In January, a controversial new podcast soared to the top of the charts. A series that promises to “challenge everything we think we know about communication and the human mind”, The Telepathy Tapes claims to show that non-verbal autistic children can read minds. Unsurprisingly, social media has been abuzz with discussion about the rigour of the science — or perhaps pseudoscience — that is presented on the show. It is easy for most scientists to instinctively dismiss the field of parapsychology, which deals with ideas like telepathy and clairvoyance, as pseudoscience. But where does the boundary between science and pseudoscience lie? And what is the best way for scientists to engage with pseudoscientists?

As historian of science, Richard Noakes, discusses in a Comment in this issue, many eminent Victorian physicists were fascinated with the paranormal. They employed the same scientific methods to probe ‘supernatural phenomena’ as they did to their work on more mainstream topics, which makes it difficult to write off their work on levitation and telekinesis as pseudoscience on methodological grounds. Instead, a more helpful framework, as Noakes describes, is to think of science as having a core of mainstream, accepted views, and a fringe of unusual, controversial views. Research topics move between the core and the fringe, as fashions, social values and experimental techniques change. What remains constant through these ebbs and flows in areas of study are the scientific methods employed to study them, and the humility and open-mindedness of scientists to accept that ideas may be wrong.

“What remains constant through these ebbs and flows in areas of study are the scientific methods employed to study them”

For a long time, the aether — a medium in which electromagnetic waves were thought to propagate — was an accepted part of core physics. Unlike the story presented in many introductory courses in general relativity, the existence of the aether was not conclusively refuted in a single experiment from Albert Michelson and Edward Morley. Instead, it was dismantled bit-by-bit over the course of about 20 years. Today, a belief in the existence of the aether is decidedly fringe, thanks to the cumulative weight of evidence for special relativity, which requires that there be no fixed reference frame. Yet, although there is community consensus that the aether does not exist, metrologists continue to engage with the aether, insofar as to rule out its existence to increasingly high levels of accuracy.

Conversely, fringe ideas sometimes move to the core of physics research. Einstein’s theories of relativity were accepted quickly, but at the same period in history, quantum mechanics took a slower path into the core of physics research, mainly because it posed such a challenge to our intuitive view of the world. Although debates about its implications on the nature of reality would have been commonplace in the 1930s, such discussions have now been taken out of physics seminar rooms and placed in philosophy departments. To a physicist, perhaps some of these debates have moved back to the fringe. To a philosopher, they remain within the core of their discipline.

Indeed, the boundaries between physics and other disciplines are a relatively recent conception and for many years, practitioners of physics would have referred to themselves as ‘natural philosophers’. As historian of science, Iwan Rhys Morus, writes in a second Comment in this issue, the term ‘physicist’ was extremely unpopular when it was first proposed, as it was felt to be far too limiting. People such as Lord Kelvin believed that their work was generalist and that concepts like electromagnetism and thermodynamics could be applied to explain everything, not just physics.

Today, most physicists would concede that maybe thermodynamics can’t explain quite everything. However, the scientific methods and analytical thinking that physicists use can lend themselves to judging the rigour of scientific claims in other areas. An article1 published by the McGill Office for Science and Society, which aims to “separate science from nonsense” does just this with The Telepathy Tapes. It carefully analyses each of the experiments presented on the podcast through a scientific lens and refers to broader literature in the field, to dismantle the claims of the show piece-by-piece. When engaging with topics at the fringes of science, it is important not to dismiss them out of hand for being esoteric, but to critically evaluate them on their methodological merits.