One of the oddest fads of the 21st century is the renaissance of “flat-Earthers,” Internet-dwelling folk who believe there’s a conspiracy in place to cover up that our globe is actually flat. Why? No one is sure, but don’t worry if truther trolls are filling up your social media feeds, astrophysicist Neil deGrasse Tyson has got your back.

In a new video on his StarTalk YouTube channel, stand-up comedian Chuck Nice and deGrasse Tyson take on the big questions of flat Earth along with the million and one ways to scientifically shut any argument down, from simple astronomical observations to an argument first made over 2,000 years ago by the ancient Greeks.

“For me, the fact that there’s a rise of flat-Earthers is evidence of two things. One, we live in a country that protects free speech,” deGrasse Tyson said. “And, two, we live in a country with a failed educational system.”

And this is the crux of the whole issue really.

“Our system needs to train you not only what to know but how to think about information and knowledge and evidence. If we don’t have that kind of training, you’d run around believing anything," he continued.

“It wasn’t until Francis Bacon, Galileo, and the 1600s that if you’re going to say something, and what you think you are saying is true, no matter how obvious you think it is, then you need to test it. There could be something fooling you in one way or another.”

Thankfully, there’s plenty of this evidence, often laying around right in front of your eyes without the need of fancy satellites or trekking to the Arctic to see if there’s an edge. Tyson suggests thinking about a lunar eclipse, the phenomenon when the Moon passes directly behind Earth and into its shadow. This results in Earth’s shadow being thrown on to the Moon – a rounded shadow, something you'd expect to see from a spherical object.

Even more interesting is the argument put forward by Eratosthenes over 2,000 years ago. As Tyson cites, the ancient Greek mathematician studied the water wells in two distant cities. He discovered that the shadows appeared different even at the same time of day. Since the Sun's rays are parallel, what could cause this disparity? The explanation, he deduced, must be that the Earth is curved and therefore a sphere

Neil deGrasse Tyson is no stranger to protesting the Earth is flat (I mean, it is pretty much his job). Back in 2016, he even got into a Twitter feud with flat-Earther and rapper B.o.B, which peaked with both releasing "diss tracks" aimed at each other. The results were outstanding, if unexpected.

In the end, Tyson said if you still believe in flat Earth after all that, it doesn't really matter... as long as you're not running NASA, of course.