The Basics of Solar Eclipses
A solar eclipse, or eclipse of the sun, actually has a lot to do with the phases of the moon. Each month of 29 and a half days, our moon cycles completely through all its phases. They are: full>waxing gibbous>first quarter>waxing crescent>new>waning crescent>third quarter>waning gibbous>and back to full.
The sun always illuminates exactly one-half of the moon’s surface, and it is always the same surface. So when the moon travels around the earth, we see a different portion of the lit surface. The unlit surface is invisible to the naked eye. This is why we have so called “moonless” nights.
When the moon is new, the earth, moon and sun are in approximate alignment, with the moon between the earth and the sun. The sunlit surface is turned away from the earth, toward the sun, and as we said above, you cannot see the unlit surface facing the earth. When the moon is full, the earth, moon and sun are in alignment again, but this time the earth is between the moon and the sun, so that we can see the entire lit surface.
It may seem as though at the full moon stage, the earth’s shadow should obliterate the moon. Actually, because the moon is about 5 degrees off from the earth-sun orbital plane, we can see the moon in its full phase.
A solar eclipse can only occur when the moon passes between the earth and the sun in the new moon phase. We don’t get to see solar eclipses every month, however, because the moon’s shadow, due to that 5 degree difference, usually misses falling upon the earth.
When the shadow does fall on the earth, it does so in a a very narrow path, called the Path of Totality. That path is normally about 10,000 miles long, but only about 100 miles wide. So to see a total eclipse of the sun twice from any single location would take many more years than the span of a lifetime.
In just a few minutes from beginning to end, the black disk of the moon covers the bright light of the sun. A spectacular light show is then seen as a fiery halo around the shadow of the moon. this is the sun’s solar corona, plasma heated to an unbelievable two million degrees in temperature! This is the breathtaking even that all eclipse watchers have been waiting for. Fortunately, science can now tell us exactly when—right to the minute and second—and where viewing this phenomenon will be possible.
The next total solar eclipse will occur March 9, 2016, at 1:58 am and will only be visible from Sumatra, Borneo, Sulawesi, and the Pacific.
For more information, check out the NASA Eclipse Website.