Ray Jayawardhana is an astrophysicist and dean of science at York University in Toronto and the author, most recently, of Neutrino Hunters.
Here's how the Earth, moon and sun move during a solar eclipse. (NASA)

Surreal doesn’t begin to describe the scene. There we were, on a scorched, rubble-strewn plateau in the Altai Mountains of western Mongolia. A shaman in a colorful cloak made of yak hair paced around an impromptu rock shrine, beating a drum and chanting. A hundred or so people stood in a semicircle nearby. Groups of three took turns kneeling in front of the shaman for a blessing, which consisted of a mouthful of alcohol spit on their foreheads and a lash from a whip on their backs.

Suddenly, the wind picked up, and I felt a chill. The shaman’s assistant lit a bonfire as the sun started to wither. The shaman turned his back on the disappearing sun, while the visibly terrified crowd roared and screamed. These age-old rituals were meant to dissuade the monstrous deity Rah from gobbling up the life-sustaining sun.

We had arrived at this remote dusty outpost after a 16-hour off-road trek (with vomit stops!) that nearly killed us when our exhausted driver nodded off at the wheel, to observe a total solar eclipse on Aug. 1, 2008. The rare astronomical event made for a wondrous experience, worthy of almost risking our lives, though the spectacle on the ground was equally mesmerizing on this occasion. The dual sights of the eclipse in the sky and the rituals in the desert reminded me of the enduring links between the celestial and the human realms.

Two months from now, on Aug. 21, people across the United States, from Oregon to South Carolina, will have the opportunity to witness a total eclipse of the sun. The path of totality will sweep from the Pacific coast to the Atlantic for the first time in 99 years, prompting some to revive the moniker “the Great American Eclipse.”

For the last such event, in 1918, the U.S. Naval Observatory, with a special $3,500 grant from Congress (the equivalent of approximately $60,000 now), dispatched a scientific expedition to Baker City, Ore. Researchers planned to measure the deflection of starlight by the sun’s gravity when the sky got dark and stars became visible during totality, thus testing a key prediction of Albert Einstein’s theory of general relativity, which had been published three years earlier. It was seen as a chance for American scientists to upstage their then-dominant European counterparts, representing an intellectual coup for a nation ascendant. Such hopes were dashed, however, because thin clouds covered the sun during the critical moments, obscuring faint background stars in its vicinity. Team member Howard Russell Butler, a physicist-cum-artist, did capture the corona and prominences of a moon-blocked sun in a historic painting.

Stunning vindication of Einstein’s theory came a year later, from English scientists who traveled to the island of Principe, off the west coast of Africa, and to Brazil for the next total solar eclipse.

This summer, the stakes are much lower, though a number of researchers aim to conduct studies of the sun and the Earth with support from NASA and the National Science Foundation. Besides, with dazzling images of intricate nebulae from Hubble and splendid portraits of ringed Saturn from Cassini popping up on our screens nearly every week, we have become quite blasé about celestial sights. Compared to those color-enhanced visuals, our glimpses of astronomical objects with the naked eye, or through binoculars or a backyard telescope, tend to leave us feeling underwhelmed.

A total eclipse of the sun is different. No photograph can do it justice, in my opinion, because it is a truly immersive experience. Seeing a partial eclipse doesn’t prepare you for the real McCoy, either.

To appreciate the phenomenon fully, you need to see (safely) the fleeting spectacle of the sun gone dark behind the passing moon, while a few bright stars appear in daytime. You need to hear the birds rushing to their nests, confused by the fading light. And you need to feel the chill in the air as an eerie darkness engulfs the land.

Luckily, the Aug. 21 eclipse will be among the most accessible in recent history. Some 10 million Americans live along its arc of totality, and tens of millions more could reach it within a few hours’ drive from home.

Even in this age of Instagram and live-streaming, it is worth making the effort to experience a total solar eclipse in person, in all its splendor. Totality will last just a couple of minutes, but it is one heavenly sight that you’re likely to remember for a lifetime.