Twice a year the moon passes between the earth and sun causing a shadow to appear on the earth’s surface. This can only happen at a new moon, and is known as a solar eclipse. In theory we would expect a solar eclipse to take place once a month; however this doesn’t occur as because the Moon's orbit around Earth is tilted 5 degrees to Earth's orbit around the Sun.
The Saros Cycle, which is approximately 18 years 11 days and 8 hours, is the period in which eclipses are measured. A Saros cycle for a solar eclipse begins with a new moon. The moon in fact has two sections: penumbra, this is the moons outer shadow in which partial solar eclipses are visible, it is also fainter than the umbra which is the moons inner shadow in which total solar eclipse are visible.
It was the Chaldeans that observed and understood the Saros Cycle first which dates back to 1200BC. They were also responsible for the system of 60’s and the idea of a system which included the sun, moon, earth and five planets.
The Egyptians were the first to observe solar eclipses, 4500 years ago. It was the Chinese and the Babylonians that first recorded these 4000 years ago.
In China eclipses were seen as signs from heaven which told of the future of their Emperor. Two Chinese astronomers were even murdered due to their wrong predictions of solar eclipses. It was also the Chinese that believed that the solar eclipse was due to a dragon eating the sun and a lunar eclipse was due to the dragon attacking the moon. There was even records found that stated “the sun has been eaten” and their term for eclipse was actually “chih” which means “to eat”.
The Athenians of ancient Greece believed that an eclipse was a sign that their gods were angry and thought that they were being punished for their sins. However Thales, a Greek philosopher, believed the sun, moon and stars were solids and that the moon shone due to light falling on it from the sun. He was also able to correctly explain lunar eclipses and it is said that he foresaw a solar eclipse.
In ancient Egypt, eclipses were not yet understood and so were seen as a terrifying occurrence. The occurrence of a solar eclipse was believed to be a punishment from the gods where people suffered partial and spiritual blindness. Although the sun played a crucial part in their beliefs, there have been few records found about this, due to the Egyptian culture being very secretive.
Although it is said that Stonehenge was built in alignment with the solstices, it is also believed that Stonehenge could have been used to predict solar eclipses. This is due to another cycle which involves the rotation of two invisible points in space, thus predicting solar eclipse.
The solar eclipse that occurred on 23rd of December 2010 was the longest solar eclipse of the millennium, lasting 11 minutes and 7.8 seconds. This year a partial solar eclipse took place on the 4th January 2011 and it is believed that four solar eclipses will take place during the coming months.
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