Once upon a time there was a boy called Baron Trump, who was growing weary of his privileged life at Trump Castle. Then, one fateful day, Baron found an ancient manuscript by a wise old man called Don, which stated that, a long time ago, “terrible disturbances” on Earth had driven humans into underground bunkers, creating a “World Within a World”. Guided by Don’s manuscript, Baron sets off to Russia to discover the secrets of this hidden land.

Don’t worry, I’m not announcing a new career as a pro-Trump children’s author. I think FBI director Kash Patel, who wrote a series of terrible kids’ stories about a King Trump, has that covered. Rather, I’m summarising a book from the late 19th century called Baron Trump’s Marvellous Underground Journey by an American lawyer called Ingersoll Lockwood.

If you’ve spotted some parallels to a famous modern family, you’re not alone. Lockwood’s writing, rediscovered by corners of the internet, has sparked a wild conspiracy theory that Donald Trump’s youngest son, Barron (with a double “R”), is actually a time traveller. This idea has been doing the rounds for a while, but new life was breathed into it last week by Trump’s daughter-in-law, Lara, who discussed it on an episode of her podcast titled Is Barron Trump a Time Traveler. (Betteridge’s law of headlines strikes again.)

“I’m not trying to … rain on any parades here,” Lara, who is married to Eric Trump, said. “Barron Trump is not a time traveller. Sorry to say it.” She added: “Name me one time traveller … It doesn’t exist … I’ve known Barron for 18 years, OK, he’s not a time traveller.”

Wow, that’s actually a really good point, Lara. I initially thought the theory might have legs but, now you mention it, I can’t actually name a time traveller! Not a single one. With analytical skills like these, it’s no wonder Lara has her own show on Fox News and once served as the co-chair of the Republican National Committee. And here I was, viciously thinking it might be something to do with nepotism.

Lara, who also writes children’s books in her spare time, had a little more to say on the matter. “I think people love to grab on to, you know, conspiracies or things that are very far-fetched like that,” she concluded.

Gosh, you think? I wonder, just spitballing here, whether that has anything to do with the fact that her father-in-law actively encourages conspiratorial thinking. Indeed, it was a core part of how he got to power: back in 2016, Trump campaigned on the racist “birther” theory that posited Barack Obama wasn’t born in the US. (To be fair, some Hillary Clinton supporters actually helped advance this lie in 2008.)

Since then, Trump has fanned the flames of various other bonkers ideas. The conspiracy theory du jour being that there is a coordinated plot, possibly involving UFOs, behind the disappearances and deaths of at least 11 US scientists linked to nuclear and space research programmes. Trump recently called the situation “pretty serious stuff”. The House Oversight Committee chair, James Comer, also went on Fox & Friends to warn that “something sinister could be happening”. Now the House Oversight Committee is looking into “a possible sinister connection between the deaths and disappearances”, and the FBI might get involved.

I think the FBI would be better off spending its time doing almost anything else. Because when you spend more than five minutes researching this admittedly tantalising theory about missing scientists, you’ll quickly find more holes than a block of Swiss cheese. There is no “sinister connection”, just a bunch of tenuous links.

Still, you can see why the Trump administration is encouraging people to think about a shadowy conspiracy involving dead scientists instead of, you know, the fact that the president’s name appears not infrequently in the Epstein files. Or the fact that the expensive and illegal war on Iran is driving up the cost of living. Or rocketing health insurance costs. Conspiracy theories are more than a good distraction; they have become a core part of the populist playbook. A 2022 paper by University of Pennsylvania professors noted that authoritarian leaders regularly use conspiracy theories “to attack opponents, galvanize followers, shift blame and responsibility, and undermine institutions that threaten their power”.

But back to Ingersoll Lockwood. Did you know that, inspired by the contentious 1896 election and an economic depression, he also wrote a book called The Last President in which a political outsider from New York gets elected president? Turmoil ensues; anger at the rich escalates. Either Lockwood was a time traveller or history keeps repeating itself.

Arwa Mahdawi is a Guardian columnist