What is a solar eclipse and how many different kinds are there?

A total solar eclipse

A solar eclipse happens when the Moon passes in between the Sun and the Earth. Eclipses of the Sun can only happen during a New Moon. During a New Moon, The Moon and the Sun look like they are very close together in the sky. Primitive people in ancient times thought that eclipses meant that something terrible was about to happen, because the sky gets unnaturally dark and the Sun can disappear for minutes at atime during these events.

A solar eclipse is an extremely rare occurence, and many people travel all over the world just to see these visual spectacles. The next total eclipse will happen on August 1, 2008.

There are different kinds of eclipses
The 4 types of eclipses are:
  • Total eclipse - The Sun is completely blocked out by the Moon and only the Sun's corona can be seen during this kind of eclipse.
  • Annular eclipse - The Moon and the Sun are exactly in line, but the size of the Moon relative to the Sun is smaller. During this type of eclipse, the Sun looks like a very bright ring.
  • Hybrid eclipse - This type of eclipse is somewhere between a total eclipe and an annular eclipse. At some places on Earth it's seen as a total eclipse, and and in other parts of the world it's seen as an annular eclipse.
  • Partial eclipse - This type of eclipse happens when the Sun and the Moon are not exactly in line, so the Sun is only partially blocked by the Moon.

How often does a solar eclipse happen?
Total eclipses are rare. On average, they happen in the same place only once every 370 years. When they do happen, they only last for a few minutes because the Moon's shadow, called the umbra moves east at 1700 kilometers per hour. Now that's what I call fast!

We know that eclipses happen in cycles and if the date and time are known, it's possible to predict future eclipses. The most well known cycles are called the Saros cycle and the Inex cycle. The Saros cycle is the more accurate predictor of eclipses. The Saros cycle says that if an eclipse of a particular type happens, the same type of eclipse will happen roughly 18 years later.

When will the last total eclipse happen?
Because of something called tidal acceleration, the Moon's orbit around our planet is a few centimeters more distant each year. So this means that in about 600 million years, the last total solar eclipse will occur.

Use caution when viewing an eclipse
Looking directly at the Sun can cause permanent damage to the retinas of your eyes, even during an eclipse. A safe way to view an eclipse is to use a method called indirect projection. using a pinhole camera is a form of indirect projection.

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