Fact check: Ample evidence the Earth is round and rotating, contrary to persistent social media claims

Eleanor McCrary, USA TODAY
·5 min read
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The claim: Earth isn't curved and doesn't rotate

Humans discovered the curvature and rotation of the Earth thousands of years ago, dating back to ancient Greece. Since then, scientists have only discovered more evidence to prove this is true – including seeing Earth itself from space.

But flat earth claims continue to circulate online.

"No one's seen the Earth's supposed curvature and no one has experienced the Earth's supposed rotation. BECAUSE THEY DON'T EXIST," reads a June 1 Instagram post.

This argument is used frequently in the flat Earth community, with similar claims garnering hundreds and thousands of social media interactions.

But the claim is incorrect.

People have both seen Earth's curvature and experienced Earth's rotation, experts say.

The poster could not be reached for comment.

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Rotation isn't felt because speed is constant

Most scientists estimate the Earth to be rotating around 1,000 miles per hour on its axis.

Proof of this includes the Coriolis force. This force explains why planes cannot simply travel in a straight line to their destination, but instead must fly along a curved route. Because the Earth rotates so rapidly, flying in a straight line would result in the plane ending up in the wrong location. The Earth is always moving, so pilots must account for how much their destination will have rotated since the start of the flight.

This effect also impacts hurricanes, which swirl counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere, said Jason Steffen, a mathematician and physicist at the University of Nevada. If the Earth were on a flat plane, this mirroring across the equator would not occur, he said. The rotation around the Earth's access and the subsequent Coriolis forces cause these differences to occur.

The post claims the fact that this motion can't be felt by humans is evidence that the Earth is not moving. But several scientists explained the motion can't be felt because the Earth is moving at a consistent speed.

"People don’t feel motion – they feel changes in motion – accelerations," said Kevin Lee, an associate professor of physics and astronomy at the University of Nebraska. "If you are on the freeway moving at 70 mph you don’t feel that motion at all, but slam on the breaks and you definitely feel the change."

David Brown, the director of undergraduate programs at North Carolina State University's department of physics, used a similar analogy.

"When we drive down the street in a straight line at a constant speed, what we feel is the bumps in the road," he said. "Without the bumps, we would not feel the motion at all, unless the car accelerates."

It's the same reason why people don't feel like they're moving in a plane, Steffen said.

"Does that mean it's also stationary? That initial argument doesn't hold any water," he said.

The Earth is curved and humans have witnessed it

Flat earth claims are often built around the observation that the horizon appears flat from a given vantage point.

This assertion ignores numerous examples of photographic evidence that illustrate the curvature of the Earth.

But experts also note the Earth is so large that people can't directly observe the curvature from Earth's surface. The curvature only becomes visible from a vantage point that is at least 40 miles above the Earth's surface, Steffen explained.

"You have to be about a percent or so higher than the radius of the surface of the Earth (to see the curve)," he said. "40 miles is 1% of the curvature of the radius of the Earth." Most people will not reach this altitude. However, those who have gone beyond this altitude have been able to provide photographic evidence of the curve.

Among other evidence: the North star, Polaris, would always be visible if the Earth was a level plane. However, people in the Southern Hemisphere cannot see the star at all. Watching Polaris shift positions across the sky was one of the ways the ancient Greeks first calculated the circumference of the Earth, Steffen said.

Our rating: False

Based on our research, we rate FALSE the claim that Earth isn't curved and doesn't rotate. The Earth is both, and there are several ways scientists have proved this, experts say. The curvature of the Earth can be seen from an elevated vantage point. And the rotation of the Earth also impacts daily functions like the route planes fly, it just can't be felt because humans "feel" acceleration, not speed.

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This article originally appeared on USA TODAY: Fact check: Ample evidence the Earth is round and rotating