On Aug. 21, a natural spectacle will sweep across the continental United States.

Astronomers and skywatchers are tuning up their telescopes to witness a total solar eclipse that will occur for several hours in states from the Southeast and pass across the Mountain West, and then proceed to the Pacific Northwest.

Neighboring states, on the other hand, will get a partial eclipse with varying duration and degrees, which will depend on their arc length from the path of the phenomenon.

Total Eclipse: Details And Explanations

The eclipse is deemed the first incidence of totality in the 48 states since Feb. 26, 1979. It will also be the first total eclipse in the central United States since June 8, 1918.

When the moon passes in front of the sun on that day, it will result in a long shadow across the planetary surface. As the moon moves in its orbit, the shadow will run from the west to the east coast, the opposite path that the moon typically takes.

“It is actually something even astronomers struggle to see,” said heliophysicist C. Alex Young in a Washington Post report, noting that at a recent scientific gathering, a bunch of astronomers ended up gathering and trying to explain it.

It’s a perspective-shifting phenomenon, as we are taught that Earth and everything else in space are in motion. The moon seems to rise in the east since that’s the way our planet spins, not because it’s circling around the planet from east to west. Meanwhile, it actually revolves – at twice the speed – in the same direction Earth spins.

The moon travels eastward at about 2,100 miles per hour, while Earth spins at a slow 1,040 mph. The path of the moon’s shadow will, therefore, track eastward across the planet’s surface at about 1,060 mph, or its speed minus Earth’s.

But does the moon do anything different during an eclipse? No, except it will display its movement in its own orbit and not as the consequence of Earth’s rotation.

Experiencing The Eclipse

For those who are wondering where to get the best eclipse views or how it will look like from one’s patio, UC Berkeley and Google collaborated to produce a simulator.

The two groups came up with the idea of producing a 90-minute video of the eclipse, dubbed the Eclipse Megamovie Project, to be accomplished by piecing together the time-stamped images captured by ordinary people.

With the simulator, users enter their ZIP code or town/city name in order to see an animation of how the sun will move across the sky over three hours. This is accelerated 1,000 or 4,000 times, and will also show how much of a bite will be taken out of the sun by the moon in eclipse.

Those within the path of totality will have the privilege of seeing the sky creepily darkening.

“Our simulation is closer to what one might experience in a planetarium show,” said Dan Zevin of the team leading the project.

The project will also reveal a map of where one lives relative to the path of totality, which will cover 11 states in a band reaching up to 72 miles wide. Getting inside this path, UC Berkeley noted in a statement, is key to fully experiencing a total solar eclipse.