The ideas behind the science of invisibility seem to come from a fantastical realm outside the reach of the laboratory. Yet, the tools used to investigate this are not in themselves complicated. Prof. Leonhardt’s work explores the practicalities of invisibility: drawing on cutting-edge optical science which also has profound implications for relativity theory.

The science of the everyday

This research is founded on the connection between geometry and optics: in exploring the space/time curvature for example. This kind of high-impact physics may seem remote from everyday life but the same physics governs the optics of magnifying glasses, or the displacement of objects in water. The best way to describe this process is to think of fish in an aquarium. We see the fish in places other than where they are actually located because the water has distorted the images. Our perception of space is then altered by the water, as our perception is created by the way in which light perceives the altered space.

The research team are testing this distinction by pushing it to extremes to see where it can be taken, and whether any new and intriguing ideas can be developed.

The fundamentals of science

The mysteries of optics have interested scientists for over a thousand years. They have inspired research into what new technology can teach us about the intersection between physics and optics. Beyond this theoretical exploration, Prof. Leonhardt is tracing the potential practical applications: for example in the sharpness and resolution of imaging techniques, and the implications for quantum physics. The forces acting in a quantum vacuum are of particular interest for this project. Whilst these concepts seem abstract, Prof. Leonhardt explains that the vacuum is something we experience day-to-day: “These forces are what make a parking ticket stick to a windscreen. Both surfaces are electrically neutral but they nonetheless attract each other. The forces are particularly important for micro-mechanical devices where they may cause parts of the machinery to get stuck. Our work should aid the development of frictionless devices. The quantum vacuum is also what drives particle behaviour at the event horizon, only on a cosmological scale. This research could shed light on the mysteries of dark energy, the repulsive force which energises the universe, but about which we understand very little.”

The appeal of optics

Prof. Leonhardt’s current line of research began fifteen years ago, when he was giving a lecture course on general relativity. The details of this were unfamiliar, and it prompted him to think about how to communicate it clearly, and to explore the connections between what he was teaching and his background in optics.

This project should enlarge our understanding of the world at both the small and the cosmological scale. Prof. Leonhardt emphasises that the ERC’s commitment to funding frontier research means that “ideas which may seem outrageous can be pursued. Because if they are right they should be taken seriously, however peculiar they may seem. The significant thing is what they teach us.”

The world beyond the laboratory

Prof. Leonhardt’s research is highly imaginative, but the tools themselves are not particularly technical. He believes this is the source of his appeal to the TEDx audience. He argues that the public can be “gripped by frontier research without even labelling it as such. They can then be made to understand that research takes time. We do not always need to think in terms of applications, though of course these can and do arise in the course of research. If we don’t support frontier research we will just carry on refining existing technologies. We may even run out of ideas.”

Discussing the TEDx event, Prof. Leonhardt is adamant that such dissemination events are vital because the science is “publicly funded and so the public should know where the money goes - that it is not wasted and that it produces interesting ideas and applications.” 

The ERC funding is focused on the individual researcher, an emphasis which Prof. Leonhardt argues ideally suits the generation of ideas. Flexibility fosters the kind of science where by definition you don’t know the answers yet. Also inspired by the relationship between imaginative literature, science and musics, he compares the science he does to an orchestra “where both the conductor and the varied musicians are necessary to complete the piece.”