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25 Questions (and Answers!) About the Great North American Eclipse

The McDonald Observatory’s guide to one of nature’s most beautiful and astounding events: What you might see, how to view it safely, how astronomers will study it, how animals might react, and some of the mythology and superstitions about the Sun’s great disappearing act.

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1. What’s happening?

The Moon will cross directly between Earth and the Sun, temporarily blocking the Sun from view along a narrow path across Mexico, the United States, and Canada. Viewers across the rest of the United States will see a partial eclipse, with the Moon covering only part of the Sun’s disk.

2. When will it happen?

The eclipse takes place on April 8. It will get underway at 10:42 a.m. CDT, when the Moon’s shadow first touches Earth’s surface, creating a partial eclipse. The Big Show—totality—begins at about 11:39 a.m., over the south-central Pacific Ocean. The shadow will first touch North America an hour and a half later, on the Pacific coast of Mexico. Moving at more than 1,600 miles (2,575 km) per hour, the path of totality will enter the United States at Eagle Pass, Texas, at 1:27 p.m. CDT. The lunar shadow will exit the United States and enter the Canadian province of New Brunswick near Houlton, Maine, at 2:35 p.m. (3:35 p.m. EDT).

3. How long will totality last?

The exact timing depends on your location. The maximum length is 4 minutes, 27 seconds near Torreon, Mexico. In the United States, several towns in southwestern Texas will see 4 minutes, 24 seconds of totality. The closer a location is to the centerline of the path of totality, the longer the eclipse will last.

4. What will it look like?

Eclipse veterans say there’s nothing quite like a total solar eclipse. In the last moments before the Sun disappears behind the Moon, bits of sunlight filter through the lunar mountains and canyons, forming bright points of light known as Baily’s beads. The last of the beads provides a brief blaze known as a diamond ring effect. When it fades away, the sky turns dark and the corona comes into view— million-degree plasma expelled from the Sun’s surface. It forms silvery filaments that radiate away from the Sun. Solar prominences, which are fountains of gas from the surface, form smaller, redder streamers on the rim of the Sun’s disk.

5. What safety precautions do I need to take?

It’s perfectly safe to look at the total phase of the eclipse with your eyes alone. In fact, experts say it’s the best way to enjoy the spectacle. The corona, which surrounds the intervening Moon with silvery tendrils of light, is only about as bright as a full Moon.

During the partial phases of the eclipse, however, including the final moments before and first moments after totality, your eyes need protection from the Sun’s blinding light. Even a 99-percent-eclipsed Sun is thousands of times brighter than a full Moon, so even a tiny sliver of direct sunlight can be dangerous!

To stay safe, use commercially available eclipse viewers, which can look like eyeglasses or can be embedded in a flat sheet that you hold in front of your face. Make sure your viewer meets the proper safety standards, and inspect it before you use it to make sure there are no scratches to let in unfiltered sunlight.

You also can view the eclipse through a piece of welder’s glass (No. 14 or darker), or stand under a leafy tree and look at the ground; the gaps between leaves act as lenses, projecting a view of the eclipse on the ground. With an especially leafy tree you can see hundreds of images of the eclipse at once. (You can also use a colander or similar piece of gear to create the same effect.)

One final mode of eclipse watching is with a pinhole camera. You can make one by poking a small hole in an index card, file folder, or piece of stiff cardboard. Let the Sun shine through the hole onto the ground or a piece of paper, but don’t look at the Sun through the hole! The hole projects an image of the eclipsed Sun, allowing you to follow the entire sequence, from the moment of first contact through the Moon’s disappearance hours later.

6. Where can I see the eclipse?

In the United States, the path of totality will extend from Eagle Pass, Texas, to Houlton, Maine. It will cross 15 states: Texas, Oklahoma, Arkansas, Missouri, Illinois, Indiana, Kentucky, Ohio, Pennsylvania, New York, Vermont, New Hampshire, Maine, Tennessee, and Michigan (although it barely nicks the last two).

In Texas, the eclipse will darken the sky over Austin, Waco, and Dallas—the most populous city in the path, where totality (the period when the Sun is totally eclipsed) will last 3 minutes, 51 seconds.

Other large cities along the path include Little Rock; Indianapolis; Dayton, Toledo, and Cleveland, Ohio; Erie, Pennsylvania; Buffalo and Rochester, New York; and Burlington, Vermont.

Outside the path of totality, American skywatchers will see a partial eclipse, in which the Sun covers only part of the Sun’s disk. The sky will grow dusky and the air will get cooler, but the partially eclipsed Sun is still too bright to look at without proper eye protection. The closer to the path of totality, the greater the extent of the eclipse. From Memphis and Nashville, for example, the Moon will cover more than 95 percent of the Sun’s disk. From Denver and Phoenix, it’s about 65 percent. And for the unlucky skywatchers in Seattle, far to the northwest of the eclipse centerline, it’s a meager 20 percent.

The total eclipse path also crosses Mexico, from the Pacific coast, at Mazatlán, to the Texas border. It also crosses a small portion of Canada, barely including Hamilton, Ontario. Eclipse Details for Locations Around the United States • aa.usno.navy.mil/data/Eclipse2024 • eclipse.aas.org • GreatAmericanEclipse.com

7. What causes solar eclipses?

These awe-inspiring spectacles are the result of a pleasant celestial coincidence: The Sun and Moon appear almost exactly the same size in Earth’s sky. The Sun is actually about 400 times wider than the Moon but it’s also about 400 times farther, so when the new Moon passes directly between Earth and the Sun—an alignment known as syzygy—it can cover the Sun’s disk, blocking it from view.

8. Why don’t we see an eclipse at every new Moon?

The Moon’s orbit around Earth is tilted a bit with respect to the Sun’s path across the sky, known as the ecliptic. Because of that angle, the Moon passes north or south of the Sun most months, so there’s no eclipse. When the geometry is just right, however, the Moon casts its shadow on Earth’s surface, creating a solar eclipse. Not all eclipses are total. The Moon’s distance from Earth varies a bit, as does Earth’s distance from the Sun. If the Moon passes directly between Earth and the Sun when the Moon is at its farthest, we see an annular eclipse, in which a ring of sunlight encircles the Moon. Regardless of the distance, if the SunMoon-Earth alignment is off by a small amount, the Moon can cover only a portion of the Sun’s disk, creating a partial eclipse.

9. How often do solar eclipses happen?

Earth sees as least two solar eclipses per year, and, rarely, as many as five. Only three eclipses per two years are total. In addition, total eclipses are visible only along narrow paths. According to Belgian astronomer Jean Meuss, who specializes in calculating such things, any given place on Earth will see a total solar eclipse, on average, once every 375 years. That number is averaged over many centuries, so the exact gap varies. It might be centuries between succeeding eclipses, or it might be only a few years. A small region of Illinois, Missouri, and Kentucky, close to the southeast of St. Louis, for example, saw the total eclipse of 2017 and will experience this year’s eclipse as well. Overall, though, you don’t want to wait for a total eclipse to come to you. If you have a chance to travel to an eclipse path, take it!

10. What is the limit for the length of totality?

Astronomers have calculated the length of totality for eclipses thousands of years into the future. Their calculations show that the greatest extent of totality will come during the eclipse of July 16, 2186, at 7 minutes, 29 seconds, in the Atlantic Ocean, near the coast of South America. The eclipse will occur when the Moon is near its closest point to Earth, so it appears largest in the sky, and Earth is near its farthest point from the Sun, so the Sun appears smaller than average. That eclipse, by the way, belongs to the same Saros cycle as this year’s.

11. When will the next total eclipse be seen from the United States?

The next total eclipse visible from anywhere in the United States will take place on March 30, 2033, across Alaska. On August 22, 2044, a total eclipse will be visible across parts of Montana, North Dakota, and South Dakota. The next eclipse to cross the entire country will take place on August 12, 2045, streaking from northern California to southern Florida. Here are the other total solar eclipses visible from the contiguous U.S. this century:

March 30, 2052 Florida, Georgia, tip of South Carolina May 11, 2078 From Louisiana to North Carolina May 1, 2079 From Philadelphia up the Atlantic coast to Maine September 14, 2099 From North Dakota to the Virginia-North Carolina border

12. What is the origin of the word ‘eclipse?’

The word first appeared in English writings in the late 13th century. It traces its roots, however, to the Greek words “ecleipsis” or “ekleipein.” According to various sources, the meaning was “to leave out, fail to appear,” “a failing, forsaking,” or “abandon, cease, die.”

13. Do solar eclipses follow any kind of pattern?

The Moon goes through several cycles. The best known is its 29.5-day cycle of phases, from new through full and back again. Other cycles include its distance from Earth (which varies by about 30,000 miles (50,000 km) over 27.5 days) and its relationship to the Sun’s path across the sky, known as the ecliptic (27.2 days), among others. These three cycles overlap every 6,585.3 days, which is 18 years, 11 days, and 8 hours.

This cycle of cycles is known as a Saros (a word created by Babylonians). The circumstances for each succeeding eclipse in a Saros are similar—the Moon is about the same distance from Earth, for example, and they occur at the same time of year. Each eclipse occurs one-third of the way around Earth from the previous one, however; the next eclipse in this Saros, for example, will be visible from parts of the Pacific Ocean.

Each Saros begins with a partial eclipse. A portion of the Moon just nips the northern edge of the Sun, for example, blocking only a fraction of the Sun’s light. With each succeeding eclipse in the cycle, the Moon covers a larger fraction of the solar disk, eventually creating dozens of total eclipses. The Moon then slides out of alignment again, this time in the opposite direction, creating more partial eclipses. The series ends with a grazing partial eclipse on the opposite hemisphere (the southern tip, for example).

Several Saros cycles churn along simultaneously (40 are active now), so Earth doesn’t have to wait 18 years between eclipses. They can occur at intervals of one, five, six, or seven months.

The April 8 eclipse is the 30th of Saros 139, a series of 71 events that began with a partial eclipse, in the far north, and will end with another partial eclipse, this time in the far southern hemisphere. The next eclipse in this Saros, also total, will take place on April 20, 2042.


First eclipse
May 17, 1501

First total eclipse
December 21, 1843

Final total eclipse
March 26, 2601

Longest total eclipse
July 16, 2186,  7 minutes, 29 seconds

Final partial eclipse
July 3, 2763

All eclipses
71 (43 total, 16 partial, 12 hybrid)

Source: NASA Catalog of Solar Eclipses: eclipse.gsfc.nasa.gov/SEsaros/SEsaros139.html

14. What about eclipse seasons?

Eclipses occur in “seasons,” with two or three eclipses (lunar and solar) in a period of about five weeks. Individual eclipses are separated by two weeks: a lunar eclipse at full Moon, a solar eclipse at new Moon (the sequence can occur in either order). If the first eclipse in a season occurs during the first few days of the window, then the season will have three eclipses. When one eclipse in the season is poor, the other usually is much better.

That’s certainly the case with the season that includes the April 8 eclipse. It begins with a penumbral lunar eclipse on the night of March 24, in which the Moon will pass through Earth’s outer shadow. The eclipse will cover the Americas, although the shadow is so faint that most skywatchers won’t notice it.

This article was previously published in the March/April 2024 issue of StarDate magazine, a publication of The University of Texas at Austin’s McDonald Observatory. Catch StarDate’s daily radio program on more than 300 stations nationwide or subscribe online at stardate.org.

15. How can astronomers forecast eclipses so accurately?

They’ve been recording eclipses and the motions of the Moon for millennia. And over the past half century they’ve been bouncing laser beams off of special reflectors carried to the Moon by Apollo astronauts and Soviet rovers. Those observations reveal the Moon’s position to within a fraction of an inch. Using a combination of the Earth-Moon distance, the Moon’s precise shape, Earth’s rotation and its distance from the Sun, and other factors, astronomers can predict the timing of an eclipse to within a fraction of a second many centuries into the future.

Edmond Halley made the first confirmed solar eclipse prediction, using the laws of gravity devised only a few decades earlier by Isaac Newton. Halley forecast that an eclipse would cross England on May 3, 1715. He missed the timing by just four minutes and the path by 20 miles, so the eclipse is known as Halley’s Eclipse.

16. What are the types of solar eclipses?

Total: the Moon completely covers the Sun.

Annular: the Moon is too far away to completely cover the Sun, leaving a bright ring of sunlight around it.

Partial: the Moon covers only part of the Sun’s disk.

Hybrid: an eclipse that is annular at its beginning and end, but total at its peak.

17. What are Baily’s beads?

During the minute or two before or after totality, bits of the Sun shine through canyons and other features on the limb of the Moon, producing “beads” of sunlight. They were first recorded and explained by Edmond Halley, in 1715. During a presentation to the Royal Academy of Sciences more than a century later, however, astronomer Frances Baily first described them as “a string of beads,” so they’ve been known as Baily’s beads ever since. Please note that Baily’s beads are too bright to look at without eye protection!

18. Will Earth always see total solar eclipses?

No, it will not. The Moon is moving away from Earth at about 1.5 inches (3.8 cm) per year. Based on that rate of recession, in about 600 million years the Moon would have moved so far from Earth that it would no longer appear large enough to cover the Sun. The speed at which the Moon separates from Earth changes over the eons, however, so scientists aren’t sure just when Earth will see its final total solar eclipse.

19. How will the eclipse affect solar power?

If your solar-powered house is in or near the path of totality, the lights truly will go out, as they do at night. For large power grids, the eclipse will temporarily reduce the total amount of electricity contributed by solar generation. During the October 14, 2023, annular eclipse, available solar power plummeted in California and Texas. At the same time, demand increased as individual Sun-powered homes and other buildings began drawing electricity from the power grid. Both networks were able to compensate with stations powered by natural gas and other sources.

The power drop during this year’s eclipse could be more dramatic because there will be less sunlight at the peak of the eclipse.

20. What are some of the myths and superstitions associated with solar eclipses?

Most ancient cultures created stories to explain the Sun’s mysterious and terrifying disappearances.

In China and elsewhere, it was thought the Sun was being devoured by a dragon. Other cultures blamed a hungry frog (Vietnam), a giant wolf loosed by the god Loki (Scandinavia), or the severed head of a monster (India). Still others saw an eclipse as a quarrel (or a reunion) between Sun and Moon. Some peoples shot flaming arrows into the sky to scare away the monster or to rekindle the solar fire. One especially intriguing story, from Transylvania, said that an eclipse occurred when the Sun covered her face in disgust at bad human behavior.

Eclipses have been seen as omens of evil deeds to come. In August 1133, King Henry I left England for Normandy one day before a lengthy solar eclipse, bringing prophesies of doom. The country later was plunged into civil war, and Henry died before he could return home, strengthening the impression that solar eclipses were bad mojo.

Ancient superstitions claimed that eclipses could cause plague and other maladies. Modern superstitions say that food prepared during an eclipse is poison and that an eclipse will damage the babies of pregnant women who look at it. None of that is true, of course. There’s nothing at all to fear from this beautiful natural event.

21. How do animals react to solar eclipses?

Scientists haven’t studied the topic very thoroughly, but they do have some general conclusions. Many daytime animals start their evening rituals, while many nighttime animals wake up when the eclipse is over, perhaps cursing their alarm clocks for letting them sleep so late!

During the 2017 total eclipse, scientists observed 17 species at Riverbanks Zoo in Columbia, South Carolina. About three-quarters of the species showed some response as the sky darkened. Some animals acted nervous, while others simply headed for bed. A species of gibbon had the most unusual reaction, moving excitedly and chattering in ways the zookeepers hadn’t seen before.

Other studies have reported that bats and owls sometimes come out during totality, hippos move toward their nighttime feeding grounds, and spiders tear down their webs, only to rebuild them when the Sun returns. Bees have been seen to return to their hives during totality and not budge until the next day, crickets begin their evening chorus, and, unfortunately, mosquitoes emerge, ready to dine on unsuspecting eclipse watchers.

A NASA project, Eclipse Soundscapes, is using volunteers around the country to learn more about how animals react to the changes. The project collected audio recordings and observations by participants during the annular eclipse last year, and will repeat the observations this year. Volunteers can sign up at eclipsesoundscapes.org

22. How will scientists study this year’s eclipse?

Astronomers don’t pay quite as much professional attention to solar eclipses as they did in decades and centuries past. However, they still schedule special observations to add to their knowledge of the Sun and especially the inner edge of the corona.

Sun-watching satellites create artificial eclipses by placing a small disk across the face of the Sun, blocking the Sun’s disk and revealing the corona, solar prominences, and big explosions of charged particles known as coronal mass ejections.

Because of the way light travels around the edges of an eclipsing disk, however, it’s difficult to observe the region just above the Sun’s visible surface, which is where much of the action takes place. The corona is heated to millions of degrees there, and the constant flow of particles known as the solar wind is accelerated to a million miles per hour or faster, so solar astronomers really want to see that region in detail. The eclipsing Moon doesn’t create the same effects around the limb of the Sun, so a solar eclipse still provides the best way to look close to the Sun’s surface.

For this year’s eclipse, some scientists will repeat a series of experiments they conducted in 2017 using a pair of highaltitude WB-57 aircraft to “tag team” through the lunar shadow, providing several extra minutes of observations.

Other scientists will use the eclipse to study Earth’s ionosphere, an electrically charged layer of the atmosphere that “bends” radio waves, allowing them to travel thousands of miles around the planet. Sunlight rips apart atoms and molecules during the day, intensifying the charge. At night, the atoms and molecules recombine, reducing the charge.

Physicists want to understand how the ionosphere reacts to the temporary loss of sunlight during an eclipse. They will do so with the help of thousands of volunteer ham radio operators, who will exchange messages with others around the planet. During last October’s annular eclipse, when the Moon covered most but not all of the Sun, the experiment showed a large and immediate change in the ionosphere as the sunlight dimmed.

NASA also will launch three small “sounding” rockets, which loft instruments into space for a few minutes, to probe the ionosphere shortly before, during, and shortly after the eclipse.

Another project will use radar to study changes in the interactions between the solar wind and Earth’s atmosphere, while yet another will use a radio telescope to map sunspots and surrounding regions as the Moon passes across them.

One project will piece together images of the eclipse snapped through more than 40 identical telescopes spaced along the path of totality to create a one-hour movie of the eclipse. The telescopes will be equipped with instruments that see the three-dimensional structure of the corona, allowing solar scientists to plot how the corona changes.

23. What have astronomers learned from eclipses?

Solar eclipses have been powerful tools for studying the Sun, the layout of the solar system, and the physics of the universe.

Until the Space Age, astronomers could see the Sun’s corona only during eclipses, so they traveled around the world to catch these brief glimpses of it.

Eclipses also offered a chance to refine the scale of the solar system. Watching an eclipse from different spots on Earth and comparing the angles of the Moon and Sun helped reveal the relative sizes and distances of both bodies, which were important steps in understanding their true distances.

During an eclipse in 1868, two astronomers discovered a new element in the corona. It was named helium, after Helios, a Greek name for the Sun. The element wasn’t discovered on Earth until a quarter of a century later.

An eclipse in 1919 helped confirm General Relativity, which was Albert Einstein’s theory of gravity. The theory predicted that the gravity of a massive body should deflect the path of light rays flying near its surface. During the eclipse, astronomers found that the positions of background stars that appeared near the Sun were shifted by a tiny amount, which was in perfect agreement with Einstein’s equations.

Today, astronomers are using records of eclipses dating back thousands of years to measure changes in Earth’s rotation rate and the distance to the Moon.

24. How did astronomers study eclipses in the past?

With great effort! From the time they could accurately predict when and where solar eclipses would be visible, they organized expeditions that took them to every continent except Antarctica, on trips that lasted months and that sometimes were spoiled by clouds or problems both technical and human.

During the American Revolution, for example, a group of Harvard scientists led by Samuel Williams received safe passage from the British army to view an eclipse from Penobscot Bay, Maine, on October 21, 1780. Williams slightly miscalculated the eclipse path, though, so the group missed totality by a few miles. (The expedition did make some useful observations, however.)

In 1860, an expedition headed by Simon Newcomb, one of America’s top astronomers, journeyed up the Saskatchewan River, hundreds of miles from the nearest city, braving rapids, mosquitoes, and bad weather. After five grueling weeks, they had to stop short of their planned viewing site, although at a location still inside the eclipse path. Clouds covered the Sun until almost the end of totality, however, so the expedition came up empty.

King Mongkut of Siam invited a French expedition and hundreds of other dignitaries to view an eclipse from present-day Thailand in 1868. He built an observatory and a large compound to house his guests at a site Mongkut himself had selected as the best viewing spot. The eclipse came off perfectly, but many visitors contracted malaria. So did Mongkut, who died a few weeks later.

An expedition in 1914, to Russia, was plagued by both clouds and the start of World War I. The team abandoned its instruments at a Russian observatory and escaped through Scandinavia.

The eclipse of July 29, 1878, offered fewer impediments. In fact, it was a scientific and social extravaganza. The eclipse path stretched from Montana Territory to Texas. Teams of astronomers from the United States and Europe spread out along the path. Thomas Edison stationed his group in Wyoming, where he used a tasimeter, a device of his own creation, to try to measure the temperature of the corona. Samuel Pierpoint Langley, a future secretary of the Smithsonian, was atop Pikes Peak in Colorado. Maria Mitchell, perhaps America’s leading female scientist, decamped to Denver. And Asaph Hall, who had discovered the moons of Mars just the year before, journeyed to the flatlands of eastern Colorado.

Thousands of average Americans joined the festivities, paying outrageous prices for some of the best viewing spots. Some things, it seems, never change.

25. What about lunar eclipses?

While solar eclipses happen during new Moon, lunar eclipses occur when the Moon is full, so it aligns opposite the Sun in our sky. The Moon passes through Earth’s shadow. In a total eclipse, the entire lunar disk turns orange or red. In a partial eclipse, Earth’s inner shadow covers only a portion of the Moon. And during a penumbral eclipse, the Moon passes through the outer portion of Earth’s shadow, darkening the Moon so little that most people don’t even notice it.

Lunar eclipses happen as often as solar eclipses—at least twice per year. This is a poor year for lunar eclipses, however. There is a penumbral eclipse on the night of March 24, with the Moon slipping through Earth’s faint outer shadow, and a partial eclipse on the night of September 17, in which the Moon barely dips into the darker inner shadow. Both eclipses will be visible from most of the United States.

This article was previously published in the March/April 2024 issue of StarDate magazine, a publication of The University of Texas at Austin’s McDonald Observatory. Catch StarDate’s daily radio program on more than 300 stations nationwide or subscribe online at stardate.org.