The discovery of quantum mechanics at the start of the 20th century shook the very foundations of physics, forcing scientists and philosophers to reexamine everything from particles upward. But as this short animation from MinutePhysics explains, the quantum revolution was jumpstarted by a rather unremarkable question. As the German government asked the theoretical physicist Max Planck: how can lightbulbs be made more efficient? To help solve the problem, Planck tried to account for the changing colour of light based on temperature, which he eventually realised couldn’t be explained by classical Newtonian physics. Working backwards from his data in ‘an act of despair’, Planck found that light wasn’t emitted continuously, but rather in discrete packets that he referred to as ‘quanta’. And the rest is the illusory arrow of time that we call history.