We’re familiar with three dimensions, where just three numbers are enough to pin down our location: longitude, latitude and altitude. We’re also surrounded by three-dimensional objects that we describe using length, breadth and height. For thousands of years, the existence of a fourth dimension was dismissed as ridiculous. After all, what would it describe?
But in the mid-18th Century, the French mathematician Jean le Rond d’Alembert pointed out that the fourth dimension could be time. This suggestion was only taken seriously in the 20th Century, when Albert Einstein put forward a new description of the Universe based not simply on location, but on events, each described by four numbers: three for where they occur, and one for when.
Thinking of the Universe as four-dimensional ‘space-time’ proved incredibly powerful, and led to a host of insights about how the Universe and the forces at work in it. For example, according to Einstein, gravity is best understood as being the result of the warping of space-time by matter.
Such insights have led theorists to investigate the idea of more dimensions – in some theories, as many as six extra dimensions, somehow crumpled up too small to observe directly. If true, these theories suggest that hints of the extra dimensions might reveal themselves as new subatomic particles at the Large Hadron Collider. To date, however, there’s no sign of them.