A Touch of NIGHT
Scientists, science buffs explain forthcoming solar eclipse
“It’s the beauty, the awe of the sky. This is one of the most spectacular sights of astronomy that you can see.” That’s Darcy Howard of the Central Arkansas Astronomical Society talking about the April 8 solar eclipse, when the moon will slip in front of the sun and temporarily dim the biggest, brightest diva in our solar system, forming a narrow swath across Arkansas, from the southwest corner to the northeast corner, known as the path of totality.
The eclipse will begin over the Pacific Ocean then travel through Mexico, into the United States and across the eastern edge of Canada as the moon’s shadow races across the
Earth at a speed of more than 1,500 miles per hour at the beginning to more than 4,300 miles per hour as it passes over Newfoundland and Labrador.
The path of totality will start out about 123 miles across and shrink to about 100 miles wide as it glides over the Labrador Sea.
The total solar eclipse begins in southwest Arkansas around 1:45 p.m., according to greatamericanelipse.com. In Little Rock, totality begins at 1:51 and should last about 2 minutes, 33 seconds, although it will be longer in other areas. Totality over Conway will be 3 minutes, 53 seconds; in Hot Springs, totality will last 3 minutes, 38 seconds; in Russellville, it is expected to last 4 minutes, 11 seconds.
During totality the moon’s shadow will make the afternoon seem like night.
“It’s really a day-and-night experience,” Howard says. “It will be about like a night with a full moon, not totally dark, but it will be dark enough, even before totality, that you should be able to see the planet Venus in the sky.”
As darkness approaches, the ambient light will cause shadows to seem fuzzy.
“The shadows become unnatural,” Howard says. “Within about three minutes of totality you will notice change in the light. Shadows beneath the trees start projecting little crescent images of the sun. It’s a wonderful experience.”
In addition, the temperature will decrease and animals and plants will start reacting to the sudden, unexpected darkness.
“The reaction of plants like tulips is something people can look for besides looking up at the sky,” says astronomical society member Carl Freyaldenhoven. “And this is springtime, so you’re going to hear all of the frogs making noise [as it gets darker].”
The astronomical society was founded in 1971 and operates the River Ridge Observatory near Little Italy. There are monthly meetings, star watching parties and other events. The group has about 135 members, with some newbies joining because of interest in the eclipse, Freyaldenhoven says.
“We’ve had people who were interested in the sky, and this was kind of like the kicker for them to go ahead and join.”
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The oldest record of an eclipse was discovered on a clay tablet unearthed at the ruins of the ancient city of Ugarit, in what is now Syria. There are a pair of dates associated with the tablet — May 3, 1375 B.C., and March 5, 1223 B.C. Most scholars agree on the latter date for the eclipse.
It wasn’t until centuries later that the idea that eclipses could be forecast took hold. It is believed that the 585 B.C. eclipse was the first to be accurately predicted. According to Greek historian Herodotus, the event was foretold by Thales of Miletus, who is often referred to as the first scientist.
In 463 B.C., Greek philosopher Anaxagoras was one of the first to propose that an eclipse happens when the moon’s shadow is cast on the Earth, making it a natural phenomena and not an omen or curse.
English astronomer Edmond Halley — he of the comet — figured out in 1775 how to determine the path of totality. Sixty-one years later German mathematician and astronomer Friedrich Bessel created a set of values that accurately calculated eclipse paths.
The discovery of helium is connected to the eclipse of 1868, which was the first time spectral lines of the gas were observed as the sun was blocked by the moon.
Arthur Eddington and Frank Dyson, astronomers from two English observatories, undertook expeditions to Brazil and Africa to observe the eclipse of 1919 and confirmed Einstein’s theory that light is affected by gravity and that space time is curved.
Daniel Kennefick, a physics professor at the University of Arkansas, Fayetteville who studies black holes and gravitational waves, knows a thing or two about the findings from the 1919 eclipse. He is the author of the 2019 book “No Shadow of a Doubt: The 1919 Eclipse That Confirmed Einstein’s Theory of Relativity.”
Having worked out his theory of relativity in 1905, Einstein began to wonder about gravity’s impact.
“Light, according to his famous equation E = mc², has energy,” Kennefick says. “According to that equation if it has energy then it has mass. And if something has mass it should be affected by gravity.”
That means that if light passes through a gravitational field it should fall. The problem is that light moves so fast, we don’t notice it falling.
Lucky for Einstein, our solar system has a really strong gravitational field. It’s called the sun. And he wondered that if light, say from a nearby star, passed close by the sun, would we see a slight change in the star’s position because the star’s light was forced by the sun’s gravity out of its straight path?
The effect, gravitational lensing, is now a key part of astronomy. In the early 1900s, though, it wasn’t yet proved. This is where a good ol’, sun-blocking eclipse comes in.
The best way to see stars close to the sun is during a total solar eclipse, with most of the sun except for the corona, blocked out.
“All they had to do is take a picture of stars during an eclipse and later take pictures of the same stars when the sun isn’t there,” Kennefick says. “If the stars’ position had changed a little during the eclipse, that would prove the theory that light has mass.”
Eddington and Dyson took him up on the arduous challenge and set out on their expeditions.
“The tests found in Einstein’s favor,” Kennefick says.
Advancements in technology, like radio telescopes, mean that scientists don’t have to wait around for an eclipse these days to study the sun.
“The ingenuity of people means that in time eclipses, which were so important in the 19th and early 20th centuries, have become a little less important [to research],” Kennefick says, “but there are still scientists going to eclipses to do experiments. It’s still a big deal for scientists, just not as important as it was a century ago.”
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Total eclipses occur about every 18 months. What makes the April 8 event so special is that about 30 million people occupy the path of totality in the United States alone, and millions more will be traveling to areas along the path. In 2017, the last time a total eclipse happened over the U.S., about 20 million people from Oregon to South Carolina witnessed it, according to greatamericaneclipse.com. Arkansas’ most recent total solar eclipse was June 8, 1918. We won’t see another around here until Aug. 23, 2044.
A lot of celestial things have to line up for us to be cast into darkness in the middle of the day.
Here’s Ann Wright, associate professor of physics at Hendrix College in Conway.
“It all depends on geometry,” she says. “The Earth’s orbit around the sun forms a plane called the ecliptic plane. … If the moon orbited in this ecliptic plane, we would have eclipses twice a month. But the moon’s orbit around the Earth is tilted out of that plane by five degrees. So to get a solar eclipse, the moon’s orbit has to intersect the ecliptic plane and the moon has to be in the new phase for a solar eclipse or the full phase for a lunar eclipse.”
When all of this comes together, we get an eclipse like the one that will happen on April 8, when travelers descend upon Arkansas and other states to be in the path of totality (and maybe buy some eclipse merch).
“The reason it’s so special,” Wright says, “is that the shadow of the moon hits the Earth in this small stripe, the path of totality. It’s a very small section of the Earth that gets to see it and that only happens when everything is lined up.”
Wright has actually taken a sabbatical to help organize an eclipse viewing from noon-4 p.m. April 8 at Young-Wise Memorial Stadium at Hendrix. There will be free eclipse glasses and telescopes with solar filters as well as games, music, food trucks and more.
“As far as viewing, the sun will be at about 60 degrees above the horizon in the southwest at the time of totality,” she says. “So we will be able to see if from the field.”
Wright has given lectures on the eclipse outside of the college, including one on March 9 at Dunbar Garden in Little Rock and on March 23 at the Extension Homemakers Club at Ferndale and says that interest has been high.
“The everyday person who is not necessarily a science fanatic like I am is getting really excited,” she says. “I love this opportunity to go and give an astronomy lesson to people who wouldn’t normally seek that out.”