The claim: Earth isn’t curved or moving; air pressure couldn’t exist ‘without a container’
Some social media users are sharing a meme that claims to present evidence that Earth is flat instead of spherical.
“Earth can’t be a spinning space ball if there is no curve, motion or gas pressure without a container,” reads the caption on a Sept. 27 Instagram post that garnered more than 900 likes in two months.
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On a picture of the Earth titled “Space Ball Earth Top Failures,” the post lists a series of statements that purportedly support the long-debunked theory that Earth is flat.
These statements include claims that Earth’s curve and movement can’t be measured. The meme also states that gas pressure – ostensibly referring to Earth’s atmospheric pressure – is not possible without a “container.”
But these claims are wrong. Earth’s curve and movement are detectable through various means, according to researchers. And Earth’s atmospheric pressure is caused by gravity.
USA TODAY reached out to the Instagram user who shared the post for comment.
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Earth is a globe shape that curves
Earth’s curve is directly observable, but because of Earth’s size, observers have to get about 40 miles above the surface to see it, Jason Steffen, a mathematician and physicist at the University of Nevada, previously told USA TODAY.
“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.”
Humans and spacecraft that have reached these heights have photographically documented Earth’s curve.
Earth’s curve can also be observed during a lunar eclipse, Steffen said in a Q&A published on the University of Nevada website. Earth’s shadow appears round on the moon regardless of the time of year, time of night, or direction the shadow moves.
“The only object that casts a circular shadow no matter how you shine a light across it is a sphere,” he said. “Any other shape would not be able to cast a round shadow under this variety of circumstances.”
In addition to being directly observable, Earth’s curve is predicted by the laws that govern gravitational force. Self-gravity pulls all of Earth’s mass towards its center, ultimately forming a spherical shape.
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Earth moves through space and rotates
Contrary to the post’s claims, Earth moves as it orbits the sun, and, on a larger scale, the center of the Milky Way galaxy, Rebekah Dawson, an astronomer at Pennsylvania State University, told USA TODAY in an email.
“One way we can detect Earth’s motion around the sun is through parallax,” she said. “As our position changes, the apparent position of nearby stars relative to more distant ones changes as well. We can also (observe) the apparent motion of different stars to work out how we’re orbiting around the center of the galaxy.”
Earth rotates in addition to moving through space. And this movement is evidenced by the behavior of Earth’s atmosphere.
“If the Earth did not rotate and remained stationary, the atmosphere would circulate between the poles – high-pressure areas – and the equator – a low-pressure area – in a simple back-and-forth pattern,” reads the NOAA website. “But because the Earth rotates, circulating air is deflected. Instead of circulating in a straight pattern, the air deflects toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere, resulting in curved paths.”
This process helps drive the formation of Earth’s jet streams – east-west flowing bands of wind in the upper atmosphere, according to the National Weather Service.
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Air pressure is because of gravity
The Instagram post also states that gas pressure can’t exist without a “container.”
However, “gas pressure doesn’t need a container to be generated,” Elise Knittle, an Earth and planetary sciences professor at University of California, Santa Cruz, told USA TODAY in an email.
She said atmospheric pressure on Earth “is generated by moving gas molecules subject to the Earth’s gravity,” which draws the molecules downward toward Earth.
One readily observable clue that Earth’s air pressure is because of gravity rather than pressurization in a container: air pressure on Earth decreases as elevation increases.
“As you go up higher into the atmosphere, there are fewer molecules and the mass of the atmosphere above you is less,” Knittle said. “The number of air molecules … is reduced and the atmospheric pressure goes down.”
This kind of difference doesn’t form in a pressurized container, she said. Instead, the pressure is the same throughout.
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Our rating: False
Based on our research, we rate FALSE the claim that Earth isn’t curved or moving, and air pressure couldn’t exist on Earth “without a container.” 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.”
Our fact-check sources:
- West Texas A&M University, Sept. 14, 2015, Why don’t I feel the miles of air above me that are crushing me down?
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This article originally appeared on USA TODAY: Fact check: Flat Earth claim misunderstands Earth’s motion, shape, gravity