Quantum Immortality: Is There Hope Yet for Schrödinger’s Cat?
By Vihaan Rathi
Am I or am I not? That is the question.
When grappling with philosophical questions, we have a tendency to be rather…cruel. Imagine (and, please, do nothing more) all of the truly twisted actions we have been compelled to do in thought experiments of days gone by. Surely you see (or, rather, you think of) trains barrelling down divergent tracks, ruthlessly slaughtering groups of people strung onto the rails while a sadistic onlooker ignores the lever beside them. Maybe a nuclear bomb is about to blow up in Manhattan and can only be defused if the state tortures some guy from the Bronx in order to to obtain its location.* In any case, our ethical dilemmas, or maybe our thoughts as a whole, emanate doom and gloom, and this brings us to the most evil of them all.
Three physicists walk into a bar in New Jersey.**
A boyish-looking Danish one says, “Measuring a quantum system will bring about a collapse into a definite state, so beforehand, it is in a superposition of states.”
A German with a ridiculous hairdo - and a more ridiculous mustache - chimes in: “But then two systems could be entangled, and a measurement of one would violate locality by affecting the other! You’re claiming that an unstable keg of gunpowder could be both intact and in smithereens at once!”
Finally, in an incredible show of psychopathy, a bespectacled Austrian with a prodigious forehead declares, “Let’s put a cat in a box.”
“What?”
Then, the ramblings of a deranged man: “The box will be impenetrable and its contents unobservable. Inside the box will be a Geiger counter with a small amount of radioactive substance in it, such that there is a fifty-percent probability of an atom decaying within an hour. If the Geiger counter detects radiation within that time frame, it will release a hammer, shattering a glass flask filled with hydrogen cyanide. The cyanide will then disperse and kill the cat. Because of the quantum nature of the radioactive atom, the cat will be in a superposition of being dead and alive until observed by an outside force.”
And so, Schrödinger’s Cat was born. A feline friend to physicists everywhere, it is constantly being subjected to different variations - doom and gloom all at once - of the aforementioned horrific conditions that we all know and love. While moralists, furries, and the city of Copenhagen have all called unsuccessfully for a collapse of the cat’s wave function - an end to its suffering - there may be a sliver of hope left for it without us having to open up Pandora’s (or Schrödinger’s) box and risk seeing a corpse in the cat’s stead. To figure out how, we must engage in a thought experiment of our own.
Imagine that the cat is not only conscious, but a leading philosopher of its time. It is completely aware of what it is being subjected to, cannot interfere with the setup of the box, and understands that its life is at the mercy of an atom that has an equal chance of decaying or not. The question posed here is this: what happens if the observer is also the observed? We know that the cat is in a superposition of states, but does it experience this superposition? In other words, How Many Lives Has Schrödinger’s Cat?****
Enter quantum immortality. Under this view, there are two equally real, branching realities for our superpositioned feline philosopher: one entails life, the other death. Death, however, is not an experience - it is oblivion. Within this multiverse, the consciousness of the cat always follows the “path” of life. When a cat dies in one timeline, in one of these branches, it deterministically lives on as the same cat in a more forgiving universe. This applies to probability distributions other than a fifty/fifty split as well - if the substance within the Geiger counter is feeling particularly murderous and has a ninety-nine percent chance of decaying, the cat’s spirit will simply continue down one out of one-hundred possibilities. Quantum immortality’s proponents argue that no matter the cat’s suicidal ideation or masochistic curiosity, it will never feel the embrace of hydrogen cyanide unless you open the box.*****
While certainly a satisfying conclusion for our cat, there are a few issues with this idea. The poor chap would not instantaneously die upon the smashing of the glass flask, so would there be a short-term superposition between the cat being unscathed and approaching death’s door? Both entail consciousness, indicating that both branches can coexist, but one eventually does lead to death - can consciousness reroute itself after already passing the point of convergence? It’s unclear how physics can protect us from aging, as it is certain that we will die at some point, but not guaranteed how. Does consciousness then follow the longest path possible before fizzling out? If there’s an afterlife waiting for our whiskered wunderkind (the one with pearly gates, hopefully), then quantum immortality is arbitrary, as all life would have spiritual immortality regardless, and the experience of death as oblivion posited by its supporters would not exist. The most divisive quality of this theory is its assumption of a multiverse - most physicists simply reject this premise, viewing the world as being a singular universe whose actual state (rather than coexisting branches) is determined by probabilistic wave functions.******
Regardless of which interpretation is “correct,” the two are empirically indistinguishable. The existence of multiple universes does not change the math that we use to calculate what happens in ours, and the cat’s medical status affects nothing until observed by an outsider anyways. A discussion about quantum immortality relies on arbitrary philosophical perspectives as to what happens when an object enters superposition, and despite the idea’s best efforts to keep us all alive, bringing it into a conversation with normal people might just kill the vibe. There’s no use slaughtering cats to try and prove a moot point, so here’s a morally palatable thought experiment for you, reader: let’s put Schrödinger’s corpse in a box and ask it how effective quantum mechanics was at keeping him alive. (Hint: not very.)
*Bastardized versions of the classic Trolley Problem and Ticking Time Bomb scenarios, but I’ve gotten rid of British balderdash and used the more assertive train in the former, and the latter experiment has already been warped by imperialist pigs attempting to justify state terrorism, so it’s not so out of line to exaggerate a bit to prove a point here.
**In reality, this was an early to mid-twentieth century academic debate between Niels Bohr, Albert Einstein, Erwin Schrödinger (all three depicted in this narrative), and several others about the validity of the prevailing Copenhagen Interpretation of quantum mechanics. If you want some more serious reading on the topic, from the EPR paradox to the Heisenberg Uncertainty Principle, check out the Stanford Encyclopedia of Philosophy.
***This is derived from physicist Eugene Wigner, who imagined shutting a human into Schrödinger’s death trap. He argued that to him, an outside observer, the system was “closed,” so it would continuously evolve into a superposition described by the Schrödinger Wave Equation, but for the poor chap within, the wave would collapse upon his observation. The two people would see two fundamentally different realities, pointing to a contradiction in the Copenhagen Interpretation. This scenario is known as the “Wigner’s Friend” experiment, which organically leads to a few upsetting questions - did Wigner have friends? Why did he feel the need to put them into closed quantum systems? Is this permitted under international law? To avoid such complications, I’ve taken the liberty of using an eerily intelligent cat instead.
****This is also the name of a lecture given by philosopher David Kellogg Lewis on the same subject.
*****The idea of quantum immortality stemmed first from a thought experiment in quantum suicide, in which current MIT Professor Max Tegmark proposed that if a person sat in front of a machine that detected the spin of a quantum particle (“up” or “down”), tied a revolver pointed at their head to it such that it would only fire if the particle had a particular spin value, and pulled the trigger, their consciousness would always move on to the timeline in which the revolver does not fire, making it impossible to die in that scenario.
******This “Many-Worlds Interpretation” of quantum mechanics so crucial to the idea of immortality was pioneered by physicist Hugh Everett, but never gained much traction among the wider scientific community.
