Have you ever had an unexplained accident when you were “supposed” to die, but managed to survive due to a lucky coincidence? Or have you ever been so sick that you narrowly escaped death? After that, did you remember the events differently than those around you?
One possible explanation is that you actually experienced death in a different timeline, but your consciousness continued to exist in an alternate reality. The possibility of this phenomenon is known as quantum immortality, and it raises many interesting philosophical questions.
The Background of Quantum Immortality: The Copenhagen Interpretation vs. The Many Worlds Interpretation
Quantum immortality began as a thought experiment in the late 1980s and was later more fully formulated by the physicist and cosmologist Max Tegmark. He suggests that we may die many times in our lifetime. Each time our consciousness moves, slides, jumps, or shifts into the next timeline, very similar to the one in which we died. It means we can experience death yet remain alive in the next timeline.
Theoretical physicists Niels Bohr and Werner Heisenberg formed the Copenhagen Interpretation in the 20th century. According to it, photons and other particles can exist simultaneously in several states. When we try to measure them, we influence them; they are changed into an observed state, and all other states are removed and never reappear.
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To understand this better, we can use the example of a cat who entered the room. Until you look at him, he could be in a state of lying down, sitting, or standing. These are the possible states. But when you look at it, the cat will be in one specific state, e.g. standing. It will become his only state, and the others will disappear as possibilities.
However, in 1957, American physicist Hugh Everett voiced the Many Worlds Interpretation (MWI) to counterbalance the Copenhagen Interpretation. According to it, when a person observes a photon, the world is divided in two at that moment. In one world, the photon goes straight, undulating in the other. We fall into one of these worlds quite by accident, without any principle.
Just imagine you decided to go to the store. Before that, your world existed in two states. You could either go or not go shopping. But as soon as you leave the house and go to the store, your world splits into two. When you enter the shop, you can either buy something in the store or not buy anything, multiplying the worlds further. This means that there are infinite possible states in the universe.
The Origins of Quantum Immortality
Quantum immortality is rooted in the concept of the Many-Worlds Interpretation (MWI) of quantum mechanics, which suggests that every possible outcome of a quantum measurement occurs in a separate parallel universe. In contrast to the idea of the universe, multiverse theory suggests an endless number of parallel universes coexisting in different timelines.
Everything that happens in one universe can affect the others, including death. Therefore, if quantum immortality is true, when we die in one timeline, we simply “move on to” the next one and continue living instead of dying.
The origins of quantum immortality can be traced back to the work of physicist Hugh Everett III in the 1950s. He proposed the Many-Worlds Interpretation to resolve the measurement problem in quantum mechanics, which concerns how the act of measuring a quantum system affects its state. According to Everett, each possibility of a quantum measurement is realized in its own unique universe. In other words, when we measure something at the quantum level, the universe splits into many different universes, each with its own outcome.
In 1997, renowned MIT physicist Max Tegmark published a revolutionary paper that proposed an experiment to test the validity of the Many Worlds’ interpretations of quantum mechanics. In the paper, Tegmark proposed that if quantum immortality is true, it should be possible to survive a fatal accident.
Furthermore, he suggested that by traveling through the multiverse, one could find a universe where they survive the accident and continue living. Despite the controversy surrounding it over time, the test remains a captivating exercise.
Schrödinger’s Cat and the Quantum Suicide Thought Experiment
“Schrödinger’s cat” is a thought experiment, and perhaps the most famous experiment associated with quantum immortality.
The experiment involves a hypothetical cat placed in a closed box with a radioactive substance, a Geiger counter, and a vial of poison. As detected by the Geiger counter, the substance has a 50% chance of decaying in a given time interval.
If the substance decays, the Geiger counter triggers the poison’s release, killing the cat. If the substance does not decay, the poison is not released, and the cat survives.
But until we open the box, the cat will be both “alive and dead” simultaneously, that is, in a state of superposition. If you think about it, the cat is in a superposition because it combines two states simultaneously: alive and dead.
The “quantum suicide” thought experiment is a variation of Schrödinger’s cat experiment. In the quantum suicide thought experiment, a person sits in front of a machine that measures the spin of a quantum particle.
The machine is rigged to fire a gun if the particle’s spin is measured as “spin down” but not if it is measured as “spin up.” The person then repeatedly activates the machine and observes the result.
According to the Copenhagen interpretation of quantum mechanics, the person exists in a superposition of states, meaning they are simultaneously alive and dead until the machine is observed.
However, in the many-worlds interpretation of quantum mechanics, the person’s consciousness would only continue to exist in the universe where the particle’s spin is measured as “spin up,” since in all other universes, the person would be killed by the gun.
If the person continues to activate the machine and observe the result, they will eventually find themselves only in the universe where the particle’s spin is always measured as “spin up.” From the person’s perspective, it would appear as if they are constantly surviving, even though they are, in fact, dying in many parallel universes.
Necessary Assumptions and Contention
Proponents of quantum immortality point out that this theory does not contradict any known laws of physics (this position is far from unanimous in the scientific world).
However, in their reasoning, they rely on the following two controversial assumptions:
- Everett’s multiverse interpretation is the correct one, and not the Copenhagen interpretation, since the latter denies the existence of parallel universes.
- All possible scenarios in which the participant may die during the experiment contain at least a small subset of scenarios where the participant remains alive.
A possible argument against the theory of quantum immortality might be that the second assumption does not necessarily follow from Everett’s Multi-World interpretation, and it might conflict with the laws of physics, which are believed to apply to all possible realities.
MWI of quantum physics does not necessarily assume that “everything is possible.” It only indicates that at a certain point in time, the universe may split into a certain number of others, each corresponding to one of the sets of all possible consequences.
Another potentially problematic aspect of the idea of quantum immortality could be that, according to it, a self-aware being would be “forced” to experience extremely unlikely events in situations where the participant would seemingly die.
Even without considering that in many parallel universes, the participant dies, those few universes that the participant can perceive subjectively will develop according to an extremely unlikely scenario. It, in turn, may in some way cause a violation of the principle of causality, the nature of which is not yet clear enough in quantum physics.
Although the idea of quantum immortality stems largely from an imaginary experiment with quantum suicide, Max Tegmark, one of the authors of this experiment, has stated that he does not consider quantum immortality to be a consequence of his work.
Instead, he claims that under any normal conditions, thinking beings go through a stage of decreasing self-awareness before death, which is in no way related to quantum mechanics (this decline can last from a few seconds to several years).
Thus, according to Max Tegmark, the participant has no possibility of long-term existence through the transition from one world to another, which would allow him to survive.
The Upshot of Quantum Immortality: Can People Really Became Immortal?
The theory of quantum immortality has been discussed both in scientific circles and among the general public. However, despite its interesting nature, it is debatable whether the idea of quantum immortality can be considered a real possibility.
While the Many-Worlds Interpretation of quantum mechanics is a valid interpretation of the theory, it is not the only one, and other interpretations do not necessarily lead to the concept of quantum immortality. Even if quantum immortality existed, it would not necessarily guarantee true immortality.
The concept suggests that our consciousness continues to exist in a parallel universe even after we die in this universe. Still, it does not address the possibility of physical decay or aging. It’s also worth noting that the idea of quantum immortality remains purely theoretical, and the scientific community has not been able to provide any empirical evidence to support it.
Therefore, it seems to be impossible for people to become immortal through quantum immortality. Nevertheless, the idea remains a fascinating and thought-provoking concept within the realm of theoretical physics, but it is not yet a proven or established scientific fact. Further research may uncover more evidence to support or refute the concept. Still, until then, we must look at quantum immortality as an interesting hypothetical possibility.