A rare treat is in store for the three major countries of North America on April 8, 2024, when a total solar eclipse follows a path making landfall starting near Mazatlán, Mexico, traveling through the south-central part of the U.S. and tracking northeast until it leaves the U.S. near Caribou, Maine. Many people in the U.S. won’t even have to travel far to see this spectacle since several large cities lie on or near its path. These cities include Dallas, Austin, and Waco, Texas, Little Rock, Arkansas, Indianapolis, Indiana, Cleveland and Akron, Ohio, Erie, Pennsylvania, and Buffalo, New York. The path of totality then continues northeast into New Brunswick and Newfoundland, Canada.
Total solar eclipses aren’t rare for the Earth as a whole, as they can theoretically occur twice a year. But because the orbit of the Moon is a bit tilted relative to the Earth’s orbit, on average a total solar eclipse happens somewhere on the planet every year and a half or so. Eclipses at any specific point on the planet, however, are rare, happening on average every 300 years or so, with a wide range possible. Very rarely, some fortunate locations can sometimes see two eclipses in a short time, such as Carbondale, Illinois, which was on the centerline for the Great American Eclipse in 2017 and will again be on the path of this eclipse.
Solar eclipses occur when the Moon passes between the Earth and Sun. An unusual coincidence results in the Moon and Sun appearing roughly the same size in the sky. Although the Sun has a diameter of roughly 400 times that of the Moon, the Sun is also 400 times farther away. Because the orbit of the Moon is not perfectly circular, and because the orbit of the Earth around the Sun is also not perfectly circular, there is a slight variation in the size of each depending on where in the orbit the Earth and Moon are. Sometimes, when the Moon is at its farthest point away from Earth and when the Earth is at its farthest point away from the Sun (summer in the Northern Hemisphere), the Moon appears slightly smaller than the Sun. Therefore, an eclipse will not completely cover the Sun’s disk, resulting in what is called an annular eclipse, in which a small ring of the Sun’s disk is visible around the Moon. Although interesting in its own right, an annular eclipse just don’t have the same wow factor as when the Moon completely covers the disk of the Sun, allowing us to see the beautiful corona. The appearance of the corona varies quite a bit, making the appearance of each total eclipse unique. A third type of solar eclipse is the hybrid eclipse which starts as one or the other and transitions into the other because the Moon’s angular size changes just enough during the course of the eclipse.
Interestingly we live in a period in which a total solar eclipse is possible. Data shows that the Moon is moving away from the Earth a few centimeters every year, so in the very distant future, the Moon will no longer appear large enough to completely obscure the disk of the Sun. Of course, that time is millions of years in the future, so there is plenty of time to observe one. On August 12, 2045, another will grace the United States all the way from the West Coast to the East Coast (mark your calendars!).
The spectacle of being precisely in the Moon’s shadow is something everyone should see at least once in their lifetime. It is possible that once you see one, you will be hooked. There are quite a few people that plan their trips to coincide with total solar eclipses, as they often occur in or near popular tourist destinations or even far-flung regions of the planet, such as Antarctica.
If 2024 is your first time viewing a total solar eclipse, I recommend just taking it all in. Don’t waste those precious few minutes trying to get photographs. There are plenty of experienced eclipse chasers who will be taking spectacular images for all of us to see. But the visual experience is awe-inspiring, almost spiritual, and cannot be reproduced in any image. The sky darkens gradually for most of the eclipse, but the last minute or so darkens quickly. Animals are tricked into thinking night is falling, and the temperature drops noticeably. Even during totality (the few minutes in which the Sun is completely covered), the sky is not completely dark. Because the shadow of the Moon is usually only 50-100 miles or so wide, the far away horizon is usually not in darkness. This gives the sky more of a dawn or dusk appearance. But directly overhead, the sky is quite dark, and stars and planets will appear. The dim solar corona will also appear, making it seem like something behind the Moon is dazzling. Those few minutes of totality will be over quickly as the Moon begins to reveal the Sun’s disk once again until the next eclipse somewhere on the planet. Get your tickets early.