It may be tempting to examine the color content of sunlight and identify the brightest color (the peak frequency) as the actual color of the sun. That is why incandescent light bulbs emit light that mimics sunlight so well: they contain metal filaments that are heated until they glow in the same way the sun does. Just like a hot coal or an electric stove element that glows, the sun glows in all colors because of its temperature. The sun emits all these colors because it is a thermal body and emits light through the process of thermal radiation. This includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, and X-rays. The sun emits all colors of visible light, and in fact emits all frequencies of electromagnetic waves except gamma rays. The fact that you see all the fundamental colors present in a rainbow (which is sunlight split by mist) and no colors are missing is direct evidence that sunlight is white. When a light bulb engineer designs a bulb that is supposed to mimic the sun, and therefore provide natural illumination, he designs a white bulb, not a yellow bulb. We can see the redness of a rose and the blueness of a butterfly's wing under sunlight because sunlight contains red and blue light. If sunlight were purely green, then everything outside would look green or dark. That is why we can see so many different colors in the natural world under the illumination of sunlight. The sun emits all colors of the rainbow more or less evenly and in physics, we call this combination "white".
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