Dr Karl: ‘Nothing will convince the flat-Earthers’


Dr Karl Kruszelnicki


Dr Karl Kruszelnicki

Dr Karl is a prolific broadcaster, author and Julius Sumner Miller fellow in the School of Physics at the University of Sydney. His latest book, Vital Science is published by Pan MacMillan. Follow him on Twitter at @DoctorKarl
ByDr Karl Kruszelnicki March 8, 2024
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In November 2023, SpaceX launched its second Starship rocket test flight. This was the heaviest, tallest and most powerful rocket ever built and – not unexpectedly – it didn’t work.

Both stages exploded – the first at an altitude of 90km, the second at 150km. This was seen by some as proof that Earth is flat, because the rocket supposedly crashed into the “firmament” above our flat Earth, rather than exploded. 

Typical flat-Earth explanations on TikTok were, “There’s no breaking through the energy dome. You cannot go to space physically. We have never been to the Moon.”

Firmament believers are a subset of the wider flat-Earth community and tend to be fundamentalist Christians. They believe God placed a physical barrier – the so-called firmament – exactly 200km above the ground. How is the disparity between the 150km where Space X exploded and the 200km mark explained? According to flat-Earthers, you can’t trust the media.

Educated people in Greece first accepted that Earth was a sphere as early as 2500 years ago. They saw evidence when a ship sailed towards the horizon. The first part of it to disappear from view was the hull, followed by the lower mast, and finally the upper mast. This was because the ship was slipping around the curve of Earth. And when it returned, it reappeared in the reverse order. 

The ancient Greeks also observed lunar eclipses, where the Moon passes into Earth’s shadow. This shadow on the face of the Moon was always circular, again indicating Earth is a sphere. 

Also, as people travelled north–south across the planet, they saw that star constellations in the night sky were different, depending on how far north or south they were.

About 2250 years ago Eratosthenes, the chief librarian of the Library of Alexandria, actually calculated the circumference of Earth. He measured the midday shadows at different distances from the Equator and then applied basic geometry to complete the calculation. Impressively, his measurements were within 10 per cent of modern estimates. 

But then, nothing will convince the flat-Earthers…

Related: Dr Karl’s message to flat-Earthers