The ADD and Randall Sundor Models

In the Cluze-Kline theory, even though that dimension wraps around on itself, it's actually flat or Euclidean. The enthusiasm for theories like this did subside when these experiments failed to detect evidence of them. So we consider the possibility that there really isn't a distinct species of particle that makes up the dark matter. It's just normal particles that happen to be moving through an extra dimension of space.