Multiverse – the quantum physics point of view

- Sadiq Siraj Ebrahim

Electronics and Telecommunication Engineering, UG1

We might have seen the multiverse in the Marvel comics, but there really exists one in our world too. The concept of multiverse was first proposed by Erwin Schrödinger to get rid of the idea of the “collapse of the wave function”. It was termed as the Many – Worlds Interpretation (MWI) or Quantum Multiverse.

As Schrödinger pointed out that there was nothing in the equations (including his famous wave equation) about collapse. In a paper he published in 1952, Schrödinger pointed out the ridiculousness of expecting a quantum superposition to collapse just because we look at it. It was, he wrote, “patently absurd” that the wave function should “be controlled in two entirely different ways, at times by the wave equation, but occasionally by direct interference of the observer, not controlled by the wave equation.”

In quantum physics, the famous thought experiment of Schrödinger’s cat states that if you place a cat and something that could kill the cat (a radioactive atom) in a box and sealed it, the cat would remain in a superposition of being both alive and dead until the system is observed, which results in the collapse of the superposition.

But later he said, there are two parallel universes, or worlds, in one of which the cat lives, and in one of which it dies. When the box is opened in one universe, a dead cat is revealed. In the other universe, there is a live cat. But there always were two worlds that had been identical to one another until the moment when the diabolical device determined the fate of the cat(s). There is no collapse of the wave function.

Everett’s Multiverse

As nobody responded to Schrödinger’s idea, it was ignored and forgotten, and regarded as impossible. So Hugh Everett developed his own version of the MWI entirely independently. He introduced the idea of the Universe “splitting” into different versions of itself when faced with quantum choices.

Everett did point out that since no observer would ever be aware of the existence of the other worlds, to claim that they cannot be there because we cannot see them is no more valid than claiming that the Earth cannot be orbiting around the Sun because we cannot feel the movement.

In the 1960s, Everett’s ideas were promoted by Bryce DeWitt who wrote: “Every quantum transition taking place in every star, in every galaxy, in every remote corner of the universe is splitting our local world on Earth into myriad copies of itself.”

Deutsch – Schrödinger Version

The precise version of the MWI came from David Deutsch, in Oxford, and in effect put Schrödinger’s version of the idea on a secure footing. In the Deutsch–Schrödinger version, there is an infinite variety of universes (a Multiverse) corresponding to all possible solutions to the quantum wave function. As far as the cat experiment is concerned, there are many identical universes in which identical experimenters construct identical diabolical devices. These universes are identical up to the point where the device is triggered. Then, in some universes the cat dies, in some it lives, and the subsequent histories are correspondingly different.

Some scientists have espoused the Many – Worlds Interpretation as the best way to explain the existence of the Universe itself. Their jumping-off point is the fact, noted by Schrödinger, that there is nothing in the equations referring to a collapse of the wave function. And they do mean “the” wave function; just one, which describes the entire world as a superposition of states- a Multiverse made up of a superposition of universes. But the parallel worlds can never communicate with one another. Or can they?