There is an active field of research in cosmology and physics seeking to explain the cosmos in terms of a radical idea: we live in a universe with some of the properties of a hologram:
At first glance, there is not the slightest doubt: to us, the universe looks three dimensional. But one of the most fruitful theories of theoretical physics in the last two decades is challenging this assumption. The "holographic principle" asserts that a mathematical description of the universe actually requires one fewer dimension than it seems. What we perceive as three dimensional may just be the image of two dimensional processes on a huge cosmic horizon.
That's a mind-being principle and the math behind it is a fearsome thing, pulling together rigorous work on everything from event horizons to string theory to the quantum information paradox. It's not easy to describe some of the ramifications that emerge in general terms.
But if you drift below the fold, thanks to no small amount of help from Jennifer Ouellette, one of the best hard-science writers in the world today, we'll at least try. And we'll do that without bringing up hyper-advanced mathematics!