RACHEL MARTIN, HOST:
On August 21, millions of people in 14 states across the country will be able to see a total solar eclipse. That's when the moon slips in front of the sun and blocks its light, creating an eerie, daytime twilight. This will be a once-in-a-lifetime thing for most of us. And then there are the folks who chase the eclipse experience all over the world. Here's NPR's Nell Greenfieldboyce.
NELL GREENFIELDBOYCE, BYLINE: To see the upcoming eclipse, all Don Liebenberg will have to do is open his front door and step outside.
DON LIEBENBERG: It's a really special treat to be able to have one in my driveway.
GREENFIELDBOYCE: In the past, he's had to trek out to places like Turkey, Zambia, China or Pukapuka, a remote island in the Pacific. How many total solar eclipses has he seen?
LIEBENBERG: Twenty-six so far.
GREENFIELDBOYCE: Liebenberg is an adjunct professor of astronomy at Clemson University in South Carolina. He's been studying eclipses since 1954. He says the complete masking of the sun by the moon known as totality is normally a brief event when you see it from one spot on Earth.
LIEBENBERG: The longest eclipse time on the ground is just shy of eight minutes.
GREENFIELDBOYCE: He has always wanted more. That's why Liebenberg helped pioneer the use of airplanes to move along with the shadow of the moon as it swept over the landscape. In 1973, French officials even let him do this in the brand-new Concorde. It's streaked across North Africa to keep up with the moon's shadow.
LIEBENBERG: Now, remember; this plane is going at Mach 2 or more than a thousand miles an hour. And the eclipse is going a thousand miles an hour.
GREENFIELDBOYCE: Was it scary?
LIEBENBERG: Not at all. It was beautiful.
GREENFIELDBOYCE: His view of this eclipse lasted an astonishing 74 minutes. That's one reason why Liebenberg currently holds the world record for the most time spent in totality. No one else is even close. And believe me. Some people keep track of records like this. They're called shadow lovers or umbraphiles. Glenn Schneider is an astronomer at the University of Arizona. He freely admits that he is an eclipse junkie.
GLENN SCHNEIDER: Yeah, people talk about eclipse addiction. And I guess I'm probably up there on the top of eclipse addicts.
GREENFIELDBOYCE: He's been to 33. Don't ask him to pick a favorite.
SCHNEIDER: I don't have a ranking. Any one of them is one of the top events in my life. It's sort of the one that I'm seeing at the moment is the best one.
GREENFIELDBOYCE: The story of how he got hooked is pretty typical. It starts with the unexpected impact of the first. As one eclipse chaser told me, your first time is always special. For Schneider, that came in 1970 when an eclipse was visible from the East Coast. He was a teenage amateur astronomer who eagerly planned out how to spend the few minutes of totality.
SCHNEIDER: I had a number of telescopes and binoculars and cameras and things all set up. And I practiced and rehearsed for months on end.
GREENFIELDBOYCE: All of that was forgotten the moment the sun blinked out.
SCHNEIDER: Staring up at that hole in the sky, I just froze. I couldn't move. It was just such an - literally awe-inspiring moment.
GREENFIELDBOYCE: He says you may intellectually understand the workings of our solar system and the vastness of time and space. But a total solar eclipse makes you feel it.
SCHNEIDER: With the darkening of the sky, the movement of the moon's shadow and you sort of at the bullseye of the confluence of where this is happening, it really is overwhelming.
GREENFIELDBOYCE: Now, there's a total solar eclipse every 18 months on average. Schneider still laments the one eclipse he didn't manage to get to. It was in 1985 in a remote, inaccessible part of Antarctica.
SCHNEIDER: That's the one that escaped - terrible thing, total solar eclipse. Nobody could see it.
GREENFIELDBOYCE: You know what else can keep you from seeing an eclipse - clouds. One lonely, little cloud wandering in at the wrong time can ruin everything. So it's not surprising that clouds never drift far from the minds of eclipse chasers. They consult historical weather charts and make contingency plans. Fred Espenak is a retired astrophysicist who's been called Mr. Eclipse. He's been to 27. And in the days leading up to this one, he'll be in Casper, Wyo.
FRED ESPENAK: If the forecast is bad for Casper, I'll be ready to travel a thousand miles east or west to get to a better location.
GREENFIELDBOYCE: What's a thousand miles to a guy who once spent 26 days on a Russian icebreaker to see an eclipse? He says his fellow eclipse chasers often bump into each other in airports in Istanbul or Beijing.
ESPENAK: We all tend to be science geeks, a good number of us.
GREENFIELDBOYCE: This next eclipse will be seen by millions of Americans, not all science geeks of course. But Espenak says it's the most beautiful, natural phenomenon anyone can experience.
ESPENAK: I have seen people witnessing their first eclipses. And after totality, they are down on their knees, weeping. (Laughter) It's just an incredibly moving event.
GREENFIELDBOYCE: So moving that somebody, maybe even you, will be instantly transformed into an umbraphile. Nell Greenfieldboyce, NPR News.
(SOUNDBITE OF THE ECHELON EFFECT'S "SIGNALS")