Imagine if your body weight depended on the colour of your underwear. Strangely, something quite similar happens when you make measurements in quantum mechanics.

The predictions of quantum mechanics have been tested endlessly in experiments and they hold true, but could it be that the theory simply isn't complete? Could there be hidden variables — some extra information — which, if we include them, give us a theory that isn't random or fuzzy? The answer is yes, but not without a price. Such a theory will always exhibit something called contextuality: the outcome of a measurement will be heavily distorted by your experimental set-up, so try as you might, you can never be an impartial observer.

We talked to Jeremy Butterfield, philosopher of physics at the University of Cambridge, to find out more.

Explore the concept of contextuality further with the articles in our Context is everything package.