General Information about the Solar Eclipse What is a solar eclipse? A solar eclipse happens when the moon passes between the sun and the Earth, with the moon’s disk covering the face of the sun. That Earth experiences eclipses at all is actually kind of a cosmic coincidence: Though the diameter of the sun is about 400 times greater than the moon’s, they appear as the same relative size in our sky because the sun is so far away. When the moon passes between Earth and the sun, it blocks its light while exposing the corona (the sun’s atmosphere). If the moon were smaller, or if the sun was closer to Earth, the moon’s disk wouldn’t cover the sun completely, and we would never experience solar eclipses. Solar eclipses happen at the new moon phase because that is when the Earth, the moon, and the sun align. The elliptical path of the moon around the Earth intersects the Earth’s elliptical path around the sun twice each lunar month because their orbits are titled 5º from each other instead of being in the exact same plane. The intersecting points of the Earth and moon’s elliptical paths are called lunar nodes. A solar eclipse occurs when the moon passes between the Earth and sun at a lunar node, blocking the sun’s light from hitting Earth. During a total solar eclipse, the sky darkens and the air gets colder by about 10ºF(5.5ºC). A solar eclipse is not the same as the much more common lunar eclipse, which happens when the Earth passes between the sun and the moon, blocking sunlight from reaching the moon. • A total solar eclipse happens when the orbital paths of the sun and the moon care aligned, so the moon completely covers the sun’s disk. The umbra hits Earth directly, and sky-gazers can see the sun’s corona radiating from behind the moon. This is the type of eclipse happening Aug. 21. What time will the solar eclipse be on Aug. 21? The eclipse will begin in the western US and move east. The partial eclipse will kick off at 9:05 am PDT in Oregon, which will experience the total eclipse at 10:16 am PDT. South Carolina will be last, with the viewing window for the total eclipse ending at 2:44 pm EDT. The eclipse will be viewable in any given location for about 3 minutes, and it will cross the country in about an hour and a half. How do I safely watch the solar eclipse? Sky-gazers should be very cautious—looking directly at the sun can permanently damage your eyes. According to NASA, looking directly at the sun during an eclipse is never safe unless during the brief total eclipse, when the moon’s disk blocks the sun’s entirely (this only occurs within the path of totality, and only for a few minutes). Otherwise, you should be using proper safety viewers for any kind of eclipse viewing. A safe way to watch the partial solar eclipse is with special “eclipse glasses” or hand-held solar filters (you can also make a homemade pinhole projector as an alternative method). Regular sunglasses, unfiltered cameras, or homemade filters are not safe and shouldn’t be used. Eclipse glasses must meet some basic criteria to be considered safe: You should put your glasses on before looking at the eclipse and remove them after you’ve completely turned away. What happens if you look at a solar eclipse? If you look directly at solar eclipse without proper safety glasses, your eyes are exposed to huge amounts of ultraviolet radiation and you could experience photo keratitis, which is like sunburn in the eyes. It is incredibly uncomfortable and makes sufferers extremely sensitive to light. Staring directly at an eclipse can also cause solar retinopathy, in which excessive light hits your retina and causes permanent damage to rod and cone cells. Looking directly at the sun, even for a few seconds, can burn your retina and lead to partial or total blindness. .