Get smarter in sixty seconds with brain Stuff from how stuffworks dot com. I am Marshall Brain Today's question, why is the sky blue? Here's something interesting to think about. When you look at the sky at night, it is black, with the stars in the moon forming points of light on that black background. So why is it that during the day the sky does not remain black with the Sun acting as another big point of light. That's exactly
what happens on the moon. So why on Earth does the daytime sky turn a bright blue and all the stars except the Sun disappear during the day. The first thing to recognize is that the Sun is an extremely bright source of light, much brighter than the other stars. The second thing to recognize is that the atoms of nitrogen and oxygen in the atmosphere have an effect on
the sunlight that passes through them. There is a physical phenomenon called ray Leigh scattering that causes light to scatter when it passes through particles that have a diameter one tenth that of the wavelength or color of the light. Sunlight is made up of all different colors of light, but because of the elements in the atmosphere, the color blue is scattered much more efficiently than the other colors. So when you look at the sky on a clear day,
you can see the sun is a bright disk. The blueness that you see everywhere else is all of the atoms in the atmosphere scattering blue light towards you. Because red light, yellow light, green light, and the other colors aren't scattered nearly as well, we see the sky is blue, and that blue color is so bright that it completely blots out all the other stars because they're so dim. Do you have any ideas or suggestions for this podcast? If so, please send me an email at podcast at
how stuff works dot com. For more on this and thousands of their topics, go to how staff works dot com. MHM