The original concept of quantum immortality was first published in 1987 by Hans Moravec. It is directly implied by the Many Worlds theory of Hugh Everett. He noticed that it was an obvious implication of the existence of many worlds, and expected to live on indefinitely.
It is increasingly accepted that the universe includes all possible worlds, as described by Everett’s many worlds theory of 1957. This means that with every event that happens in the world, the other possible versions of that event happen, in other versions of the world. Thus as Everett stated, the reality of the individual is a branching tree of possible sequences of events. This leads directly to the idea of quantum immortality. Whenever you might die at the next moment, there is always an alternative moment, a different variation of reality, in which you survive. Since there is nothing to experience in the version of reality where you die, you only ever experience the one where you survive. As Marcus Chown states:
If the Many Worlds is correct, it seems the only certainty in life is not death but immortality. We’re all gonna live forever. (2002, 40)
Russian Roulette is often used as an example. There are six possible positions of the bullet, so mechanically there are six possible outcomes. In five of them you just hears the gun just go click. There is a lot more noise in the other outcome, but you cannot hear it because in this version of reality you no longer exist. But as there is nothing to experience in that version of reality, you inevitably experience one of the other five. That is the theory. It is examined in coulourful detail in the article Does Quantum Theory Imply You Are Immortal?.
That is the standard idea of quantum immortality. In a quantum world all possibilities are real, and there is always some variation of reality in which you survive. The world branches into all possible versions as in the standard Schrödinger’s cat illustration.
Max Tegmark has examined this idea in some depth, and he describes it in his New Scientist interview with Marcus Chown Dying to Know. (That article is behind a paywall, but Tegmark reproduces it on his site – it is about a third of the way down his page The Universes of Max Tergmark.) This kind of idea is seldom taken seriously, but this is perfectly reasonable because it makes no sense in the perspective of standard physics, namely the outside view. On the inside view things are once again very different.
On the inside view you are already in all possible worlds in which you are instantiated. In some of them you survive a specific moment, and so this is the experience of the next moment. In this context it is just that all the versions in which you die are subtracted from the superposition of worlds in which you exist. And this happens at every moment as each specific version of an observation is made.
The Moravec Jump
Taken literally this is not a particularly happy thought. If we just go on and on and on, the body must fail more and more. We would turn out like the characters in Death Becomes Her. Their bodies start to literally fall apart, but they go on living. Clearly that does not happen, and the reason is that a different kind of event happens first. As Moravec states, when we die:
We lose our ties to physical reality, but, in the space of all possible worlds, that cannot be the end. Our consciousness continues to exist in some of those, and we will always find ourselves in worlds where we exist and never in ones where we don’t. (1998)
In other words, given the universe of all possible worlds, there is inevitably a version of the world in which there is a logical continuation of your experience of reality. So the experience of death in this world leads straight on to the experience of life in the next world.
On the outside view this is a bit of a stretch of the imagination, but given the nature of consciousness it must be right. Consciousness is to the space of all possible worlds as a computer system is to all of its memory. The computer can access any place in the memory, and it can jump from one point to another. It can play Part 1 of a movie from one block of memory then continue straight on and play Part 2 of the movie from a different block of memory. Consciousness does exactly the same thing except that each part of the ‘movie’ is a lifetime in the space of all possible worlds. When there is an end to one lifetime, consciousness simply experiences the lifetime that makes the most natural continuation, wherever that happens to exist in the universe. So death is not the end. It is just a jump from this lifetime to the next – the Moravec jump.
The Functional Identity
One can imagine getting a new body, but surely you have to have the same mind to be the same person. Can just the world hologram, the memories of a lifetime, constitute a whole person? It not only can, it does. This is where we get to the next massive idea. In the QBism reality, even the physical body is indeterminate except where observed as described in Identity. This means that on the inside view, in the reality you know as the world, the world hologram is what you really are.
It helps to make sense of this that as Deutsch states, it is not only all the memory of one’s life that is contained in the world hologram, but also the particular way one processes information. Just as all the knowledge about the world and oneself is contained in the world hologram, so too is every aspect of the character, and how one thinks and makes decisions. As Deutsch states:
… every last scrap of our knowledge ― including our knowledge of the non-physical worlds of logic, mathematics and philosophy, and of imagination, fiction, art and fantasy ― is encoded in the form of programs for the rendering of those worlds on our brain’s own virtual-reality generator. (1997, 121)
In other words the ‘functional identity’, meaning the character and the psychology, what you are like, how you think, is all defined in the world hologram. So all the attributes of the mind that make up the identity are defined in the world hologram. In terms of character, memory, beliefs and criteria, you are the world hologram.
What will it be like? As Deutsch explains, with advanced technology it is possible to make complete, functional human bodies:
Illness and old age are going to be cured soon – certainly within the next few lifetimes … by creating backups of the states of brains, which could be uploaded into new, blank brains in identical bodies if a person should die. (2011, 455)
Somewhere in the space of all possible worlds, some society in the future will be using this technology to make new people, complete with adult characters and capabilities. They can give each body a character by uploading an adult world hologram into the brain, a record of a lifetime of experiences. Let’s say they want a broad spectrum of characters, so they make sure that this initialisation is random.
Because the initialisation of the character is random, in the universe of all possible worlds, every possibility will actually happen. So in one of these worlds, it is your world hologram, exactly as it is at the moment of your death, that gets used to initialise this brand new body. So you are the one that wakes up in this new body, next moment after death.
Of course, this is fantastically improbable, but it happens only as survival in the existing body becomes vastly more unlikely. The improbability of one’s survival climbs and climbs as one gets older, and at a certain point, where survival would be theoretically possible but monumentally unlikely, the Moravec jump occurs, the jump to a highly improbable but slightly more likely next moment, elsewhere in the space of all possible worlds.
The logic is very simple in IT terms. Each observation made is essentially a computation, the addition of that structure of information to the body of information of the world hologram. The effect of this computation is that the frame of reference defines this individual existing in a later moment in time. Quantum immortality essentially holds that if there is any possible version of a next moment that instantiates such a world hologram, then, since that is all that is available to be experienced, that is what gets experienced. Moravec is applying the same logic, but expanding the possibilities to choose from. In quantum immortality, we are only looking at all the possibilities in a specific reality. So all the possible snapshots defining the possible versions of the next moment have to be possible versions of the next moment, in this reality. Moravec is pointing out that it is not just this physical reality which could be experienced in the next moment, but any physical reality. As Deutsch states:”… ‘other times in our universe’ are distinguished from ‘other universes’ only from our perspective, and only in that they are closely related to ours by the laws of physics. (1997, 278)”. Instead of the next moment in this physical reality, the next moment could be a moment in any physical reality, provided that it contained the world hologram of this individual. And Moravec’s point is that in the space of all possible worlds, there must, inevitably, be physical worlds where exactly this world hologram is present in that world, for whatever reason.
You die. You wake up. This is one of the greatest revelations in the meaning of the new physics we have discovered. In the light of an eternity of lifetimes everything is different. We are infants compared to what we will become in due course. As we now know our bodies are stardust, quite literally. The truth about the true identity of each individual is even more marvellous. The world hologram is the soul. And we are worlds in action. Each one of us is the experiencing of a specific human reality, a movie of life, by the universe itself. We are parallel realities, worlds among Everett’s many worlds. We are immortal, empowered, and we have free will. All we have to do is get with the programme. We are constantly evolving. What we will become in time we can barely begin to imagine. Time to wake up and take a hand.