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No, this video isn’t proof that Earth is flat


Social media users are sharing a video of a sunset which they claim provides proof that Earth is flat and the sun is “local”, by which they mean that it orbits a flat Earth at cloud level. This is actually an optical illusion.

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4 min

If you only have a minute… 

  • A video of a sunset has been widely shared on social media by people who believe the sun is “local” and that it orbits at the same level as the clouds, above a flat Earth. 
  • The social media users sharing the post focus on the fact that the sunset seems to be happening below the horizon and that the clouds seem to be going behind the sun.  
  • However, a careful analysis of the video shows that the sunset does actually take place at horizon level. The fact that the clouds seem to go behind the sun is actually an optical illusion.

The fact check, in detail 

A video showing a sunset that seems to happen below the horizon, at the same level as the clouds, has been going viral on Facebook, TikTok and X among accounts belonging to people who believe that Earth is flat, so-called “Flat Earthers”.

“Travelling from Cairns (Australia) to Japan. Over the Philippine sea we captured a setting sun… not over the horizon but in the clouds. A local sun on a flat Earth and not as the lies they tell us,” reads the caption on a TikTok post by the account compte flatearth_flatearth. The video has garnered more than 1.8 million views.


This claim, however, is false, says Frédéric Pitout, an astronomer and planetary research scientist at the Research Institute in Astrophysics and Planetology in Toulouse, France, who spoke to the FRANCE 24 Observers team.

The horizon isn’t a line that separates the clouds from the sky, but the line that intersects the sun. We see it through a thin, cloudy layer [Editor’s note: check out the screengrab below where the horizon appears as a transparent reddish line]. The sun isn’t at all under the horizon.

You can see the horizon as a thin reddish layer right by the sun.
You can see the horizon as a thin reddish layer right by the sun. Screengrab from the TikTok account flatearth_flatearth © FRANCE 24 Observers

Clouds behind the sun? An optical illusion 

As for the image where the clouds seem to be behind the sun: it is an optical illusion, says Éric Lagadec, an astrophysicist at the Côte d’Azur Observatory, who spoke to our team:

This kind of thing happens because of the luminosity and the thickness of the clouds. If a cloud goes in front of the moon, it might look like it is behind the moon. Why does this happen? The cloud is in front of the moon, but, because it isn’t very thick, the light of the moon goes through it.

“You can also see the same phenomenon in stadiums. When the projectors are on, you can no longer see the stars,” Pitout says.

An optical illusion that you can reproduce with a lamp and some negatives 

You can reproduce the way the sun makes a cloud invisible with a simple experiment. 

“I’ve been asked why clouds and wires and things sometimes appear to be behind the sun,” says Mick West, the owner of fact-checking site Metabunk in a YouTube video. “The reason is because the sun is so bright, it simply washes out anything that is in front of it that is partially transparent, small enough or out of focus enough. The sun’s light basically goes through it or around it.”

Using a lamp and negatives, West is able to reproduce the effect caused by the sun’s luminosity (YouTube video).

To prove this effect, West uses a lamp and a piece of paper to simulate the sun and then photographic negatives to represent clouds. If you put a single layer of negatives in front of the lamp, then you’ll see them disappear in the light. But when you add a second layer on top of the first one, the thicker negatives become more visible.

“There is a defiance towards authority, whether it is political or scientific”

Despite the abundance of scientific explanations that prove them wrong, Flat Earth theories have been going viral on social media. On TikTok, videos linked to the key words “flat earth local sun” have been viewed more than 26.7 million times.

Pitout wrote a book about false beliefs and ideas about astronomy. In it, he analyses Flat Earther thinking:

Flat Earthers are trying to create a model based on alternative thinking that makes no sense with our scientific knowledge. They try to confuse their listeners with what we call in France  ‘mille-feuille argumentation’ (Editor’s note: This is when you overwhelm your listener with a bunch of arguments relating to different fields of knowledge, replacing the quality of an argument with quantity.)

Many of these people also feel a defiance towards both political and scientific authority. Some Flat Earthers reject the idea of a round Earth for religious reasons. They don’t believe the Earth is just one planet in the universe. 

Finally, Flat Earthers get a sense of power from being part of a community dedicated to a ‘truth’ that only they understand. As a result, trying to convince them with rational arguments doesn’t work at all. 

One out of every six French people between the ages of 11 and 24 believe that the world is flat, according to a study carried out by Ifop in December 2022.

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