How important are experiments in science? Scientists use experiments to check whether a theory's predictions match up with reality, so without them you can't pick out bad theories.
In theoretical physics, however, there are many theories that cannot be tested. Not only because our experimental tools are nowhere near good enough, but also because there's some fundamental reason that stops us exploring some of the predictions those theories make. Examples are string theory, M theory and the various multiverse theories. Should we pursue them anyway, or dismiss them as speculation?
This debate, featuring one of our favourite theoretical physicists, David Tong (among others), explores this question and asks whether physics has strayed too far from experiment. It's been produced by the Institute of Art and Ideas in London.