We've talked about that conflict and its possible resolutions before, but the upshot is that we just don't know how the universe behaves in those conditions. But we do know that pure general relativity is not a good description, and so we probably shouldn't believe its prediction that all space was compacted into a single point and that this is where time started. Okay, so what are the alternatives? Can we really track geodesics and the timelines they embody through the Big Bang and out the other side? If so, what do we find there? There are several possibilities, and they deserve their own episodes, and we'll actually get to those soon. But to whet your appetite, first up, cosmic inflation can offer a temporary reprieve from the singularity. Eternal inflation suggests that our universe appeared as a regularly expanding bubble in an unimaginably larger, continuously inflating space-time. In that case, before the Big Bang was a period of exponential expansion that could have lasted indefinitely. We'll get to the nitty-gritty of that with its inflotons and bubble universes real soon. There are also various cyclic universe options. The first cyclic universe idea was the Big Bounce, in which the gravitational attraction of all matter in the universe was enough to cause it to re-collapse and then presumably bounce outward again. We now know that there isn't anywhere near enough matter to do that. Unless we bring in string theory. The Steinhardt-Turok model suggests that our universe floats in a high-dimensional space, living on geometric objects called brains. Collisions between those brains initiate cycles of expansion and contraction. Then there's Roger Penrose's conformal cyclic cosmology. It's even weirder because it postulates the infinite future boundary of an eternally expanding universe looks like the Big Bang of a new universe mathematically. So our heat death is someone else's Big Bang. There are some less abstract ways to get a new Universe out of an old one. For example, an extreme quantum fluctuation could initiate a new Big Bang given infinite time. Or the same amount of time could lead to all particles randomly converging back to the same spot. Or maybe black holes birth new universes as in Lee Smallins' fecund universe hypothesis. There's a poetry to that last one. The geodesics approaching the black hole singularity become the geodesics emerging from the new Big Bang singularity. People love cyclic and regenerating universes. They appeal to our sense of narrative, which might be a reason to be wary of these hypotheses. Now, they also appeal to our intuition for causality.