Florence Andsager and her siblings were playing outside their Kansas farmhouse one afternoon in June 1918 when the cloudless sky began to darken and day turned to night.
The children hurried inside and huddled with their parents, the whole family convinced that the world was coming to an end. It was before the days of radio and the family had no way of hearing about a total eclipse of the sun, nor did they know what to expect.
Now almost a hundred years later, thanks to advancing technology, we can pinpoint not only the day but also the exact time of an eclipse.
On Monday, August 21, a total solar eclipse—when the disk of the moon completely covers the sun—will be visible in the United States along a path that is 2,500 miles long and 70 miles wide, from central Oregon through Tennessee and on to South Carolina. View an online map to determine cities in the path of totality and exact eclipse times.
“We’re very lucky here on Earth that the moon is 400 times smaller than the sun but 400 times closer. There’s no place else in the solar system that gives a view like this,” said Mark Littmann, a UT expert who has written extensively on solar eclipses and viewed five of them around the world.
Littmann—the Hill Chair of Excellence in Science Writing in the School of Journalism and Electronic Media—includes Andsager’s 1918 recollection in his new book, Totality: The Great American Eclipses of 2017 and 2024, to demonstrate how odd and jarring the experience of a total solar eclipse can be. The book is a comprehensive guide for the eclipse.
In Tennessee, many points to the south and southwest of Knoxville will experience a total eclipse. Knoxville, however, will have only a 99.75 percent partial eclipse. Littmann encourages those who live in areas with a partial eclipse to drive short distances to places that will have a total eclipse.
“I cannot emphasize strongly enough that the difference between a 99.75 percent partial eclipse and a total eclipse is literally the difference between day and night,” he said. “Almost everything that makes a total eclipse special will be missing from a partial eclipse. Imagine having tickets to see Hamilton or some event that you are dying to see, and imagine going to that event and standing in the lobby. You sense the excitement but you’ve missed the main event.”
Enjoy the Eclipse, Protect Your Eyes
This year’s phenomenon marks the first time since 1979 that a total eclipse has been viewable from the mainland United States.
Sean Lindsay, astronomy coordinator and lecturer in the Department of Physics and Astronomy, described a total solar eclipse as if “reality got suspended.”
“It goes from as bright as day to as dark as dark twilight in a matter of minutes. Your brain is not ready to handle this, because all of a sudden it is nighttime in the middle of the day,” said Lindsay, who saw his first total eclipse in Svalbard, an archipelago between Norway and the North Pole. “You can see some of the bright stars. Even more strange is you look up and where there used to be a sun, it literally looks like there is a black hole in the sky.”
Then comes the most important part of a total solar eclipse: the corona, which is a brilliantly glowing white light—almost like a halo—around the sun. It is the outermost layer of the sun’s atmosphere and never seen except during a total eclipse.
Up until this point, solar glasses are needed to view the eclipse safely, Lindsay said. The corona is the only part of a total solar eclipse that is safe to view with the naked eye. The solar glasses are made up of black polymer that blocks out everything but the sun. Learn more about how to get solar glasses.
This summer, Lindsay and Paul Lewis, director of space science outreach in the Department of Physics and Astronomy, will host Solar Sundays, a series of educational seminars about solar science, with a heavy emphasis on eclipse viewing safety.
They also have hosted trainings for schools, civic organizations, municipalities, the National Park Service, and the National Forestry Service about how to prepare for the eclipse and advise people who will watch at their locations.
“We want to help viewers maximize the experience,” Lindsay said. “You can damage your eyes if you don’t view it safely.”
Lewis added: “Do not consider sunglasses as a safety mechanism for looking at the sun.”
The Final Countdown
The length of the total eclipse will depend on where inside the path of totality one is. It could range from a second to 2 minutes 40 seconds, said Littmann. But the experience from partial eclipse to total and back to the end of partial can last more than two and a half hours.
“Fifteen minutes before the eclipse, strange things begin to happen,” he said. “The sky turns a steely gray color. The color begins to fade from the grass and the trees. The animals are completely confused. The birds will be flying about squawking and not understanding what’s happening. They may go to their nest and go to sleep. Cows will go on their own back to the barn. Chickens will go to roost. The temperature begins to drop. You’ll see night critters coming out. The bats will begin to fly. Watch other human beings and their reactions, too.”
Right before and right after the total eclipse, another phenomenon—the diamond ring effect—occurs. During this stage, a glow of sunlight appears around the rim of the moon just before it covers the sun, he said.
“The neat thing about this eclipse is that it has chosen to follow American interstates and US highways,” Littmann said.
It will be within a day’s drive of at least 80 million Americans, not to mention the more than 100,000 people from foreign lands who will travel to the United States just to watch the total eclipse.
“It is the most amazing of celestial sights,” Littmann said.