Celestial navigation confirms Earth's motion, rather than disproving it | Fact check

Kate S. Petersen, USA TODAY
·3 min read
1

The claim: Celestial navigation would be impossible if Earth is globe-shaped and orbits the sun

A Feb. 22 Instagram post (direct link, archive link) claims a form of navigation that relies on celestial objects such as the sun, moon and stars proves the Earth is flat and stationary.

"The Ancients navigated by the stars because they never change," reads the post. "That would be impossible on a globe that revolves around the sun."

The post garnered more than 100 likes in a week.

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Our rating: False

Celestial navigation is a technique still used to determine location based on the positions of celestial objects. Because the Earth and other celestial bodies are in motion, the apparent position of stars, planets and the sun in the sky changes. These changes must be taken into account for successful celestial navigation.

Celestial navigation accounts for the Earth's movement

Celestial navigators have traditionally used a special instrument called a sextant to measure the angle between a celestial object and the horizon, but more complex instrumentation is also used in modern times, according to The University of New South Wales.

"Before the emergence of radio navigation, celestial navigation was the primary marine navigation method of seafaring navigators, where there were no landmarks for centuries," reads the university's website. "Celestial navigation might be the only feasible method to guide spacecraft to the far reach of the solar system, where nothing but celestial bodies are around."

The apparent position of celestial objects changes as the Earth moves, but celestial navigators take this into account, according to the university. Special almanacs that provide the positions of celestial objects at different times are published to address this issue.

Ocean Navigator Magazine also discusses the apparent movement of stars in its nine-part instructive series on celestial navigation, addressing how stars' location from a vantage point on Earth varies based on the Earth's spin and tilt and must be factored in.

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The post was captioned with a series of hashtags related to flat Earth theory ? the errant idea that Earth is flat instead of roughly spherical. Flat Earth theory adherents often leverage purported inconsistencies in scientific narratives to bolster their inaccurate claims.

In addition to the apparent movement of celestial bodies, evidence that Earth is roughly spherical and in motion includes direct observations from space, the fact that Earth's shadow is always round during a lunar eclipse and that atmospheric circulation patterns only make sense if Earth is spherical and rotating.

USA TODAY reached out to the Instagram user who shared the post for comment but did not immediately receive a response.

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This article originally appeared on USA TODAY: No, navigation by 'ancients' does not show Earth is flat | Fact check

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