Outside World

Five Things to Know about the Great American Solar Eclipse

For the first time in nearly 100 years, a total solar eclipse will span the country.

What is a total solar eclipse?
Every year, there are a minimum of four eclipses: two solar and two lunar. However, the eclipse on August 21 is especially unique; there hasn’t been one like it since 1918. During this eclipse, the sun will be covered—totally or partially—for approximately three hours, with the longest period of complete coverage lasting just under three minutes. At this time, the only visible portion of the sun will be its hazy atmosphere known as the corona.

Why is this such a big deal?
Scientists have been studying data and patterns from the eclipses for the past 60 years to learn more about the sun. The Applied Physics Lab (APL) at Johns Hopkins University will send the Parker Solar Probe to the sun’s corona in 2018 in hopes of answering questions that have plagued scientists for decades. “It’s the first time in 99 years that we’ve had a total solar eclipse that’s gone right from one coast all the way across the U.S. to the other coast,” said Dr. Nicola Fox, project scientist at APL. “The corona is about two million degrees, but the surface is only 10,000 degrees, that doesn’t make sense. From a logical standpoint, the further away from the surface, it should get cooler, not hotter.” Events like the total solar eclipse bring scientists one step closer to answering these questions. 

Will we be able to see it in Baltimore?
Each state along the 70-mile wide path of the eclipse—Oregon, Idaho, Wyoming, Montana, Nebraska, Iowa, Kansas, Missouri, Illinois, Kentucky, Tennessee, Georgia, and The Carolinas—will witness a total solar eclipse, in which the moon will completely cover the sun, while the rest of the country will see varying views of partial eclipses. “In Baltimore, it will be a partial eclipse for about two hours,” said street astronomer Herman Heyn. “One hour as the moon approaches the sun, and another hour as it leaves the sun.” According to an interactive map created by NASA, a partial eclipse will begin in Baltimore at approximately 1:18 p.m., with maximum visibility occurring at 2:42 p.m., and ending at 4:01 p.m. “You’ll see something, it won’t be 100-percent totality, but it will darken up a bit, and part of the sun will disappear,” Fox said. “It’s really dependent on the cloud coverage. As long as you’re somewhere pretty open, with a good view of the sun, you should be fine.”

Can I take pictures of it?
Heyn explained that a total solar eclipse is actually safe for unprotected viewing, but looking directly at a partial eclipse is harmful for the eyes. There are creative alternatives to view the eclipse that will occur over Baltimore. Purchasing “eclipse glasses” is one way to protect your eyes from the suns harmful rays. These glasses are specially designed to look directly at the sun. “You don’t want to use regular dark sunglasses,” Heyn cautioned. “Those don’t block enough of the infrared light that would burn your eyes.” Creating a pinhole camera is another safe way to experience the eclipse, using materials already available around the house. “Take a piece of cardboard, about a foot square, and poke a hole in it with a straight pin,” Heyn explained. “Take another piece about half that size and place it under the first. That will give you a small image of the eclipsed sun.” There will also be workshops at Cylburn Arboretum the day of the eclipse to create pinhole cameras for ages seven and up. Taking pictures of the eclipse should be done cautiously, due to the extreme heat—two million degrees Fahrenheit—emitted from the sun’s corona. A typical photo lens will burn up without a heavy-duty filter.

What does this mean for the future of astronomy?
The total solar eclipse later this month will be another piece of data that the APL and NASA can use toward their mission. “It’s kind of cool because we’ve discovered so much about the sun’s corona itself during eclipses,” she said. “The huge temperature difference was found during an eclipse and what the corona’s structure looks like was found during an eclipse. Without the solar probe, we’ll never fully understand what we are really seeing.”