Here is a brief recap of Peter Brannen’s recent piece in the Atlantic: “Why Earth’s History Appears So Miraculous: The strange, cosmic reason our evolutionary path will look ever luckier the longer we survive.”
Brannen begins by introducing us to the observer selection effect. (An observation selection effect exists when some property of a thing is correlated with the observer existing in the first place. For example, if intelligence hadn’t evolved, we wouldn’t exist, and couldn’t evaluate the probability of intelligence evolving.) The question Brannen asks is whether this bias applies to our planet.
If you consider all the existential threats our planets faced: “It’s something of a miracle that life on our planet has been left to evolve without fatal interruption for billions of years.” Of course, if we had been wiped out we wouldn’t be here to contemplate our existence. Thus, as a result of the selection effect, we probably underestimate the observed frequencies of cataclysmic events. And this means that “our forecasts about the future could be blinded by our necessarily lucky past.”
As Anders Sandberg, a senior research fellow at Oxford’s Future of Humanity Institute says:
Maybe the universe is super dangerous and Earth-like planets are destroyed at a very high rate, but if the universe is big enough, then when observers do show up on some very, very rare planets, they’ll look at the record of meteor impacts and disasters and say, ‘The universe looks pretty safe!’ But the problem is, of course, that their existence depends on them being very, very lucky. They’re actually living in an unsafe universe and next Tuesday they might get a very nasty surprise.
Perhaps this explains the Fermi paradox too. The reason we find no evidence of alien life is because there are no (or few) aliens that have survived and we exist only due to unimaginable good luck.
Consider, for example, that so far we haven’t destroyed ourselves with nuclear weapons. This may lead us to believe that nuclear war is unlikely, but if we take observer selection effects into account we’ll realize that the fact that we’re still here tells us little about our chances for future survival. Nuclear annihilation may be virtually certain but in a big enough universe some civilizations avoid extinction for a long time. We may seem safe but more likely we’ve just been lucky. (In fact, we’ve come close to destroying ourselves with nuclear weapons multiple times. Our planet is just the one where Stanislav Petrov didn’t push the button.)
Extending this insight further, the observer selection effect may explain why the universe hasn’t succumbed to vacuum decay or some other catastrophe. We exist so we think such a scenario is unlikely, but that’s because we’re in a universe that has survived. The situation gets even stranger if you consider the “many worlds” multiverse. As the cosmologist, Anthony Aguirre states:
… suppose the many-worlds interpretation of quantum mechanics is right … So, one of the two versions of us ceases to exist, but do we actually notice that? So one of us keeps going on just as if nothing happened. Arguably, from moment to moment, I can’t rule out that five minutes ago the other version of us died. There’s no way for me to say that. So there’s an interesting, troubling question as to whether these things could be happening all the time and we just don’t even notice it.
All I can say is that the mind boggles at such suggestions. When confronted with possible implications of multiple realities my mind recoils.