The letter arrived in Physics World‘s in-tray last summer. Written in blue ink, with occasional recourse to red for especially important points, it claimed to predict the date of “The Second Coming of the Lord Jesus Christ” using images from the Hubble Space Telescope. The specified date came and went without incident, and we were somewhat surprised to receive another letter from the same source. This one was labelled “The Second Coming of the Lord Jesus Christ (Correction)”, and it posited a new, later date for Jesus’s arrival. The revised date was calculated using the rotation period of the planet Venus, plus a simple mathematical identity that, according to our correspondent, “angels know and use”. Two subsequent letters contained further revisions, and the current predicted date is 22 September 2012. But in the letter-writer’s words, “only GOD knows whether the new presented date is the correct one”, so mere mortals like us will just have to wait and see.

Nearly all professional physicists receive at least one letter like this a year. In most cases, such letters go straight into the recycling bin, although a handful of the best – including Physics World‘s “Lord Jesus Christ” correspondence – end up in semi-permanent storage. But these ad-hoc attempts at crackpot curation pale in comparison with those of the science writer Margaret Wertheim. For the past 15 years, Wertheim, a physics graduate, has assiduously collected all the letters, books, glossy brochures and poems she receives from people peddling their own theories of the universe. After accumulating two long shelves full of such material, and investigating a few of the authors, she has distilled her experience into a fascinating and occasionally frustrating book called Physics on the Fringe: Smoke Rings, Circlons, and Alternative Theories of Everything.

Wertheim’s book is fascinating in large part because she has boldly gone where few trained scientists have gone before. Rather than ignoring the people she calls “outsider physicists”, she has engaged with their ideas, attended annual conferences organized by their professional body (yes, they have one) and even driven 1000+ miles to visit one of them. All of this qualifies her to draw conclusions about who outsiders are and what makes them tick, but for the most part, she avoids sweeping generalizations. The truth, she writes, is that outsider theorists are a varied bunch, and as for their ideas, “there is very little that unites the disparate range of theories in my collection except for the sense that mainstream physics is badly off course”. They also display what Wertheim calls “a startling inattention to copy-editing”.

A few common threads do emerge. For example, Wertheim observes that the men (and they are almost all men) who create alternative theories of physics frequently have some kind of technical background, such as engineering. Despite this, they reject mathematics as a means of understanding the world, and rely on words rather than equations to explain their ideas. They write in a kind of scientific pidgin, they describe their work as “revolutionary” – and, of course, they view the establishment’s failure to acknowledge their brilliance with dismay and befuddlement.

In the middle part of her book, Wertheim turns away from studying outsider physics as a whole, and instead focuses on one particular outsider, whom she dubs “the Leonardo of the field”. For me, this is where the book’s frustrating aspects begin. The object of Wertheim’s journalistic interest and affection is Jim Carter, a successful inventor who lives in a trailer park in rural Washington State. It is not hard to see why she has singled him out. For starters, Carter is obviously sane and, as a theorist, he is clearly operating on a more sophisticated level than Physics World‘s “Lord Jesus Christ” correspondent. Carter’s “circlon” theory of atomic structure is unusually coherent, lacking the non-sequiturs and characteristic rambling style so beloved of outsiders and, like many mainstream physicists, he is motivated by a deep desire to understand how the universe works. To this end, he has spent more than 50 years developing his theories. Remarkably, one of them even makes a prediction that could be tested – albeit only during a space mission.

And therein lies the nub of Wertheim’s argument. In 2010 she attended the annual conference of the outsiders’ professional body, the Natural Philosophy Association, which that year featured 121 outsider physicists presenting 121 different theories of the universe. This might sound bizarre, but in Wertheim’s opinion it was beaten hands down by the string cosmology conference she attended in 2003. At this star-studded event, she writes, participants were “fired up” by the idea that there could be as many as 10⁵⁰⁰ different variants of string theory, each of them totally different – and all utterly unsupported by a shred of evidence. So why are string theorists respected physicists with television programmes and book contracts, while Jim Carter and his brethren are regarded as a bunch of cranks?

One answer is that the string theorists have gone through a lengthy training process. This is rather a straw-man argument, though, and Wertheim is accordingly quick to demolish it. Some fields of endeavour, she reasons, should indeed be restricted to trained and accredited personnel: brain surgery, for example. But others, such as art and lovemaking, are rightly left open to pretty much anyone, regardless of their qualifications or ability. The question, she suggests, is whether theoretical physics is more like brain surgery or more like sex.

In case this argument fails to convince, Wertheim has another. Outsider theorists draw meaning and personal satisfaction from their work, she observes. For this reason, she writes, “Might we not simply enjoy their alternative narrative arcs?”

Physics on the Fringe is a great read, and Wertheim a persuasive writer with a knack for challenging unspoken assumptions. But there are two significant problems with her thesis. The first is that most theoretical physics is not like string theory. Wertheim sort of acknowledges this when she discusses string theory’s critics within the physics community, but I wish she had said more about the role of experimental evidence, since many areas of theoretical physics are supported by truckloads of it. One does not need to be an elitist or a fan of mathematical elegance to believe that quantum mechanics – to take just one example – is “true”, while alternative theories are “false”, in the scientific senses of these words.

The second problem is that most outsider physicists are not like Jim Carter, and unfortunately this is something Wertheim addresses only obliquely. Carter comes across as an intelligent and likeable eccentric, and I wouldn’t mind visiting him, as Wertheim did, in his remote forest idyll. But some outsiders are not so amiable. There is a distinct streak of anger and grievance running through their letters, and while Wertheim claims that mental illness is rare in the alternative-physics community, I am not so sure. In any case, even if the self-regard of outsider theorists falls short of pathology, the sheer chutzpah required to persevere in the face of universal condemnation is not always benign. People who fervently believe their theories are correct sometimes react badly to criticism, and if they have enough money and power, they can do real harm.

That statement might sound like hyperbole, but I know of at least one person who learned, to his cost, just how true it was. I would like to name him, but unfortunately, some cranks have a penchant for making legal threats, and England’s strict libel laws mean it is safer not to. So you will just have to trust me when I say that this particular “alternative narrative arc” was not, in fact, very enjoyable for any of the people who found themselves enmeshed in it.