Like the cosmos littered with stars,
the dark ages were sprinkled with beacons of scientific light.
When physicists translated a 13th-century Latin text into modern equations, they discovered that the English theologian, who wrote it had unwittingly predicted the idea of the multiverse in 1225.
While the work probably won't advance current models, it does show that some of the philosophical conundrums posed by cosmology are surprisingly pervasive.
Tom McLeish, a physicist at Durham University, UK, and his colleagues applied modern mathematics to a 1225 treatise on light, "De luce", written by medieval philosopher Robert Grosseteste.
"We tried to write down in maths what he's said in Latin words," says McLeish. "Then you have a set of equations, which you can then go about putting it in the computer and solving. We're mathematically exploring a new type of universe, which is what string theorists do all the time. We're just medieval string theorists."
Grosseteste had been studying the recently rediscovered works of Aristotle, which explained the motion of the stars by embedding Earth in a series of 9 concentric celestial spheres. In "De luce", Grosseteste proposed that the concentric universe began with a flash of light, which pushed everything outwards from a tiny point into a big sphere.
Grosseteste assumed that light and matter are coupled together. When the initial pulse of expanding light-matter reached a minimum density, it entered what he called a perfect state and stopped expanding. This perfect sphere then emitted a different form of light called lumen, which propagated inwards and swept up lingering "imperfect" matter, compressing it like a snow plough. The less dense region of light-matter left behind could then reach its perfect state and crystallise into a new sphere embedded in the first one, which would emit its own lumen. This process continued until only a core of imperfect matter was left behind, which gave rise to Earth.
Crunching the numbers, McLeish's team found that computer models of this process will yield exactly the sort of universe Grosseteste was describing: inwardly propagating concentric spheres. This is analogous to the way modern cosmologists use observations of the cosmic microwave background, relic radiation from the big bang, to test out mathematical models of the modern universe, including a predicted period of rapid expansion called inflation.
"The paper formulated the Grosseteste model in terms of differential equations that can be solved with modern numerical techniques," says cosmologist Avi Loeb at the Harvard-Smithsonian Center for Astrophysics in Cambridge, who was not involved in the work. "As such, the model is well defined."
And unbeknown to Grosseteste, his universe predicts one of the most puzzling possibilities of big bang cosmology: the multiverse. Current models agree with observations only if certain parameters take particular values – if the forces holding matter together were stronger or weaker, for instance, the universe would not look the way it does.
Scientists call this the fine-tuning problem, and one way to solve it is to say there must be an infinite number of universes in which all outcomes are possible. We live in this one because it happens to be well-suited for life. The outcome of Grosseteste's model depends similarly on its initial state. Change the way light and matter couple together, and you can get a different number of spheres.
"Obviously he didn't realise that there could be many multiverses," says McLeish. "But what will people in 800 years' time be thinking about the assumptions we're making? There's a bit of humility in realising that we're constrained by what we can see and what we can't."
Loeb agrees that the results echo some of the philosophical trademarks of modern cosmology. "Once future generations of cosmologists have a better understanding of inflation, they might look at our current world view in much the same way we look at Grosseteste's worldview. We have made a lot of progress since the 13th century, but we still have a long way to go."
Reference: arxiv.org/abs/1403.0769, and accepted to the Proceedings of the Royal Society A