Two-hemisphere global composites of Moderate Resolution Imaging Spectroradiometer (MODIS) data, taken in 2001 and 2002. Image credit: NASA.

Ask Ethan: How do we know the Earth isn’t flat?

Today, it’s the most obvious thing in the world. But how do you prove it to yourself?

Ethan Siegel
Starts With A Bang!
7 min readJun 4, 2016

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“A long time ago people believed that the world is flat and the moon is made of green cheese. Some still do, to this day. The man on the moon is looking down and laughing.” -Vera Nazarian

Every once in a while, a hoax or claim that’s so spectacularly absurd goes viral that even the most circumspect bystanders can be taken in. Yet science doesn’t stop being true just because some people refuse to accept it. The beautiful thing about any scientific question is this: if you yourself become enough of an expert, you can figure out the answer for yourself. This ability to convince yourself of the truth, despite what any authority figure might say, is what separates science from all other endeavors. And with a round-Earth denying friend, that’s exactly what Michael Gratton wants from this week’s Ask Ethan:

“[I] have this friend who thinks and preaches the “flat earth” theory for a few years now, I don’t believe the planet or any is flat for that matter but what are your views on this topic/theory?”

The wonderful thing is it’s not a belief for me; it’s a conclusion.

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Ethan Siegel
Starts With A Bang!

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.