A rubber band stretched in different directions behaves differently from a whole sheet of paper. If you pull on an edge, the deformation does not spread evenly but seems to linger in certain spots. Similarly, fractional gravity describes space where the influence of mass is distributed not smoothly but in chunks, as if space itself had not an integer number of dimensions but, say, three and a half.
In the new work, scientists applied this idea to the entire Universe for the first time. They took the equations of fractional gravity and simplified them for a homogeneous cosmos — one where matter is smeared out evenly, like milk in a glass. The result surprised them: expansion can be stable, and the Universe itself may have no starting point. Instead of a big bang, it bounces from a minimum size, like a ball off the floor.
These results were obtained for different mathematical representations of the same theory, and they all agreed. This means that fractional gravity belongs to a universal class of models where the details of space smoothing do not matter. And although a full theory of quantum gravity is still far off, the work shows that our world could have arisen not from a point but from an eternal cycle of contractions and expansions.
The idea of fractional dimensions is not new: a coastline, if measured with an ever-shorter ruler, has a dimension between 1 and 2—it is more jagged than a line but less than a plane.
In Vernor Vinge's novel A Fire Upon the Deep, the laws of physics vary from region to region — fractional gravity could describe such a world, where space has different “graininess.”