Even if only a fraction of the outsiders decide to see the eclipse, their travel could have outsized effects. “Only 4 percent of the population of the U.S. has to travel to the path of totality to double the population there,” said Angela Speck, a professor of astronomy at the University of Missouri. That kind of population spike would probably barely be noticeable if eclipse seekers were to spread evenly across the path. But where you are on the path matters — the closer you get to the central strip of that ribbon of land, the longer the sky show will be. It’s the difference between a few seconds of darkness at the edge of the path and a full two minutes at its center. Because visitors get the longest show on the path’s centerline, they’re likely to converge on the towns there.