Why does colour exist?

[WouldBe]

Don't eat that red berry, it is red as a warning!

Stops eating strawberries and raspberries.

 

[weltweit]

If all colour seeing animals were extinct and only deer and other colour blind animals remained, would colour still exist?

 

[Bob_the_lost]

If all colour seeing animals were extinct and only deer and other colour blind animals remained, would colour still exist?

Different energy photons would. But you're /we're getting a bit "if a tree falls in a wood..." now.

 

[weltweit]

Different energy photons would. But you're /we're getting a bit "if a tree falls in a wood..." now.

Yes twas intended ..

I mean the question > does colour exist?
is easily answered, yes it does and we can see it and measure it.

But the question > why does colour exist?
Well why does anything exist, it exists because it is .. as it does .. there is no why .. there is how when and where but not a why .. imho

 

[povmcdov]

If all colour seeing animals were extinct and only deer and other colour blind animals remained, would colour still exist?

No. Colour is not wavelength, it is a perceived phenomenon, ie. a quale, so if nothing percieves it it doesn't exist. If you doubt that it is a quale, consider the fact that there is no "red" cone cell. Light of the wavelength we consider to be red (~650nm), does not maximally activate the red cone, instead its peak sensitivity lies in the yellow part of the spectrum (~580nm). "Redness" is detected not as 650nm wavelength light per se, but as a differential activation of the "red" and "green" cones. ie. orange light will activate the "red" cone more, but will also activate the "green" cone, whereas red light will activate the "red" cone less than orange light, but will hardly activate the "green" cone at all. The processing for this differential is mostly done on the retina at the level of ganglion cells.

edit: I got the graphs out first, does that mean I win?

 

[Crispy]

Wow, I knew blue sensitivity was low, but not that low!

 

[povmcdov]

It surprised me too. I had forgotten about that. The caption to that picture says that in reality the blue peak should be 1/3 the height that it is shown there.

It is doubly surprising when you consider that the blue photon is more energetic.

Edit: it may be because "visual purple" in rod cells is green/blue sensitive and there is enough detection capability already for blue light.

 

[kyser_soze]

Would having a different coloured sun (e.g. white or blue) alter the colours we see? If so, would it be a complete transform (i.e. a tomato would look blue), or would it look like sunglasses?

 

[WouldBe]

Would having a different coloured sun (e.g. white or blue) alter the colours we see? If so, would it be a complete transform (i.e. a tomato would look blue), or would it look like sunglasses?

White may make things brighter.

Blue would make red things look shades of grey.

You can try it at home in a darkened room with a torch and coloured filters (sweet wrappers would work).

 

[povmcdov]

On the other hand, photo-receptors have evolved to use the light that is available on earth. If the sun was a different colour it would have applied different evolutionary pressures to that process and you would expect that the receptors would have different sensitivities.
This can be seen in deep sea fish, which tend to have a single photosensitive pigment with maximal activation being between 474 and 490nm, which tallys with the available light at depth.
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1095-8649.1997.tb01340.x

Interestingly the mantis shrimp has photoreceptors for 10 different frequencies and 2 more types that respond to different polarisation planes. That's more than any other known eye.

 

[Crispy]

Seeing polarisation would be
Not sure what it would be useful for, but LCD panels would look weird

 

[povmcdov]

As a guess its something to do with air/water interfaces in this case, as these shrimp live in shallow water and I think these boundries can polarise light in some way.

 

[kyser_soze]

Yeah, I was more thinking when we arrive at III Eridani or something, and have earth peeps under other suns.

Personally I want to see a binary system from a nicely hospitable planet...I think that would be teh kewl...

 

[povmcdov]

It does make a difference, yes. Orange sodium vapour streetlamps really mess with your colour perception.

 

[stavros]

Because that's how it is.

It was that way before we were here, so we developed at least in part, in reaction to the fact of how light is.

So you could say, why do we have eyeballs that can unscramble white light? Because of how light is.

Thanks for all the response, although there does seem to be a certain amount of disagreement/loss of communication between us.

Given that not every organism or particle is photosensitive or coloursensitive, is it a reasonable hypothesis to make that colour is merely a biproduct of objects' other properties and we, along with other organisms, have evolved to employ this biproduct to our benefit?

 

[Crispy]

It does make a difference, yes. Orange sodium vapour streetlamps really mess with your colour perception.

That's because sodium lamps are (almost) monochromatic - they only emit light in 2 frequencies, both of them smack bang in the middle of yellow.

This is quite different to the light from a hotter or cooler star, which will have a distribution of emitted frequencies that peaks bluer or redder, respectively.

 

[Crispy]

Thanks for all the response, although there does seem to be a certain amount of disagreement/loss of communication between us.

Given that not every organism or particle is photosensitive or coloursensitive, is it a reasonable hypothesis to make that colour is merely a biproduct of objects' other properties and we, along with other organisms, have evolved to employ this biproduct to our benefit?

'Colour' is a property of our senses. With different senses, we would have different colours. Even a different distribution of frequency sensitivity within the current visible spectrum would result in different 'primary' colours. (and this is what colour blindness means)

 

[Bob_the_lost]

I think povmcdov's got the way "colour", rather than photon emission, works dead right.

"Colour... is a perceived phenomenon, ie. a quale, so if nothing percieves it it doesn't exist."

Colour is nothing more than the way our eyes process different frequencies of light. If it's a byproduct it's one we create rather than the objects reflecting/emitting light.

 

[Crispy]

This shows why blue sensitivity is lower - sunlight contains more blue than any other colour, so detectors do not need to be so sensitive.

Note that the 'notches' in the distribution represent absorbtion of specific wavelengths by specific chemicals.

 

[Bob_the_lost]

Wouldn't the amount of blue be something to do with the water in the atmosphere rather than the light source itself? Why is the sky blue and all that?

 

[Crispy]

The sky being blue is a coincidence. The skies on other planets are different colours, but the still receive a similar spread of wavelengths from the sun. It's all to do with the temperature of the sun, which is approx.5800K at the surface.

You'll notice that the peak of this graph is the 400-700nm range in the visible spectrum - no coincidence. This is the range that vision has evolved to detect.

 

[kyser_soze]

Is it? I thought it was due to the % of oxygen in the atmos...

 

[Crispy]

the sky is blue due to scattering of light by the gases and vapours in it. blue light is absorbed and scattered more, so the sky appears blue.

 

[kyser_soze]

*slaps self for not remembering GCSE physics*

 

[Crispy]

don't worry, I always have to look it up too

 

[povmcdov]

Colour is nothing more than the way our eyes process different frequencies of light. If it's a byproduct it's one we create rather than the objects reflecting/emitting light.

Its a product of the brain too of course. Its very uncommon, but brain damage can cause colour-blindness too, known as aquired cerebral achromotopsia IIRC.

Oliver Sacks covered it very well in his book of case histories, "An anthropologist on Mars". He describes the "case of the colourblind painter". This guy was a professional artist so was able to decribe very accurately what he was experiencing. The subjective experience was very different from retinal colourblindness, with everything replaced by grayscales, but not in the way that a B&W TV does it. For instance a blue sky looked black to him. He found it very disturbing and found that the only time things looked halfway right was under sodium vapour streetlamps.

As with almost all Oliver Sacks stuff its well worth a read. (hes the real life doctor from "awakenings", the film with Robert Deniro and Robin Williams if you havent heard of him)

 

[weltweit]

But But .. we are getting away from the OP question which was :

WHY does colour exist ?

Why .. not how, when where etc but why.

And its plainly so that smarties are more appealing.

 

[Jonti]

Green is an interesting colour.

We have the same *identical* conscious sensation when we look at monochromatic green light as we do when we look at a mixture of monochromatic yellow and monochromatic blue!


ETA: this ties in nicely with BtL's point above ...

I think povmcdov's got the way "colour", rather than photon emission, works dead right.

"Colour... is a perceived phenomenon, ie. a quale, so if nothing percieves it it doesn't exist."

Colour is nothing more than the way our eyes process different frequencies of light. If it's a byproduct it's one we create rather than the objects reflecting/emitting light.

See, the brain *could*, I guess, cause us to perceive the mixture of blue and yellow light differently to the monochromatic green.

 

[dash_two]

Some women have two types of red receptor, one of which is maximally responsive to a slightly different wavelength than the standard red receptor. This means they can make finer colour distinctions around the red portion of the spectrum. Why this is, who knows.

 

[kyser_soze]

But But .. we are getting away from the OP question which was :

WHY does colour exist ?

Why .. not how, when where etc but why.

And its plainly so that smarties are more appealing.

What you mean metaphysically? There isn't a 'why' - if we only saw in B&W while 'colour' would still exist (in the sense that a tree falling etc), we wouldn't know anything about it (although if we understood how our vision worked we could probably theorise that there was more to life than the greyscale). Colour is a physical property, not a metaphysical one.