Khan Academy: Why Is The Sky Blue?

Founder Sal Khan walks "Nightline" anchor Terry Moran through one of his science lessons.
2:26 | 01/03/13

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Transcript for Khan Academy: Why Is The Sky Blue?
-- -- Why the sky is blue and -- -- sudden changes color. That -- -- simple question 38. -- this is circus of the year. And -- just be neutral only it was just the atmosphere here it's. Here quote and here's me UV oxygen and nitrogen. Molecules here oxygen. Very small molecules. And few people realize the sun the light that it makes his white light. And -- it might affect -- the full spectrum has all the colors of the rainbow in it. It's as the white light come to this is the father -- As it comes and in. The blue light of the high small wave -- gets -- gets scattered by small molecules. Of the blue light get scattered in different directions. The blood. And it's taken out of the white -- To -- the content or more blue light hits scattered and that's -- -- was sitting right here they -- bullet. They won't see the white from the sun as -- -- the blue -- out of that -- -- -- -- what's left -- is more -- yellow -- And so that's -- dangerous on. It looks that looks more and more orange or yellow as it as it goes -- why why -- -- change from blue in the silence at noon. It's over years of as good as -- life goes through the atmosphere. The blue light to scattered mountain of the line and -- enough left as the origin of the young islanders on Saturday it's even more -- -- So I know you're not -- a lot of the so looks a little bit and probably you know when the -- -- -- and he flew right over here the sun setting now. Now the -- as white light is traveling or with initially like -- in space is traveling to further distance. So it's getting it's getting scattered more -- has more opportunity for more polluted beaches in the -- more he gets taken out of like -- scattered out when it gets to the observers it looks. Really orange or almost read this is no blue there's no -- -- when -- still clouds that are known are red that's because traveling even more associate the sunlight. Is reflecting all the cloud and then going to the so there's a lot of opportunity for the blue. To get taken out of it and even over here so -- -- -- taken out of that that this cloud itself with trying to look -- And then when the light -- your excuse me. And that's that's what's catching just -- -- was actually just color.

This transcript has been automatically generated and may not be 100% accurate.

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