Flat Earth claim based on gas pressure fails to account for gravity's impact | Fact check

The claim: Space is 'fake' because it's impossible to have a gas gradient without a container

A Dec. 4 Instagram post (direct link, archive link) shows an image of Earth from space. Earth's atmosphere is labeled "pressurized gas," while outer space is labeled "infinite vacuum." A third label asserts, "Outer Space is Fake."

The post also shows a vacuum chamber and a can of pressurized gas, each labeled with the words "requires containment."

"Nobody will ever demonstrate how to have a gas pressure gradient WITHOUT a container because it’s impossible," reads the post's caption.

The post garnered more than 800 likes in two days.

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Our rating: False

Scientists say a container is not the only way to create a gas gradient. The gas pressure gradient in Earth's atmosphere is maintained by gravity.

Pressure gradient in Earth's atmosphere due to gravity

Regions of high pressure tend to diffuse to regions of lower pressure, Elise Knittle, an Earth and planetary sciences professor at the University of California, Santa Cruz, previously told USA TODAY. The walls of a container can help prevent that from happening − maintaining a constant pressure inside the container.

However, a physical container is not the only way to maintain gas pressure. For instance, atmospheric pressure on Earth "is generated by moving gas molecules subject to the Earth's gravity," Knittle said.

Gravity draws the molecules down to the Earth, increasing pressure near the surface and decreasing it at higher elevations. This air pressure gradient is a clue that Earth's atmosphere is maintained by gravity as opposed to pressurization in a container.

This kind of gradient does not form in a container (in the absence of gravity), Knittle said. Instead, the pressure is the same throughout.

Fact check: Post misleads using space shuttle speed in attempt to prove flat Earth

The meme was posted on an Instagram page that promotes flat Earth theory – the erroneous idea that Earth is flat instead of a globe. Flat Earth proponents often wrongly claim that space isn't real and use purported inconsistencies in scientific narratives about space or space travel to bolster their errant claims.

The Instagram user who shared the post could not be reached.

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This article originally appeared on USA TODAY: Gravity creates gas pressure without a container | Fact check