The sun is the dominant source of visible light on Earth. Blue light from the sun scatters more than other colors when passing through the atmosphere, which is why the sky appears blue. During sunrises and sunsets, light must pass through more atmosphere and scatters red light more, making the sky appear red or orange. Rare atmospheric events like the northern lights can also color the sky through light refraction and scattering in the atmosphere.

1. Refraction of light in the atmosphere! Why is the sky blue?

2. The Atmosphere http://www.visionlearning.com/library/module_viewer.php?mid=107

3. Particle Density http://www.visionlearning.com/library/module_viewer.php?mid=107

4. LIGHT!!! 186,282 miles/sec

5. Colors in that Light! http://missionscience.nasa.gov/ems/09_visiblelight.html

6. SUNLIGHT http://missionscience.nasa.gov/ems/09_visiblelight.html

7. THE SUN'S CORONA The Sun is the dominant source for visible-light waves our eyes receive. The outer-most layer of the Sun's atmosphere, the corona, can be seen in visible light. But it is so faint it cannot not be seen except during a total solar eclipse because the bright photosphere overwhelms it. The photograph below was taken during a total eclipse of the Sun where the photosphere and chromosphere are almost completely blocked by the moon. The tapered patterns—coronal streamers—around the Sun are formed by the outward flow of plasma that is shaped by magnetic field lines extending millions of miles into space. http://missionscience.nasa.gov/ems/09_visiblelight.html

8. Sun Temperature http://missionscience.nasa.gov/ems/09_visiblelight.html

9. Absorption Gas molecules are smaller than the wavelength of visible light. If light bumps into them, it acts differently. When light hits a gas molecule, some of it may get absorbed. After awhile, the molecule radiates (releases, or gives off) the light in a different direction. The color that is radiated is the same color that was absorbed. The different colors of light are affected differently. All of the colors can be absorbed. But the higher frequencies (blues) are absorbed more often than the lower frequencies (reds). This process is called Rayleigh scattering. (It is named after Lord John Rayleigh, an English physicist, who first described it in the 1870's.)

10. Rayleigh Scattering

11. Percent Scattered

12. At the Horizon

13. Space View of Sun

14. Red at night….

15. Northern lights http://www.youtube.com/watch?v=PaSFAbATPvk&feature=related