And he dreamed, and behold, there was a ladder set up on the earth, and the top of it reached to heaven. And behold, the angels of God were ascending and descending on it! And behold, the LORD stood above it and said, “I am the LORD, the God of Abraham your father and the God of Isaac. The land on which you lie I will give to you and to your offspring. Your offspring shall be like the dust of the earth, and you shall spread abroad to the west and to the east and to the north and to the south, and in you and your offspring shall all the families of the earth be blessed. Behold, I am with you and will keep you wherever you go, and will bring you back to this land. For I will not leave you until I have done what I have promised you.” Then Jacob awoke from his sleep and said, “Surely the LORD is in this place, and I did not know it.”

- Genesis 28:12


That night Jacob arose and took his two wives, his two female servants, and his eleven children, and crossed the ford of the Jabbok. He sent them across the stream along with everything else that he had. And Jacob was left alone; and a man wrestled with him until the breaking of the day. When the man saw that he did not prevail against Jacob, he touched his hip socket, and Jacob's hip was put out of joint as he wrestled with him. Then the man said, "Let me go, for the day has broken." But Jacob said, “I will not let you go unless you bless me.” And he said, “What is your name?” And he said, "Jacob." Then he said, "Your name shall no longer be called Jacob, but Israel, for you have striven with God and with men, and have prevailed."

- Genesis 32:22


The ineffable is dead; science has killed it. Oh, there are still open questions, there are still things we don’t know, but almost none of it is truly unimaginable any more. The origins of life: tide pools, maybe, or hydrothermal vents—we’ll know once we can run more powerful simulations. Consciousness: looks like it’s a pattern of recursive attention in a neural network, we’ll be able to recreate it once we get better architecture searches working. Even the laws of physics themselves we can chalk up to the multiverse: if all possible universes exist, we can think of our own as just a random draw from the set of universes in which it’s possible for life to flourish.

There’s only one real mystery left. One thing that feels impossible to understand, even in principle: why here? Why have we found ourselves in this part of the multiverse, when there are so many other parts containing far more people? Why did I wake up as me, not them? Why am I living in the 21st century, balanced on a knife-edge, staring down ruin, instead of in a teeming glorious future? 

It all came down to force versus momentum, in the end. Despite all our fancy technology, our god-like knowledge of the building blocks of the universe, only a single simple question ended up mattering: how much force can we apply, how fast, to deflect an asteroid how far?

There wasn’t a single point where we found out that this was going to be the overriding purpose of our lives. But I remember where it started for me: at Andrea’s watching party for the kickoff of the first big asteroid mining project. This was merely one of many steps, of course. Technically it didn’t even involve any mining: they were just going to redirect the asteroid into orbit around Mars so that it’d be more accessible later on. But the metals from this asteroid would be used to set up factories on Mars to produce more asteroid-movers, which would be used to gather more resources, in a compounding spiral of astronomical-scale expansion. So it felt like a huge milestone: an unprecedented feat of human ingenuity, paving the way for our eventual conquest of the stars. 

I’d met Andrea through our shared work on rocketry, so it wasn’t a surprise that the whole crowd was massive nerds. Everyone knew someone on the team that had launched the asteroid-movers, and everyone was cheering for them. Well, almost everyone. “I still don’t like it”, my friend Vlad was saying to the guy next to him. “It feels like playing God.” He was a theoretical physicist too, but much more religious than me: the sort who saw God’s presence in the order and regularity of the universe.

“But what could go wrong?” I butted in. “Worst-case, we get a big crater on Mars, right? I know the hippies hate that idea, but it’s basically a wasteland anyway, that won’t change much.”

Vlad grimaced. “You think it’s fine to just throw around the equivalent of, what, ten billion nukes? Jacob, do you hear how arrogant you sound right now?”

Andrea shushed us before the argument could get any more heated. We turned to see that the screen projected onto the wall had cut to a close-up of the asteroid. It was huge: fifteen kilometers in diameter, dwarfing the dozen rockets we’d attached to it at different angles. It seemed impossible that we'd ever be able to move it—but I'd done the calculations, and knew that the power of persistent nuclear thrust would eventually add up. The mood in the room rose steadily as the timer slowly ticked down, second by second, until finally we saw the rockets engage and start firing. A cheer went up.

The next two hours were raucous; we all felt on top of the world. The first sign that something was wrong came from Vlad. “Hey, guys, look”, he says quietly, then louder, cutting through the buzz of conversation. “That’s not on track, is it?” On the screen, the asteroid had slightly but noticeably deviated from the green outline that was meant to forecast its progress. A few voices rose to offer dismissive explanations—a graphics glitch, or a newsroom mistake. Vlad pushed back, and a corner of the room broke off to try to figure out what was going on.

The rest of us managed to ignore it for another hour, until Andrea turned the volume back up and waved for our attention. “I’m hearing that the rockets are no longer responding to commands”, one of the commentators was saying. “It looks like the asteroid is only very slightly off course, but we can’t fix it.” The room let out a collective sigh. We were all old hands at this. We’d seen dozens of rockets blow up, and we knew that no matter how well you test things, on unprecedented missions like this one failure is more likely than not. But we were still disappointed.

Disappointment turned to confusion as the rumors trickled in over the next few days. It’s still heading into Mars orbit. No, it’s going to miss Mars, and head into deep space. No, it’s going to slingshot around Mars, spend two years looping past the sun, then end up on a direct collision course with Earth. The last we ruled out as soon as we heard it. It was astronomically improbable, like hitting a bullseye with a dart thrown from orbit. But somehow, impossibly, that’s what all the data seemed to suggest. We argued back and forth in the group chats, running our own analyses, trying to reconcile the measurements with the wild implausibility of a random misfire sending the asteroid anywhere near Earth. That’s how we entered our new reality: not with a bang, but with a growing sense of disorientation and dismay.

I was never really religious, despite my parents’ best efforts. They sent me to Sunday school every week, but I was an introverted child, and always felt out of place. The only thing that ever caught my attention was the lesson where we learned about my namesake, Jacob: how he’d gone into exile, was promised a grand destiny by God, then returned, fought an angel, and fathered a whole nation. I’d been rapt. I tried to imagine myself in his shoes, doing all those great deeds. I couldn’t really picture what it would look like to fight an angel, but I told all the kids at school that I was gonna kick its ass, and theirs too, until one of the teachers called my parents to report me for threatening violence.

Even after their reprimands I’d still secretly tell myself that I, like Jacob, was destined for greatness. But over the years the story faded in my memory, and I’d almost forgotten about it by the time I started my PhD. My research was draining and disorienting: I was trying to invent algorithms for manoeuvring rockets in ways nobody had ever managed before, and I had no idea if they would work out. Throughout the long nights in the office I started thinking about Jacob again—but rather than admiring him, I now envied him. Jacob must have doubted himself sometimes too. But instead of leaving him in the agony of uncertainty, God sent a dream to reassure him, and then an angel to bless him directly. 

I pictured the angel appearing out of the blue, and Jacob straining every sinew and fibre of his body to come out on top. As I wrestled with the equations, abstraction piled on top of abstraction, I wished that I had Jacob’s opportunity to fight for his future so directly—just muscle against muscle, will against will—instead of slogging it out year after doubtful year. I sat in my shabby apartment, the best I could afford, and wondered what it would feel like to have my destiny come hurtling towards me, all fire and glory.

Now, of course, I don’t need to wonder. Now I know.

Eventually we figured it out. Faced with the impossibility of denying that the asteroid was heading toward us, but the equal impossibility of it steering towards us by accident, we realized what should have been obvious all along: that it wasn’t chance, but malice. We were scientists and engineers, and didn’t naturally think in terms of treachery or sabotage—but by the time they announced it publicly, we were already all but certain. It was just one guy, they confirmed, working alone. He’d been one of the programmers on the software controlling the asteroid-movers, and had somehow managed to subvert the failsafes and lock in Earth as the new target. He’d waited just long enough to make sure that the asteroid was fixed on its fatal trajectory before killing himself. The megalomaniacal sort of suicidal, determined to make the planet into his tombstone.

After that things got very serious very fast. We had two short years before impact. That was time enough to build another set of asteroid-movers, and even a few spares. But with the asteroid looping around on its long journey, we could only feasibly reach it during a small window right at the end. We’d need to throw every rocket we had at it, because we’d only get one shot.

The hundreds of scientists who were pulled together to take that shot were the greatest concentration of talent the world had ever seen. A lot of familiar faces as well: they put Andrea in charge of one of the core teams, and she snagged the best of our old crowd. I was one of the first she recruited; Vlad too. He thinks we’re already dead men walking, but he’s got that fatalistic Russian temperament which means it somehow just inspires him to new heights of brilliance. Then there are the others: George, my friend from college, steady and reliable, who always makes sure that the things which need to get done actually get done; Jinyang, who worked on the original mining project, and is single-mindedly obsessed with making amends. And there’s Andrea herself, terrifyingly competent even by our standards. Of course we need more and better people, we need them badly, we need them months ago. But every minute spent trying to find them is a minute we’re not focusing on our work, so we’re gritting our teeth and doing the best we can.

Will that be enough? Maybe—maybe—maybe. Moving the asteroid is the hardest job in the world, but the hardest part of that hardest job is simply facing up both to the terrifying prospect of failure, and the even more terrifying prospect that we might succeed if only we’re good enough: that it’s all on our shoulders. Almost nobody can handle the uncertainty. After they played slow-motion visualizations of what the asteroid will look like when it hits our atmosphere—a corona around its head, and long wings of debris trailing behind it—people started calling it “the angel of death”, and the name stuck. Now there are angel cults worshiping it, and angel mystics, and on the opposite side the skeptics who insist that it’s all a hoax, just another apocalyptic religion: that everything will be fine. Even the scientists working on the project tend to drift away into either euphoric confidence or deep fatalism; and after that it’s not long before their work starts getting slipshod, and they become dead weight. Sometimes I picture myself trying to balance on the narrow ridge separating denial and despair, knowing that if I slip off to either side I’ll lose the ability to grapple with reality. Maybe—maybe—maybe, I whisper to myself. We could die. We could survive. Maybe.

“We need to reshuffle everything to make room for China.”

I’m staring at Andrea, incredulous, but after a moment I realize she’s dead serious. I open my mouth to object, buts she cuts me off. “I know it’s frustrating, but they want to launch asteroid-movers of their own. They say that they don’t trust ours, and they want theirs as backup. Our current planned launch trajectory makes it too likely that they’ll collide somehow, so we’ll need to change it.”

“God damn it”, I mutter. I wish I could focus only on the physics, without accounting for any of the politics and negotiations. But we only have one launch window, and interference between different projects would be the most ignominious way to go out. Vlad and I spend a few hours puzzling over new launch trajectories, but progress is slow, so we break for dinner. Both of us chew in silence, turning the problem over in our heads. “Vlad, what if we spread out the launch sites more? Could that help?”

“No”, he says solemnly. “I know already: nothing will work. We’re all going to die.”

“We’ll—what?” My stomach clenches for a moment, but relaxes again as I see the smirk on Vlad’s face, the one which signals that he’s pulling your leg. It can be so goddamn frustrating: everyone’s humor has taken a turn towards the morbid, but none more so than Vlad. But I can empathize with the feeling—we’ve all been there—so I play along. “Why will nothing work?”

“You know the doomsday argument?” I shake my head, so he elaborates.

“Think about it. Suppose we manage to redirect the angel. We already have all the tech we need to settle the rest of the solar system; and once we’re off Earth, it’s far less likely that a single accident could kill all of us. So we'd probably end up colonizing the galaxy eventually. Let’s say we’d settle a billion solar systems, and end up with a trillion people on each. That's a billion trillion people total; probably far more.

“But tell me: if there’s a plausible future with a billion trillion more people, then why the hell did you and I end up here instead? Why would we be in the first 0.00000001% of all humans to ever live?" He enunciates every zero carefully, to make sure it sticks. "That's so incredibly unlikely that it's basically impossible. No way it could ever happen by chance.

“So the obvious conclusion is that the future where we succeed isn’t really possible. We weren't born early, because humanity ends here. We're the last generation, and there's nothing we can do about it, so we should just kick back and relax while we can.”

“Vlad, you’re talking bullshit.”

“Probably”, he says, flashing a sharp grin. “But can you explain why?”

“Well—” I pause for a second. “You can’t just assume that there’s some fixed set of possible worlds, and try to figure out which one we’re in.”

“But that’s what we do all the time: pick hypotheses, and condition on the evidence! Is it going to rain tomorrow, or will it be sunny? Will the lottery be won with an odd or an even number? Will we colonize the galaxy, or all die in-” he checks his watch “-eight months’ time?”

I’m stumped for a moment. “Well, I don’t know what’s wrong with it, but there’s clearly something. And we’ve got too much work to bother figuring it out. Let’s go.”

Despite my dismissive tone, Vlad can tell that he’s hooked me, and is still smirking as he stands.

I work late the next few nights, but it pays off. I figure out a staggered pattern for launching our rockets that minimizes the chance they interfere with China’s, without significantly reducing our own likelihood of success. We’ll still need to get them to agree, but that’s above my pay grade: all I know is that there’s a path forward. Will it actually make a difference? I don’t know.

On my walk home, shivering a little from the cold, I look up at the sky, and wonder for the first time why Jacob chose to fight. Did the angel hail him from afar, or silently confront him? Was he angry, or afraid, or both? I imagine Jacob slowly realizing that he was grappling with strength beyond any human’s. I imagine his muscles straining to hold back an impossible force—and yet, minute after minute, still clinging on. Did he think he was battling for his life? Was that how he found the strength to endure those endless hours of overwhelming struggle? Or was he simply the type of man who would never back down?

I picture in my mind another Jacob, as cunning as he’d been when he stole his brother’s birthright—one who, after recognizing his foe, threw himself down in surrender and humility. God had already promised Jacob a multitude of offspring; safe in that knowledge, why should Jacob put himself through such a trial, with such slim chances of victory? Far more likely that God had preordained the outcome, and that none of Jacob's efforts would make any difference.

Then, just like that, the answer to Vlad’s riddle clicks into my head. Vlad had asked me about the likelihoods of different worlds—but that’s not what matters, I suddenly realize. What matters is what we can do about it. Maybe nothing Jacob did would have made a difference to God’s plan—but with innumerable descendants on the line, even the slenderest of chances was worth the struggle. Maybe the world in which we deflect the angel and bring forth a billion trillion descendants is a billion times less likely. But in it, our actions are a billion times more important. So it all cancels out to common sense.

It feels strange to sidestep the question of probabilities like that. Isn’t there some truth to whether we’re here or there; doomed or saved, or anything in between? But in another way, it feels right. When the angel arrives it gives no reasons, and offers no justifications. Is this the best of times, or the worst of times? We can’t know. We can only fight.

In addition to the story of Jacob, this story was inspired by Nick Bostrom’s work on the doomsday argument and Stuart Armstrong’s anthropic decision theory as a resolution to it.

New to LessWrong?

New Comment
7 comments, sorted by Click to highlight new comments since: Today at 5:06 PM

I think the claim that we basically understand the universe is misleading. I'm especially unconvinced by your vague explanation of consciousness; I don't think we have anything close to an empirically supported mechanistic model that makes good predictions. I personally have significant uncertainty regarding what kinds of things can have subjective experiences, or why they do.

This also feels like a good opportunity to say that the Doomsday argument has never made much sense to me; it has always felt wrong to me to treat being “me” as a random sample of observers. I couldn’t be anyone except me. If the future has trillions of humans or no humans, the person which is me will feel the same way in either case. I can't possibly condition on being me, because I couldn't be anyone else. The doomsday argument treats my perspective as a random sample of all possible humans, or even all possible observers, which feels like a massive type error.

On a similar note, why is it remotely surprising that we live in a universe with laws of physics that support our existence? We couldn't possibly observe any laws of physics except the ones we have. Does it even make sense to say that the laws of physics "could be different"? I'm not convinced we can even imagine a coherent universe with different fundamental laws of physics, in the same way that I can't imagine what it would mean to live in a universe where the circle constant is something other than  This may well just be a failure of my imagination, however – more crucially, hypothesizing that there are lots of universes with different laws of physics doesn't actually explain why we observe our universe.  This kind of multiverse idea is a strictly more complicated hypothesis than just accepting that our universe exists and being agnostic about others, right? The only remotely reasonable argument I've heard in favor of some kind of multiverse is that many-worlds is a simpler interpretation of quantum mechanics than wavefunction collapse. This is a distinct idea from the proposal that our universe was born as a random sample among countless others with different physical laws, which is not a simpler explanation of anything at all as far as I can tell.

If I have misunderstood or mischaracterized these arguments, please let me know.

Your objection against the Doomsday does not make much sense to me. The argument is simply based on the number of humans born to date (whether you are looking at it from your own perspective or not). 

Okay, suppose I was born in Teenytown, a little village on the island nation of Nibblenest. The little one-room schoolhouse in Teenytown isn't very advanced, so no one ever teaches me that there are billions of other people living in all the places I've never heard of. Now, I might think to myself, the world must be very small – surely, if there were billions of people living in millions of towns and cities besides Teenytown, it would be very unlikely to be born in Teenytown; therefore, Teenytown must be one of the only villages on Earth.

Clearly, this is absurd, right? The Doomsday argument says that if there are lots of other people in X scenario that is different from mine (be it living in the future or across the ocean), then it would be unlikely for me to experience not X, therefore those other people most likely don't exist. But I am me, and I couldn't be anyone else. It makes no sense to talk about the "probability of being me". I don't think it is possible to "assume I am a randomly sampled observer" or something like that.

The number of humans that I notice have been born to date does not depend whatsoever on how many humans might exist in the future. My experience looks exactly the same whether humanity will be deleted tomorrow by a rogue black hole or spend billions of years spreading across the universe.

It seems that your understanding of the Doomsday argument is not entirely correct - at least your village example doesn't really capture the essence of the argument.

Here is a different analogy: Let's imagine a marathon with an unknown number of participants. For the sake of argument, let's assume it could be a small local event or a massive international competition with billions of runners. You're trying to estimate the size of this marathon, and to assist you, the organizer picks a random runner and tells you how many participants are trailing behind them.

For example, if you're told that there are only 10 runners behind the selected participant, it would be reasonable to conclude that this is likely not a marathon of billions. In such a large event, the odds of picking a runner with only 10 people behind them would be incredibly low. This logic also applies to the Doomsday Argument, whether you're an outside observer or one of the 'participants'. The key piece of information here is that you only know the number of individuals 'behind' you, which can be used to infer how likely it is that the total number of total 'participants' is more than X.  

In the doomsday argument, we are the random runner. If the runner with only 10 people behind him assumed his position was randomly selected, and tried to estimate the total number of runners, he would be very wrong. We could very well be that runner near the back of the race; we weren't randomly selected to be at the back, we just are, and the fact that there are ten people behind us doesn't give us meaningful information about the total number of runners.

Humans alive today not being a random sample can be a valid objection against the Doomsday argument but not for the reasons that you are mentioning. 

You seem to be suggesting something along the lines of "Given that I am at the beginning, I cannot possibly be somewhere else. Everyone who finds themselves in the position of the first humans has a 100% chance of being in that position". However, for the Doomsday argument, your relative ranking among all humans is not the given variable but the unknown variable. Just because your ranking is fixed (you could not possibly be in any other position), does not mean that it is known and that we cannot make probabilistic statements about it. 

I didn't realize humans fighting angels was canonical. Evangelion is an obvious rec for a depiction of that. Specifically, Evangelion Rebuild 3.33 is my most rewatched movie. I thought it was a mess the first time I saw it but I think it is actually pinnacle.