Sunrise and sunset is often astoundingly beautiful and can vary in color according to atmospheric conditions. When the sun is nearer the horizon, its rays pass through a thicker atmosphere than when the sun is directly overhead. This produces shades of yellow, orange and red. An abundance of volcanic ash in the air tends to bring on the most dazzling array of color in deep hues of red.
Astronauts from the Apollo missions were able to see earthrise over the moon's horizon.
TWILIGHT
Twilight is the time of partial darkness before sunrise and after sunset. Technically, twilight lasts in the morning from the time that the stars and the moon are still faintly visible until sunrise.
The colors of twilight are generally deeper and more intense than those of sunrise or sunset, adding a sense of drama to this tranquil time of day.
The earth's atmosphere scatters the sunlight across the sky, enabling you to see a light just before sunrise and after sunset. The farther north you go during the summer months, the longer twilight lasts. If you live in Maine, for instance, you have a little extra time to enjoy twilight in the early morning and evening hours than do folks in southern California.
AURORA BOREALIS
The aurora borealis, or Northern Lights, is a bright display of constantly changing lights seen in the Northern Hemisphere.
The florescent lights of the aurora borealis are created when high-energy electrons from the sun come in contact with atoms and molecules, primarily oxygen and nitrogen, in the earth's upper atmosphere. These electrons emanating from the sun's radiation get trapped in the earth's magnetic fields and are directed by magnetic attraction to the North and South Poles.
The aurora borealis is formed in the ionosphere at altitudes of 50 to 600 miles (80-960 kilometers). When these electrons become excited, they move to higher energy levels. This added energy is released into the upper atmosphere, causing the bright displays which may appear as arcs, curtains or rays of color across the night sky.
The color of the lights largely depends on the gaseous molecule that was energized. An excited oxygen molecule may emit a green light, whereas nitrogen will emanate a red to purple light.
The aurora borealis is most frequently seen in a zone encompassing northern Alaska in the United States, as well as the Yukon, Northwest Territories, northern Quebec, and Labrador in Canada.
Sunspot activity can increase the amount of electrons the sun sends to the earth and cause the aurora borealis to be seen over a much larger area. In fact, the Northern Lights have been seen as far south as Texas and Mississippi.
The aurora borealis can also be seen in areas near the South Pole. In the Southern Hemisphere, the aurora is called the aurora australis, or Southern Lights.
ECLIPSES
An eclipse is an alignment of the moon, the earth and the sun which takes place during either the new or full moon phase. Lunar eclipses can best be seen at night and solar eclipses during the daytime hours.
In our solar system, the earth and the other planets rotate around the sun. The moon orbits the earth. In order for an eclipse to take place, the moon, the earth and the sun must all be in alignment with one another.
LUNAR ECLIPSES
During a full moon, when the earth is perfectly aligned between the moon and the sun, the earth casts its shadow on the moon, blocking the earth's view of the lunar surface. If the earth completely blocks the light from the sun, it is called a total eclipse of the moon.
During a new moon, the moon is at its farthest orbit point away from the earth. When the moon, earth and sun align at this time, the moon can block the light from sun.
Major lunar eclipses for the rest of the century include:
-April 4, 1996 visible in Africa, Europe, South America, the eastern part of North America, and West Asia.
-September 27, 1996 visible in North & South America, Africa, and Europe.
-March 24, 1997 visible in North & South America, West Africa and western Europe.
-September 6, 1997 visible in Asia, Europe, Africa and Australia.
-July 28, 1999 visible in the Pacific Ocean, Australia, East Asia and NW North America.
SOLAR ECLIPSES
At the time of the new moon, the moon sometimes is perfectly aligned between the sun and earth, blocking the sun's light to the earth's surface in the daytime. If the sun completely vanishes, this phenomena is known as a total eclipse. Otherwise, it is called a partial eclipse.
A partial eclipse of the sun happens when the moon is at the far end of its orbit and appears smaller than the sun. Here, an annular eclipse occurs, with a brilliant ring of sunlight around the moon. During partial solar eclipses, it doesn't get nearly as dark as during a total eclipse.
A total eclipse of the sun is rare. People from all over the world travel to get the most favorable viewing spots for a glimpse of this event.
Total eclipses of the sun for the rest of the century include:
-March 9, 1997 visible in Siberia and over the Arctic Ocean.
-February 26, 1998 visible over the Pacific Ocean, Columbia, the Caribbean Sea and the Atlantic Ocean.
-August 11, 1999 visible in much of Europe, the Middle East and India.
