Our Universe appears to be expanding and cooling, having originated some 13.8 billion years ago in a hot Big Bang. However, it’s plausible that what we see from inside our Universe is simply the result of being inside a black hole that formed from some parent Universe. If the black holes that form in our cosmos give birth to baby Universes, perhaps we arose from the formation of a black hole ourselves.
One thought that always fascinated me was the idea that maybe our universe does appear to outsiders … but it only appears as a sudden momentary flash. We see billions of years, they barely notice a spark.