Does color exist, or does is it a product of the brain?
Color plays a vitally important role in the world in which we live. Color can sway thinking, change actions, and cause reactions. It can irritate or soothe your eyes, raise your blood pressure or suppress your appetite. When used in the right ways, color can save on energy consumption. When used in the wrong ways, color can contribute to global pollution. As a powerful form of communication, color is irreplaceable. Red means "stop" and green means "go." Traffic lights send this universal message. Likewise, the colors used for a product, web site, business card, or logo cause powerful reactions. Articles Color Matters: Color & Vision: How the Eye Sees Color Color originates in light. Sunlight, as we perceive it, is colorless. In reality, a rainbow is testimony to the fact that all the colors of the spectrum are present in white light. As illustrated in the diagram below, light goes from the source (the sun) to the object (the apple), and finally to the detector (the eye and brain). 1. All the" invisible" colors of sunlight shine on the apple. 2. The surface of a red apple absorbs all the colored light rays, except for those corresponding to red, and reflects this color to the human eye. 3. The eye receives the reflected red light and sends a message to the brain. The most technically accurate definition of color is: "Color is the visual effect that is caused by the spectral composition of the light emitted, transmitted, or reflected by objects."
Does color exist in the dark?
An apple appears to be "red" when the light reflects off of it and enters our eyes. Our brains then process it and let us see the color red. Which leads to another question: Is an apple still red if no one is looking at it?
Do unseen colors exist?
There is radiation above and below the spectrum we see. SOme animals are very good at seeing them. Pit viper snakes see into infrared, it would be as if we could directly see heat but notice that we do not perceive heat as a color. Pit vipers do see heat in a way. Where we see white flowers many insects see flowers of many colors and patterns moving into the ultraviolet range. You can look at photos of these plants where the spectrum has been shifted so we can get an idea of what bees see when they see these white flowers. The shift puts the colors into the range we see but they are not the colors the insects see. Since we can't see these colors they go unnamed. There are cases of people who can see a little farther into the infrared and ultraviolet ranges, but not much. The problem of seeing new colors isn't that they do not exist, they do, but we haven't the capacity to see them. SO they all get lumped together as electromagnetic radiation with subdivisions that we can use. Radio, x-ray gamma ray and so on.
Why do we perceive the sun as yellow?
Light having a shorter wavelength (blue light) is more readily scattered by the atmosphere. This is why the sky looks blue... The bluish part of the spectrum from the Sun tends to reach us indirectly from the whole sky and the rest, which reaches us directly tends to be yellowish if we look directly at the Sun (although our senses may "saturate" and perceive the Sun as white nevertheless). This separation of sunlight into a direct and indirect part means that shadows will have a blue hue because they are lit only by the sky and not directly by the Sun... Beginning in the 19th century, artists started painting shadows with a touch of blue, (sometimes exaggerating the effect, which is actually barely noticeable). When the Sun is low on the horizon, its rays travel a longer distance through the atmosphere and the effect becomes more pronounced (even more so if there's moisture in the air). This is when the Sun may start to look really yellow, or orange, or red... Enjoy the Sunset ! FOOTNOTE: Don't let me get started on the reasons why, under the right conditions, the last rays of the Sun may look green (or white) for a fraction of a second before it disappears under the horizon. This is called the "green flash" and it's really amazing the first time you see it. You have to look for the effect when the Sun sets over the Ocean in calm weather through some thin distant haze... Pay attention when the edge of the disk is about to disappear and don't blink at the wrong time !