Tennessee municipalities set sights on solar eclipse

BY KATE COIL
TML Communications Specialists

Cities and towns across Tennessee are gearing up to view a once-in-a-life-time event.
On Aug. 21, Tennessee will experience its first total solar eclipse in more than 500 years, with another total eclipse not predicted to occur in the same area for nearly 550 years afterward.

Billy Teets, an outreach astronomer with Vanderbilt University’s Dyer Observatory in Brentwood, said a solar eclipse requires both the moon and the sun to be in exactly the right position when compared to the earth.

“You have to be in the inner shadow of the moon to see a total solar eclipse because it is not very wide by the time it reaches the earth,” he said. “It is rare to be in that direct path. We have a solar eclipse whenever the moon passes directly in front of the sun. Because the moon’s orbit is titled when compared to the earth’s orbit around the sun, it has to be a new moon to set up a solar eclipse. Typically, the moon is going to be too high or too low in the sky in respect to the sun to pass in front of it. Basically, we miss the shadow of the moon most of the time.”

While a solar eclipse occurs somewhere around the globe once every five months, most of these are only partial eclipses where the moon doesn’t manage to completely cover the sun.

Total solar eclipses also aren’t exactly rare across the earth – one occurs roughly every 18 months or twice every three years. What is rare is to be in the exact path of that totality, a path that is usually less than 100 miles long and can take hundreds of years to cycle back around to the same location.

Once a total solar eclipse has occurred in an area, scientists estimate it takes another 400 years on average for another total eclipse in that same spot. As a result, most people don’t see a total solar eclipse unless they are willing to travel the world looking for one.

“This will be the first time since 1979 any total solar eclipse has been visible in the mainland U.S.,” Teets said. “There were total solar eclipses visible in parts of the mainland U.S. in the 1800s, but the last time a total eclipse passed through the area where Nashville would be founded was in 1478 – 539 years ago. The next time that Nashville will see another total eclipse will be 2546, roughly 549 years from now.”

Teets said the path of the eclipse is only about 75 miles wide, meaning that only those within that range will see the total eclipse. Those outside that range may experience a partial solar eclipse.

In addition to being awe-inspiring viewing, Teets said eclipses can also give astronomers and other scientists valuable information about the world we live in.
“The 1918 eclipse was used to help confirm the predictions of Einstein’s theory of general relativity,” he said. “Eclipses have been used for determining distances, like the distance between the earth and the moon.”

To view an eclipse, Teets said specialized glasses are needed up to a point.
“During totality, when the sun is completely blocked out and no part of its surface is visible you have to see the eclipse with the naked eye,” he said. “When any part of the sun’s surface is visible you have to be wearing the special glasses or you will suffer eye damage. Once the moon completely moves in front of the sun you have to remove the glasses. The corona – the part of the sun you can’t see without a total solar eclipse – is only about as bright as the full moon and is safe to look at. When the sun pops back out, you put the glasses back on.”

For those looking to purchase their own glasses, Teets recommends checking with local observatories, science centers or NASA to purchase glasses or find reputable glasses to purchase them from. He said eclipses that are safe for eclipse viewing will have the ISO certification number 12312-2 on them.
Teets said the eclipse is also best viewed through the eye and not a camera.

“Folks who have been in the path of a total solar eclipse before say there is nothing like experiencing that totality,” Teets said. “There is no sunrise that can compare to it. There is simply nothing like the beauty of it and the way it looks. We try to stress that, especially if this is the first total eclipse you see, don’t try to take pictures of it. You have a very short period of time to view totality, so just take it in with your own eyes and try to experience it so you remember this for the rest of your life.”