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Eclipse map
The path of totality for the total solar eclipse of August 21, 2017. (credit: NASA)

The science and spectacle of the Great American Eclipse

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Alex Young had a confession to make.

“There’s going to be traffic like we’ve never seen,” Speck said, comparing it a football game day. “We’re going to have traffic like that all the way along the path.”

The associate director for science in the heliophysics division at NASA’s Goddard Space Flight Center, Young was at last month’s meeting of the American Astronomical Society (AAS) in Texas to talk about the solar eclipse that will be visible across the United States this August, both at a press conference near the end of the meeting January 7 and a plenary speech immediately afterwards. There was just one thing.

“I have yet to see a total solar eclipse,” he said, despite spending his professional career studying the Sun. “Life always seemed to get in the way.”

Young, and millions of others, will have an opportunity to finally see one on August 21. In what may be the biggest astronomical spectacle in US history, people will gather from Oregon to South Carolina to observe—weather permitting—what’s being dubbed by some the Great American Eclipse.

The path of totality will come onshore from the Pacific on the Oregon coast west of Salem. It arcs gently southeast, crossing over the Rockies and into the Great Plains and Midwest, skimming Kansas City and St. Louis. It goes through Kentucky and Tennessee, including over Nashville, before crossing the southern Appalachians and crossing the Atlantic coast near Charleston, South Carolina.

Some people have been preparing for this event for months, if not years. Hotel rooms in prime viewing areas on and near the path of totality have long been booked. Many have planned events in the weeks and days leading up to the eclipse. One minor league baseball team, the Salem-Keizer Volcanoes in Oregon, rescheduled their game that day to take place during the eclipse, so that they can have what the team believes to be the first-ever “eclipse delay” during totality.

Many others, though, particularly those people who aren’t even aware of the upcoming eclipse, likely won’t make any viewing plans until the last minute. Twelve million people won’t need to go anywhere: they live on the path of totality, noted Angela Speck, a professor of astronomy at the University of Missouri and chair of the AAS’s Solar Eclipse Task Force. That includes Speck herself: she noted she lives about ten kilometers from the centerline.

A far larger number live within a few hundred kilometers of the eclipse’s path, and more within a reasonable day’s drive. “Basically every single person in the US is within a long day’s drive,” she said.

There’s the potential, therefore, for massive traffic the day of the eclipse as people hop in their cars and drive to where they have the best chance to see the eclipse. “There’s going to be traffic like we’ve never seen,” she said, comparing it to the onslaught of traffic that comes into a college town on a football game day. “We’re going to have traffic like that all the way along the path.”

“This is a huge logistical nightmare,” Young said. “There are a lot of people that are going to be trying to get the path of totality, and especially people who decide to do it on the morning of, or even the day before. There’s just not enough port-a-potties in the world to handle this many people and to deal with the kinds of traffic flow.”

Young said the National Park Service is particularly concerned about being flooded with visitors for the eclipse at various parks, “stomping everything down” in a quest to observe the eclipse. State and local transportation agencies are also concerned about dealing with unusual traffic flows around the event. NASA, he said, is using “its reach and even its brand” to work with those agencies and others to prepare for the eclipse, including a website with information about the eclipse.

Some of that work involves coordinating observing areas along the path of totality. “I don't think you’ll be able to go anywhere along the path in Missouri and not find somewhere to view it,” Speck said, with locations that will also offer water and shade on what’s likely to be a hot summer’s day.

“What federal agencies and state agencies can do is get the message out to municipalities” who are the ones planning many of those observing locations, said Rick Feinberg, AAS press officer. “That’s what we’re trying to do: push the message out from the top down.”

Young noted that while NASA is not directly planning observing sites for the eclipse, it is listing those sites where local planners “have actually thought about this and have a plan” for dealing with various logistical issues.

There’s more to planning the eclipse, though, than the logistics of getting people to viewing sites. Observations of eclipses, even in the modern era of advanced observatories and spacecraft, can still yield useful science.

“There is a whole zone best studied from the ground,” said Jay Pasachoff, a professor of astronomy at Williams College and a veteran eclipse hunter, who will observe his 34th total solar eclipse in August. “Spacecraft can’t get down to the surface of the Sun.”

“Everyone has emphasized, time and time again, that absolutely nothing compares to a total solar eclipse,” Young said. “So, I’m champing at the bit.”

That includes studies of the solar corona and its magnetic field, collecting data that can explain why the corona is so hot. “One of the things we’ve been studying is the temperature of the corona, and the question of just how the corona gets heated to a million degrees is something we do investigate during eclipses,” he said.

“We can look at the Sun now in 4K-by-4K, in ten different wavelengths, with the Solar Dynamics Observatory, and see all that amazing structure,” Young said. “Even with all that, we still can’t do everything we need to do to really understand what’s going on.”

Eclipses, he said, allow them to see the inner corona that otherwise can’t be seen: even the coronagraph instruments on spacecraft designed to allow observations of the corona are sized such that they block the innermost regions. “The science is extremely important and extremely unique, and is still a critical part of getting the big picture, of seeing all the pieces to understand this phenomenon,” he said.

The combination of scientific interest and mass public interest also provides a unique opportunity for what’s known as “citizen science.” One such effort, called Citizen CATE, for Continental American Telescopic Eclipse, involves a network of 60 telescopes spread out along the path of totality to capture images of the solar corona. Combined, it will provide scientists with insights into how the corona changes during the 90 minutes it takes for the shadow to traverse the country.

And while Young has been busy coordinating planning for the eclipse, he’s looking forward to finally seeing one himself in August. “Everyone has emphasized, time and time again, that absolutely nothing compares to a total solar eclipse,” he said. “So, I’m champing at the bit. I can’t wait.”

“I know that, once I see it, it’s all over,” he added. “I’m going to keep going, again and again. And I’m going to make sure life doesn’t get in the way.”