Call it eclipse economics.
When a large swath of America is bathed in midday darkness for a couple of minutes on Aug. 21, hundreds of cities in the path of the eclipse are hoping it will be a once-in-a-generation boost to local economies.
Or it could be a dud, and a costly one at that. Planners admit they are basically in the dark about how much the eclipse might help or hurt.
While much of the continental United States will enjoy at least partial darkness on eclipse day, only a 70-mile-wide strip will be in the critical "zone of totality," where the blackout will be complete. Coast to coast, cities in the zone are bracing for a huge influx of visitors.
In Casper, Wyoming, construction workers are racing to complete a new town square that will be the centerpiece of a weeklong eclipse festival.
In Hopkinsville, Kentucky, which city planners have dubbed "Eclipseville," they have rebuilt sidewalks and repainted the town clock. Meanwhile, in Columbia, Missouri, University of Missouri astronomy professor Angela Speck warns that the state's collection of portable toilets will have to be moved into town from the state fairgrounds 70 miles away. The fair ends the night before the eclipse.
About 12 million Americans already live in the zone, but many more can easily commute to an eclipse-friendly locale. Some 88 million Americans live within 200 miles, according to GreatAmericanEclipse.com, and virtually all of the lower 48 is within a long day's drive. They're all going to need to eat, and perhaps sleep somewhere, not to mention they'll need to buy eclipse-ready glasses and T-shirts.
"As a city we've invested $500,000 on improvements," said Brooke Jung, solar eclipse coordinator for Hopkinsville. The town of 30,000, which is ideally situated in the path of darkness, expects between 50,000 and 100,000 visitors. "We estimate the economic impact will be $30 million."
They're going big in Wyoming, too, where the state expects the population to double. In Casper, the new downtown plaza will cost $8.5 million. That's a big bet, but the city was told by consultants last fall that eclipse chasers can spend up to $5,000 each. The square had been planned anyway, and the solar event just provided an excuse to close the deal, officials say.
America's Eclipse '17 is a little different, however.
Generally, chasers have to go to some trouble to get in the path of darkness. This time, for millions of people, there's an exit for the eclipse on the interstate.
"Being one of the most accessible eclipses in history will result in the percentage of eclipse chasers being very low compared to 'first timers' or your average Joe," said Anna Wilcox, Casper's executive director of the city's eclipse festival. "The overall economic impact has been questioned quite a bit over the last month."
Source: U.S. Energy Information Agency
In one sense, the eclipse couldn't come at a better time. It's in summer. It's even on a Monday, creating a three-day weekend.
But Mary Eschelbach Hansen, a professor of economics at American University, worries that many towns are being overly optimistic about the windfall. For starters, the summer weekend effect means it might just shift some money around that was already being spent by travelers, rather than create new economic activity, she said.
More important, since many towns don't have hotel capacity for such a huge influx of visitors, many eclipse watchers will come and go, leaving very few dollars behind.
"What we know from tourism research is that if there's no place for people to stay overnight, (tourists) don't leave that much money there. There's no real benefit," she said.
Plenty of other capricious factors — like rain that sends visitors scurrying to another part of the state — could turn eclipse day into a dud. That could really hurt small towns that are already spending extra money on police, emergency services, cleanup crews and all those portable toilets.
But one thing could hurt more: An eclipse party that exceeds expectations. That's what has kept Speck up at night for months.
"I'm trying to help communities understand the potential here. We fully expect to double population in the path. Some towns are going to be really struggling with these numbers," said Speck, who is also co-chair of an American Astronomical Society task force on eclipse preparedness.
There might be gas shortages. Supermarkets could run out of food. More crucially, emergency services could be overrun. If it's hot out, towns might not have enough cooling stations.
Geography will play a big role. As one example, Speck points to a spot just north of Kansas City where the zone passes over Interstate 35.
"This is the closest point for 12.5 million people," she says. If even a small fraction decide on eclipse morning to take a ride, the situation could get out of control very quickly.
Hansen warns that if a town experiences some kind of high-profile embarrassment — visitors get sick and can't get care, or there's abandoned cars and long traffic lines — that could ruin all the hard chamber of commerce work.
"A PR nightmare could undo everything," she said.
So towns should worry less about cashing in and more about studying up, she thinks. The main benefit for a town in the zone is a chance to gather research on big events. For example: Should a town build a soccer facility so it can host tournaments?
"It's a natural experiment in tourism economics," she said.
Back in Hopkinsville, Jung is pretty certain her town is ready. They're taking reservations for viewing areas where street lights will be turned off, which gives planners some clues on crowd sizes. But she concedes folks don't quite know what to expect when the spiffed-up town clock shows 11:56 a.m. on Aug. 21.
"We are kind of writing the playbook as we go along," she said.