Natural Phenomenom

 SUNRISE

At sunrise, a glowing red ball peeks above the eastern horizon. As it rises, it shades to orange and then yellow. The day dawns bright and full of hope.

Just as awesome is the sparkling palette that sunset paints across the sky. While the eastern sky may still be deep blue, streaks of orange, pink, and red light the western sky. Like a glowing ball, the sun sinks lower and lower. Finally, it slips below the horizon.NEVER look directly at the sun. No matter what time of the day it is, harmful ultravioletrays can damage your eyes. Instead, focus away from the sun on the rest of the sky.

 What causes sunrise and sunset? Although the sun seems to move, it's really Earth that's moving. Earth always spins, or rotates, toward the east.

Unless clouds block the sun, the sky usually looks blue. In fact, however, sunlight contains all colors of light. Red, orange, yellow, green, blue, indigo, and violet make up the visible spectrum of light. Put them all together, and you get white.

Different colors of light have different wavelengths. A wavelength is the distance between one wave crest, or top, and the next one. Violet, indigo, and blue have the shortest wavelengths. Red, orange, and yellow have longer wavelengths.

You and a friend can demonstrate wavelengths by holding two ends of a rope. Move one end slowly from side to side for long wavelengths. Wiggle it quickly for shorter wavelengths.

As light waves enter the atmosphere, they strike gas and particle molecules in the air. The molecules scatter the light. That is, they split the different colors apart. This phenomenon is called Rayleigh scattering.

The shorter bluish wavelengths get scattered about four times more easily than the longer reddish wavelengths. Because they reach our eyes from all directions in the sky, the sky looks blue.

Near sunrise and sunset, however, the sun's rays must travel through more of the atmosphere to reach us. By then, most bluish wavelengths are scattered away. The longer red wavelengths make the sky glow orange or red.