Will Monday's solar eclipse lead to the worst traffic chaos in US history? Will visitors overrun campsites and National Parks?
It's hard to say, but one thing's for sure: the phenomenon will be the first coast-to-coast solar eclipse in the United States in 99 years.
Preparations for what is being called the "Great American Eclipse" are in full swing, including an online marketing blitz for eclipse glasses, commemorative stamps and T-shirts saying "Eclipse it!"
Astronomers and star-gazers alike are looking forward to it with great anticipation.
"This will be the most photographed, most shared, most tweeted event in human history," said University of Redlands, California astronomer Tyler Nordgren.
"This will be like Woodstock 200 times over - but across the whole country," said Alex Young, solar scientist at NASA's Goddard Space Flight Center.
Much of the excitement will be in the so-called "zone of totality" stretching from Lincoln Beach, Oregon on the west coast, to Charleston, South Carolina on the east coast.
Around 12 million people in 14 states will be in the zone, which is about 100 kilometres wide. Astronomers say it will fall into an eerie darkness lasting about two minutes as the eclipse moves across the US. Animals will become very quiet and the temperature will drop.
Observers outside that path will still see a partial solar eclipse where the moon covers part of the sun's disk. In fact, everyone in North America plus parts of South America, Africa and Europe will see at least a partial solar eclipse.
Officials in the state of Oregon in the north-western United States expect masses of solar eclipse visitors because that is where the best chances for clear skies are.
Officials in California are concerned about the eclipse's impact on the solar power industry.
"Our solar plants are going to lose over half of their ability to generate electricity during the two to two and a half hours that the eclipse will be impacting our area," Steven Greenlee, spokesperson for the California Independent System Operator told the website Vox.
Many schools in the zone of totality will either close or students and teachers will go outside to watch the event together.
Eclipse festivals are planned in many communities, including Hopkinsville, Kentucky, which is expecting 100,000 visitors for a three-day festival.
Charleston, South Carolina on the east coast will be the last place in the US to see the eclipse.
