A new theory called the Many Interacting Worlds (MIW) suggests that parallel worlds exist, and their mutual interaction gives rise to the weird quantum effects observed in nature.
But, this does not mean we can talk to our better selves in parallel worlds, like Coop does in Nolan's Interstellar.
The interacting worlds proposed by a Texas physicist are very close to each other, as close as nanoscales.
Quantum mechanics, that explains the world of atoms and quarks, confers certain weirdness on the world by referring to objects in terms of the wave function. This only gives a probability of finding an object at a certain position and time.
Hence, the world is not well-defined.
Texas Tech University chemical physicist Bill Poirier's theory does away with the wave and gives a classical world status to quantum reality.
Multiple, classical-like worlds give an object differing, but definite attributes in each by chucking away the probability.
In short, it is a well-defined world. Or, quantum mechanics without the wave function!
Within each world, objects interact with each other classically (defined by Newton's laws) but quantum effects are the results of interactions between objects in parallel worlds.
Poirier clarifies to Huffington Post that only very close by worlds interact, and these are imperceptibly different from each other.
While the distance between each particle and its copy must be in the nanoscopic scale, different particles themselves do not need to be close together in order to experience quantum effects.
In quantum entanglement, a pair of particles once entangled retain their 'memory' of each other even when separated by worlds. This has been tested but on smaller scales than worlds.
In fact, quite recently scientists demonstrated this by using an image taken by light that never saw the object.
Poirier says his theory can account for entanglement.
The MIW theory does not oppose existing theories but merely fits its mathematics into observed phenomena. In fact, its mathematics is equivalent to that of standard wave function-based quantum mechanics.
An earlier interpretation of quantum mechanics by Hugh Everett in the 50s had proposed what is now called the "many-worlds interpretation" (MWI) of quantum mechanics. But it spoke of worlds that continually "branch" into new worlds over time, but do not interact.
The new MIW worlds never branch out but they interact.
As the MIW fits in with experimental observations, it could be correct, says Poirier in the study published in Physical Review X.