Video: Kayvan Ghavim

Flat Earth conspiracy theorists are having a moment.

A couple of celebrities have recently come out as flat-Earthers on Twitter. The rapper B.o.B., for example, even went so far as to release a diss track directed at astrophysicist Neil deGrasse Tyson after the scientist debunked some of the claims in his tweets on Tuesday.

See also: Neil deGrasse Tyson wants the rapper B.o.b. to know that the Earth is not flat

Scientists and members of the public have long accepted that the Earth is round even before Aristotle posited the theory more than 2,000 years ago (and Pythagoras before him), but that doesn't mean too much to some celebs on social media today.

So, in honor of these celebrities and others who believe in a flat Earth, here's a (not so comprehensive) history of “flat Earthers” through time:

Ancient Egyptians and Babylonians

Like B.o.B., at least some ancient Egyptians (3,100 B.C.E. to 332 B.C.E) believed in a flat Earth as well, scholars have said.

Historians suggest that the long-lived civilization believed the planet was square-shaped with four corners and an underworld below. The Babylonians also had similar views about a flat, enclosed Earth.

Other ancient cultures in the Americas, China and India also likely held the belief that the Earth was flat.

Samuel Birley Rowbotham

Rowbotham founded the Flat Earth Society in the 1800s.

Rowbotham's “system, called Zetetic Astronomy, held that the earth is a flat disk centered at the North Pole and bounded along its ‘southern' edge by a wall of ice, with the sun, moon, planets, and stars only a few hundred miles above the surface of the earth,” according to the Flat Earth Society's website. His beliefs began to spread, and others took up the flat-Earth cause after his death, though it was never widely accepted.

The website says that the society was largely inactive early in the 2000s but had a bit of a resurgence starting in 2004 and began accepting new members in 2009.

Tila Tequila

Tequila posted her doubts about a round Earth in early January, when she tweeted about the planet's shape, saying that she can't see the planet's curvature when she looks out on the horizon.

Tequila even went so far as to say that NASA fakes all of its images of the Earth from space — a common refrain among flat Earth truthers — and she even suggested that her speaking publicly about the flat Earth could lead to her being killed in 2016.

B.o.B.

B.o.B. is the most recent celebrity to make his beliefs about a flat Earth publicly known. He managed to ignite a social media debate large enough that Tyson jumped into the fray, leading both to release diss tracks specifically targeted at ripping into one another's arguments.

The rapper went on a tweetstorm that hit all the high points of the flat Earth conspiracy theory, posting photos of diagrams based in part on Rothbotham's ideas from the 19th century, “proving” the Earth is actually flat.

And hey, if B.o.B. doesn't convince you, here are some “suspiciously” flat places on Earth just to whet your conspiracy whistle.

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