Scientists have battled for a long time with a niggling philosophical concept known as the anthropic principle. The gist of it is that humans shouldn’t consider themselves special; despite the laws of physics appearing to be favorable to intelligent life like us, there must be other reasons for its emergence.
A particularly fascinating application has to do with gravity and space-time. We live in a pretty good continuum with three spatial dimensions and a time dimension, but is this 3+1 configuration the only possibility for life? Having more than one dimension of time throws predictability out the window and more dimensions of space make orbits unstable, meaning the existence of the solar system is impossible.
The argument for less than three dimensions is not as strong. Physicist James Scargill has recently published a paper in arXiv showing that there are ways to make gravity work in a 2+1D universe. The theory of gravity doesn’t work like ours, but it does allow for stable orbits. The researcher describes it as “a not-obviously-fatal (though unusual) cosmology."
Scargill decided to take this a step forward. Having established that gravity works (albeit differently), he looked at ways for life to exist. He went for a simplistic approach to life based on mathematical concepts, although not like that of the sentient geometric shapes of Abbott’s satirical work Flatland.
“I have turned to research that has been conducted into the properties of biological neural networks, and created a family of planar graphs which seem to exhibit many of the properties which have been conjectured to be important for complex brains,” Scargill, who works at the University of California, Davis, said in the paper.
These networks are complex, but the researcher states that while it is intriguing, it is certainly not conclusive to declare that a complex brain inhabits the gravitationally bizarre 2D universe. Scargill is actually intrigued if he has overlooked some consideration necessary for this complexity to exist.
His argument brings us back to the anthropic principle. If a 3+1D universe is the only one that works, this cannot be because of life, as a 2D universe might also be in the running for that. Maybe a more complete theory of physics (or a better consideration of biological neural networks) will help us to clear that up.
[H/T: MIT Technology Review ]