It does! We predicted that if you zoom in far enough, space-time loses its 4D nature. To see it, you have to study another sort of dimension, the dimension revealed by diffusion. For example, an ink drop spreads differently on a 2D page than it does in a 3D water glass, so by looking at diffusion you can get a sense of what sort of space you\u2019re in.<\/p>\n

Here, we found a remarkable result. When we simulated the release of an ink drop in our 4D universe, it spread out as if it were stuck in a roughly 2D space \u2014 although only for a few instants. Once it has time to spread out further, it spreads in a normal fashion.<\/p>\n

But it\u2019s not like it\u2019s literally spreading through a flat sheet. It\u2019s more as if the quantum structure of space-time over very short distances is fractal-like. That is, the space is fully filled in, but it\u2019s wired up in such a way that certain parts of it aren\u2019t initially as accessible as other parts. Here we have a microstructure that has a quantum imprint, but if you zoom out, everything looks fine and 4D. Hooray!<\/p>\n