On Aug. 21, a narrow, 70-mile wide swath of the United States from Oregon to South Carolina will be the stage for one of the most (if not the most) spectacular celestial events, a total eclipse of the sun.

Space.com has put together a nice informational guide, including a video and a map explaining where to go, what to expect, and how to watch it safely. This is the first total solar eclipse in America in almost 40 years. The next one in the U.S. will be on April 8, 2024.

If you've never witnessed a total solar eclipse, this is an experience not to be missed. There's something deeply moving about watching the sun become progressively covered by the moon until, at totality, the sky goes dark, and a blast of light from the corona surrounds the black disk of the moon. If the skies are clear, you can see Mercury, Venus and stars shining, as day turns to night for a brief few minutes and the temperature drops.

And to think that total solar eclipses happen only due to a remarkable cosmic accident, as the relative sizes of the sun and moon stand roughly in the same proportion in their distances to the Earth. That they don't occur at every new moon — when the moon is between the sun and the Earth — is due to several factors, from the tilting of the moon's orbit by 5 degrees to its shape being elliptical and not circular. Roughly, we can expect one or two total solar eclipses a year somewhere on Earth.

Totality only occurs for a few minutes, and its time varies from place to place and from eclipse to eclipse. The maximum time of totality for this eclipse will be 2 minutes and 40 seconds around Southern Illinois and its surrounding areas. In May, I was at Southern Illinois University's graduation ceremony in Carbondale — and I can attest that the locals are eager to receive the expected throngs of out-of-towners. A local winery (yes, there are wineries in Southern Illinois) has its own eclipse wine label and glasses.

For those interested in the history, mythology and astronomical details, there are many books to answer your questions. Sun Moon Earth: The History of Solar Eclipses from Omens of Doom to Einstein and Exoplanets, by astronomer Tyler Nordgren, is a highly readable account from myth to science, including how eclipses have been used to prove theories from antiquity to Albert Einstein's theory of relativity. My own The Prophet and the Astronomer: Apocalyptic Science and the End of the World explores how religious and scientific accounts of the end of the world are interwoven throughout the past millennia. In many cultures, including in Christian eschatology, the temporary disappearance of the sun signaled the upcoming end of times. A disruption of the heavenly order was taken as a message for people to prepare for the worst. If the sun could disappear for a few minutes, why not forever?

Big Kid Science, an educational company founded by astrophysicist Jeffrey Bennett, has created Totality, a free app to help people plan for the eclipse. San Francisco's Exploratorium also has its own app, beautifully put together and with a few extras that include a during-eclipse performance by the Kronos Quartet. There is even a book in braille explaining the details of the eclipse to the visually impaired, a NASA-funded project by College of Charleston's geology professor Cassandra Runyon and Edinboro University's David Hurd. With the NASA funding, 5,000 free copies of the book are being distributed in schools, libraries and museums, in the hope that this will attract the blind and visually impaired to science and help them share and enjoy this grand event.

Bill Nye — The Science Guy and president of the Planetary Society — will be at the Homestead National Monument of America promoting a series of events, many involving children.

The eclipse is an opportunity to lift our heads away from the many screens that dominate our lives and focus on the grandest screen of all — the one above our heads.

The most authoritative and engaging of the many books out there on the history, lore and magnificence of total solar eclipses is Anthony Aveni's In the Shadow of the Moon: The Science, Magic, and Mystery of Solar Eclipses. Aveni, who has appointments both in the physics and astronomy and the anthropology departments at Colgate University, is one of the pioneers of archeoastronomy, the study of astronomical knowledge from ancient cultures. Remember the supposed end of times "predicted" by the Mayan calendar for 2012? Aveni was the one who explained how such fears were foolish in his book The End of Time: The Maya Mystery of 2012. During the fall, he will be a visiting fellow at Dartmouth's Institute for Cross-Disciplinary Engagement, an institute devoted to bringing the sciences and the humanities into constructive dialogue, a perfect theme for eclipses, given their many overlapping humanistic and scientific aspects.

I watched my first partial eclipse when I was 7, growing up in Rio, and was lucky to witness two total ones later on in life, including the last one of the past millennium, on Aug. 11, 1999, aboard a ship in the Mediterranean. (It was one of those educational cruises and I was lecturing.) This is how I described it:

"A diamond ring exploded around the dark disk of the Moon, its intense light etching its patterns onto our memories forever. I looked around; the sky had turned into a majestic metallic blue, and two dots of light were barely visible around the darkened Sun: Venus and elusive Mercury. We had a 360-degree view of the horizon, which turned into a pink band, as if the sunset was coming from all points in space at once...I was invaded by a completely irrational reverence for what was happening; there was no room for the steady eye of reason now.

There was the eye of God again, staring at us down below. To the Persians, the Sun was the eye of Ormuzd; to the Hindus, the eye of Varuna. To the Ancient Greeks, it was the eye of Zeus; to the early Teutons, the eye of Wodan (or Odin). I was invaded by a soft sense of terror, at once primal and sublime, as the silver-blue darkness engulfed us all, a light from the world beyond, a light from death. Here I was, 33 years later staring at eternity. A total solar eclipse is a deeply subjective experience, each person's reaction no doubt a mirror of what he or she carries inside...The event's primal energy epitomizes the archetypal struggle between good and evil, light and darkness."

Certainly, many eclipse viewers stick only to the scientific narrative and compare notes and photos of their experiences. But even with (or actually due to) my scientific training, I find it a rare and powerful chance to look at nature from a cross-cultural perspective that links, in unique ways, the rational and the visceral. If you've never witnessed one, make sure you try.

Marcelo Gleiser is a theoretical physicist and writer — and a professor of natural philosophy, physics and astronomy at Dartmouth College. He is the director of the Institute for Cross-Disciplinary Engagement at Dartmouth, co-founder of 13.7 and an active promoter of science to the general public. His latest book is The Simple Beauty of the Unexpected: A Natural Philosopher's Quest for Trout and the Meaning of Everything. You can keep up with Marcelo on Facebook and Twitter: @mgleiser

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