By around 500 BCE most ancient Greeks believed our planet was round. For a long time before this, it was believed to be flat. It was only when we started to map the trajectory of the Sun and the stars and applied mathematics to speculation that we rejected the disc model and accepted the spherical model. You can see the evidence of this curve yourself. Just sit on a clear day and watch a sailing boat as it cruises over the horizon, and you will see it slowly disappear as it dips beneath the horizon and eventually out of sight. This was just one argument made by Aristotle (circa 384–322 BCE), who was possibly the first person to propose a spherical Earth based on physical evidence in around 350 BCE. So what evidence do modern flat Earth societies have to continue to believe claims that are flat out unsubstantiated? These conspiracy theorists reject the irrefutable evidence of gravity and instead favour the position that we are on a disc that is being pushed upwards through space by a mysterious force called dark energy. They believe that our planet is a disc-shaped world with the Arctic Circle in the middle, with a rotating dome of stars over our heads. Among other absurdities are theories that the Sun is only several hundred kilometres away from us, the Moon is transparent and a giant magnet under the ocean controls the tide. Perhaps the most outlandish aspect of the flat Earth conspiracy theory is the belief that our planet is surrounded by a huge, 45-metre-high ice wall on the coast of Antarctica that holds our ocean in and prevents us from falling o the planet. Flat Earth conspiracy theorists not only reject the shape of the Earth but also deny the irrefutable evidence of almost all of the scientific evidence underpinning our understanding of physics, mathematics and our origins.

Five reasons why we know the Earth is round

1. Photography from space 

Countless photographs taken by satellites, probes and from the ISS show our Earth as a beautiful globe, which is unarguably the greatest piece of evidence that the world is not flat.

2. Lunar eclipse shadows 

During a lunar eclipse, the Earth is placed between the Moon and Sun. The shadow cast by our Earth is visibly round as a result of its spherical shape.

3. Different visible constellations

From a flat Earth, all the stars would look the same no matter where in the world you were standing, but this isn’t the case — different constellations can be seen in different parts of the globe.

4. We can see further with altitude 

The higher up you are the further you will see. This is a result of the Earth’s curvature. On a flat Earth, elevation would not make a difference and curvature would thereby not occur.

5. Time zones

If Earth was flat the Sun’s light would be equally distributed everywhere; similar to placing a plate beneath a desk lamp. This would mean we wouldn’t have any time zones, or day and night.

This article was originally published in How It Works issue 108, written by Charlie Evans 

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