00:00Why is the sky blue?
00:03When you look directly at the sun, you see white light.
00:07But that white contains all the colors of the rainbow.
00:10Red, orange, yellow, green, blue, and violet.
00:14Why we see blue light when looking at the daytime sky has to do with each color's wavelength.
00:21You can think of it like waves in water.
00:24Some are longer than others.
00:25Red, for instance, has a longer wavelength, blue has a shorter one.
00:30Here's how it works.
00:34Before it can reach your eyes on the Earth's surface, sunlight has to pass through the air
00:39in the atmosphere, which is made up mostly of nitrogen and oxygen.
00:44The light is scattered when it strikes these gas molecules, deflected in all directions.
00:49Short wavelength blue light keeps bumping into molecules over and over, scattering more and
00:55more.
00:56Long wavelength red light passes through more directly, and we only see the parts of the
01:02sunlight that are scattered by the air.
01:06So the color of the sky depends directly on atmospheric composition.
01:11Other gases and particles could make the sky look different.
01:16On Mars, for example, reddish tones dominate during the day.
01:23Even here on Earth, the sky often looks red at sunrise and sunset.
01:29That's because when the sun is low in the sky, the angle you're looking at it means the light
01:34passes through a much longer stretch of atmosphere than during the day.
01:38Because the blue light is mostly scattered high up, we see mostly longer wavelengths, reds,
01:45oranges and yellows.
01:46So the atmosphere is what determines the sky's color.
01:50Without it, we would only see white light from the sun and the blackness of outer space.
01:57If you want more balcony, the rear view, would only squeeze.
01:59You
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