A total solar eclipse is not the same as a partial eclipse, even if it is 99% partial: NPR

Eclipse watchers enjoy the totality on Aug. 21, 2017, on the Isle of Palms, and SC Eclipse experts say the partial eclipse isn't nearly as dramatic.

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Eclipse watchers enjoy the totality on Aug. 21, 2017, on the Isle of Palms, and SC Eclipse experts say the partial eclipse isn't nearly as dramatic.

Pete Marovich/Getty Images

When the moon slides in front of the sun on April 8, many places will hold eclipse viewing parties. For example, the Alamo Hotel in San Antonio, Texas will do this note Special viewing glasses in the shape of the historic building.

“We encourage everyone to come to the Alamo,” says Jonathan Hohn, spokesman for the Alamo Trust, who notes that past astronomical events have drawn thousands to Alamo Square. “We hope to have another 5,000 people in front of the Texas Freedom Shrine to witness this beautiful celestial event.”

But the Alamo lies outside what's called the path of totality, the strip of Earth stretching across 13 states, from Texas to Maine, that will see a total solar eclipse. During a total eclipse, the Moon completely blocks the Sun.

“We're not 100% in the totality zone,” Hohn says, and he thinks the Sun will be about 99.9% obscured. “It's very, very close.”

Close but no cigar, according to eclipse experts.

“I would never tell anyone that 99% is close enough.” “This is certainly not the case with a solar eclipse,” he says. Michelle Nicholswho manages public observation programs at the Adler Planetarium in Chicago.

“Drive those last few miles to college,” she urges. “People go to a total eclipse to get the full experience, and 99 percent won't get the full experience.”

“It's 100% or nothing,” he agrees Fred Espinak, a retired NASA astrophysicist who has witnessed 30 total solar eclipses. “There is a radical and dramatic difference between partial 99% and 100% total. There is no comparison.”

During a total eclipse, the sky suddenly becomes dramatically dark. The temperature drops. The stars are coming out. Beautiful colors appear around the horizon. The once familiar sun turns into a black void in the sky surrounded by the glowing corona, the ghostly white ring that makes up the sun's atmosphere.

“It seems supernatural,” Espenak says. “It is so far beyond the scope of normal everyday existence that it seems more like a dream or a hallucination.”

A partial solar eclipse offers none of that magic, according to Rick Feinbergproject director of the Solar Eclipse Task Force of the American Astronomical Society.

“Even at 99%, it doesn't get any darker than it is on an overcast day,” Feinberg says. “You could have a 75% or 80% partial solar eclipse, and if you don't know it's happening, you might not notice it because the environment changes a little bit.”

This is because the sun is so bright that even a small, exposed sliver can light up the sky — or hurt your eyes if you're not wearing safety glasses. Only during the short phase of totality when the sun is completely covered (which varies depending on your exact location but can take about four minutes) is it safe to look toward the sun without special eye protection.

“The Sun is about a million times brighter than the full Moon,” he explains. Angela Speck, an astronomer at the University of Texas at San Antonio. So, if 99.9% of the sun was blocked, there would still be “a thousand times more light than a full moon, and thus it would still be as bright.”

The last time parts of the United States saw a total solar eclipse was in 2017, Nichols says, and the path of totality passed over a lot of rural areas. This time, the route passes through more urban areas.

This means that while about 32 million people live on the trail, many more live within a short distance of it.

For them, the difference between seeing a partial eclipse and seeing a total eclipse might mean going across town.

“If you get right into the path, but you don't go to that last path, you know, a few hundred yards from it, you're going to get a very deep partial eclipse,” Feinberg says. “It will definitely get dark, but nowhere near 100% dark. You won't see the corona.”

Popular places outside the path of totality will have to decide what type of event, if any, to hold that day.

The San Antonio Zoo is located on the side of town that won't see a total eclipse. Unlike the nearby Alamo, you will focus on pre-eclipse activities the day before.

“We are hosting an Eclipse Prep event on Sunday instead of a Monday event,” zoo spokesperson Hope Roth told NPR via email, adding that astronomers will attend and free sunglasses will be available. “We will encourage guests to visit the zoo, pick up their glasses and have a good time while preparing for the eclipse the next day.”

The Historic Cincinnati Observatory, which frequently holds skygazing parties, will only witness a 99.7% partial eclipse. The staff there thought carefully about whether or not to hold an eclipse celebration.

“For the longest time leading up to this eclipse, we were committed to staying closed,” the CEO says. Anna Hehmann“Because the total eclipse, if the sky is clear, is an hour away from us.”

Ultimately, they decided to hold an event for members of their community who, for whatever reason, were unable to travel to College Road.

“While we encourage everyone to head to the college if possible, we love that people want to be at the Cincinnati Observatory to witness out-of-this-world events like this one. So, if you can't make it to the college, please join us,” observatory website He says.

After all, a partial eclipse is still an interesting celestial event that people have observed since ancient times, even if it's not quite as dramatic.

“The hype around a solar eclipse is usually focused on totality, and seeing it as a total eclipse is worth all the hype. But the vast majority of people won't be in the path of totality,” astronomy teacher Shauna Edsonat the National Air and Space Museum, told NPR in an email.

This is why the museum is held Eclipse celebration At the National Mall in Washington, D.C., which will witness an 89% partial eclipse.

“This eclipse falls during the cherry blossom season, so many people will be visiting the capital, and the museum wanted to provide a space where they could enjoy the eclipse together,” Edson noted, adding that participants will be able to enjoy seeing the crescent moon. Shadows forming under trees and try different ways to view the partial eclipse.

After April 8, the contiguous United States will not see another total solar eclipse for 20 years. What comes in 2044 will only be visible in less populated states like North Dakota, South Dakota, and Montana.