Most of the light we encounter every day is a chaotic mixture of light waves vibrating in all directions.
Some materials contain long molecules which are lined up, like the slats on a wooden fence.
As the light passes through this material, some of waves can pass through the slats, while others cannot. It's like trying to put a letter in a mail slot - the letter has to be lined up just right in order to get through the slot. By determining the amount and direction of polarization and how these change with wavelength, scientists can learn about what causes the energy to become polarized. As you rotate the glasses, the brightness of the sky will vary because the light has been polarized by being reflected in the atmosphere. Updated July 18, 1995.