Spectral Eclipses

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During the year as the Earth rotates around the Sun there are occasions when the Moon moves in direct alignment between the planet and the Sun.  When this occurs there can be two basic eclipses,  lunar or solar.   The more common to witness, the lunar eclipse, is seen when the full Moon passes through the shadow of the Earth.  This places the Sun and the Moon on opposite sides of the Earth.  Seen only at night during certain full Moons the bright lunar disk turns dark, sometimes almost a coppery red for up to an hour or longer.  These lunar eclipses are beautiful to watch but do not inspire as much awe as the total solar eclipse.  For a total eclipse to occur the new Moon must pass directly between the Sun and the Earth.  There is only a narrow path where the eclipse is seen as total called the umbra.  It is at this time day turns into night in an eerie few minutes.  The wispy halo of the Sun, called the corona is seen as the Moon for a few moments blocks out the brilliance of the Sun.  Outside of umbra is the penumbra where some portion of the Sun remains visible.

Although there are partial eclipses where the path, (the umbra) misses the Earth passing just above the North Pole or just below the South Pole, and the eclipse is not total.  There is also a third type of solar eclipse called an annular eclipse.  Annular from the Latin word for "ring", because the Sun is not completely covered by the Moon.  In this case the Moon is father away in its orbit around the planet and appears smaller and therefore not large enough to fully cover the Sun.  It is only during the total eclipse that the darkness is experienced with a view of the corona. 

It is a rare event when the Sun, Moon and Earth are so perfectly aligned for this phenomenon to occur when a total eclipse can be seen. There are not eclipses every month during the new Moon or a full Moon because the Moon's orbit is tilted approximately five degrees with respect to the Earth's orbit.   This results in the Moon passing slightly above or below the between the Sun and the Earth.  Yet about every six months the conditions are right for lunar or solar eclipses.  Even though this is a relatively frequent situation it is far more common for a lunar eclipse to be seen than a solar eclipse.  The reason for this is the darkened full Moon can be seen from anywhere on the nighttime half of the Earth during the eclipse.  The total solar eclipse will only be seen from the umbra, the path of totality.  The path is sometimes two hundred miles wide, which results in approximately one-half of one percent of the Earth's surface.  To add to the rareness of the event being viewed it often passes over open seas or remote regions of the planet.   With less than seventy total eclipses per century the opportunity to view one is considered a once-in-a-lifetime event.  Today people may travel to see this event and yet others like myself because of relocation across the country may have been fortunate to see more than one.  It is an event that is unforgettable and events in history as well as in the life of the individual are marked and remembered by these eclipses.    It becomes almost a spectral illusion as the Sun, which is about four hundred times the diameter of the Moon appears to be blocked as the Moon passes.  The Sun which is so much greater in size than the Moon is also about four hundred times further away from the Earth allowing the Moon and Sun to appear nearly the same in size.  If the Moon's diameter of (2,160 miles) were 140 miles less it would not be large enough to fully block the sun on these rare occasions and a total eclipse would not be possible from anywhere on Earth. 

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If you are fortunate to view an eclipse it  appears slowly at first almost unnoticeable as only a small portion of the Sun is blocked.  Gradually more and more of the face of the Sun is hidden.  The phase can take up to an hour and until the last few minutes there is little indication that within a few minutes that the daylight will be replaced by darkness.

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As the crescent of the Sun narrows and begins to disappear, tiny beads around the dark disk called Baily's beads are formed.  These beads are actually the last few rays of sunlight shining through the valleys on the edge of the Moon and are seen for up to 15 seconds before the eclipse is total.  When all but one point is remaining it is called a diamond effect.  The final spark of light before the outline of the Moon blocks the Sun.

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Suddenly the sky is dark leaving only the corona of the Sun.  A halo of light that shines in all directions around the darken body of the Sun.  It looks and feels like nighttime and the plants and animals respond accordingly.  Birds stop singing and may go to roost and daytime flowers begin to close.  The air cools as the temperature drops.  All of nature reacts as if it were nightfall.  Then as the Moon continues its path all the events that preceded the total eclipse are viewed in reverse.  First Baily's beads are seen and then the thin crescent of the Sun.  Gradually daylight returns as more of the Sun is revealed as the Moon passes it.

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There is a specific pattern to an eclipse and it is calculated on those times when the new Moon is near one of its nodes, or two points where the Moon's orbit intersects the plane of the Earth's orbit, the ecliptic.  The new Moon must be close enough to the ecliptic plane so that so that its shadow will touch some part of Earth.  When the new Moon appears with in 18-3/4 days before or after the alignment of the node, a solar eclipse will take place.  This creates a 37-1/2 day time window for eclipse, called the eclipse season to occur.  The lunar nodes are not quite stationary but near enough that the an eclipse year of about 346.6 days has been established and a pattern of eclipse can be established using a 18.6 day earlier date from the previous year's eclipse season.  It was the Babylonian astronomers of ancient times that discovered this repetition of cycles of exactly 223 months or a period of 18 years 11-1/3 days between eclipse years.  The repetition of eclipses follows a fairly regular pattern in time but not so the given place on Earth. The average is 360 years for a total eclipse to be seen at the same location, with some areas seeing eclipses more frequently and other over even greater periods of time.


Imagine what a total eclipse was like for the people of ancient times.  To some it was an omen of some natural disaster that was to befall them or the death of a ruler. The Chinese thought it was an invisible dragon trying to consume the Sun. They made a lot of noise and beating of drums and pans to scare the dragon away and restore the light and even as recent as the last century the Chinese Imperial Navy fired its ceremonial guns during an eclipse to frighten off the invisible dragon.  The dragon theory seemed popular also in India where people immersed themselves in water up to their necks, believing this act of worship would help the Sun and Moon defend themselves against the dragon.  In Japan the wells were covered so as to prevent poison from dropping into them from the darkened sky.  In Tahiti the eclipse was seen as the Sun and Moon making love.  In Arctic America the Eskimos, Aleuts and Tlingits believed that the Sun and Moon momentarily left the skies to insure all was as it should be on Earth.

The people who constructed Stonehenge in England, some believe them to be Druids, had been able to mark the summer solstice the longest day of the year through the alignment of the massive heel stone, thus marking the beginning of each year.  By counting the days between the annual alignments they could determine the length of the year, mark holidays and seasonal festivals and ensure the timely planting and harvesting of crops.  However to predict eclipses they had to know two other cycles one the length of the lunar month which is simply the number of days between one full Moon and the next.  The other was more complex as it was the knowledge of the rotation of the two invisible points in space where the Moon's orbit tilted at a slight angle intersects the plane of the Earth's orbit.  There is evidence showing that the builders of Stonehenge did have the knowledge to predict eclipses.  It would have taken decades of watching countless rising and settings of the Moon to figure out the cycle of the lunar nodes, Latin for "knot" when the intersection would occur.   It is believed that information which must have been handed down through the generations was preserved at Stonehenge.  Even more amazing when you look at the time of the construction of Stonehenge being before the first metal tools were used by man. The law of averages confirm that either a partial solar eclipse or lunar eclipse can be seen from the same point on the Earth about once a year.  This does not explain the ancient people of the Stonehenge recording these periods as danger periods or an omen of disaster.   What seems to hold more merit is the eclipse being an element of their religion.   Stonehenge may have been the center of some kind of worship, a sacred place where at special times such as the solstices, equinoxes and eclipses people came to reaffirm their belief through ritual practices.  The Druids were known to worship the serpent and serpent temples, similar stone circles were called "Dracontia".  Draco is the Latin for "serpent" or "dragon".

As the Babylonians were developing the science of astronomy the ancient Egyptian civilization was thriving.  Pyramids and temples marked the high state of development of their art and technology.  The length of the year was measured by observing the rising of Sirius the brightest star in the sky.   The Great Pyramid of Giza is aligned to the four points of the compass.  This was a people who watched the heavens and observed celestial movement, however there is no mention of an eclipse of either the Sun or the Moon in all of ancient Egyptian history.   An apparent gap in Egyptian astronomy with confirmation that ancient Egypt had been in the paths of total eclipse visible from across the Nile Valley in the second and third millennia B.C.  The solar corona was visible from somewhere in ancient Egypt during this period on an average of once every 75 years.  It is hard to accept that a total solar eclipse would have gone unrecorded by a culture that so worshipped the Sun.   Some believe the view of the eclipse was preserved in symbolic form as the solar corona has a distinctive appearance with extending long streamers of light and might be the symbolic wings of the Egyptian Sun.  The image of the winged sun appears above the entrances of many tombs and temples and is said to commemorate the victory of light over darkness.  Sometimes the symbol includes the heads of two serpents and the horns of a goat, also solar symbols.

Stonehenge, Babylon, Egypt they each had a unique approach to eclipses but the Babylonians by discovering the long range prediction of the cycle also established a technique to fix exact dates in the past.  Numerous systems were used in ancient civilizations to record the passage of time so days, months and years and some memorable events or natural catastrophes were reported.  If an eclipse was described when the reference event took place it could be compared with actual eclipses that were known to have happened near the time and place in question.  If only one eclipse could fit the description then the dates could be established with certainty.   Many historical chronologies have been verified or compared using this method.

The earliest record of a solar eclipse comes from ancient China the date given is October 22, 2134 B.C.   It is said "the Sun and Moon did not meet harmoniously" and that during this period there were several total eclipses visible in China and the two royal astronomers Hsi and Ho failed to predict the eclipse on this date.  The emperor was caught unprepared and when the daylight returned after the invisible dragon had devoured the Sun.  Even without the customary drumming and noises to frighten the dragon off the ruler was so angry that they had failed to predict the event that he had the astronomers beheaded.

The date of an eclipse mentioned in the Bible that is known for certain is: "`And on that day,' say the Lord God, `I will make the Sun go down at noon, and darken the Earth in broad daylight'." (Amos 8:9) That day was June 15, 763 B.C. and the date of the eclipse if confirmed by an Assyrian historical record known as the Eponym Canon.  In Assyria the year was named after a different ruling official and the events of the year were recorded under that name in the Canon.   Under the year corresponding to 763 B.C. a scribe at Nineveh recorded this eclipse and highlighted the day by drawing a line across the tablet.  These ancient records have allowed historians through the knowledge of eclipse data to improve the chronology of early Biblical times.

One of the most famous eclipses of ancient times ended a five-year war between the Lydians and Medes.  These armies had been locked in battle when day turned into night and the total solar eclipse of May 28, 585 B.C. was enough to stop the fighting, a treaty was made and bonded by a double marriage.

There are many instances in history where an eclipse had an affect on the outcome of an event.  Sometimes it was seen as an celestial omen and soldiers were reluctant to obey.  Charlemagne's son, Emperor Louis was reported as so perplexed by the five minutes of totality he witnessed May 5, 840, that he died shortly after of fright.

Another condition that seems present with eclipses is earthquakes.  There is a compelling number of literary and historical connections between eclipses and earthquakes.  Even as recent as September 16, 1978 in Iran, and earthquake that killed more than 25,000 people occurred just 3-1/2 hours before a total lunar eclipse was visible there.

There have also been records of abuse of the knowledge of eclipses to gain God-like status or to use an eclipse as a sign from God.   Christopher Columbus while stranded on the island of Jamaica with damaged ships and low provisions resorted to his knowledge of a total eclipse of the Moon on February 29, 1504 to obtain supplies from the natives.  They had not wanted to trade for baubles and trinkets and the Spanish would have faced starvation. However Columbus arranged a meeting that night with the natives, announcing God did not approved of the way the natives were treating him and his crew and that the Almighty had decided to remove the Moon as a sign of his displeasure.  The timing was perfect and the natives were terrified as the light of the Moon faded they offered him all the food and water he wanted if he would restore the Moon.  Columbus playing the role of a servant of God pleaded their case and appeared to convince God to restore the Moon.

What of the future eclipses in the decade to come there are some that will be relatively easy to view and others less accessible.

2000 January 21 -- A total lunar eclipse will be visible from all of North and South America and Europe, lasting for 1 hour and 18 minutes.

2000 July 16 -- Another total lunar eclipse six months later will give early risers on the west coast of North America a chance to see the eclipsed full Moon set in the west at sunrise.

2000 December 25 -- A partial solar eclipse , visible during mid-day from the entire 48 states of the U.S., graces the final Christmas Day of the Second Millennium.

2001 June 21 and 2002 December 4 -- A forty-mile stretch of the Atlantic coast of Africa, just north of Lobito, Angola, experiences totality twice in 18 months. The June 21st eclipse occurs just 4.5 hours after the solstice (winter in the Southern Hemisphere). The December 4th eclipse track passes 50 miles south of Victoria Falls in Africa, ending at sunset on the southern coast of Australia on the shoreline of the Great Australian Bight, near the Yalata Aboriginal Reserve.

2003 May 31 and 2003 November 23 -- Two opposite polar eclipses in the same year -- a double "polar solar" -- and each in the corresponding warmer half of the year. The May 31st event is an annular solar eclipse that starts at the northern tip of Scotland and actually moves westward across Iceland and southern Greenland. The November 23rd eclipse is total, lasting up to 1 minute 57 seconds as it sweeps across Antarctica near the Amery Ice Shelf. Partial phases of each eclipse are visible from the respective Poles themselves.

2005 April 8 -- The total phase of this annular-total eclipse, with a maximum duration of 42 seconds, traverses a 15-mile wide path entirely over a remote region of the southern Pacific Ocean.

2006 March 29 -- Although this 110-mile wide path of totality crosses Africa and much of Asia, there are no major population centers in its path. However, you can try to catch a brief glimpse of totality exactly at sunrise near Natal, on the northeastern coast of Brazil.

2008 August 1 -- A "midnight Sun" total eclipse visible from the northern tip of Greenland, and parts of northern Russia. The path of totality crosses the Great Wall of China near sunset.

2009 July 22 -- The next eclipse in the July 11, 1991, saros series begins in the Arabian Sea just off the coast of India between Bombay and Ahmadabad. The path traverses central India (including Indore, Benares, and Patna) and the Himalayas through eastern Nepal and Bhutan, passing 75 miles south of Mt. Everest. The shadow engulfs the Chinese cities of Chongqing, Wuhan, and Shanghai before passing out into the East China Sea and halfway across the Pacific.

2010 July 11 -- After crossing Easter Island in the South Pacific, this total solar eclipse path barely touches land in southern Chile and Argentina at sunset.

  Click here to view a total eclipse video

                                   Cheryl C. Helynck


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