Date: Unspecified
Time: Unspecified
Location: Myriad Cosmos Corridor, Unknow
The Big Crunch.
It was a scenario predicting a hypothetical fate of the universe, in which the expansion that began with the Big Bang eventually halts and reverses.
They believed the trigger would be gravity. If the universe contained enough matter and energy, the gravity between them would slowly overcome the outward expansion, pulling galaxies, stars, and eventually all of space itself back together into a single singularity.
However, observations of the universe's accelerating expansion suggested that the Big Crunch was unlikely, and most scientists began to favor scenarios like the Big Freeze, in which the universe expands forever and gradually cools toward absolute zero.
Now that I'm listening to BoBo, I realize they got it right, only it didn't apply to their universe.
