Why not two or four spatial dimensions? One researcher, James Scargill, argues that we could possibly have made do with two dimensions:
There’s a pretty convincing anthropic argument against life in a universe with more than three spatial dimensions. Newtonian gravity predicts that orbits aren’t stable in a universe with additional spatial dimensions. Without orbits, you don’t get galaxies, stars, planets, atoms, or life.
Stable orbits are possible in a universe with two spatial dimensions, but there are other anthropic arguments against the possibility. Here are two of the most common:
-General relativity isn’t consistent with a 2D universe -Complex life can’t form in a world where things like neurons don’t cross paths…
“Overall it would seem that if one wishes to use anthropic reasoning to explain the observed dimensionality of spacetime, then the possibility of life in 2+1 dimensions [includes time – News] requires further investigation.”
This research raises so many fascinating questions. What conditions are necessary for complex life? On the flip side, what would rule out the possibility of life? If life could have existed in 2+1 dimensions, why do we exist in 3+1? What would life look like in 2+1 dimensions?Kendra Redmond, “Why do we live in a three-dimensional world?” at Physics Central
Scargill’s paper. (open access)
Note: As Redmond notes, a satirical 19th century novel, Flatland, depicted a two-dimensional world.
See also: Flatland: The Movie (2007) :