A recent cosmological model combines two of the most eccentric ideas in contemporary physics to explain the nature of dark matter, the invisible substance that makes up about 85 percent of all matter in the universe. To understand it, it's necessary to look beyond the Big Bang we all know and consider two concepts that rarely intersect: cyclic universes and primordial black holes. A Different Kind of Multiverse There are different versions of the “multiverse.” The most popular model—that of the Marvel Cinematic Universe—proposes that there are as many universes as there are possibilities and that these versions of reality are parallel. Physics proposes something more sober and mathematically consistent: the cosmic bounce. In this model, the universe is not born from a singularity, but expands, contracts, and expands again in an endless cycle. Each “universe” is not parallel, but sequential—that is, one arises from the ashes of the previous one.…