According to a study by French researchers, our universe could well be a three-dimensional torus; a form which, if confirmed, would involve many topological peculiarities.
Our Earth may be very large, it remains almost insignificant on the scale of the universe. It extends far beyond what our technology allows us to observe, and many secrets remain hidden at the far ends of the cosmos. And among these burning questions, there is one that has always fascinated astrophysicists: the shape of the universe. Is it a simple sphere, as intuition might suggest, or is the reality more complex? Recently, French researchers at the University of Lyon have added a new layer of complexity to this gigantic puzzle. According to them, the universe is in fact shaped like a torus, better known as a donut. But not just any: it would be a three-dimensional donut – or more precisely, a 3-dimensional manifold torus-, with properties as interesting as they are confusing.
The diffuse cosmological background sells the fuse
To come to this conclusion already considered in the past, Thomas Buchert and a team of astrophysicists have analyzed one of the oldest phenomena in existence: the diffuse cosmological background. This is the residual radiation dating from the Big Bang, at the origins of our world; it is so interesting for many reasons, but in this specific case its interest is that it can tell us a lot about the shape of the universe.
Indeed, in an infinite space, the theory stipulates that these disturbances of the cosmological background would be visible at all scales, from the smallest to the largest. With the help of the probe WMAP from NASA and satellite Max Planck of ESA, the researchers therefore scrutinized this radiation to map it at different scales. And there surprise : Researchers’ surveys show that certain wavelengths of this radiation are missing.
These results correspond rather badly to those which one would expect to find in the standard cosmological model, in which the universe is considered to be infinite. On the other hand, they very similar to the models made with a tore; that strongly suggests that the universe would indeed be a 3-dimensional donut. “The conclusion of our paper is that the model of the finite universe corresponds much better to observations of the cosmological background than the model of the infinite universe”, Summarizes Thomas Buchert.
A change of model to be expected?
This statement could have significant implications. Because according to the various existing models, a toroidal universe would not only be finite, but also much smaller than one thought; it would be barely three or four times the size of the observable universe, against several hundred for the theory in force so far.
It would also mean that eventually, the universe would end up “bouncing” to collapse on itself, rather than stretching indefinitely. Another potential consequence of this curious form: the universe could theoretically present what mathematicians and astrophysicists call topological mirages. If a spaceship travels in one direction without stopping, it should eventually end up at its starting point … provided it moves beyond the speed of expansion of the universe, however.
If you wish to delve deeper into the fascinating but extremely complex question of cosmic topology, this excellent introduction by Jean-Pierre Luminet is a formidable gateway.