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

Humans first theorized the Earth may be spherical in ancient Greece thousands of years ago, according to the American Physical Society. Since then, scientists have discovered an abundance of evidence to confirm this is the case – including seeing Earth itself from space.

Claims the Earth is flat continue to circulate, though.

Why people think the Earth is flat

Experts say flat Earth claims endure in large part because of the repetition enabled by social media.

"There's what you might think of as a misinformation feedback loop," said Jeffery Blevins, a professor at the University of Cincinnati who specializes in misinformation. "If you have just one false claim from one source that gets repeated by other sources on social media and fringe outlets, suddenly it sounds like it's coming from all these different sources. And if all these sources are saying the same thing, then people – erroneously – think there must be something to it."

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The USA TODAY Fact-Check Team has investigated a wide range of flat Earth-related claims, including those built on misunderstandings about feeling the Earth's rotation or how planes can fly "straight and level" if the Earth isn't flat. We also debunked variations of the related conspiracy theory that space isn't real.

Here's a roundup of our work:

Flat Earth theories on movement, other science

Claim: Earth isn't curved and doesn't rotate

Our rating: False

The Earth is curved and does rotate, 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 impacts daily functions like the routes planes fly. This rotation just can't be felt because humans feel acceleration, not speed. Read more.

Claim: Earth isn't curved or moving; air pressure couldn't exist 'without a container'

Our rating: False

Ample evidence, including photos, atmospheric processes, lunar eclipses and the movement of stars, demonstrates Earth's curve and motion. Gas pressure in Earth's atmosphere is caused by gravity pulling matter toward the planet's core, so there's no need for a "container." Read more.

Claim: A compass wouldn't work if Earth is spherical

Our rating: False

Compasses orient themselves to the magnetic field lines that circle the Earth. The needle does not point at the actual geographical location of magnetic north. Read more.

Claim: Antarctica is an ice wall that surrounds a flat Earth

Our rating: False

Satellite imagery shows the shape of the continent, which is not an ice wall around the world. Explorers have circumnavigated the land mass, and people visit it every year. The ice wall concept is also not realistic from a structural perspective, experts said. Read more.

Claim: Laser tests show bodies of water are level, which proves the Earth is flat

Our rating: False

Scientists say the claim is built on flawed logic. Laser beam tests in uncontrolled conditions, especially over water, are not a reliable means to prove the Earth's shape due to atmospheric refraction. Furthermore, scientists say the test outlined in the post’s diagram is not at a large enough scale to show the Earth’s curve. Read more.

Claim: The Earth is flat because cities cannot be upside-down

Our rating: False

Gravity pulls objects to the center, no matter where people or cities are located on Earth. There is no true "up" or "down" in space. Read more.

Claim: Earth's oceans have no 'elevation features' and are in a 'container'

Our rating: False

The ocean surface has topography due to currents, underwater features and other factors. Ocean water is held onto Earth by gravity. Read more.

Claim: Radar technology wouldn’t work if the Earth was a globe

Our rating: False

Scientists say the post’s logic is flawed and that radar technologies account for

the Earth’s curvature. Furthermore, the curvature of the Earth plays into some of the limitations of radar technology. Read more.

Flat Earth theories on the horizon line

Claim: Photo of solar eclipse taken at the South Pole proves Earth is flat

Our rating: False

Scientists explained that a variety of factors including the location and time the photographs were taken account for why the sun appears to be moving in a straight line. Timelapse pictures of the eclipse from anywhere else in the world show a curved path in the sky. Read more.

Claim: Planes flying ‘straight and level’ prove the Earth is flat

Our rating: False

That concept doesn't mean planes are flying in a literal straight line. It's a technique that involves flying at a consistent altitude in the same direction. Pilots constantly have to make adjustments to maintain speed and altitude. A plane flying from one location to another would never end up upside down because the Earth does not have an inherent top or bottom. Read more.

Claim: Image of Chicago skyline taken in Indiana proves Earth is flat

Our rating: False

Scientists say the post’s calculations are incorrect and the photo actually proves the opposite. The Chicago skyline is visible from the photo’s location at the Indiana Dunes State Park, but the curve of the earth means the bottom of the buildings is obscured. Read more.

Flat Earth theories on space and astronauts

Claim: Lack of stars in space photos means they were created with a green screen

Our rating: False

Stars don't show up in many space photos because they are too dim to be detected with the camera settings required to capture brighter objects. Read more.

Claim: Video shows NASA astronaut Karen Nyberg in front of a green screen

Our rating: False

The woman in the video is not Nyberg but a flat Earth believer participating in a skit. Nyberg's representative confirmed it is not her in the video. Read more.

Claim: Propulsion can't work in a vacuum, so space travel isn't real

Our rating: False

Rocket engines function by creating thrust, which moves the spacecraft in the opposite direction. This process works in a vacuum. Air or another "external medium" is not required. Read more.

Claim: Space is a hoax because astronauts don't train in vacuum chambers

Our rating: False

NASA astronauts train in both pools and vacuum chambers to prepare for life in space, according to a NASA spokesperson. Furthermore, there is ample evidence from earthbound observation and space missions that space is real and a vacuum. Read more.

Claim: Different appearance of launch sites on moon, Earth prove space isn't real

Our rating: False

Different forces of gravity, the absence of an atmosphere on the moon, the weight of cargo, varied types of fuel and the need for reusability on Earth are all factors in why launch sites look different on the Earth vs. the moon. Read more.

Claim: Photos appearing to show clouds behind the sun suggest it orbits the Earth, isn't millions of miles away

Our rating: False

This is an optical illusion. The clouds only appear to be behind the sun when too much light passes through the cloud and strikes the camera's film or sensor, causing overexposure. Read more.

Claim: NASA admits the Earth is flat and non-rotating

Our rating: False

NASA has consistently said the Earth is a round, rotating globe, and the documents referenced in the post don't prove otherwise. The "flat, non-rotating earth" model is a common technique used to generalize mathematic equations, experts said. Read more.

Claim: Moon visible in the daytime proves Earth is flat

Our rating: False

The Earth is not flat, it's spherical, as proven by photos from space and an array of observations and calculations that can be done from Earth. Planetary scientists say the visibility of the moon and sun during the daytime, doesn't prove a flat Earth – it is in fact proof of the motion of the sun, moon and Earth in space, along with the Earth's rotation. Read more.

This article originally appeared on USA TODAY: Fact check roundup: Proof that the Earth is round