I'ts a theory of a cyclic universe where there is no pulsing (expansion/contraction) but an eternal "outward" expansion where the state of the infinitely sparse and empty, cold dead cosmos is indistinguishable from the state of the universe at the big bang.
The reasoning goes that since this disolved universe is equal to the big bang, it is a big bang and… we have another beginning.
Related:: [[Cosmology]]