The universe is expanding faster and faster, but not all scientists agree that dark energy is the cause. Perhaps, instead, our universe keeps colliding with and absorbing smaller 'baby universes,' a new theoretical study suggests. Our universe is expanding at an ever-accelerating rate — a phenomenon that all theories of cosmology agree upon but none can fully explain. Now, a new theoretical study offers an intriguing solution: Perhaps our universe is expanding because it keeps colliding with and absorbing "baby" parallel universes. Studies of the cosmic microwave background, the afterglow of the Big Bang, have revealed that our universe is...