Theoretically, how can I travel to a parallel universe?
You’re doing it every time you make a decision.
Let me explain, before going all reality based on me.
While only hypothetical, there is a possibility that there are an infinite number of universes out there. I know, I know… universe technically means “everything”. But there is at least one prevailing theory with some compelling evidence… We exist.
There are an infinite number of possibilities for physical laws. A universe may have any number of gravitational strengths, energy may behave differently, matter might be non existent. The fact that we are in this “Goldilocks” universe, not too hot or too cold, suggests there may be an infinite number out there. In fact, if the strength of gravity was changed just a very minute amount (I’m talking by trillionths of a fraction), our universe would be very different than it is now, without stars, or crushed back to a singularity before it could inflate for more than a few years.
This is called the Many Worlds Interpretation, or MWI, originally formulated by Hugh Everett in 1957.
In MWI, there is a view that every action that has the possibility of one outcome or another, will actually produce two, each diverging into a new, and alternate universe.
Take the Schrodinger’s Cat mind experiment. A cat is placed in a box that is sound proof and completely enclosing, preventing any indication of what is happening inside the box from reaching an outside observer. Inside this box is a device that will release a deadly poison that can kill that cat. The release of this poison is dependent upon a very small amount of a radioactive substance in which the chance of one atom decaying in one hour is 50/50. If the atom decays, the poison is released and the cat is killed.
Erwin Schrodinger posited that while the cat was in the box, it was neither alive or dead, but in a state somewhere in between. It wasn’t until the box was opened and the fate of the cat observed that the actual state coalesced into one of either dead or alive. In other words, the observation actually dictated an outcome.
MWI says that upon observation, the cat is both alive and dead, but in a divergent universe. If we observe the cat as alive, a parallel universe is created at that moment in which our dopplegangers are observing a dead cat.
These are all mind experiments, admittedly, but seriously considered in some circles.
If this is the case, we are travelling into parallel universes all the time, but we just don’t know it, since it appears to be continuous from the previous moments we have experienced.