Jul 30, 2025 19:00:00

What does 'quantum immortality' mean, a parallel world in which people are alive despite being dead?

In quantum mechanics, particles are said to be in a probabilistic '

superposition ' state until they are observed. The idea that the state is not determined by observation, but rather that the universe branches with each observation, is called the ' many-worlds interpretation .' Based on this many-worlds interpretation, there is a hypothesis called ' quantum immortality ,' in which immortality is achieved by continuing to 'observe surviving outcomes' forever. The science-based YouTube channel Kurzgesagt explains the theory of quantum mechanics and quantum immortality in a video.

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To understand quantum immortality, we first need to understand the characteristics of quantum matter. If you flick a physical object like a marble, with the exact same shape, with the same force and at the same angle, it will always fall in the same place. However, if you flick an electron in the same way, it will move to different places. Quantum mechanics explains this by saying that at the electron level, randomness is fundamental, and it exists in a constantly changing wave-like state. Electrons are not waves of matter or energy, but rather immaterial waves of probability with values between 0% and 100%.

A famous experiment that demonstrates the strange properties of electrons is the '

double-slit experiment .' When electrons or photons are sent through two slits, a pattern of stripes is formed behind the slits, not a point where the particles collide, but rather a pattern of two waves interfering with each other. This result led to the conclusion that electrons and photons are both particles and waves, and that 'their locations are not determined until they are observed.'

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Quantum mechanics does not allow us to observe electrons or understand their shape; it merely allows us to infer the properties of electrons from experimental results. However, some people argue that quantum mechanics is a study of reality and can be used to interpret the world. Such 'many-worlds' believe that the universe exists in a quantum state in which all physically possible outcomes coexist simultaneously, and propose a scenario in which the theory of quantum mechanics can be applied to reality.

For example, if we consider a scenario in which 'the electron exists with an 80% probability in the living room and a 20% probability in the kitchen,' we can rephrase this as 'there are four patterns of 'I' observing the electron in the living room, and one pattern of 'I' observing the electron in the kitchen.' The five 'I's' never recognize each other, but they exist simultaneously at this very moment. In other words, even if 'I' observes the electron in the living room, this is not the correct scenario; it is merely 'one of multiple versions of 'I'.' In a different world, there is also an 'I' observing the electron in the kitchen.

In the many-worlds interpretation, countless scenarios arise in the universe, and countless new worlds overlap and branch off every second. However, since we cannot communicate with other different 'selves,' it is impossible to prove that multiple worlds exist. 'Quantum suicide' is a thought experiment that assumes the observation of 'selves' in countless branching worlds.

In a scenario where 'electrons exist in the living room with an 80% probability and in the kitchen with a 20% probability,' switches that react to electrons are placed in the living room and kitchen, and a bomb is connected to both. If the switch in the living room is activated, the bomb will explode, and if the switch in the kitchen is activated, nothing will happen. If an electron is sent into the house under these circumstances, there is an 80% chance that it will be caught up in the explosion, and a 20% chance that it will survive. In the many-worlds interpretation, the result is that four out of five 'I's' will die, and one 'I' will survive.

While it may be just luck that an 'I' in one world survives one trial, the probability of surviving 100 consecutive trials is extremely slim, about one in a billion. However, in the many-worlds interpretation, this scenario always repeats 'four 'I's die and one 'I' survives,' so there must be an 'I' observing the world after the experiment. This is the theory of 'quantum immortality.'

Quantum suicide is merely a thought experiment, and quantum immortality is not a theory that shows the truth. Even if quantum immortality were true, it would simply mean that somewhere in the many worlds there exists an incredibly lucky 'I,' and there are countless unfortunate 'I's' who cannot avoid dangerous scenarios. Kurzgesagt states, 'Quantum immortality is an interesting and attractive idea, but it does not mean it is true. For now, the world we can perceive is unique, and we need to cherish the existence of that 'I.' However, if you believe in the many-worlds interpretation, even if you have an unfortunate experience, you can feel positive by thinking that there is another world where you are experiencing the same situation but fortunately.'