Though currently relatively rare, will there be an increase of occurrences of annular solar eclipses in the future?
By: Ringo Bones
When it comes to total solar eclipses, annular solar
eclipses offer little, if any, importance to earthbound astronomers despite of
its relative rarity in occurrence. I mean when was the last time an annular
solar eclipse made headline news or was used to verify an astrophysical
hypothesis? And the only well-photographed annular solar eclipsed was the one
that occurred over the North African desert back in December 1955. But believe
it or not, annular solar eclipses could occur more frequently in the future
because the Earth’s Moon is moving farther away from us.
Ever since its formation and held in orbit, our Moon had
been moving farther away from us because the tidal friction it caused is
slowing down planet earth’s rotation for several billion years. Currently, the
Moon is orbiting 240,000 miles or 384,400 away from us and when it was newly
formed, it was actually 10 times closer and a day on Earth only lasted 2 to 3
hours. But back then, the Earth was rotating faster and the tides were more
than a thousand feet high according to unearthed geological evidences. But over
time, tidal friction caused by the Moon orbiting the Earth slowed the planet’s
rotation to what it is today – 24 hours.
Ever since the Apollo 11 astronauts installed that quartz
retro-reflector on the Moon back in July 20, 1969 that allowed precise laser
measurements of the Earth-Moon distance down to the nearest fractions of an
inch or millimeter, we have known for sometime now that the Moon is moving away
from us at a rate of 2 to 3 centimeters per year. And it is only a matter of
time that when a total solar eclipse occurs, the Moon is now too far away from
the Earth’s surface to fully cover the Sun – thus the increased frequency of
annular solar eclipses.
