Scientists are a bit like bird watchers. They set up their experiment and then observe unfolding events from their hide, taking no part in the action, to see what nature reveals to them.
One of the theories that has emerged from such careful observation is quantum mechanics. It's been hugely successful and it dominates modern physics. But perhaps ironically, the theory seems to suggest that passive observation is impossible: the very act of looking at something can change what's being looked at.
In this video interview, we talk to David Wallace, a philosopher of physics at the University of Oxford, and Adrian Kent, Professor of Quantum Physics at the University of Cambridge, about the role of the observer in quantum mechanics.
Explore more about the role of observers in physics with this package of articles and videos.