WEBVTT - Why the Sky is Blue?

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<v Speaker 1>Get smarter in sixty seconds with brain Stuff from how

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<v Speaker 1>stuffworks dot com. I am Marshall Brain Today's question, why

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<v Speaker 1>is the sky blue? Here's something interesting to think about.

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<v Speaker 1>When you look at the sky at night, it is black,

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<v Speaker 1>with the stars in the moon forming points of light

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<v Speaker 1>on that black background. So why is it that during

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<v Speaker 1>the day the sky does not remain black with the

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<v Speaker 1>Sun acting as another big point of light. That's exactly

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<v Speaker 1>what happens on the moon. So why on Earth does

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<v Speaker 1>the daytime sky turn a bright blue and all the

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<v Speaker 1>stars except the Sun disappear during the day. The first

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<v Speaker 1>thing to recognize is that the Sun is an extremely

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<v Speaker 1>bright source of light, much brighter than the other stars.

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<v Speaker 1>The second thing to recognize is that the atoms of

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<v Speaker 1>nitrogen and oxygen in the atmosphere have an effect on

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<v Speaker 1>the sunlight that passes through them. There is a physical

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<v Speaker 1>phenomenon called ray Leigh scattering that causes light to scatter

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<v Speaker 1>when it passes through particles that have a diameter one

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<v Speaker 1>tenth that of the wavelength or color of the light.

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<v Speaker 1>Sunlight is made up of all different colors of light,

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<v Speaker 1>but because of the elements in the atmosphere, the color

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<v Speaker 1>blue is scattered much more efficiently than the other colors.

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<v Speaker 1>So when you look at the sky on a clear day,

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<v Speaker 1>you can see the sun is a bright disk. The

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<v Speaker 1>blueness that you see everywhere else is all of the

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<v Speaker 1>atoms in the atmosphere scattering blue light towards you. Because

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<v Speaker 1>red light, yellow light, green light, and the other colors

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<v Speaker 1>aren't scattered nearly as well, we see the sky is blue,

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<v Speaker 1>and that blue color is so bright that it completely

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<v Speaker 1>blots out all the other stars because they're so dim.

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<v Speaker 1>Do you have any ideas or suggestions for this podcast?

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<v Speaker 1>If so, please send me an email at podcast at

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<v Speaker 1>how stuff works dot com. For more on this and

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<v Speaker 1>MHM