Editor's Note: (For complete coverage of the Eclipse of the Century go to cnn.com/eclipse. Watch live, in virtual reality, as the eclipse moves coast to coast on August 21st.)
(CNN) They travel the world, but their focus is never on a destination. They're obsessed with one type of experience, but they're not addicts. They sometimes wager their finances, safety and time on one specific outcome, but they're not gamblers. They're eclipse chasers, and on August 21, they have the chance to show millions of Americans why their passion is worth the sacrifice.
"It's a really fantastic time for us, because everybody is focused on this thing we love," said David Makepeace, an eclipse-chasing filmmaker. His website, eclipseguy.com, features numerous videos from his adventures tracking down these events. "It's the most spectacular natural event that you can witness from Earth."
On August 21, the moon will block part of the sun in every place in the United States. Within a narrow band from Oregon to South Carolina, there will be a total solar eclipse. It's been 99 years since a total solar eclipse crossed the country in this manner.
To the average person, an eclipse may sound like just another weird science event that might be cool to see if it isn't too inconvenient. But for those who've been under the shadow of the moon, it's a life-altering experience.
"The awe that we experience is just huge. You just can't convey how stunningly beautiful it is to see where you are looking, where the sun should be, and there's just a hole in the sky, and it just blows your mind," said author, psychologist and eclipse chaser Kate Russo.
Amateur astronomer Bill Kramer has seen 16 total eclipses. "You can't put words to it. You stepped into a surreal painting. You know, for two minutes or so, the world has gone weird. It's a weird-looking thing. It looks like an eyeball staring back at you, almost. And you can see very easily how ancients would have just fell over themselves and gone, 'God is looking at me! I better be cool.' "
Fred Espenak, scientist emeritus at NASA's Goddard Space Flight Center who is known as Mr. Eclipse, pushes the concept a little further.
"I've seen people praying after an eclipse. I've seen a lot of people on their knees weeping after an eclipse. It is an emotional experience to see this event. For me, I get a great sense of our place in the solar system, in the universe. You realize how tiny we really are and how insignificant some of our day-to-day problems and arguments and jealousies and petty fighting really are in the scheme of things."
Most eclipse chasers want non-umbraphiles ("shadow lovers") to know that a total eclipse is a completely different experience from the more common partial eclipse.
"There's definitely a difference," said Paul. D. Maley, an expedition coordinator for NASA's Johnson Space Center Astronomical Society who has witnessed 24 total eclipses.
"A partial eclipse is like no eclipse at all. I mean, if you went outside and the moon partially covered the sun and it didn't get dark and nothing happened around you that was any different, you probably would think, 'Oh, this was a nothing burger,' so to speak. You know, it just has no effect."
Makepeace, who has seen 16 total eclipses, added, "So you sort of get that little scale of diminishing grandness. There's no fireworks like there is with a total eclipse. So we'll go to the ends of the Earth for that."
These astronomical events are so powerful for those who see them that most can easily recall the first time they witnessed a total eclipse.
Decades after his first event, Glenn Schneider, an astronomer at the University of Arizona's Steward Observatory, can still describe exactly how he felt as the shadow of the moon passed over him.
"Once I saw it, I instantly became hooked. It was not so much from a scientific perspective but an aesthetic perspective. One that just really overwhelmed me, and it turned me into an eclipse chaser."
Russo says the first one is always the most intense.
"It blows you away," she said. "I knew that the moon was going to move in front of the sun, that it would be blocked out, that we would be in the shadow, that it would get dark, so I knew all those things were going to happen. But, oh, my God, when it happens to you, you have no idea. I think it's just so different to what you know about the world. And so you just cannot imagine how this is going to be."
The hook is instantaneous for eclipse chasers. And though every experience is different, they all share one thought: When can I see the next one?
"I've seen 16 of these things, and I'm still not done looking at it," said Kramer, the amateur astronomer. "Each time, you notice more details. Each time, you see more of the actual event."
"It's like the best ride that you have ever been on," filmmaker Makepeace added.
This quest for the next eclipse fix propels them into a journey without end.
"Seeing something that you really love for only 60 minutes, spread over an entire lifetime, is not a very large piece of time. So it's the rareness of the eclipse and the beauty of it each time," Espenak, the astrophysicist, said.
"It might be called OCD or something like that, from a scientific perspective," NASA's Maley said. "But in fact, it's just something remarkable, because it doesn't last very long. It's really amazing to see visually. And you just want to keep looking at it over and over again."
The problem with eclipse chasing is that the events occur for a finite amount of time in sometimes difficult locations. As a result, the journey usually involves overcoming frustrating hurdles.
"The sad fact is, most eclipses don't occur close to home like (the one in August), so you can't drive to them. It requires being willing to do some international traveling, and you got to be OK with that," Espenak said. "It's not something you can do on a shoestring, usually."
Unfortunately, as Steward Observatory's Schneider explains, not every eclipse trip rewards the cost involved.
"In 1977, it was sort of the expedition where everything that could go wrong did, including vehicles breaking down, rainstorms that resulted in mud making other vehicles that were replacements unusable because roads became unpassable, one of the guys we were traveling with getting bitten by a bat and having to undergo rabies treatment, and being clouded out" from seeing the eclipse.
Despite the many difficulties that a chaser may endure, these world travelers really fear only one thing: clouds blocking their view.
"Cloud-outs are traumatic events," Schneider said of his specific star-crossed trip. "If we would have seen the total eclipse, everything else would have just vanished into insignificance."
But the endless quest for the moon's next shadow offers more rewards than just a unique view of our local solar system.
"Eclipse chasing has really delivered some of the most spectacular adventures I could have ever imagined," Makepeace said.
"If you love nature and you love to travel, chances are you will become an eclipse chaser," Russo said. "Just combine your holidays with a total eclipse, and it enriches your life in so, so many ways."
The experience becomes a bonding one in which people from all over the world and from all walks of life come together.
"Eclipse chasers are worldwide, you know. There's people from Japan, from China, from Israel, from England, from Russia. I mean, all over the world, basically," Maley said. "It's a small community, yet it's sort of a big one."
Makepeace agreed: "We come from all walks of life, every country, every continent. It doesn't matter what your rank and file job is or how you were educated or where you came from. There's this certain type of personality that sees this incredible vision in the sky and it really, it means something to us. It's an incredible part of our lives, and then the need to chase, the need to have that experience again, the need to get back on that ride and experience the solar system in a way that you only can during a total eclipse of the sun, becomes paramount in our lives."
It's for this reason that eclipse chasers are excited to share their passion and to see how many new followers join their ranks after this year's total eclipse on August 21.
Normally, eclipse chasers are in the middle of the desert, flying over the ocean or on another continent, Makepeace said. This time, he and his friends will take an RV trip through the mountains.
"While it may not change everyone's life, it will be one of the most memorable things in their life without question," Schneider said.
Kramer agrees, but he shares a piece of advice for anyone caught within the path of the shadow of the moon, "Don't overburden yourself overthinking what you are about to see. Enjoy it. Take it in, just like a sunset."