Not just an item of science fiction and comedy TV shows, the theory of our universe existing as a part of a multiverse does exist and real physicists do believe it. The idea is simple enough; take our minimum-four dimensional universe (some theories put the count at 7 or more) and place it in a bubble with dimensionality of at least one higher. Of course our bubble is not alone in its multiverse environment, and every other bubble contains its own universe. These universes may be very different from ours though, and not in the simple goatee-wearing way, but the strength of forces and masses of particles being different way, hence why physicists are interested. Imagining a universe with weaker gravity than our own, not only would we have all lost a few pounds but, potentially, there would be fewer stars, as more mass is required to start their nuclear fusion cores. If the masses of particles were different, let’s say greater, than stars could possibly be bigger and burn brighter than those we see at night, as more energy may be released by fusion.
Researchers from University College of London have proposed a way to observe if these other universe-containing bubbles exist by viewing the cosmic microwave background radiation. Their theory is that when our bubble collides with others, a mark will be left on the universal pattern. To test this they have devised an algorithm to examine the information and discern patterns from noise, a difficult task.