Despite an abundance of evidence to the contrary, thousands of people still believe that the Earth is flat. Christine Coffey explains why this group are wrong, using common sense and centuries-old knowledge.


The UCD Flat Earth Society might disagree, but we’ve had evidence of the curvature of the earth since ancient Greece, and we’ve got Bill Nye the Science Guy, Neil deGrasse Tyson and Aristotle on our side. While few of us will ever get to see our planet from space, centuries of reasoning and evidence mean that we do not need to do this to know that the Earth is not flat.

The ancient Greeks observed that our planet would sometimes cast a shadow on the surface of the moon during what we would know today as a lunar eclipse. This shadow was always circular in shape, and the only shape that could create such a shadow would be a sphere, not a rectangle or a square. After travelling to Egypt, Aristotle observed that different constellations were visible at different distances from the equator and from this made the correct inference that the Earth was approximately round. He also noted that not much distance was required for these differences to be noticeable, and so assumed the earth wasn’t very big.

We, like the Greeks, can also use the simple method of watching distant objects sinking under the horizon as we move away from them to understand that the Earth is not flat. The progression of the Age of Exploration brought with it a further understanding of our planet. Many instruments used widely during this period, such as sextants and the astrolabe, operate on the assumption that the Earth is spherical. Any self-respecting navigator has no choice but to believe in a round planet.

“Any self-respecting navigator has no choice but to believe in a round planet.”

The flat Earth theory does not hold up when tasked with explaining the effects of gravity. The force of attraction due to gravity is towards the centre of the earth, a specific point of reference. On a flat Earth, objects placed further from the middle of the Earth would move towards the middle, as this would be the gravitational centre. This would also be reflected in the growth of plants, which would grow at increasingly obtuse angles the further you planted them from the centre of the planet.

“At the end of the day, the flat Earth theory falls flat on its face.”

Incidentally, there is a measurable difference in the force due to gravity, for example, in Hudson Bay, Canada when compared to that experienced near the equator. This is because the rotation of the earth on its axis causes a slight bulging at the equator. So, in this limited sense, the flat-Earthers are right – the Earth is not spherical, exactly. Rather, it is what is called an oblate spheroid (a sphere which is flattened at the poles). The flat Earth theory does not accommodate for this difference. At the end of the day, the flat Earth theory falls flat on its face.