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Is the Earth flat?

The first indication that it is not, however, is the effect of the horizon. Looking around we can only see places up to a certain distance. If we climb a hill or a tower, we will see further away. This means that the Earth must be convex.

What could we see from Wrocław if the Earth were flat? Everyone who lives in Wrocław knows that in good weather we can see the Ślęża massif on the southern horizon. If the Earth were flat, to the west of Ślęża we would also see the only slightly lower Karkonosze. Looking south-east, we would easily see Babia Góra and the Tatra Mountains protruding above it. The reality is different. The Karkonosze can be seen from Wrocław, but they barely protrude above the horizon. There is no way to see Babia Góra and the Tatra Mountains. The Earth is convex, making it impossible to see distant places, even places as high as the Tatras.

But maybe the Earth is not a sphere, but only the convex shell of a giant tortoise? For a long time we have known the answer to this question thanks to observations of lunar eclipses. These eclipses only occur during full moons, when the Moon is on the opposite side of the Earth to the Sun. The Moon then has the chance to enter the Earth’s shadow. We then see the shape of the Earth’s shadow on the Moon’s disc. This shadow is always a part of a circle clearly larger than the Moon itself. If the Earth was flat, we would have to see a shadow of a different shape during eclipses occurring just after sunset or just before dawn. This is because we then see the shape of the Earth illuminated from the side. However, we do not see any other shape of the Earth’s shadow other than circular during any eclipse. There is only one shape that, when illuminated from any direction, gives a circular shadow. This is the sphere. This was already well understood by the ancients, and you yourself can see this effect with your own eyes.

Don’t believe the myths, trust the science!

Dr Paweł Preś