We’re all familiar with the TV episode where characters dream up an alternate universe, and wake up to their familiar one where everything goes back to ‘normal.’ This is typically regarded as a scientific plot device, though from a hard science point of view parallel universes are nothing to be scoffed at, as the study of these universes and ‘many worlds’ is a prominent point of research among physicists. (Though the ability of humans to travel between them is not.) New research in this field challenges current thought about parallel universes and suggests not only their existence, but also their interaction.
Quantum mechanics is a notoriously tricky subject with complicated equations for wave functions that attempt to describe strange phenomena where objects can be found in two places at once. It tells us that electrons and photons exist as superpositions of waves and particles, and it is impossible to know which form the electron/photon is in until a measurement is made on the system. Without that measurement/observation it is assumed that the electron has wave-particle duality. However, upon observation the wave-function is predicted to ‘collapse’ and resemble a particle (the Copenhagen Interpretation). One of the fathers of quantum mechanics, Erwin Schrödinger, created a famous thought experiment now known as Schrödinger’s Cat to help depict this, in which he described a box containing both a cat and a vial of poison controlled by the atomic decay of a radioactive substance. As there is no way to know if the vial breaks and kills the cat until the box is opened, in the universe outside of the box the cat remains simultaneously dead and alive. In more scientific terms, in the macroscopic system outside of the microscopic electron system, the electron is simultaneously a wave and a particle.
An early and novel challenge of the Copenhagen Interpretation was proposed by Hugh Everett in the 1950s, as he made the observer part of the system under observation and postulated that interaction with the observer would cause the universal wave function to branch; the branch being the alternative outcome from the observation. An example of this ‘Many Worlds Interpretation’ is to make an observation on an electron, which causes the electron wave-function to collapse and allow us to see the electron as a particle at point A. Meanwhile in another branch of this wave-function, the electron is seen a point B. These branches are independent and are a fundamental concept of quantum theory, though whether all branches truly represent existing realities is not fully agreed upon. However, new research from Griffith University is calling the Everett interpretation into question, as Dr. Howard Wiseman and colleagues are introducing the idea that not only are parallel universes actually in existence, but that they do not remain independent and in fact may interact with each other. This new theory states, “The universe we experience is just one of a gigantic number of worlds. Some are almost identical to ours while most are very different; all of these worlds are equally real, exist continuously through time, and possess precisely defined properties; all quantum phenomena arise from a universal force of repulsion between ‘nearby’ (i.e., similar) worlds which tends to make them more dissimilar.”
This fascinating ‘Many Interacting Worlds’ approach is novel in that these separate worlds are governed by classical Newtonian physics, which were deemed unable to explain observations such as the wave-particle duality of light. However, when these worlds interact with each other, quantum mechanics arises. Wiseman describes this as two worlds in parallel existence, where one can penetrate an energy barrier while the other bounces off of it. This new theory will lead to interesting tests of quantum phenomena, and can perhaps produce a more coherent mental image of the quantum world. Though, as once put by famed physicist Richard Feynman, “I think we can safely say that nobody understands quantum mechanics.”