The well-known Drake equation, created by Dr. Frank Drake in 1960 to predict the number of extraterrestrial civilizations in the Milky Way, gets an upgrade to take into account the concept of multiple universes. Turns out our knowledge is so limited as to make the exercise essentially impossible.
From the second link:
But there’s a problem: this is not an equation. To form a true Drake-like argument, Gleiser would need to assign probabilities to each of these sets allowing him to write an equation in which the assigned probabilities multiplied together, on one side of the equation, equal the fraction of universes where complex life emerges on the other side.
Here he comes up against one of the great problems of modern cosmology–that without evidence to back up their veracity, many ideas in modern cosmology are little more than philosophy. So assigning a probability to the fraction of universes in the multiverse in which the fundamental constants and laws satisfy the anthropic principle is not just hard, but almost impossible to formulate at all.
Gleiser’s take on the Drake equation for the Multiverse is an interesting approach. What it tells us, however, is that our limited understanding of the universe today does not allow us to make any reasonable estimate of the number of intelligent lifeforms in the multiverse (more than one). And given the limits on what we can ever know about other universes, it’s likely that we’ll never be able to do much better than that.