Ditching the Indeterminate Cat: Griffith Scientists Suggest Testability of their Many Interacting Worlds Theory

Author: Belinda Ongaro

Institution:  University of Alberta


It may be a bit mind-bending to consider the possibility of parallel worlds interacting, let alone existing, but a recent theory proposed by Griffith University researchers suggests that there may be more to their model than science fiction. Professor Howard Wiseman and researcher Michael Hall, PhD, from Griffith University, along with Dirk-Andre Deckert, PhD, of the University of California, recently reported that their radical “Many Interacting-Worlds”(MIW) theory is not only plausible, but also potentially testable.

MIW theory postulates an abundance of parallel worlds that coexist and interact with one another, including our own. On the other hand, the prevailing Many-Worlds Interpretation (MWI) envisions a continuous propagation of worlds that never interact, with “each universe branch[ing] into a bunch of new universes every time a quantum measurement is made,” according to Wiseman. Clearly, the prospect of coming in contact with parallel worlds holds a little more intrigue.

The MIW approach posits that the parallel universes have always existed and that they experience interaction with other worlds. The “interaction” they refer to is one of mutual repulsion between similar worlds, comparable to how the common poles of a magnet will repel each other, which consequently renders them more different.  

The research team describe the “interacting” aspect of their theory by means of analogy. If world A and world B are represented by independent gas entities they will experience the presence of each other much the same as they would experience the presence of particles of their own respective entities. The interaction is negligible unless all of the A gas particles are in close proximity to their B counterparts, at which point their interaction becomes quantifiable. The associated particles hold similar locations in both worlds; therefore, when they are in close proximity they experience repulsion. The whole point of parallel worlds is that they are unique, so this force prevents the configuration of any two parallel worlds from becoming too similar.

Furthermore, the Griffith researchers propose that worlds comprising our universe are equally real; there is no “true” world that serves as a reference point outside of our own subjective frame of reference — a common and natural assumption. Egocentric people often need to be reminded of the fact that they are not the center of the universe; coincidentally, our universe may not be the center of all universes either.

As a result, MIW approach differs from preceding models on the basis of wave function; the solution to the Schrödinger equation, which describes how a physical system’s quantum state changes with time. In the approach taken by the Griffith scientists, probabilities of different states being realized only arise because we don’t know which world we occupy, so wave function is essentially irrelevant. How could all possibilities “collapse” or settle on existing in a single state if the observer’s perspective is arbitrary? Dead or alive, Schrödinger’s cat gets to sit this one out.

"Once you have six or seven quantum particles interacting, the Schrödinger equation is far too hard to solve, even approximately," Hall says. "With our theory, we just have to worry about where the particles are in each world, and calculate that inter-world force between them."

Conceptualization aside, the findings of this model, where a large but finite quantity of worlds are considered, may someday give rise to real-world applications in technology, although the “how” and “what” are still a little fuzzy. Being in its early stages, their model has yet to explain quantum entanglement – the idea that particles are linked in terms of their properties although they may be located a distance away from one another.

“By no means have we answered all the questions that such a shift entails,” says Wiseman.

Looking ahead, Wiseman hopes to delve deeper into the nature of world interaction, looking at the forces and conditions behind the theoretical phenomenon. The team anticipates that the deviations from quantum theory will be subtle but valuable – that is if they can successfully identify means of testing their theory. Perhaps in one parallel universe they already have.

This News Brief was produced under the guidance of Science Writing Mentor Brian Clark Howard.



  1. Griffith Scientists Propose Existence and Interaction of Parallel Worlds
  2. Quantum Phenomena Modeled by Interactions Between Many Classical Worlds
  3. A Quantum World Arising from Many Ordinary Ones