Solar eclipses are one of the true wonders of nature. From the innocuous viewing of partial eclipses to the lifetime event of experiencing a total eclipse it is interesting to gain an understanding of the facts behind these sometimes mysterious events.
A basic explanation of what a solar eclipse is that it happens when the moon comes directly between the sun and the earth in either a partial or total fashion. Solar eclipses can only occur during new moons. This is the time of the month when the illuminated surface of the moon lies on the opposite side of the earth. It would seem that this implies a solar eclipse would occur once a month but in actuality the moon’s orbit around the earth is slightly elliptical and tilts varying over an angle of five degrees relative to the earth. The moon only blocks the sun roughly twice a year when the new moon coincides with the tilt of the moon’s orbit lying directly between the earth and the sun. The shadow of the moon is not large enough to cover the total surface of our planet so only a portion of the earth experiences an eclipse at a time.
The difference between the more common partial eclipse and the more dramatic total eclipse is simply that in a total eclipse the moon is directly lined up so that it blocks out the sun in its entirety for a short period of time. Also, because the moon varies in distance from the earth during its orbit with time, it looks larger to the earth during some eclipses and smaller at others. When the moon is close to the earth during a total eclipse a total blockage of the sun’s surface will occur. When the moon is further away it appears smaller and a slight ring of the sun around the moon’s surface is visible. The result is an annular eclipse.
A total eclipse is regarded as one of the true wonders of nature. Near its climax the world is cast into a different kind of darkness with an eerie orange and yellow twilight effect. Just as the sun passes under the cover of the moon the last sliver of the sun breaks into points of light known as Bailey’s Beads. Bailey’s Beads are the last remnants of light passing through the lunar valleys of the moon. Soon the last brilliant bead remains resembling a diamond ring. Finally totality is reached. At this point the actual gases emitted from the sun are visible around the perimeter of the moon at a luminosity equivalent to that of a full moon. The sun is perfectly safe to look at during this time in the form of a black disk in the sky. The magnitude of a total eclipse’s beauty can not be over exaggerated. The eclipse then reverses with the sun once again becoming visible and the sky returning to normal.
During a partial eclipse viewing the sun will cause permanent damage to the retina of the eye. Special techniques such as the use of pinhole cameras or special filters should be used to view the sun at this time. The outer portion of the sun that is visible during a partial eclipse is known as the penumbra. The black inner portion of the eclipse that occurs during total eclipses is termed the umbra.
The occurrence of eclipses is predictable and well known. The known frequencies of exactly identical positions of the moon with respect to the sun and the earth are called the saros of eclipses. Formulas from calculations based on the saros enable astrophysicists to determine both when and where partial and total eclipses will take place. In addition, the percentages of partial to total eclipses, as well as what are called hybrid eclipses, can be determined beforehand. Hybrid eclipses are a combination of both total and annular eclipses which occur along different portions of their paths.
Eclipses are beautiful and precious natural phenomena whose wonder only increases when one understands the science behind them. These solar phenomena evidence the full glory of nature’s grand design.
1) Solar Eclipses for Beginners by Fred Espenak; 2000
2) Eclipses and the Saro; Fred Espenak
3) Totality – Eclipses of the Sun – Second Editio by Mark Littmann, Ken Willcox & Fred Espenak; Publisher: Oxford University Press
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