This may sound like a silly question, but does such a thing exist that can create shade?

Question

I don't mean by covering up light, but by emmitting something that takes away light.

Answer 1

From your question, I understand that you are asking about something like "anti-light".

Due to its wave nature, it is possible in theory to generate a wave which can cancel light waves. This is used, for examples, in noise-canceling headphones; these have a microphone just outside which captures the outside noise, then generate a wave with exactly the opposite phase, thus cancelling outside noise. Light has much, much higher frequency, and it is impossible to control its shape (frequency and phase) with any degree of accuracy needed to obtain anything remotely ressembling "light cancelling". Light is produced by electrons in tranzition from one state to another, which happen at random intervals and can not be controlled.

As far as particles are concerned, there is no such thing as an "anti-photon", the eay there is an "anti-electron" (the positron). When they interact and cancel each other, they produce gamma rays, which in fact are electromagnetic waves - the same as light, but at much higher energy.

Other ways proposed for creating shade, such as electric fields and magnetic fields, will not work; by themselves, because the vacuum is a perfectly linear medium - meaning that any electric/magnetic wave will behave as if it was alone. The only way to influence light with an electric or magnetic field is in a medium with a strong nonlinear response, and this happens only in extremely strong firlds even in the best of materials.

Answer 2

No.

The closest you could get would be interference - a second source of light that was tailored exactly in wavelength, amplitude and phase (a technical term meaning the alignment of peaks and troughs in the wave) could cause a cancellation of the original light in some places. In fact a rippled pattern would be generated of dark and light bands - not a complete absence of light.

If you are talking about sunlight or normal artifical lights then even interference is unlikely since it would involve matching the wavelength and phase across a broad band of colours and multiple point sources: sunlight can be scattered by the clouds so seems to be coming from multiple directions and lightbulbs etc are not point sources.

So really it is extremly difficult to imagine it happening.

However - similar technology to cancel out sound waves has been developed. See the new scientist article

Answer 3

Interference is the only practical way to do such a thing. In an interferometer, two paths of light are overlapped by reflecting one off a half-silvered mirror (one that transmitts half the light and reflects the rest). If the beams are coherent (from the same laser) and the path length is adjusted so that one is perfectly out of phase, all the light transmitted by one may be eliminated.

Answer 4

An interesting question - the answer (with the greatest respect to those who have already answered) is essentially no. Shade is, by definition, an area where light is partly or fully blocked. This question sort of reminds me of the old "What is the speed of dark?" conundrum - if light has a speed that can be measured, you would tend to logically assume that the opposite of light would also have a measurable speed. However, dark is simply the absence of light, so I guess if you had to give an answer, the speed of dark is the same as the speed of light.

Answer 5

You could do this with single frequency light by making the waves from two sources mismatch by 180 degrees and then on will counter act the other creating a dark patch. Radio waves do this when one is bounced off the ionosphere and takes a longer route which makes the reception vary.

Answer 6

I guess you could use prisms to refract light in such a way that there are brighter areas and darker areas.

Answer 7

A black hole (highly dense mass ) has such a strong gravity that even light cannot escape it .

Scientists say that a black hole takes away light.

The presence of black hole has been predicted but the existence or creation of black hole in a laboratory has not been proved.

Answer 8

Lots of items can absort light (refract more than they reflect,) but none will ever be truly transparent for this to be noticable.
(i.e. by blocking the light by being solid you will never notice the effects of absorbtion.)

Answer 9

I am a bit confused as what you are trying to achieve here? You are trying to omit light where? Indoors... like a bedroom? Outdoors... like a patio? Just a question that might help other people with answering your question...

Answer 10

Theoretically, you could produce a magnetic field strong enough to deflect light but it would need to be way powerful and would probably cause issues of its own.