A mix of misinterpreted French wordplay, locker-room humor, and stubborn defiance has resulted in a wave of online backlash against a star physics professor who made a crude joke about black holes during a recent talk.

Li Miao was giving a lecture at the Chinese University of Hong Kong’s Shenzhen campus when he said, “The French thought of the concept of black holes in an amusingly different way,” according to a domestic media report Thursday that cited a student who attended the talk. He then asked “the boys in the room — not the girls — to think about this a bit more,” suggesting a comparison between black holes and vaginas.

When a student in the audience asked Li, who teaches at Southern University of Science and Technology in Shenzhen, to elaborate on what he meant, the professor replied with a dismissive “I can’t explain that here.” Unsatisfied with this explanation, the student pressed Li, who finally said he had been referring to sex.

Li appears to have confused a well-worn joke in the European physics community. In French, the term for a black hole — trous noir — is slang for “anus,” not “vagina.” Consequently, French physicists find it notoriously challenging to give talks on black holes to auditoriums of young people without eliciting the occasional stifled snicker.

Based on the online comments, however, it seems many on Chinese social media were particularly triggered by the implied sexism of Li’s remark, rather than its puerile vulgarity.

The back-and-forth continued after the lecture, with users on microblogging platform Weibo taunting Li — who has over 1 million followers on the platform — for what they viewed as inappropriate humor. In a flurry of now-deleted posts, the professor shot back, saying he had only repeated a similar joke made by the late physicist Stephen Hawking. (In fact, Hawking did not make such a joke, but merely explained the French context.)

Li further threatened to sue the Chinese University of Hong Kong and its students, whom he referred to as feiqing, or “trash youth” — a phrase often used derisively against Hong Kong’s young protesters.

By doubling down on his comments and refusing to apologize to anyone apart from the student who first objected to them, Li only stoked the flames of the social media kerfuffle. In addition to eventually deleting his posts, he also restricted commenting on his account.

Born in 1962, Li graduated with a bachelor’s degree in astrophysics from Peking University, one of China’s top schools, before earning a master’s degree at the University of Science and Technology of China in the eastern city of Hefei, as well as a Ph.D. from the University of Copenhagen. He has published two books, both on physics, and won a number of honors and awards over the course of his distinguished career.

“Instead of telling dirty jokes, he should really work on his lectures,” read one Weibo post, including a related hashtag viewed over 140 million times. “What’s wrong with livening up the atmosphere a little?” rebutted another user. “Why so serious?”

Contributions: Du Xinyu; editor: Kevin Schoenmakers.

(Header image: YAY Images/People Visual, re-edited by Sixth Tone)