There’s some, but not overwhelming, evidence that dark energy is evolving. What would it take for a “Big Crunch” to be our cosmic fate?
Back in the 1920s, the first pieces of crucial evidence came in that indicated a truth about our reality that we’ve been stuck with ever since: the Universe is expanding. This simple fact has led to an enormous suite of subsequent discoveries: the hot Big Bang, the cosmic microwave background, the growth of the large-scale structure of the Universe over cosmic time, and much more. It’s also led to a profound existential question: how will the Universe end? If it’s expanding, which it is, and the expansion rate has decreased over time, which the evidence also supports, then what will happen in the far future? Will the expansion continue forever? Will it continue to decrease, or will it increase again? And if it does decrease, will it ever drop to zero and then, afterwards, reverse itself?
That last scenario, once favored by many, would lead to a set of circumstances that would behave like a “Big Bang in reverse,” also known as a Big Crunch. It would have seemed to many, with the discovery of dark energy (and the consistency of dark energy with being a cosmological constant), that the Big Crunch…
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