On Friday, people across Europe, Northern Africa, and parts of Asia and the Middle East saw a partial solar eclipse.
And a few lucky folks in the Faroe Islands and Svalbard saw something even rarer: a total solar eclipse, in which the moon completely covers up the sun.
1) What is a 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.
2) What did the eclipse look like?
As the Earth rotated and a particular location entered the penumbra, the moon gradually passed in front of the sun and blocked 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.
People in the Faroe Islands or Svalbard were treated to an even cooler sight: the moon completely covered the sun, eerily darkening the sky and revealing the faint corona of light emanating from the sun's edge:
3) Who was able to see the eclipse?
Depending on local cloud cover, people in Europe, North Africa, and parts of Asia and the Middle East were able to see the partial eclipse — with people living farther north seeing a greater portion of the sun covered up by the moon.
In Germany — a country that gets about 7 percent of its electricity from solar power — the eclipse significantly interrupted power generation, forcing utilities to proactively store power and turn to alternative sources.
4) How can I watch eclipses?
If you live in a place where an eclipse is visible, 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.
5) How common are these 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.