Imagine being a scholar who does not subscribe to the current consensus in your specialised subject. In order to promote your ideas to colleagues in other universities you arrange a specialist talk. Then someone you barely know disinvites you because she has looked at your twitter feed and finds an unspecified tweet that ‘appears rude’, and is ‘not the opinion of your employer’. What do you do? Hearing this story, on Twitter, I was horrified. I work in Academia and the idea that someone might cancel a talk of mine on the basis of personal opinions not related to mathematics (my subject) appals me. In my book on one of the great modern quests in mathematics, I wrote about several mathematicians who worked in Nazi Germany and experienced worse discrimination because they were Jewish. We all know how that ended.

In this case the man is a physicist and his Twitter feed shows opinions that might be considered slightly left of centre, but are firmly in favour of freedom of speech. Is this why he was banned? Or should I say ‘disinvited’? It was certainly the excuse given by the head of the theory group in the Astronomy Department, but there is another possibility. He does not agree with the current emphasis on ‘dark matter’ in astronomy. No-one has ever seen it, but attempts to detect it have led to elaborate experiments and lucrative grants for those who study it. Why then do the proponents of this mysterious matter think it exists? They use it to explain why distant galaxies remain stable despite not containing enough mass for the gravitational attraction that is supposed to hold them together. Dark matter is proposed as the solution. Does it make sense?

This is the problem with physics. Contrivances that fit the observed data but are fundamentally wrong

Before answering that, here is a personal story. When I was in the sixth form at school I asked my physics teacher why two types of mass, gravitational and inertial, were treated as the same. Gravitational mass is the type that keeps the earth held in orbit around the sun, or indeed makes apples on the earth fall to the ground. Inertial mass is what makes a 50-ton truck difficult to move or, if it’s moving, difficult to stop. The teacher did not understand the question. So I asked a different one: why does a body continue in its state of motion unless acted on by outside forces. “That’s Newton’s First Law” came his abrupt response, as if Newton made the laws and the universe obeyed them. My follow-up question asked ‘why’, and suggested the curvature of space-time in General Relativity provided the necessary structure. It was lost on him. Yes, I was an awkward pupil, but let me return to the awkward physicist who had his talk cancelled. He claims that gravitational mass and inertial mass are different, and you don’t need the extra gravitational attraction of dark matter to explain how galaxies hold together.

His explanation involves waves. The universe is made of waves. We may talk of tiny quantum particles like electrons, but they behave like waves. Waves can have vastly different wavelengths. Radio waves have wavelengths measured in metres or even kilometres. For X-rays they are in the range of nanometers (one billionth of a metre). Waves can cause things to move. Take a ship in a harbour. The waves on one side extend out to the open sea and can have wavelengths of almost unlimited extent. Those on the other side are limited by the distance between the ship and the dock. So there are more on the side of the open sea, and that causes the boat to draw towards the dock. This example was pointed out by the awkward physicist — his name is Mike McCulloch — who works in the School of Marine Sciences at the University of Plymouth.

His work shows how waves from deep space can affect anything whose motion changes speed or direction. This includes orbital motion, and he applies these ideas to galaxies where the stars move around a central nucleus. When planets orbit the sun the outer planets take longer than the inner planets because the sun’s gravitational field is weaker as one goes further afield. But the stars in a galaxy keep orbiting at a steady rate. Here’s where dark matter comes in. Not only does it help explain why galaxies do not fly apart, but it can be used to explain the orbital rates by placing it in a ring around the galaxy. How wonderful! Except it seems a bit contrived.

This is the problem with physics. Contrivances that fit the observed data but are fundamentally wrong. In the ancient world think of the theory that the sun orbited the earth in a circle. To explain why the solstices and equinoxes are not quite evenly spaced through the year they offset the centre of this circle from the earth. Aristotle had averred that all cyclic motion must be based on circles, so ellipses were not acceptable. This idea led to the absurd contrivance of circles whose centres moved on other circles (epicycles) to explain the motion of the planets around the earth. These explanations were abandoned for good in the seventeenth century. But science is a continual struggle. In the eighteenth century fire was explained by the loss of a substance called phlogiston into the air as something burned. Nice idea, but wrong. I remember an experiment in school showing that after substances burned down to ash their weight increases rather than decreases. Then in the nineteenth century there was a theory that something called the aether filled regions of the universe above the terrestrial sphere. That failed when the Michelson-Morley experiment to detect the motion of the earth against this aether showed no change as the earth orbited the sun. The resulting confusion led to Einsteins’s Special Theory of Relativity where space and time had to be combined into space-time. The speed of light became a major issue, and although Newtonian dynamics continued to work well at normal speeds, it fell apart at very high speeds. Also at very small and very large scales. The really small scale stuff is brilliantly modelled by Quantum Electrodynamics, but the seriously large scale stuff may need a new theory, because it fails to explain the rotation of galaxies. Hence the theory of dark matter. But McCulloch avoids it using waves emanating naturally from distant horizons in the universe, hence the title of his book: Physics from the Edge. He is even supported by the US Defense and Advanced Projects Research Agency (DARPA) as these ideas may lead to interstellar motion without rocket power.

We make progress by allowing new ideas, and if we don’t do that this country will become a backwater

Abruptly disinvited by the Theory Group at the University of Leeds for an alleged but unproved twitter infraction, he quite rightly struck back and wrote to the head of the Astronomy Department and the Vice Chancellor of the University claiming ‘intellectual bullying’. His talk was reinstated for a later occasion to the department at large, along with the Engineering Department. Apparently it went well, albeit in the new environment where presentations are done on-line. But in the end I don’t know what to make of the dis-invitation. Was it a small-minded attempt to vet the political opinions of physicists from outside the department, or simply a fear of allowing new ideas to contaminate a cosy consensus that pays the bills?

Whatever the truth, one thing is clear. Some academics can be very mean-spirited. I’ve experienced this first hand during a long career, but I worked mainly in America where ideas and research grants are usually wide open to those who want to pursue them. Academics in this country need to allow new ideas rather than orthodoxy and group-think. As for no-platforming people because you don’t like their social media posts, that is childish and absurd. We make progress by allowing new ideas, and if we don’t do that this country will become a backwater.