View Full Version : Understanding colour

29-01-2007, 06:13:36
The following is a quote from my wildlife calendar:

"The blue jay's (Cyanocitta cristata) vivid blue feathers make an exotic contrast against brown leaves or green grass. However, their colour is actually the result of optical illusions created by light, not pigmentation."

This is very disturbing to me! Blue jays aren't really blue? Colour is something other than optical illusions created by light? Does any knowledgeable science type understand this?

29-01-2007, 08:19:51

29-01-2007, 08:23:22
there was an article last week on the economist about it

29-01-2007, 09:11:22
Originally posted by RedFred
Colour is something other than optical illusions created by light?
yes, it's an opticall illusion created by your brain, optionally using inputs from your eye

Greg W
29-01-2007, 10:32:16
Maybe it's just the wingspeed causing blue shift of light.

29-01-2007, 10:36:58
I understand it.

You've seen a rainbow right? The rain isn't really all those colours, but the light is refracted through the rain in different directions so you see different colours. Something similar will be happening with the blue jay.

Also in this category, a polar bear isn't really white. It's fur is transparent and it's skin is black.

Mr. Bas
29-01-2007, 10:47:41
It's probably a photonic crystal type of thingie. Normally, if something is blue, it means that blue light is absorbed less strongly by the material than other frequencies, so that what is reflected is predominantly blue. However, if you have some structure that's periodic in refractive index, the object may only be transparent to certain frequencies, while it may fully reflect others (blue light in this case). And that is a result of the periodic structure, not directly of the material properties. The color is probably altered if you submerge it in alcohol or water or something else with a different refractive index than air. It's completely analogous to the electronic band gap in solids, FYI.

Now that was a seriously serious reply. :nervous:

29-01-2007, 10:59:46
Originally posted by Funko
a polar bear isn't really white. It's fur is transparent and it's skin is black.

hey, is that where polarised light comes from???

Immortal Wombat
29-01-2007, 11:24:21
Originally posted by Mr. Bas
Now that was a seriously serious reply. :nervous:
I think you just about saved it by suggesting submerging blue jays in alcohol.

30-01-2007, 02:39:36
Actually, the Bluejay is constantly followed by another creature that holds a projector emitting a blue light pointed at the Bluejay at all times. Bluejays are actually babyshit brown.

30-01-2007, 05:36:45
Well the CeeGees aren't very helpful.

Think of the Toronto sports teams. They have already misnamed the Maple Leaves the Maple Leafs. They came up with the goofy name of Raptors shortly after Jurasic Park came out. And now this.

The Not-So-Blue Jays. The Optical Illusion Jays. The Mystery Jays. :(

Mr. Bas
30-01-2007, 09:17:07
The photonic crystal bandgap jays!