Los Angeles ? When the moon blots out the sun’s blinding rays today, a sliver of the Earth’s surface will be plunged into eerie darkness.

Travelers who have crossed thousands of miles to witness the celestial show will gaze at the sky and, for a few minutes, see a thing most people never get to see: a halo of fire — the sun’s corona — flickering around the edges of the silhouette of the moon.

But Jay Pasachoff, over on Easter Island, may be looking down more than up — calibrating his instruments, checking for technical glitches, peering through lenses. He doesn’t need to look up. He’s seen 28 total eclipses, and 50 eclipses in all.

The Williams College astronomy professor saw his first total eclipse at age 16, when he was a freshman at Harvard. Flying with classmates above the cloud line in a DC-3 just north of Boston in October 1959, he gazed at the spectacle through the double-pane airplane window. “I could see it low in the sky, see it straight out — and it was wonderful,” he said.

He fell in love.

He’s looked up the details on eclipses set to occur in upcoming decades. He has a list of them out to the year 3000.

To some, such single-mindedness might be considered extreme. Not to Tom Thornbury, 68, of Los Angeles, who’s racked up seven total eclipses so far. He recalls dolphins doing back flips in the Sea of Cortez during his first, in 1991. Six years later, as the corona glowed above Mongolia, he proposed to his now wife.

Nor to Alex Filippenko, a University of California, Berkeley, astronomer who’s seen 10 total eclipses and is awaiting his 11th on the cruise ship Paul Gauguin, in waters southeast of Tahiti.

“The first is in some ways the best. Most people I’ve met become transformed by the experience,” Filippenko said. (Eclipses aren’t a big slice of his day job; quasars and black holes are more his thing.)

If they don’t feel the wonder, he added, “I think they’re brain-dead.”

Some eclipse chasers describe the feeling they get during totality — those moments when the sun is fully covered — as spiritual, others as a high. The self-described “coronaphiles” often form tight networks and eagerly log the minutes spent in totality at websites such as eclipse-chasers.com.

“A lot of people say it’s as good as sex. Well, it’s right up there. It’s close,” Thornbury said. “It makes you realize how extraordinary this universe in which we live actually is.”

Solar eclipses are the result of a mathematical coincidence: The sun’s diameter is roughly 400 times that of the moon’s, but it’s also roughly 400 times as far away. So when sun and moon line up right — as they do roughly every 18 months along a given path over Earth — the moon almost perfectly covers the sun.

Each total eclipse is unique, aficionados say, because so many factors are at play. The corona can appear sparser at some times and more dynamic at others, depending on where the sun is in its 11-year sun spot cycle. Bad weather might obscure the sun at given points. And the length of each totality will vary — as will the path along which totality can be seen.

Anywhere outside that narrow path, the sun will peek over the moon’s edge, destroying the effect. That’s why eclipse chasers often must travel to some of the world’s most remote lands — and even its seas, as with today’s eclipse. For this event, the path of totality will cross eastward through the South Pacific, making landfall only at the Cook Islands and Easter Island until it reaches the tip of South America.

‘Triumph of science’

Eclipses have long been a way of life for the Pasachoff family — Pasachoff’s wife, Naomi, also works at Williams College, and their daughters Deborah and Eloise often accompanied them on eclipse expeditions as children. Even when Pasachoff went solo, the family was standing by at home, on call.

“There’s always eclipse errands. It’s a very drama-filled lifestyle,” said Deborah Pasachoff, who has observed eight total eclipses, the first when she was an infant.

In many ancient mythologies, eclipses were seen as a bad omen, said Isaac Kikawada of Mountain View, Calif., a retired professor of Babylonian studies at UC Berkeley who got hooked after viewing his first total eclipse in 2001 and who takes amateur photos of the spectacles. (He is on Easter Island with his wife, Heidi Gerster.) Even now, people in some parts of the world act strangely when confronted by eclipses, beating on pots and pans, for example, or sacrificing chickens.

“Until modern times, an eclipse was something to be feared. … Now we can predict exactly to the second where it happens,” Kikawada said. “I celebrate this triumph of science.”