It’s possible that the universe isn’t uniform past what we can see, and conditions are wildly different from place to place, says Caltech astrophysicist Sean Carroll. “That possibility is the cosmological multiverse. We don’t know if there is a multiverse in this sense, but since we can’t actually see one way or another, it’s wise to keep an open mind.”
The universe we see –stars, moons, planets, galaxies– is but a small, accidental tip of an infinite cosmic iceberg. During the epoch of inflation, thought to have been triggered by the phase transition that marked the end of the grand unification at approximately 10−36 seconds after the Big Bang, the accelerating expansion of space was far more dramatic than in today’s universe, expanding at an absolutely staggering rate, tearing space asunder. During this period no objects—even two elementary particles—remained close enough to one another for long enough to interact.
“Dark energy is incredibly strange, but actually it makes sense to me that it went unnoticed,” said Noble Prize winning physicist Adam Riess in an interview. “I have absolutely no clue what dark energy is. Dark energy appears strong enough to push the entire universe – yet its source is unknown, its location is unknown and its physics are highly speculative.”