Is Schrödinger’s Cat immortal? And by extension, does that mean that both you and I will live forever as well?
In the famed thought experiment devised by Austrian physicist Erwin Schrödinger in 1935, a cat, a flask of poison, and a radioactive source are placed in a sealed box. If an internal monitor detects the radioactivity from a single atom decaying, the poison is released into the sealed box, killing the cat. But in the weird world of quantum mechanics – or more specifically in this case, the ‘Copenhagen interpretation’ of quantum mechanics – the cat would supposedly remain in a state of ‘superposition’, both alive and dead, until an observation or measurement is made by an external observer opening the box, collapsing the wavefunction – and finding the cat either alive or dead. Schrödinger did not see this as a serious possibility – instead, his thought experiment was meant to show a problem with the Copenhagen interpretation.
Another interpretation of quantum mechanics, formulated in 1957 by Hugh Everett, removed the problematic wavefunction collapse. In the ‘Many Worlds’ interpretation, rather than collapsing from superposition into a single reality, the wavefunction branches into multiple realities consisting of each possible outcome. This interpretation of quantum mechanics carries with it the mind-boggling implication that all possible histories exist, each contained within its very own universe (or ‘world’, as per ‘Many Worlds’). Every time a decision is made, another complete universe splits off from this one.
In the Many Worlds interpretation, Schrödinger’s experiment has created two completely separate universes…one in which the cat is dead, and another in which it remains alive. The ‘collapse of the wavefunction’ is an illusion caused by viewing the outcome from only one of the universes. And if Schrödinger carries out the experiment again, he creates another two universes, one with another dead cat, and another with the cat still alive.
Keen observers might note that, in Many Worlds, among the infinite branching of universes, there remains one branch in which the cat continues to be alive. It is claimed that Hugh Everett saw his theory as guaranteeing immortality to conscious beings: at each branching of universes between death and living, a being’s consciousness is bound to continue following the living path (given that consciousness, according to orthodox modern science, does not continue beyond death).
[See this fantastic documentary on Hugh Everett and Many Worlds Theory, as explored by his rock-star son, Mark Everett of Eels, for more insights]
The ‘quantum suicide’ thought experiment, devised in the 1980s as the Many Worlds parallel of the Schrödinger’s Cat thought experiment, illustrates the concept: