Astrophysicist Neil deGrasse Tyson, in a photo promoting a 2014 television series that he narrated called “Cosmos: A Spacetime Odyssey.” (Patrick Eccelsine/FOX)

Neil deGrasse Tyson, perhaps the most famous astrophysicist in the world and a seemingly affable guy, upset teachers and started something of a Twitter frenzy with a tweet blaming U.S. schools for people who believe the world is flat:

With this tweet, which had more than 72,000 retweets and more than 188,000 “likes” late Friday afternoon, Tyson was expressing alarm at “flat-Earthers,” people who believe the Earth is flat and who have been able to grab some headlines in recent months as videos insisting the Earth is not a sphere have become popular on social media.

The Daily Mail recently ran a story titled, “Inside the World of flat Earthers,” and the famous former basketball Shaquille O’Neal was in the news a few months ago when he said the Earth was flat — and then later said, “I’m joking, you idiots.” And the Courier just published a story noting that flat-Earthers had posted signs along a highway in Scotland urging people to research the flat Earth.

Flat-Earthers believe NASA is part of a broad conspiracy to fake the evidence of a spherical Earth, and there are societies of people, such as this Flat Earth Society, that produce materials “proving” the conspiracy. For example, this is the description of one of the podcasts available on this group’s website:

In this series we will be dispelling a number of globularist claims. This week we take a look at lunar eclipses in the ball model and using the Parallaxian mind-set put forth by Samuel Rowbotham showing the globe earth theory to be incoherent with observed phenomena.

Tyson’s tweet blames America’s schools — most of which are traditional public schools — for such ignorance, but is that really fair? It is true that science education is not a priority in too many schools, and young people don’t learn anywhere near enough about the world. But a refusal to believe basic science like this suggests something other than minimal or lousy teaching, such as willful ignorance, a rejection of science and/or religious beliefs.

I sought comment from Tyson but didn’t hear back.

It is worth noting, as I wrote here, that the true shape of the Earth has been known since ancient times. Historians say there is no doubt that the educated in Christopher Columbus’s day knew quite well that the Earth was not flat but round — and as early as the sixth century B.C., Pythagoras — and later Aristotle and Euclid — wrote about the Earth as a sphere.

Ptolemy wrote “Geography” at the height of the Roman Empire, 1,300 years before Columbus first sailed across the Atlantic Ocean in 1492, and considered the idea of a round planet as fact. (Columbus owned a copy.) During the early Middle Ages, it is true that many Europeans succumbed to rumor and started believing that they lived on a flat Earth, but Islamic countries knew better and preserved the Greek learning, and by the late Middle Ages, Europe had caught up and in some cases surpassed the knowledge of ancient Greece and medieval Islam.

Several books published in Europe between 1200 and 1500 discussed the Earth’s shape, including “The Sphere,” written in the early 1200s, which was required reading in European universities in the 1300s and beyond.  But in the 1800s, a myth was perpetuated that Columbus thought the world was flat.

In a 1991 book, “Inventing the Flat Earth,” retired University of California professor Jeffrey Burton Russell pointed to writers, such as  Washington Irving, who in 1828, Irving wrote the mostly fictional “The Life and Voyages of Christopher Columbus,” which says that Europeans learned from Columbus’s trips to the New World that the planet was round.

There were some cheeky responses to Tyson’s tweet:

But others were offended or took issue with his swipe at schools and teachers:

(Correction: Fixing attribution to a news story)