Is There a Fifth Dimension?
In particular, an extra dimension which behaves like space (instead of like time) but is compact rather than infinite features in many theories of particle physics. There are now a lot of theoretical physicists who make a living calculating details of models with extra dimensions like, say, if a fifth dimension existed with these specific properties what would it do to this bump in the cosmic microwave background or such. Peter Woit
Senior Lecturer in the Mathematics department at Columbia University
There are lots of ways of adding a fifth dimension, the problem is just that if it’s anything like the other four, there’s no experimental evidence for it at all, and no viable theory that uses a hidden fifth dimension to explain anything convincingly.
Source: gizmodo.com