95% of the Universe is missing

Professor Malcolm Fairbairn is a member of the Theoretical Particle Physics and Cosmology Research Group, Kings College London. His research lies at the boundary between cosmology, particle physics and astrophysics. In particular, he is interested in dark matter, dark energy, cosmological inflation and particle astrophysics. He has been awarded an ERC consolidator grant running from 2015-2020 to study dark matter and particle physics in the early Universe.

Richard Bright: Can we begin by you saying something about your background?

Malcom Fairbairn: I am originally from Wigan in the northwest of England, I did my UG and PhD at Birmingham, Cambridge and Sussex then I did postdocs in Brussels, Stockholm and at CERN before coming to King’s College London just over a decade ago. I am a theoretical physicist (so I do calculations rather than experiments), and I work at the intersection of Particle Physics, Astrophysics and Cosmology. I spend a lot of time thinking about the nature of dark matter and how we might learn more about it or even better, discover what it is precisely.

RB: You are involved in a season of events, ‘Dark Matter: 95% of the Universe is missing’, taking place at the Science Gallery, London. Can you say more about your involvement in this and what this season is hoping to achieve?

MF: I had two main roles.  The first was as curatorial advisor to the curators who were putting the exhibition together. The team has evolved a lot because of maternity leave and changes in personnel. When we started the core was myself, Jen Wong, and the main curator Sandra Ross. The old director of Science Gallery London, Daniel Glaser, was also involved in the motivation for this season. There was also a bigger advisory pool of artists but in the early days, Sandra and myself formed the core of putting the exhibition together under moderation by Jen. My main job, the guess the role my personality drove me towards, was to be open minded to the different kinds of artistic interpretations that Sandra would try to discuss and develop, the different threads and kinds of ideas she wanted to develop. However, when I felt she was moving too far away from anything even remotely related to the science that we do, I expressed myself quite clearly. Sometimes we had quite deep differences of opinion. It was not easy for me to work with Sandra and it was not easy for her to work with me, but I am proud of what emerged and I am proud to now call Sandra a friend.

RB: What is dark matter and how is its existence and properties inferred?

MF: We think Dark Matter is some mysterious particle which we think is zooming around, through the earth, through rooms, through the air, through whatever environment you are reading this. I say “zooming” because we think it is moving at several hundred kilometres per second. We think it is there because when we look at the motion of objects such as stars and galaxies, we can only explain how fast they are moving due to some extra gravitational acceleration created by some matter which must be there but which we cannot see.

From a physicist’s point of view, dark matter is rather simple, actually much simpler than normal matter. Normal matter is governed by several forces, gravitational force, electromagnetic forces and the nuclear forces, so it sticks together to form different elements and molecules and emits radiation to cool down and stuff like that.

The only force that dark matter appears to obey is gravity. In particular, it doesn’t emit any light and you can’t bounce light off it, so it’s transparent. Perhaps we should have called it invisible matter, but because we deduced its existence by looking into the night sky and because it doesn’t emit any light, we ended up calling it dark matter.

We can tell it doesn’t stick together or emit any invisible light or even collide with itself by mapping out its distribution in space due to its gravitational effects.

RB: Are there differing theories that aim to provide an explanation for dark matter?

MF: There are lots of different kinds of ideas as to what kind of particle the dark matter could be, and lots of different experiments trying to find the dark matter. Some of physicists favourite theories are the kinds of particles that explain some other complicated problems in physics, such as why there is more matter than anti-matter, but there isn’t really any reason why dark matter should do this. Some physicists think that there is no particle at all, but rather that we have misunderstood the force of gravity on huge scales, but most physicists, including myself, think that some particle which emits no light is the culprit.

RB: Dark Energy is pushing the universe to expand faster and faster. What is dark energy?

MF: Haha! What is dark energy? Well, this is the trillion dollar question. In some sense dark matter is quite boring in comparison, dark matter is just like normal matter that you can’t see, and as the Universe expands it gets spread out. Dark energy is an energy field which doesn’t get spread more thinly as the Universe expands, as if it is being constantly created from nothing. This sounds impossible but we think such exotic forms of matter and energy could exist in the Universe. It turns out we seem to require both dark matter and dark energy to explain the Universe, which is very unsatisfactory for science, but honestly, if you try to live without either it is very difficult to explain the observations.

RB: You collaborated with artists, Carey Young, Agnieszka Kurant and Aura Satz, who are taking part in the Science Gallery, London exhibition. Can you say something about your involvement in these collaborations?

MF: So, mainly I spent time with the artists, many happy hours, listening to their thoughts and explaining about dark matter and dark energy. They often generated analogies and asked me if this is a good fit to what I am describing. They wanted to describe things in terms of things they were familiar with. In some sense this is something we don’t need to do so much as physicists since we describe things in terms of mathematics. Sometimes there are analogies which are pretty exact, and sometimes this kind of exercise fails completely.

Agnieszka Kurant was extremely challenging since she tried to make a lot of connections between many different areas with a freedom I hadn’t experienced before working with artists. It was pretty vertiginous trying to keep up with her train of thought sometimes and the logical jumps that she took in using one issue to mirror another one were quite stretching for me, but in a fun way. She was trying to understand the link between invisible structure emerging from randomness both in society and in the Universe in dark matter. The link is less obvious than in other pieces and also contains elements which are based upon the transformation of energy from one form to another, which is very important in cosmology.

Aura Satz was perhaps more measured in her approach to the piece which she developed. I facilitated a collaboration between herself and some of my colleagues from Goettingen who had performed simulations of dark matter in galaxy. The piece is ten simultaneous pieces of sound which are representations of ten different positions in the galaxy and the interference between them as you move around gives rise to interesting effects. The idea was based upon the idea that you need to tune into the dark matter to detect it in certain models of dark matter referred to a axions.

RB: What questions do you want to address in these collaborations that could not be addressed before?

MF: Each artist had a different set of ideas they wanted to explore. The work with Carey Young, for example, was created nearly a decade ago, with me, and it explores ideas of ownership.  A vessel will have dark matter inside it but it isn’t trapped there – it is constantly flyting through it so if you were to sell the vessel you would be selling dark matter too, although not always the same dark matter.

Many of the pieces in the exhibition question the nature of scientific belief. I guess it takes a great deal of trust in the scientific method to convince oneself that dark matter should exist especially because you can’t see it. We try not to use the word “belief” as scientists but it regularly pops out of our mouths by accident. The word means something different for us though, I think the way physicists believe in things is somewhat different.

RB: What have you personally learnt from working in these collaborations and has this approach thrown up any surprises for you?

MF: It is surprisingly difficult to try to explain why you have come to the conclusions that you have about the Universe to someone who is coming from such a different perspective. I think some of the logical steps that you take about various things are shown to be slightly weaker than you expected.  Ultimately, I think explaining this stuff over and over again to different artists has at least explained to me what I am comfortable with and where my uncertainties lie.

RB: In terms of ‘ways of seeing’ what do regard as the main meeting points between artists and scientists? And what are the differences?

MF: I think artists and scientists are trying to represent things they observe around them in different ways, a scientist will take a thing and only record certain characteristics (position, mass, velocity etc.) and interpret it in a certain way. An artist will record an event using totally different information (feelings, colours) which may transmit equivalent data, with perhaps gross features explained less precisely but detailed features pointed out more clearly.

Obviously the biggest differences is the fact that scientists use mathematics to deduce things, and some things are discovered unexpectedly through calculations and simulations, which often we are not clever enough to predict until they fall out of the mathematical equations. So that is something that doesn’t follow over too well.

RB: Collaboration between the arts and sciences has the potential to create new knowledge, ideas and processes beneficial to both fields. Do you agree with this statement?

MF: I think that working deeply with artists is a healthy exercise for a scientist and will always help them to question their own ideas and practise. There are things that I learnt and new techniques that I picked up which are not immediately useful for my research, but I am a theoretical physicist, so it is quite difficult to come up with stuff that directly affects the day to day work I do. However, I do think it has led me to analyse the kind of ways I present arguments in papers. I think it has affected the way I write introductions and conclusions, and the kind of statistical analyses that I use to prove a point. I think that these changes are subtle, but the kind of self-questioning of practice that you can only get by literally spending hours with someone who is almost trying to understand an alien culture is deep and remains with you.

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