How rare are total solar eclipses?
If you look at a school text book and see the way the sun, moon and Earth align you’d think some place on the Earth would get a total solar eclipse every month. But this isn’t the case.
On average a total solar eclipse occurs on the Earth once every 18 months. And the odds getting one where you live is once every 375 years!
This is despite the moon crossing in front of the sun twice a year as seen from somewhere on Earth. What you may not realize is the sun, moon, and Earth are not perfectly aligned.
5° tilt of the moon:
The moon passes between the Earth and sun once every 27 and a half days. But it doesn’t not pass along a flat plane. The moon circles the Earth at a 5° tilt. From the below image you can see the view from the earth. If the moon were on a straight path it would cross between the Earth and sun once a month. But on a 5° tilt most of the time the paths do not line up. Some times the path is close but not perfect. When that happens only a partial eclipse occurs.
Lunar perigee and apogee:
Because the moon travels around the Earth in an ellipse, there are times it is closer to Earth (perigee) and farther from Earth (apogee.) The moon varies in size by 14°. Perigee comes from Latin meaning “Near the Earth.” Apogee means “Away from the Earth.” In October 2023 the Earth, moon and sun did align along a path over the United States but the moon was at perigee. So instead of getting a total eclipse, we got an annular eclipse. Annular is Latin for “Ring” so we had a partial eclipse that looked like a ring. April 8th the moon will be at apogee and the sun’s disk will be completely covered.
Moon & sun relationship:
What is incredible to me, in the design of our universe, is the gift we have seeing a total solar eclipse. Did you know, the sun is 400 times bigger than the moon? And the sun is 400 times farther away from the moon? Because of this relationship, during the solar eclipse they appear the same size. This matching size creates a perfect shadow blocking out the light from the sun. When this occurs, and you are in the path of totality, you’ll see the intricate feathery corona of the sun. This is the outermost atmosphere of the sun. Without an eclipse you could not see this. The sun’s corona is 2 million degrees! The surface of the sun is 10,000°. What a difference!
Where will you be April 8th?
Approximately 12.8 million people live in the eclipse path in Texas. In comparison, the population living within the entire path through the USA is approximately 31.8 million. Houston is 125 miles outside the path of totality. Houston will get a partial eclipse with the moon covering 94% of the sun. If the skies are clear, It is well worth the trip to be in the path of totality.
