How a medieval philosopher dreamed up the ‘multiverse’
The idea that our universe may be one among many has intrigued modern cosmologists for some time. But this concept might have appeared, albeit unintentionally, back in the Middle Ages. When scientists analysed a Latin text and applied modern mathematics to it, they found hints that the English philosopher who wrote it in 1225 was already toying with concepts similar to the multiverse. Scientists translated the text – De Luce, which means ‘On Light’, by philosopher Robert Grosseteste – into English. They then tried to understand what he was aiming to explain, and wrote down his ideas as if they were modern mathematical equations. A team used a computer to solve these equations and to see whether they explained the universe as Grosseteste imagined it.
In his time, the dominant cosmological model was the one developed mainly by Aristotle. He postulated that there were nine planets (spheres), one inside the other, with Earth at the centre. Grosseteste assumed that the universe was born from an explosion that pushed everything, matter and light, out from a single point – an idea strikingly similar to the modern Big Bang theory. However, Grosseteste’s reasoning only works if there’s the right number of properly ordered celestial spheres, and this only happens in simulations if there are very specific starting points.
The medieval philosopher realised this problem. To deal with it, he added an extra reason to explain why there were exactly nine celestial spheres plus one – an ‘imperfect’ Earth. His explanation was remarkably similar to the reasoning applied in modern cosmology. Today, the laws of general relativity and quantum mechanics are used to explain the origin of the cosmos, but they don’t tell us the amounts of normal matter, dark matter and dark energy in the universe. In other words, current models work for only certain specific values, and if the values are chosen at random, the explanation fails.
To satisfy these conditions, some physicists suggest that we live in a multiverse – that there is not one universe, but an infinite number of them. In this way, any outcome can be accounted for, if not in ours, then in a neighbouring universe. In the same way, if the parameters in Grosseteste’s model are modified, there will be a different number of spheres around Earth. Although De Luce never mentions the term ‘multiverse,’ Grosseteste seems to realise that the model does not predict a unique solution and that there are many possible outcomes.