North America will experience two solar eclipses within the next year: an Annular Solar Eclipse on October 14, 2023 and a Total Solar Eclipse on April 8, 2024. What is an eclipse and what’s the difference between these two events?
The word “eclipse” comes from the Greek word ekleipsis, which means “to leave out” or to abandon. It’s an apt term because an eclipse occurs when the Sun, Moon, and Earth align in a straight or nearly straight line, and one celestial body appears to be left out of the scene. Astronomers call this alignment syzygy, but, as The Exploratorium explains, “quite literally, the Greeks saw a solar eclipse as the Sun abandoning the Earth.”
In the eclipse explainer above, Exploratorium senior scientist Dr Julie Yu introduces the different types of eclipses that we can see from Earth: total, partial, and annular solar eclipses and total, partial, and penumbral lunar eclipses.
“The order they’re in when they line up determines what type of eclipse there will be. A solar eclipse happens when the moon passes between the sun and Earth and either fully or partially blocks the sun’s light. This only happens occasionally because the moon doesn’t orbit in the exact same plane as the sun and Earth do…”
The route the moon’s shadow takes across the earth’s surface is called the Path of Totality, and it’s around 16,000 kilometers (10,000-ish miles) long and 160 kilometers (100 miles) wide. You must be within this traveling shadow to view the eclipse.
“Solar eclipses,” Yu continues, “only happen during the day because you have to be on the side of the earth that’s facing the sun. If you’ve seen an eclipse at night, you’ve experienced a lunar eclipse.”
“Now we can see the moon because it reflects sunlight. At night, you’re on the part of the earth that’s facing away from the sun, and the moon becomes visible against the night sky. Lunar eclipses occur when the earth lines up between the sun and the moon and blocks the sunlight from hitting the moon.”
During a lunar eclipse, the moon can appear reddish due to sunlight only reaching it from the edges of the earth. This would cause an observer on the moon to see all the earth’s sunrises and sunsets simultaneously.
For Spanish speakers, watch ¿Cuáles son los diferentes tipos de eclipses? with senior scientist Dr Isabel Hawkins:
Eclipses are fleeting events that only last for a few minutes, adding to the wonder that captivates skywatchers from all corners of the globe. While lunar eclipses are safe to view with the naked eye, safety while viewing solar eclipses is paramount. Via the Exploratorium:
“Solar viewing glasses—also called eclipse glasses—are an easy, affordable way to safely look at a solar eclipse. Without these special glasses, the Sun can permanently damage your eyes or cause blindness.”
But how can the moon, which is only around a quarter of Earth’s width, block out a star that could swallow around 1.3 million Earths within it? The Exploratorium explains:
“Both the moon and Sun are about 100 times farther from Earth than the sizes of their respective diameters. This means that the moon will block out, or ‘eclipse,’ anything behind it that has the same 1-to-100 size/distance ratio. This is the ‘cosmic coincidence’ that makes solar eclipses possible.”
Learn more about eclipses at exploratorium.edu/eclipse and solarsystem.nasa.gov/eclipses.
Watch these eclipse videos next:
• The science of solar eclipses: How do solar & lunar eclipses work?
• The 2017 Solar Eclipse from the shores of Palisades Reservoir, Idaho
• A solar eclipse as seen from the edge of space
• Strange & beautiful shadows created by the annular solar eclipse
• Eclipses Throughout Our Universe – Out There
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