Thursday, 19 March 2015

5 things you have to know about 2015 solar eclipse


On Friday, people across Europe, Northern Africa, and parts of the Middle East will be able to see a partial solar eclipse.
The eclipse will begin at 7:41 am GMT, when people in West Africa and then Western Europe will see the moon start to take a bite out of the sun. The total eclipse will begin around 9:10 am, hitting the Faroe Islands at 9:40 and Svalbard at 11:10 local time, and the whole thing will finish at 11:50 (again GMT).
There are five things to know about solar eclipse.
What is solar eclipse?
A solar eclipse occurs when the moon's orbit of Earth positions it directly in between us and the sun, causing the moon to temporarily block out some of the sun's light. Places on Earth that fall within the moving path of the moon's umbra — the central part of its shadow — can briefly see a total eclipse, in which the moon blocks out the entire sun, leaving just a faint shimmering ring of light in the otherwise darkened sky.
Partial eclipses are much more common, because they occur throughout the much wider penumbra region. The vast majority of people who will be able to see Friday's eclipse will see a partial one.
What will the eclipse look like?
As the Earth rotates and a given location enters the penumbra, the faint moon will gradually pass in front of the sun and block out a portion of it. Depending on the viewer's location, the moon could block out larger or smaller portions of the sun, in some cases reducing it to a crescent-shaped sliver.
Who will be able to see the eclipse?
People in Europe, North Africa, and parts of Asia and the Middle East will be able to see the partial eclipse — with people living farther north seeing a greater portion of the sun covered up by the moon.
The eclipse will start earliest for people living in the western part of this region, and will last for more than an hour of the mid-morning in most places.
How can I watch the eclipse?
If you live in the US or another place where the eclipse isn't visible, you can watch a live stream from the Faroe Islands by the Slooh Community Observatory. Coverage starts at 4:30 am ET.
Meanwhile, if you do live in the eclipse zone, it bears repeating: do not look directly at the eclipse. It's never safe to look directly at the sun, even if it is partially blocked out. It might be tempting to try, but the light's intensity can quickly cause permanent damage to your retinas, potentially even leading to blindness. Using binoculars, a telescope, or a camera is an even worse idea, as the lenses focus the light further.
There are, however, a few different solutions. One is a pair of eclipse glasses, which are specifically made to block dangerous wavelengths of light. Don't try substituting normal sunglasses, as they're not designed to do this.
Alternatively, you can make a pinhole projector by poking a small hole in the side of a cardboard box or in a piece of paper. Hold the cardboard or paper in the sunlight as the eclipse occurs, and it'll project a miniature image of the eclipse onto the ground. NASA has more detailed instructions here.
How common are these eclipses?
Solar eclipses actually happen pretty regularly — they occur in cycles called saros, and during the 21st century, there will be a total of 224 eclipses.
But total eclipses like this one are more rare. That's because in many instances when the moon eclipses the sun, its umbra (the central part of its shadow) doesn't actually hit Earth, instead getting projected out into space. In other instances, the umbra hits Earth, but only a tiny slice of it — so the eclipse only appears total in locations along a thin strip of Earth, in this case places like the Faroe Islands and Svalbard.
The next time Americans will have the chance to see a total eclipse will be in August 2017.

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