I am somewhat surprised that this idea has not become more popular yet, even though it’s yet the clearest “scientific proof” that we are, in fact, all immortal.
The “many worlds” interpretation of quantum mechanics says that the wave function never collapses: instead, every time a measurement is made, corresponding to each possible outcome a new universe comes into existence. You measure the spin of an electron and presto: there are now two universes, in one of which the spin is +1/2, in the other, -1/2. You flip a coin and presto: there are now two universes, the “heads”-universe and the “tails”-universe. (And many other universes in which the coin lands edgewise, explodes in mid-air, gets snatched by a passing eagle, or any other bizarre, improbable, but not impossible outcome that you can imagine.)
But if this is true, well, human death is just another measurement; and whereas in one universe, your heart might stop beating, in another, it beats one more. Or two more. Or two hundred million more.
In other words, as the universe keeps branching, you may cease to exist on many of those branches but there will always be branches on which you continue to live.
Think about it. That which you call your present consciousness will exist in an ever growing number of copies; some of those will be extinguished, but a few won’t be, not for a very, very, very long time. There is a continuous line from the here and now to the then and there, no matter how far that “then” is in the future, along which you continue to live. In other words, you can look forward to everlasting life… at least in a few of the many universes that await you.
How do you know if you’re on one of those “lucky” branches? Well, so long as you’re still alive, you are on a lucky branch, since the possibility exists that you will stay alive. Forever.
Of course there is a downside. Among the many parallel universes that represent possible futures, there are those in which you stay alive, but just barely, and in terrible pain and suffering. Or, you stay alive but you lose all your loved ones and even when you decide that it’s time to end your own life, you cannot… there is, after all, a nonvanishing probability that all your attempts at suicide fail.
But that doesn’t change the basic concept: in the multiverse, everyone is immortal. Although I am personally not too fond of the many worlds interpretation of quantum mechanics, I remain a little surprised that this idea has not yet become more popular among the religiously inclined.