The bizarre behaviour of the quantum world — with objects existing in two places simultaneously and light behaving as either waves or particles — could result from interactions between many 'parallel' everyday worlds, a new theory suggests.

“It is a fundamental shift from previous quantum interpretations,” says Howard Wiseman, a theoretical quantum physicist at Griffith University in Brisbane, Australia, who together with his colleagues describes the idea in Physical Review X1.

Theorists have tried to explain quantum behaviour through various mathematical frameworks. One of the older interpretations envisages the classical world as stemming from the existence of many simultaneous quantum ones. But that ‘many worlds’ approach, pioneered by the US theorist Hugh Everett III in the 1950s, relies on the worlds branching out independently from one another, and not interacting at all (see 'Many worlds: See me here, see me there').

By contrast, Wiseman’s team envisages many worlds bumping into one another, calling it the 'many interacting worlds' approach. On its own, each world is ruled by classical Newtonian physics. But together, the interacting motion of these worlds gives rise to phenomena that physicists typically ascribe to the quantum world.

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