Eclipse Facts

Here are some of the facts about Eclipses.,

• Lunar eclipses can only occur during a full moon.
• Solar eclipses can only occur during a new moon.
• A Solar eclipse always occurs two weeks before or after a lunar eclipse.
• Eclipses very often occur in threes, alternating lunar, solar and lunar.
• The maximum time a lunar eclipse can last is 3 hours and 40 minutes.
• The longest time the Moon can stay in totality is 1 hour 40 minutes.
• The maximum time for a total solar eclipse is 7 minutes and 40 seconds.
• The maximum time for an annular solar eclipse is 12 minutes 24 seconds.
• Lunar eclipses can occur up to 3 times a year.
• Solar eclipses can occur at least 2 and no more than 5 times a year.
• Lunar eclipses are visible over an entire hemisphere.
• Solar eclipses are visible in a narrow path a maximum of 167 miles wide (269km.)
• At any geographic position on the Earth, a total solar eclipse occur an average of once every 360 years.
• The cycle of eclipses repeats every 18.6 years called the saros.
• The eclipse shadow moves at 2,000 mph at the Earth's poles and 1,000 mph at the Earth's equator.

What is a Solar Eclipse?

A solar eclipse occurs when the moon passes between the Sun and the Earth so that the Sun is fully or partially covered. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth. At least two and up to five solar eclipses can occur each year on Earth, with between zero and two of them being total eclipses.

By a fortunate coincidence, the sun's diameter is 400 times larger than that of the moon, and at the same time, it is 400 times as far away. From where we are, this creates the illusion that they are the same size. If we look through a filter at the sun, it looks exactly like the moon on a full moon night. When the moon passes in front of the sun, the shadow falls on the earth and it appears to exactly cover the sun's disc. This is what a solar eclipse is - a shadow.

During a solar eclipse, the moon actually casts two shadows towards earth. One shadow shaped like a cone is called the umbra. This becomes narrower as it reaches the earth. No direct sunlight penetrates into this area. The path of this is called the path of totality. If you are positioned in this area than you can see a complete blocking of the sun and view a total solar eclipse. Total eclipse is observable only within a narrow strip of land or sea over which the umbra passes.

The second shadow is called the penumbra which spreads out as it reaches the earth. The penumbra is spread over a large area. People viewing the eclipse from this area of the earth's surface will see only a partial blocking of the sun.

Solar Eclipse - July 22, 2009

On Wednesday, 2009 July 22, a total eclipse of the Sun is visible from within a narrow corridor that traverses half of Earth. The path of the Moon's umbral shadow begins in India and crosses through Nepal, Bangladesh, Bhutan, Myanmar and China. After leaving mainland Asia, the path crosses Japan's Ryukyu Islands and curves southeast through the Pacific Ocean where the maximum duration of totality reaches 6 min 39 s. A partial eclipse is seen within the much broader path of the Moon's penumbral shadow, which includes most of eastern Asia, Indonesia, and the Pacific Ocean.

The moon's shadow blocked out the sun, leaving only the solar corona visible in west China's Chongqing Municipality and Guang'an City in neighboring Sichuan Province.

The cities turned off many street lights to allow the public to better observe the total eclipse, which lasted about four minutes.

The July 22 eclipse is the longest total solar eclipse of the 21st Century. It is expected to pass across China from Tibet to the coastal city of Shanghai, where 300 million people live.