Tyson explains the “Big Rip” theory is based on cosmic expansion, which says the universe continues to expand after the “Big Bang,” and all of the energy and matter within it has remained constant. As the universe expands, the density of all that energy and matter must become thinner.
Tyson says scientists don’t really know why it’s happening, but they know dark energy is causing it to happen, and it is measurable. The expansion rate will eventually outstrip the gravitational forces that hold things together, even overcoming the molecular bonds that hold our bodies together. Those forces will continue to gain strength as the universe expands because as it gets bigger, more vacuum is created. This dynamic will continue until it “rips” or separates our molecules and atoms apart, including the very fabric of space and time.
During the same interview, Tyson dips briefly into the wildly confusing topic of the multiverse and the fact that there might be layers of them stacked on top of each other. Because the existence of a single multiverse, let alone layers of them, isn’t a maddening enough topic.