Is black a colour

LoLth

OK, a quick question which seems easy enough (and makes for great arguments in the pub!)

Is black a colour?

If colour is the reflection of light, colourless is the 100% passing through of light (badly worded but you know what I mean). then surely white is the 100% reflection of all light in all spectrums (spectra?)(lets ignore non-visible for now but could they be included without changing the argument too much?).

So black would be the complete absorbtion of all light. which means nothing is being reflected so there is no colour. Black is the absence of colour ==> it is not in and of itself a colour.

any views? flames? calls of "muppet"?

Samson

Originally posted by LoLth
Is black a colour?

No, it's a shade of grey.
As is white.

Emboss

so if purple is the 'new black' does it cease to be a colour also ?
:ninja:

WhiteWashMan

Originally posted by LoLth


If colour is the reflection of light, colourless is the 100% passing through of light (badly worded but you know what I mean). then surely white is the 100% reflection of all light in all spectrums (spectra?)(lets ignore non-visible for now but could they be included without changing the argument too much?).

So black would be the complete absorbtion of all light. which means nothing is being reflected so there is no colour. Black is the absence of colour ==> it is not in and of itself a colour.

any views? flames? calls of "muppet"?

by your own theory above, black is a colour.
you have said that black is a reflection of all colours.
is green not a reflection of various shades of yellow and blue?

by that, it would mean that black is a colour made up of all the other colours?

what you have said is that the surface that is reflecting the light is black. ie made up of all colours.

is the colour of the light and the colour fo the surface interchangable? if so then i guess you have your answer, if not, then surely you could use the conservation of energy to say that the energy was transfered from the light to the surface and thus providing the effect known as black.



of course, we all know that white is the complete spectrum of colours, but have you ever made white paint by pouring all the colours of paint together?
bizarre huh?

Capt'n Midnight

If you can see a black object - then black most definitely has a colour.

If you are looking at the void and see nothing - then it can be described as black - but without colour...

Note: black holes aren't really black... and no one has made a perfect black box (in the radiation sense)

Irish and Italian do not have seperate words for Pink
Russian uses two words for what we would see as shades of blue
Italian also uses Azurro but not the same way we use Blue ( Blu is a bit different )


PS. Black boxes are of course Orange.

This post has been sponsored by the letter Alpha and the colour Black.

WhiteWashMan

Originally posted by Capt'n Midnight


Note: black holes aren't really black.

not true!

light cannot escape the gravitational pull of a black hole, so therefor light cannot reflect from them.

personally i believe they are a rather virilant pink, but i cant prove it!
goddamn it!

Capt'n Midnight

'cos it emits very few photons. (virtual pairs - one on each side of the event horizon - so they may not combine and cancel each other out)

Not sure of the colour - it depends on the temperature - which being a measure of entrophy depends on the size of the said hole.

After many many years a black hole radiates off enough energy so that light can finally escape from it - and then the whole thing explodes - runaway effect - no problem seeing it then.....

Giblet

I'll try come up with a simple example. Colour is seen by how much light is absorbed by an object. It could be said that and object is green if the red and blue wavelenghts are completely absorbed, and Black is seen when all wavelenghts are absorbed.
Just because all the spectrums are absorbed doesn't mean that all colour is absent, black is just a product of the absorbation, the same way green is.

GuanYin

Originally posted by Giblet
I'll try come up with a simple example. Colour is seen by how much light is absorbed by an object. It could be said that and object is green if the red and blue wavelenghts are completely absorbed, and Black is seen when all wavelenghts are absorbed.
Just because all the spectrums are absorbed doesn't mean that all colour is absent, black is just a product of the absorbation, the same way green is.

Nope the big problem here is what you define black as.

Black as in the absorption of all light is not a colour.

Black as in the things we can see that look black but really arent (because light is indeed escaping) , is a colour.

DeVore

Actually WWMan you are closer to the truth then you think.

Black holes emit whats called Hawking Radiation and are actually very visible to the right equipment.

DeV.

bonkey

Originally posted by WhiteWashMan
you have said that black is a reflection of all colours.

He hasn't said anything of the sort. Go back and look at what you quoted :

So black would be the complete absorbtion of all light. which means nothing is being reflected

How can that mean its a reflection of all colours. Thats what he said white was.

(Are you saying black is white? That you are really BlackWashMan?)

Black is the absence of all light (emitted or reflected).
Colour is nothing but the perception of emitted and reflected light.

Black would be the absence of light, and therefore must be the absence of colour.

jc

Zukustious

No. Black is not a colour. We see colours when light bounces off things. We see black when there is no light so black is the absence of colour.

Originally posted by WhiteWashMan
not true!

light cannot escape the gravitational pull of a black hole, so therefor light cannot reflect from them.

personally i believe they are a rather virilant pink, but i cant prove it!
goddamn it!

Black holes are white hot at the center but the light emited doesn't get to escape. So black holes are white.

Capt'n Midnight

First any light you see can't be black.

400-700 is generally visible - dark adaption needed to see others 380nm to ~740nm ish

Range (nm) Colour
380 _ 450 Violet
450 _ 490 Blue
490 _ 560 Green
560 _ 590 Yellow
590 _ 640 Orange
640 _ 730 Red

"Infrared radiation cannot enter the eye, and only warms its surface. Long-wave ultraviolet radiation causes fluorescence in the eye (especially in the visual purple), and the fluorescent radiation can be seen. Short-wave ultraviolet again cannot penetrate, but irritates the conjunctiva. Ultraviolet is damaging to the eye, causing irreversible changes. The dark-adapted eye is also sensitive to X-rays, which are not refracted by the eye and pass freely through it. This appears to be a direct sensitivity, since there is little fluorescence, and the stimulus can be moved around on the retina. Gamma rays can also be perceived, but this is again due to fluorescence, so a diffuse glow results. Do not try this at home!"

So any wavelength above 400nm is potentially visible (though not recommended) - the famous "blue flash" of SiFi
So only radiation of wavelength longer than 740 nm can be considered black ....

Links I found looking for the wavelengths...

http://www.deltacolours.com/color_theory.htm - nice colours - I like the daylight curve.

http://www.psych.ucalgary.ca/pace/va-lab/colourperceptionweb/congenital.htm - what the world looks like if you have colour vision problems

http://www.du.edu/~jcalvert/optics/colour.htm - nice bit about the eye - I ripped the paragraph above from it.

ecksor

I can't help thinking that the most relevant example here would be the black that somone might decide to paint their bikeshed with.

Giblet

Colour is formed by the absorbtion and/or the reflection of light.
Not just the reflection.
You see a colour because the material reflected it and absorbed others.
So if it reflects all lightwaves its white, if it absorbs all lightwaves its black. Anything inbetween is the other colors.
Colour is the product of reflected and absorbed light.

Sarky

Black is an absence of colour. You only really "see" it because the sudden absence of colour is conspicuous. It's called a colour because it's easier than being accurate all the time.

Ry

Black is a manufactured colour. Nowhere in natural life will you find true black other than man made things. Anything on animals or plants that looks black to our eyes is actually always just a very dark something else ie: blue brown or any other colour. For example People with black hair don't actually have black hair it's just very very dark brown to the point where it looks black in our eyes. Black and white are not colours they are just the mix of colours to produce eachother. Black is artificial. There ye go. If this has been said before sorry I just wasn't arsed reading past the 3rd or 4th post

Ry

Victor

It is a matter of definition. Black coloured paint and dyes and so on exist - although they are not 100% black in the scientific sense.

Science generally refers to only the ROYGBIV colours as colours. Black and white are the absolute presence or absense of these.

Looking beyond the universe would be black (although your view would be obstructed).

nesf

Originally posted by Capt'n Midnight
'cos it emits very few photons. (virtual pairs - one on each side of the event horizon - so they may not combine and cancel each other out)

Not sure of the colour - it depends on the temperature - which being a measure of entrophy depends on the size of the said hole.

After many many years a black hole radiates off enough energy so that light can finally escape from it - and then the whole thing explodes - runaway effect - no problem seeing it then.....

No colour, colours refer only to visible parts of the EM spectrum (which this radiation is not part of, he only refers to it as a colour in his book because it's aimed at lay people and not physicists), plus read Hawking's books again, you've not got it totally right (oh and it's spelt entropy).

Colours are formed by an object absorbing certain parts of of the EM spectrum, and refecting the others. The result is an absorbtion spectrum. This is percieved by our eye as a colour which we have names for, but which in reality do not fall into easily defineable catagories.

Black is formed when an object ,nearly, perfectly absorbs all the visible wavelenghts of the visible part of the EM spectrum. Black is a colour in that it is what the eye percieves that type of asorbtion spectrum to be. This is also the reason why black things are hotter when left in the sun. They absorb more of the light than other things of a different "colour" and thus more energy and thus get hotter.

See simple as that
(i thought i'd expand on the absorbtion/reflection point you made Giblet and try to explain it)

-Pádraig

Victor

Originally posted by nesf
They absorb more of the light than other things of a different "colour" and thus more energy and thus get hotter.

They are also better radiators - hence light coloured clothing is worn in Arctic areas and many arabs wear dark clothing.

Capt'n Midnight

Surely some of the photons will be in the visible spectrum - or possibly have higher energy - in which case the "colour" will depend on the % of photons of each wavelenght....

(ammitedly most will not be visible)


Polar Bears have Black skin - and many desert tribes wear black robes (or a similar colour)