In almost exactly one year, Americans will have the opportunity to experience the first total eclipse of the sun in nearly four decades. 

On Aug. 21, 2017, the "Great American Total Solar Eclipse" will mesmerize Americans across a 70-mile path from coast to coast, including states from Oregon to South Carolina.

According to astronomer Jay Passachoff of Williams College in Massachusetts, people lucky enough to be in the path of the total eclipse are in for a unique and unforgettable experience. 

"It's a tremendous opportunity," Pasachoff told Space.com. "It's a chance to see the universe change around you."

First Total Eclipse in Four Decades

The last time a total solar eclipse darkened the U.S. mainland was on Feb. 26, 1979.

What makes next year's eclipse even more unique is that it will be the first total eclipse that will be "readily available to people from coast to coast," Pasachoff said.

That path goes from the Oregon coast through Idaho, Wyoming, Nebraska, Kansas, Missouri, Illinois, Kentucky, Tennessee, Georgia, North Carolina and South Carolina.

Space.com's columnist Joe Rao notes that 12 million people or so live within the narrow viewing band, but there are another 220 million who reside within a day's drive of it.

(PHOTOS: The Total Solar Eclipse)

Pasachoff said the event is so unique and memorable that he advises people to make the journey to the narrow path and experience this amazing celestial event.

"Though the rest of the continental U.S. will have at least a 55 percent partial eclipse, it won’t ever get dark there, and eye-protection filters would have to be used at all times even to know that the eclipse is happening. The dramatic effects occur only for those in the path of totality," Pasachoff said in a statement.

"If you are in that path of totality, you are seeing the main event, but if you are off to the side — even where the sun is 99 percent covered by the moon — it is like going up to the ticket booth of a baseball or football stadium but not going inside," he added.

How to Watch Safely

According to exporatorium.edu, no one should ever view the sun with the naked eye or by looking through optical devices such as binoculars or telescopes. 

One of the best ways to view an eclipse is with a pinhole camera. NASA's Jet Propulsion Laboratory has a great explanation on how to make one here. 

(MORE: 'Great American Eclipse' Expected to Treat U.S. to Amazing Views in 2017)

Exploratorium.edu also has some other great ideas on how to safely view the eclipse on its website.

For more precise details on the path and where to best watch the eclipse state by state, check out eclipse2017.org's website.

MORE ON WEATHER.COM: Solar Eclipse, May 10, 2013