# why do we see the sun as yellow

Raleigh scattering is very weak so the vast majority of the light from the Sun passes through the atmosphere without being scattered. That means when we look at the Sun we see the 99% of the light that isn't scattered, and that light has the original 5,700K colour spectrum. The only light we see directly from the Sun is the light that travels in a straight line from the Sun to our eye - that's the horizontal yellow line in this diagram. If you consider the upper yellow line we can't see this light ray because it misses our eye. However the Rayleigh scattering due to the air scatters in all directions, so some of this scattered light reaches our eye. That means when we look away from the Sun we only see the scattered light and not the direct sunlight. The Rayleigh scattering depends on the wavelength and blue light is scattered most.

That means the light we see coming from directions away from the Sun has a spectrum weighted towards the blue. NB it isn't pure blue light. It's a spectrum of light enriched in blue compared to the direct sunlight. A spectrum of the scattered light from the blue sky
( And that's why the Sun looks yellow and the sky looks blue. If the Sun is supposed to be producing white light, why does the sun appear yellow to the eye instead of white? We need to start with the fact that white light is a combination of all colors produced equally by a glowing object. A glowing object that appears blue is blue because it's producing more blue light than it is producing red, orange, yellow, green light. The color of a glowing object depends on the temperature of the object.

Now we can proceed to your question. Two Reasons why the Sun appears yellow: 1. The Sun's surface temperature (5,500 degrees C) produces a range of visible light (red to blue) in which yellow is the most plentiful, but not much more than other colors it produces. If the Sun were cooler, say 2,500 degrees C, it would look red, like the stars Antares and Betelgeuse. Or if the Sun were hotter, say 15,000 degrees C, it would look blue, like the star Rigel. 2 The Earth's atmosphere acts as a kind of light filter. Some colors are filtered more than others. The Sun is a yellow star, but the Earth's atmosphere makes the Sun look more yellow than it appears than if you were to observe it from space where it would appear more white than yellow.

But you don't have to leave Earth to see that the Sun is really less yellow than it appears. If you are in the Rocky Mountains at 11,000 ft elevation, the Sun looks less yellow and more white than it does at sea level. There are fewer air molecules at this elevation to filter the Sun's other colors. Imagine what the Sun would look like from an airplane at 40,000 ft altitude--quite white! Also, when you are able to look at the Sun where you live, it's morning or late afternoon. It's easier to look at the Sun for a few seconds than it is a noon. The Sun appears more yellow at those times than it would if you were to observe it at noon (12 PM) when Sun is highest in the sky for the day; it's at its brightest and whitest--hard to look at.

Because of the Sun's high position at noon, the sunlight has less air to travel through. Less air means less filtering of other colors. Remember: Light appears white because all colors are equally reaching your eyes. So, at noon the Sun appears to be more white, less yellow--closer to the way it really is! (Don't try to make this observation without hi-tech eye protection). Answered by: J Taras, M. S. , Earth Science teacher, Slate Hill, NY The short wavelengths (blue) of light from the sun are scattered by the atmosphere (which is why the sky appears to be blue. ), leaving behind the longer (yellow-red) wavelengths. From a high-flying airplane, or from the moon, the sun appears to be white. Answered by: David Kessel, Ph. D. , Professor, Wayne State University, Detroit

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