A solar eclipse occurs when a portion of the Earth is engulfed in a shadow cast by the Moon which fully or partially blocks (“occults”) sunlight. This occurs when the Sun, Moon, and Earth are aligned. Such an alignment coincides with a new moon (syzygy) indicating the Moon is closest to the ecliptic plane. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured.
Humans have always sought to bring order and stability to their lives. From the earliest times, ancient people were drawn to the majesty and permanence of the heavens. Over time, early societies attached religious and spiritual significance to the regular motions of the celestial realm. When an astronomical event such as an eclipse took place, most ancient people believed it was the action of a divine being. When the rays of the Sun or the glow of the Moon were extinguished, early societies believed this was a terrible omen and that some type of disaster was imminent.
Looking directly at the sun without eye protection can cause serious eye damage or blindness. However, there are ways to safely observe the sun. During a partial solar eclipse, people often use pinhole cameras to watch the progress of the moon across the sun’s surface (pinhole cameras are easy to make at home). This is an “indirect” way of observing the sun because the viewer sees only a projection of the sun and the moon. To view the sun directly (and safely), use “solar-viewing glasses” or “eclipse glasses” or “personal solar filters” (these are all names for the same thing), according to the safety recommendations from NASA.
The “lenses” of solar-viewing glasses are made from special-purpose solar filters that are hundreds of thousands times darker than regular sunglasses, according to Rick Fienberg, press officer for the American Astronomical Society (AAS). These glasses are so dark that the face of the sun should be the only thing visible through them, Fienberg said. Solar-viewing glasses can be used to view a solar eclipse or to look for sunspots on the sun’s surface. There are serious consequences for staring into direct sunlight, said Peter Bex, an expert on vision science at Northeastern. “Invisible ultraviolet sunlight would permanently damage cells in the back of your eyes,” Bex explained. “This condition is known as Solar Retinopathy, and it usually affects several unprotected people every time there is an eclipse.”