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While a lunar eclipse interrupts the cycle of lunar phases, which many people are totally unaware of, a solar eclipse interrupts the most fundamental cycle of nature – day and night. It is impossible to ignore a total solar eclipse. Within minutes, the Sun is blacked out, the temperature drops and stars visible that should be the middle of the day. Birds exhibit bedtime behavior. We now know that period of a total eclipse during which the Sun is totally blacked out can last no longer than 7 minutes and 40 seconds, and generally for a much shorter period of time. But until man was able to predict eclipses, they must have been terrifying events. The constant rising and setting Sun would suddenly grow dark. According to one story, two men in China, His and Ho, were executed in 2137 BCE for failing to predict a solar eclipse. People took skygazing seriously in those days.
A solar eclipse takes place like its lunar counterpart when the Sun, the Moon and the Earth are in a direct line, but with the Moon in the middle instead of the Earth. This arrangement of Earth, Moon and Sun can only occur during a new Moon. There is not a solar eclipse during every new Moon for the same reason that there is no lunar eclipse during every full Moon. During a new Moon, the Sun, Moon and Earth are usually not in the same plane. When all three of these bodies are in a straight line, the Moon blocks the Sun as it is viewed from some point on the Earth. This occurs because of a coincidence. The massive Sun is about 400 times as large as the Moon, and it is also approximately 400 times as far from the Earth. Both the Moon and the Sun appear to have the same size to an Earth- bound observer. This is a bit of a simplification because both the Earth-Moon distance and the Earth- Sun distance very slightly throughout the year. When the Sun is relatively far and the Moon relatively close to the Earth, the Moon will appear larger and totally block the Sun. In the opposite situation when the Sun is close and the Moon far, the Sun will appear larger to us and will appear during a solar eclipse as a ring around the Moon.
The problem with viewing a solar eclipse is not their frequency (there are two to five each year) but that solar eclipse can only be seen over a small area of the Earth. A solar eclipse that is total and fully blocks out the Sun on the East Coast may be undetectable on the West Coast. During a solar eclipse, the Moon forms a shadow on the surface of the Earth. If conditions are favorable, the umbra of the Moon’s shadow will touch the surface of the Earth. At that point and time there will be total eclipse of the Sun. The Sun’s surface will be totally dark except possibly for a small ring around the edge. The Earth and the Moon are of course moving, so that the point of totality is rushing over the Earth's surface at a speed of about 1,2000 miles an hour. The width of this path is a mere 200 miles. To the sides of the path, a partial eclipse of the Sun is seen in which only part of the Sun’s surface is blackened.
As I have mentioned previously, looking directly at the Sun is dangerous, whether with an optical aid such as binoculars or a telescope or with the naked eye. Viewing the Sun during a solar eclipse is particularly dangerous because there is a natural tendency to direct one’s eyes towards it for an extended period of time. Also, when except during a solar eclipse does anybody bother to stare at the Sun? Some people solve the problem of Sun gazing by the use of filters. The safest method is observing the Sun indirectly by projecting its image onto some sort of screen and looking at that. The simplest technique is to prick a small pinhole at the narrow end of a shoebox. The hole acts as a simple lens. By directing the end with the hole towards the Sun, the Sun’s image will appear on the opposite side of the box. The image will be quite small. You might try experimenting with using binoculars or any other set of lenses to sharpen the image. With a bit of trial and error, it is not difficult to obtain a nice sharp and safe picture of the Sun.
Although solar eclipses can be predicted many years in advance, nobody can be sure of the exact appearance of a coming eclipse. Many observers of the solar eclipse in 1985 were treated to the sight of Baily's beads. The Moon's image was just a shade smaller than the Sun's. The difference was so light that the Sun's rays were blocked by the Moon’s mountains and shined through the Moon Moon’s valleys, which gave the appearance of bright shifting beads around the Sun's perimeter. While the appearance of Baily's beads was expected, the eclipse was more spectacular than anyone had hoped for. As the Moon's shadow sped through the eastern United States and into Mexico, it left a wake of skygazers, from those using sophisticated photographic equipment to a group of fourth and firth-graders watching through mylar-filtered windows cut in cardboard boxes placed over their head, in awe of a solar event that was both predictable and wondrous.