Solar eclipses, partial or total, occur on average 2.4 times every year. Total eclipses occur on average every 18 months, but are only visible on less than half a percent of the earth’s surface.
Any particular point on the earth experiences one eclipse in an average of more than 350 years. Total eclipses require the moon to be in close orbit to the earth, or perigee, in order to fully cover the sun. If the moon is farther away, at apogee, than the moon cannot totally block the sun. Because the moon varies its distance to the earth, the width of the shadow cast in an eclipse varies with every eclipse.
There would be more frequent eclipses, except the moon’s orbit is off about five degrees in relationship to the earth’s orbit around the sun. This results in the moon typically passing a little bit above or below the sun. The moon is getting farther from the earth at a rate of 1.48 inches per year; hundreds of millions of years from now the moon will no longer be able to totally cover the sun.
Severe eye damage can occur if observers look directly at an eclipse with the naked eye, telescopes or anything not approved for eclipse viewing. Scientists use special filters and equipment to view eclipses.