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Solar eclipses! The moon moves into a specific location that blocks the sun's light from reaching earth. But how often do eclipses occur and what are their conditions? What kinds of eclipses exist?
Now, Solar Eclipses don't happen once in a blue moon... actually, more like once in a new moon, when the Sun and the Moon are in "conjunction" with each other. If you're not an astronomy buff, conjunction most simply means that the celestial bodies have the exact same ecliptic longitude (they are in a line with each other). Now, if you think about it, by that definition, a solar eclipse would happen every month! Unfortunately, though, the moon's orbit is elliptical, rather than circular. This makes the overlap much more rare, so of the two to five eclipses that occur every year, only two are total eclipses.
Wait. What's a total eclipse? Well, a total eclipse is just one of the four different types of solar eclipses that can happen throughout an eighteen-month cycle. The total eclipse is very simple, just what it sounds like -- the moon completely blocks out the sun. Similarly, an annular eclipse is when the moon and the sun are completely aligned, but the "size" of the moon is just a tad bit smaller than that of the sun. This causes an annulus, or a bright solar ring, to form around the moon. When both a total and annular eclipse seem to coexist, the phenomenon is called a hybrid of the two... the hybrid eclipse (how original). Although the hybrid is one of the most fascinating eclipses that exist, it is potentially the rarest -- very few have occurred in the past few decades, given that they are also extremely difficult to predict. The last, and most common, type of eclipse is the partial eclipse, where the Sun and the Moon aren't completely in line and, as a result, the sun is only partially covered.
Ok, so you've gotten your fill of background information on eclipses, but where's the cool stuff? To me, what's cool is the facts and fiction behind eclipses. For example, is it really necessary to wear eye protection during an eclipse? I mean, the sun is being covered by the moon, and the last time I checked the moon didn't scorch my eyelids. Well, I hate to be the bearer of bad news but, during annular, partial, or even hybrid eclipses, the small amount of sunlight which the moon doesn't block has the same destructive effects as the regular sun. To guarantee your safety, it is highly recommended that you follow either of these two precautionary measures:
1) Wear eclipse glasses, which use specialized solar filters to block out the solar rays.
or
2) Use indirect projection. Potentially the safest method, this is done by projecting an image onto a white piece of paper using a device called a pinhole camera (see image to the right). Remember to take precautionary measures even during a total eclipse; they only last around seven and a half minutes and the sun could peek out at any time and fry your eyeballs!
Additionally, over the years, some people have reported other anomalies that happen during solar eclipses. In 1954, Maurice Allais reported strange movement, later attributed to shifts in gravity, during the eclipses. In 1970, Erwin Saxi noted changes in pendulum motion during eclipses; a phenomenon known now as the Saxi effect.
Probably the coolest phenomenon, though, is the transit of another planet during a solar eclipse. A transit is another technical term that means that the planet "transiting" moves in front of the field of vision of another celestial being. In this case, the transit of planets like Mercury or Venus during a solar eclipse would cause them to come into perfect view without any magnification! However, this is EXTREMELY rare -- for example, the next transit of Mercury is predicted to be on July 5th! of 6757...
It's really easy to find out when the next eclipse is -- check out this awesome link to stay updated: http://www.moongiant.com/Solar_Eclipse_Calendar.php. Better get your eclipse glasses ready!
References:
Espenak, Fred (July 11, 2005). "Eye Safety During Solar Eclipses". NASA Goddard Space Flight Center.
Littmann, Mark; Espenak, Fred; Willcox, Ken (2008). Totality: Eclipses of the Sun. Oxford University Press.
Schaefer, Bradley E. (May 1994). "Solar Eclipses That Changed the World". Sky and Telescope 87 (5): 36-39.
I will totally try to make a pinhole camera, and maybe post it as a P.S. on our next post. So be sure to check out our next article to see IF I could make it haha.
that URL you gave showing the eclipse calendar is great--i saw there are globe maps of where the eclipses are visible. cool!
looks like the next one for north america will be in Oct 2014.
if folks want to make their own pinhole camera, they can go here for step-by-step with photos to guide you:
http://www.instructables.com/id/How-To-Make-A-Pinhole-Camera/