From Ross Pomeroy at RealClearScience, on understanding the Big Bang:
“It certainly looks like the universe that we observe around us… definitely had a beginning,” MIT cosmologist Alan Guth, the originator of the theory of cosmic inflation, said in an interview for the PBS show Closer to Truth. “That doesn’t mean that that beginning was necessarily the ultimate beginning of all of reality. There may have been some prehistory to what we’re here calling the beginning.”
Fanciful ideas abound to account for that prehistory. Eternal inflation suggests that our universe is but a mere bubble in what physicist Matt Francis described as a “larger froth of inflation” of an even grander universe. Cyclic inflation proffers that our observable universe is the region in between two membranes of parallel shadow universes. Another theory proposes that our universe emerged from the singularity of a black hole and we are contained within the event horizon. More.
None of these ideas are testable, as Pomeroy notes. Maybe one can have cosmology or science.
See also: The Big Bang: Put simply, the facts are wrong.