  It is often thought that the existence of other worlds cannot be
scientifically verified and therefore should be treated as philosophical
speculation. In this article, I describe several methods for determining if
other worlds exist, even without interacting with them. These methods are based
on the following premise: if there are many worlds, then the statistical
properties of a natural process are biased when measured by an observer whose
existence was influenced by the process. The bias is always in the same
direction, making the process appear more beneficial for the existence of the
observer than it actually is. I suggest several potential ways of measuring the
bias, show through a simple model of population dynamics how the bias is
generated, and briefly consider whether our current drop in population growth
is evidence of many worlds.
