What is a Solar Eclipse?

Mary McMahon
Mary McMahon

A solar eclipse is a celestial event in which the Sun is obscured by the moon. For viewers on certain parts of the Earth, the Sun may appear to completely or partially disappear. Before the mechanism of solar eclipses was understood, a great deal of superstition and mythology surrounded them. Historical documentations of solar eclipses indicate that people greeted them with fear and awe, especially when the sun was totally eclipsed.

In a solar eclipse, the sun is blocked from view on Earth by the moon.
In a solar eclipse, the sun is blocked from view on Earth by the moon.

Put simply, an eclipse happens when the moon gets between the Earth and the Sun. The moon casts a shadow on a certain section of the Earth, and while that section is in the moon's shadow, the sun appears to vanish. Typically, an eclipse of the sun will not last for more than around seven minutes, as the various astronomical bodies involved move out of alignment very quickly. Eclipses will also not strike the same place twice within 300 years, as a general rule.

In order for a solar eclipse to occur, several conditions must be satisfied. First, the moon must be in the phase known as a new moon, meaning that it is not visible in the sky. The new moon happens once a month, when the moon is between the Earth and the Sun, so that the illuminated portion of the moon faces away from Earth. The moon must also be at an angle which will intercept the sun, which is why solar eclipses are not observed on a monthly basis.

A total solar eclipse occurs when the Sun is totally covered by the moon. In another type of eclipse, an annular eclipse, the moon appears slightly smaller than the Sun, and the Sun shows up as a bright ring around the sun. In a partial eclipse, the sun is only partially obscured. In all cases, the solar eclipse falls along a predictable path which crosses the illuminated surface of the Earth.

The times and paths of eclipses can be predicted, using basic scientific principles. Many nations publish lists of predicted future eclipses, so that observers can optimally position themselves. Many people try to position themselves in the umbra of the eclipse, directly below the moon. Others settle for a position in the perumbra, where the sun will appear only partially eclipsed.

When people observe a solar eclipse, they should use eye protection, as the light of the sun can still hurt the eyes. Many people use indirect viewing methods to observe the eclipse without the risk of eye damage.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


@Highlighter- I was vacationing in Grenada Spain and Fez Morocco in the fall of 2005 when I saw my only annular eclipse. We were staying in a small flat near a vineyard in Grenada when the eclipse occurred. We did not have television, so we did not even know there was going to be an eclipse. It was one of the coolest things I have ever seen. We woke up to the beginning of the eclipse, and sat in the garden eating breakfast while the eclipse progressed.

As for future solar eclipses, I know there will be another annular eclipse visible from many of the western states on May 20, 2012. Those living in Oregon, Nevada, and Arizona will be able to see the eclipse in all of its beauty. If you are traveling anywhere in southeast China and Tokyo, you will also be able to see the eclipse. This eclipse will occur about five months before the next total eclipse in Australia.


@submariner- One important factor in the type of eclipse not listed in the article is the distance of the sun and the moon from the earth. An annular eclipse happens when the moon is at its farthest from earth (Apogee). The ring around the moon in an annular eclipse is at its thickest when the sun is at its perihelion (closest to the earth).

These scenarios will create an ant-umbra (a type of angle based on the sun and moon). At the ant-umbra, an annular eclipse is visible. To the sides of the ant-umbra, a partial eclipse is visible.

When the moon is close to the earth (perigee), the eclipse is a total eclipse. Annular eclipses are a little more common than total eclipses because the moon spends more time farther away from the earth than it does at its closest point. I am not sure when the next solar and lunar eclipses will happen, but I am sure a search will tell you when they occur.


What causes an annular solar eclipse? Is an annular or total eclipse more common? How often do solar eclipses occur? Why is it only possible to view an eclipse from certain parts of the world?

I have never seen a total eclipse, but I would like to see one. Mor said there will be an eclipse in Australia in 2012, but that is probably the farthest point on the earth from where I live. Are there going to be any other total or annular eclipses in the next few years?


There's going to be a total solar eclipse in Cairns, Australia towards the end of 2012. About a month before the world is supposed to end, according to some theories.

I don't really believe the theories, although I do enjoy "end of the world" parties. So I think people should gather in Cairns (which is already a fun place to party, this would be summer, right on the beach) to witness this eclipse and mark the end of an era!

The world is supposed to end because the Mayan calendar ran out on that date, and ancient people (as is mentioned in the article) were superstitious about eclipses, so I think this is a perfect combination to acknowledge.

Also, I've never seen a solar eclipse and I'd like to, and this would give me an excuse.


I remember a solar eclipse from when I was a child. I went to my parent's work after school and they had bought glasses for us to look at the eclipse together.

I'm not sure if the glasses, which were just cardboard with dark plastic lenses, were given out with newspapers or available through supermarkets or what, but I remember that everyone seemed to have a pair and the whole workplace came out to look at the sun in the parking lot.

It was really pretty, although even with the glasses it still hurt my eyes a bit and it seemed like it was over really quickly.

I think it's a good thing to encourage your kids to see things like this, because they will definitely remember! That must have been at least twenty years ago and I still remember it really well.

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