Have you heard of the "Many Worlds" hypothesis? This theory tended to keep the parallel universes separate yet within the same time frame as our own, but now there's a new theory called "the many interacting worlds" hypothesis. This theory states at a quantum level our world interacts with parallel worlds. If this theory proves true, we could one day interact with other parallel universes and maybe even time travel.
Here are a couple articles about this theory: "Parallel worlds exist and interact with our world, say physicists" by Bryan Nelson and "New Radical Theory Shatters What We Know of Parallel Universes, Space and Time."
What do you think of "the many interacting worlds" hypothesis?
I hope everyone is having a good holiday. To celebrate the end of 2016 and the beginning of 2017, I'm giving away a paperback copy of Parallels: Felix Was Here on Goodreads. There will be two winners. You can enter here.