or no water, rain or no rain.
I suspect that because in early history people did not understand the nature of light and absence of light a specific name, darkness, was coined.

If there is no water in the sink there is air (or something else.)  If there is no sound there is silence .. silence is a reality although I don't know if there is absolute silence anywhere outside, possibly, the realm of absolute zero.
Not only that .. but photons themselves as they travel are said to leave an echoing trail from which information can be extracted .. this different from the 'light echo' surrounding images of stars.  However, I can't find a url to confirm this, which I read about in a recent edition of a science magazine at a library.

[Alohascope]

Symmetry is not universal. There is no antigravity, so why should there be antilight?

I disagree .. I believe anti-gravity bubbles are what is propelling the expansion of the universe.  These bubbles are commonly known as Voids. 

[evan_au]

the Cosmic Microwave Background Radiation has been found to be, simply, heat from dust.

This article was not critiquing the existence of the CMBR.

It is saying that the BICEP2 experiment at the South Pole did not have enough resolution to detect the impact of gravitational waves on the CMBR. It was pointed out that the BICEP2 authors had not properly taken into account the impact of dust particles on the polarisation of the CMBR.

The Planck spacecraft has mapped the CMBR over a greater range of wavelengths, for a longer time, with greater sensitivity and over more of the sky than you can achieve with a telescope at the South Pole, which must peer through Earth's atmosphere.

See: http://en.wikipedia.org/wiki/List_of_cosmic_microwave_background_experiments

[CopperKnickers]

Light is an electromagnetic wave, as such two photons of the same energy meeting at the same point in space but with opposite phase will interfere destructively to yield no photon at that point in space.
But then... the same thing happens (stochastically) with electrons when you do the double slit experiment...

This is definitely different to particle-antiparticle interactions where energy is liberated from the annihilation, but there might be something mathematically similar in it.  Naturally, I lack the brain-smarts and learning to explore this further. (sadface)

[puppypower]

One could argue that matter is the opposite of energy/light, with the equivalency of matter and energy defined by Einstein's famous  equation E=MC2. The speed of light; C, is the dividing line between matter and energy, where each phase, although equivalent, cannot go on the opposite side, unless it first converts to the other. This dividing line is not plus and minus by convention. However,  but if we used the speed of light as the zero point or ground state of the universe, then matter and energy would be defined as plus and minus.

[alysdexia]

It seems that most things have an opposite either in existence or in theory such as Matter and anti-matter.  Does this extend to Light.  Rather than just dark or the absence of light is there such a thing as "Dark-Light"?

Opposite in what?

Symmetry is not universal. There is no antigravity, so why should there be antilight? 

The Hubble flow and Einstein field equation disprove you.

Light is its own anti-particle. When a gamma-ray photon strikes another gamma-ray photon, both can disappear, and the energy is released as matter (eg an electron and positron).
This process plays a major role in the Big Bang theory.
See: http://en.wikipedia.org/wiki/Matter_creation

It's a real wave which holds imaginary (virtval) motes.  The wave and mote together make a complex—that is, periodic—field.

For some particles like the ghostly neutrino, it is still not established if its antiparticle is the same or different.
See: http://en.wikipedia.org/wiki/Majorana_fermion

That is, whether the π⁺-e⁻ and π⁻-e⁺ compounds are equivalent.  They hold mass, so they shouldn't be.

Many things don't have an opposite, just an absence. We can have a sound or no sound, water in the sink or no water, rain or no rain.
I suspect that because in early history people did not understand the nature of light and absence of light a specific name, darkness, was coined.

Accountants disagree with you.  However this may come down to the distinction between a state and a delta-state.

[Colin2B]

Accountants disagree with you. 

Many other types of creative artist do.
They might consider nighttime is a debt to be repaid the following day, but average interest is not good. They might also want to try sunlight as an overnight loan, but again the interest rate is not good.
Personally I account sunlight as an overhead.

[Alohascope]

It seems that most things have an opposite either in existence or in theory such as Matter and anti-matter.  Does this extend to Light.  Rather than just dark or the absence of light is there such a thing as "Dark-Light"?

Scientists used to think space held a vacuum .. 'an absence of anything."  Now they know there is no absence, there is energy arising from the absence of matter .. so yes, an absence of light could very well create energy .. maybe that is what Dark Energy is .. who knows.  If they say they do know they probably are guessing.

[the5thforce]

mass reflects light, and since a true vacuum is impossible even opposites are part of the same spectrum- in this case mass is the opposite of light on the energy spectrum.