Every now and then, the sun grows dark in the daytime. It is not a result of cloudy weather or storms. Solar eclipses are rare, and there are several different kinds of eclipses. People buy special glasses for eclipse viewing to protect their eyes. But what is an eclipse and why is it dangerous to look at? Here is a brief explanation.
Earth Shadows
The earth rotates and revolves around the sun, and the moon revolves around the earth. On its annual journey, sometimes the earth gets between the moon and the sun. This position causes a lunar (moon) eclipse because the earth’s shadow temporary blocks the sunlight from the moon.
Moon Shadows
Sometimes the moon is between the earth and sun, and this casts a shadow on the earth. When the moon blocks sunlight from the earth, this is a solar (sun) eclipse. People witnessing solar eclipses usually wear glasses for eclipse viewing.
Not All Eclipses are Total
Depending on your position on the planet, you may not see a total eclipse. Some eclipses are only partial, and some block out sunlight except for a rim around the sun (annular eclipse). Partial lunar eclipses are common and happen twice each year, but total lunar eclipses are uncommon. Partial solar eclipses are rare and total solar eclipses even rarer.
Eye Damage
Why are special glasses for eclipse viewing so important? The sun emits ultraviolet and infrared light which can affect the retinas of your eyes. Your retinas are like special linings on the back of mirrors, and they have many photocells which take in light. Once received, the retina turns this light into electrical signals which pass through the optic nerve to the brain. The brain turns this signal into vision. UV light can damage retinal cells and cause temporary or permanent vision problems. This is why you need protection for your eyes.
