The sun and moon will perfectly align during the total solar eclipse on April 8 to cast a narrow shadow of darkness on Earth in the middle of the day, a surreal event that has renewed debunked conspiracy theories that clash with a proven scientific explanation.

Experts say it's another example of how easily anti-science conspiracy theories can spread.

“I’m already seeing it more and more as we get closer to the April 8 eclipse,” said Jeffrey Blevins, a professor of journalism at the University of Cincinnati, who studies social media and disinformation.

Blevins is among the experts who say the debunked "flat Earth" conspiracy theory doesn't slow down when an eclipse happens – even though the event is precisely explained because of scientists' deep understanding of celestial bodies and their orbits.

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There are a whole spectrum of conspiracy theories, some harmless or thoughtful, others are based on a wholesale rejection of science and still others are promoted for financial or political gain. Thinking the Earth is flat is generally considered a more concerning conspiracy theory because it feeds into paranoia and leads people to an unhealthy skepticism of all science and credible authorities, said Blevins.

“They’re not just primed to believe the Earth is flat, they’re primed to believe you can’t trust science, academics, the media or government,” he said. “And it might also lead you to see other extremist views as plausible.”

What do flat Earthers believe?

In general, most Flat Earthers believe the Earth is a flat, hockey puck-like object covered by a dome, sometimes called a firmament, with walls of ice around the edges of the dome. They believe they can prove this because the seas appear level, not curved, and say it is not possible to view the curvature of the horizon from airplanes.

They also dispute photographic evidence from space, saying it cannot be trusted and that the NASA moon landing was a hoax.

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Doesn't a solar eclipse prove the Earth is round?

Flat Earth supporters don't see it that way, although they offer no unified alternative theory. In general, flat Earth believers think the sun and the moon glide above the ground at a much closer distance than astronomers have measured.

Total eclipse explained in graphicsWhat is a solar eclipse?

During the last U.S. total solar eclipse, news site Mic.com cataloged numerous flat Earth objections to the scientific understanding of the eclipse, including the size of the shadow cast. More recently, a YouTube video promoting flat Earth ideas suggested the sun and moon are a similar size.

But scientists have a comprehensive understanding of how total solar eclipses occur. They happen when three spheres — the sun, moon, and Earth — line up in a specific way in space.

According to NASA, a solar eclipse happens when the moon passes between the sun and Earth. That alignment casts a moving shadow on Earth that either fully or partially blocks the sun's light in some areas. This leads to a period of partial or full darkness on a narrow stretch of Earth. 

The path is so narrow because of the huge distance and size of the sun — as well as the moon's distance from Earth. That focuses the moon's shadow on an area of land much smaller than the moon itself. The movement of the shadow across the land happens as the Earth's rotation interacts with the orbit of the moon.

A total eclipse only happens occasionally, because the moon doesn't orbit in the exact same plane as the sun and Earth do. In addition, a solar eclipse can only happen during a new moon.

There are multiple videos and explanations online covering what happens in a solar eclipse. NASA will also live stream the total solar eclipse on April 8.

Fact check roundup:Debunking the flawed science behind flat Earth claims

When did people learn the Earth is round?

There's another, different, flat Earth error out in the world. This common mistake, popularized in the 19th century, suggested that prior to the rise of scientific study beginning in the 17th century, most people believed the Earth to be flat.

In fact, the ancient Greeks figured out the Earth was round around 500 B.C. and it’s been commonly accepted by scholars, navigators and cartographers ever since.

The flat Earth belief as a kind of conspiracy theory popped up again in the mid-1800s in England. The Flat Earth Society was founded in 1956.

"It certainly is one of the oldest conspiracy theories," said Blevins.

Flat Earthers had something of a renaissance beginning in the 2010s.

"That’s when social media really started to grow in popularity when you had 4chan and subreddits. You could find all sorts of wacky stuff out there and it had a chance to reach a larger and larger audience," he said.

Why do people believe in conspiracy theories?

There are three general reasons, says Karen Douglas, a professor of social psychology who researches conspiracy theories at the University of Kent in the United Kingdom.

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The first is a desire to know the truth and have clarity and certainty. The second is the need to feel safe and to have some control over things happening around us. Finally there is the social need to maintain self-esteem and feel positive about the groups we belong to.

“Anyone can fall into conspiracy theories if they have psychological needs that are not being met at any particular time,” she said.

During times of social change and uncertainty, conspiracy theories can be especially appealing.

“This is perhaps one explanation why we tend to see a lot of conspiracy theories when things happen like sudden deaths of celebrities, or during pandemics,” said Douglas. “A simple explanation is often not very appealing for such a significant event. People assume that a big event must also have a big or more sinister cause.”

Contributing: Doyle Rice, USA TODAY