The idea of living forever is an important part of many religious belief systems. Although the key to such eternal existence differs from faith to faith, it seems as if avoiding death is a desirable state. Yet, it is not clear in avoiding death what we would gain.
In the recent finale of The Good Place, a TV show that explores the philosophical aspects of afterlife and morality, eternal life in some pleasurable, heavenly realm is portrayed as being a way to tie up loose ends, live a while free from care, repair broken relationships, and then, when one feels complete, return to the great ocean of the universe. This take was motivated by Eastern spiritual traditions such as Buddhism where true freedom means freedom from self, the freedom from having a separate existence from all things.
This got me to thinking about what physics might say about eternal life. While physics may not have much to say about how to live a good life, it does have a lot to say about what “eternal” means.
Most pictures of life after death take for granted that time somehow continues in a more or less linear fashion and our lives continue on in some similar fashion to here on Earth.
Perhaps it doesn’t exactly match up with how time is progressing here on Earth when one is in the heavenly realm, but at least for your passed-on existence, you experience one moment after another. Without death, this means that you theoretically would experience no end to such moments.
This sounds incredibly dull and also impossible to keep up forever. Even if you could store all your memories (doubtful) you would have no sense of growth or trajectory as you do with a mortal life. Would you even be motivated to do anything at all after a while?
Then again, there is no reason to assume that, once we have shuffled off this mortal coil, that we would experience an existence where we remember the past, do not know the future, and experience one moment after another in linear fashion. All of these effects come from thermodynamics, and, more deeply, from quantum information theory. That is, the existence of memories (and memory storage devices) and the linear experience of time all arise because of how information grows through increasing entropy and, at the quantum level, increasing correlations between quantum fields.
There is no reason to believe that an afterlife would obey the laws of physics in the same way or that we would experience time flowing as we do now. For example, we could just experience all of time at once. This is how many religions believe that God experiences time. We would not produce new memories because we would already have all of them. We would not learn because we would have learned everything. We would not grow bored because there would be no growth. Rather, life might be a changeless flow like a gas that has reached thermodynamic equilibrium. There might still be activity, not a crystalline freeze, but there would be literally nothing new under the sun.
This existence sounds plausible but barely alive. Then again, what does a mortal like me know?
Another possibility is that one would simply have the ability to experience many separate lives. This idea, which might be considered reincarnation, is popular not only in the east where the idea arose but also increasingly in the west, even among Christians. While Christians have always believed in resurrection, the similarity to reincarnation is superficial.
Reincarnation doesn’t sound like a particularly pleasant afterlife unless the lives one experiences are all pleasant ones. And, of course, if this went on for eternity you would be guaranteed to experience the same lives an infinite number of times. As long as you didn’t remember anything of past lives, you wouldn’t know. Buddhism portrays this kind of repeating lives as being a bad thing, as being stuck on the wheel, so to speak, forever turning. Karmic forces forever glue one to the wheel.
Physics allows for the possibility that the universe might be recycled many times by, for example, collapsing on itself in some way or perhaps via some false vacuum bubble appearing and creating a new universe out of a dead void.
The ancient Stoics as well as others also believed in this idea that the universe was continually recycled.
In each recycled universe you might experience new lives via transmission of your quantum information. If this went on eternally, you would be almost guaranteed to be reborn just by probability alone.
Resurrection is distinct from reincarnation. Whereas reincarnation means being born in another body, resurrection means to be brought back to life in your own body or a similar one.
Your dead will come back to life; your corpses will rise up. Wake up and shout joyfully, you who live in the ground! For you will grow like plants drenched with the morning dew, and the earth will bring forth its dead spirits.
Isaiah 26:19.
It is entirely possible, from a physics standpoint, for the dead to come back to life provided that a sufficiently advanced technology (or Divine being) could recover the quantum information that constitutes a living being.
Since information is not lost in any quantum transformation (unitarity), all the dead still exist in the universe. They are just scattered.
Of course, resurrection simply implies a second life, not necessarily eternal life, but certainly this is what the Bible promises. What does physics say about this?
It depends on what that life is like. If it is a life in which a person is continually resurrected, then it could theoretically be eternal.
But, would not living an eternal life the same way one would live a finite, mortal life be a kind of miserable existence?
One alternative possibility is that, while time would march forward as it does now, our feelings about our lives would be different. We could just be happy all the time, as Doestoyevsky wrote in The Dream of a Ridiculous Man:
I suddenly, quite without noticing how, found myself on this other earth, in the bright light of a sunny day, fair as paradise. … Oh, everything was exactly as it is with us, only everything seemed to have a festive radiance, the splendour of some great, holy triumph attained at last. … I saw and knew the people of this happy land. That came to me of themselves, they surrounded me, kissed me. The children of the sun, the children of their sun — oh, how beautiful they were! Never had I seen on our own earth such beauty in mankind. Only perhaps in our children, in their earliest years, one might find, some remote faint reflection of this beauty. The eyes of these happy people shone with a clear brightness. Their faces were radiant with the light of reason and fullness of a serenity that comes of perfect understanding, but those faces were gay; in their words and voices there was a note of childlike joy.
This portrayal of a world of perfect happiness may seem a fantasy, but it may also be that is because it is beyond our experience. Perhaps we can’t imagine Eternal life as being anything other than dull and eventually wanting to end it because for us, even in our short lives, happiness is always fleeting.
Physics can’t answer that question, but time will tell for us all.
Dostoevsky, Fyodor. The dream of a ridiculous man. Read Books Ltd, 2019.