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Comment by causality0 | Hacker News Reader

The universe we find ourselves in isn't very compatible with a species like our surviving for an extended period. If humans exist for millions of years we're going to either spread out to fill the galaxy or our machines will. The fact earth was free to develop us means that no other species like us existed long enough to beat us to it.

We ought to hope that's because species find some other priority besides expansion and power, because otherwise the reason we're free to exist is because species like us always wipe themselves out before they spread.

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That argument seems to violate the basic rules of exponentials. If an advanced species did settle on an stasis, then that will only last until some subset of the population decides to go beyond the stasis. Particularly for a space-faring civilization, the time scales and resources are so fast, that any multiplication factor beyond unity will eventually go bananas. Any individuals with the prerogative to multiply will swamp those who lack it, same with Earth evolution. The selfish gene will prevail unless there is centralized control.

I don't have any problem with this reading - advanced space-fairing beings have never existed in our light cone. SETI won't find anything because there's nothing there. We have a good chance of making it ourselves, but it's 50/50 because we have no priors, our decisions actually matter.

I think the answer is pretty obvious, we are the precursor species.

Or it could be any number of things other than nobody out there. For example, advanced life could be out there but it might be rare enough that you only end up with a handful of space capable civilizations at any one time. The milky way is a big place. If we assume that ultimately there isn't a clever way around the speed of light then two civilizations on the opposite side of the galaxy will never encounter each other.

Or maybe its rare enough that you are only likely to have at a time in a galaxy.

Or maybe the prerequisite tech to thrive on an interstellar level means they simply aren't detectable by out primitive sensors. Poor backwards humans, still using the electromagnetic spectrum to measure things!

Hell, we could have a Prime Directive situation on our hands too. Although I think that one is really really unlikely.

Us being (one of) the first species is the most likely answer IMO. It violates the anthropic principle, but that doesn't account for everything.

By all estimates of the age and expected lifespan of the universe, we are extremely close to the beginning of all existence. We know that life takes an extremely long time to evolve, and life on Earth is young compared to the age of the system.

That we don't see a sprawling galactic civilization means one thing: there hasn't been enough time for one to emerge.

All the great filter arguments fall apart when you consider the nearly infinite nature of the universe. Given enough life supporting planets, at least one species would emerge, pass the great filters, and become large enough for us to observe.

That we don't see anything just means no one is there, yet.

Being alone in this universe would be terrifying and frankly untenable. Being first, however, is exciting.

I doubt that we are the first and only life in this universe, but it seems obvious that we are very, very early in the life of the universe, and we therefore are one of the first species to ask this question.

we are extremely close to the beginning of all existence

This is the one that always causes me to wonder.

I was born in a major metropolitan area, which makes sense, statistically. I'm a native speaker of the 3rd largest language on the planet. That also makes sense. The 3rd largest country by population. Nothing out of the ordinary statistically speaking.

But to exist extremely close to the beginning of all existence

Huh? What are the chances that I, or any of us, would exist now? It's like being born on some island in the Pacific. Sure, it happens, but only to a few.

It really is nothing short of wondrous and awe-inspiring.

We could very well be one of the first species on the galactic stage, how absolutely awesome is that??

It violates nothing. Your intuitions are expanded at length here http://grabbyaliens.com

The anthropic principle would hold that we as a species and our circumstances of existence are entirely average and not at all special.

Being one of the first species, at the relative dawn of the universe is very special.

I'm not such a huge fan of the grabby alien model. It's internally logically consistent, but I think it's too rooted in human psychology. Plus I have serious doubts about the ability of any species to maintain a multi-planet empire, let alone a multi-system one. Barring something like a hive mind I suppose.

Ultimately it's just conjecture and we'll probably never know within our lifetimes.

Maybe no one comes here because Earth is deep inside the Veil of Madness...

https://creepypasta.fandom.com/wiki/Mankind

Von Neumann pointed out that an advanced civilization, with technology that we can predict should be developable, can colonize the entire galaxy in roughly 10 million years.

Which is a blink of time by geological standards.

Von Neumann was much smarter than I but for such a calculation you have to make so many assumptions as to make it worthless. How can we possibly be able to predict what happens to a civilization in 10 million years?

And yes I am aware of Von Neumann probes. But as someone else pointed out there may be secondary effects we aren't even aware of.

> How can we possibly be able to predict what happens to a civilization in 10 million years?

Obviously under the assumption that no other changes but growth and colonisation happens to that civilisation.

or we are in a simulation

That doesn't really solve the problem because the simulation is (apparently) big enough to allow life to evolve. Why couldn't life evolve multiple times in a simulation?

Isn't the argument about simulation more about pondering the question "what is the fundamental nature of reality?", not "why is there life?". If you say that some beings are interfering with our simulation (either designing life, or preventing other life, etc...), that is just another word for god.

It's another word for God even without interfering. There's still the Creator(s).

"Why couldn't life evolve multiple times in a simulation?"

Because the Grad Students don't want it to, and act to prevent it? :-)

Why would they bother making a sim that big if it was empty? Even No Man's Sky is full of cookie cutter creatures.

You don't actually make that big a sim.

You just fiddle with the render distance so the sims think it's that big.

It's more of a psychological experiment, perhaps?

But in real life, it never actually is an exponential. There always is some limiting resource or saturation point or something, that turns it from an exponential into an S curve. An argument based on "the basic rules of exponentials" typically ignores second-order effects (there seem to always be some, even if we may not be able to see them in advance).

> that will only last until some subset of the population decides to go beyond the stasis.

You are assuming that they can go beyond the stasis. I'm not sure that's a valid assumption.

Well yes, after the distance to the our solar system’s other resources, the next pauses in exponential expansion would be crossing to the next star system, then the spaces to other galaxies, and then to other galaxy clusters.

There are not a lot of opportunities to saturate & stall once we sustainably develop resources beyond Earth

And stalls or extinctions due to conflict become very unlikely after we colonize a few systems

It never is truly an exponential in the limit, but exponential growth for surprisingly long times is very common.

There's no exogenous law that exponential trends continue indefinitely. In fact I'd argue it's much more common to see sigmoid behavior where eventually negative feedback loops cause a plateau.

> the basic rules of exponentials

A space-faring civilization cannot expand faster than O(n^2) because physics.

Yes, this is true but only from the reference frame of the cosmic background radiation. It is still possible that you can get O(n^3) from the reference frame of the aliens themselves, because time dilation makes travel fairly fast. You get into some spacetime philosophy about what metrics are worth evaluating O against in the first place.

OK, but even O(n^3) is still polynomial, not exponential. That matters. There's a reason that P=?NP is a thing.

> because otherwise the reason we're free to exist is because species like us always wipe themselves out before they spread

That's a complete non-sequitur. There can be plenty of reasons for a species like us never appearing on the first place, and they are way more reasonable than postulating that life like us always destroy itself.

> There can be plenty of reasons for a species like us never appearing on the first place

We already have an example of it, too: Look how long the dinosaurs were around compared to humans.

Yes I wonder if there was some particular condition that prevented higher intelligence to occur before recently. Or if it's just sort of "pure chance".

Abiogenesis seems so absurdly unlikely that it's enough to explain the Fermi paradox a couple of times and still get some extra margin all by itself.

We are actually running out of places in our history to fit a great filter. Most of the events in our evolution seem probable, even inevitable. In fact the only place IMO that's really left is the emergence of the first self replicating RNA molecule. But even that seems too probable to be a great filter.

And if its not behind us, it has to be in-front of us or we are under a great misapprehension about the nature of the universe.

BS.

Filter 1. If we had no large moon, roughly every 30 million years or so our axial tilt would become too extreme for life. We do not have another example of a planet with a moon to rival ours in relative size.

Filter 2. Without Jupiter acting as a cosmic vacuum cleaner, we'd predictably be hit by enough asteroids and comets that we'd never have evolved. In thousands of solar systems that we've found, we've found lots with rocky planets, and lots with gas giants. Ours is the only system with BOTH rocky planets AND gas giants.

Filter 3. Supernovas are dangerous. For example we are currently in the Local Bubble. Which is the result of a supernova about 4 million years ago which would have wiped us out if we were this close when it happened. Luckily for us we have a weird orbit where we only pass through the galactic plane every 30 million years or so, and spend most of our time well away from potential supernovas.

Filter 4. Planets need to be in the habitable zone, around a star where that zone remains habitable for a very long period. Most solar systems have no suitable planet.

Putting these together on a back of the envelope, it is likely that we're the only solar system in our galaxy which is likely to remain habitable and stable for long enough that complex intelligent life could evolve.

Good comment. I would add that our Sun is alone, while up to 85% of solar systems are at least binary. It's possible multi-star systems make life more difficult. Similarly, Earth's magnetosphere may be uncommon, since we don't see a similar one on Mars or Venus. And maybe Earth's rotation is uncommon and many planets are tidally locked.

I wonder, though, how this stacks against the sheer size of our galaxy. There are 100 - 400 billion stars in the Milky Way, including about 4 billion Sun-like stars. Plus we keep revising estimates upward when it comes to exoplanets. Recent observations seem to indicate that 33% - 90% of Sun-like stars have rocky planets at a distance where liquid water is possible.

Are features like an unusually large Moon or a protective gas giant so rare that our planet and solar system are truly unique?

We don't know how rare either actually is. For both we have just one example - us. This suggests odds of no more than one in several thousand. But it doesn't take too many filters of that order of magnitude for a few hundred billion to become a handful, and the handful to become just one.

Your point about binary star systems is interesting. Orbital dynamics have a well-known tendency to be chaotic. In a single star system, this chaos is significantly less of a problem. But in a double star systems, the odds of moving in/out of the habitable zone over time are much higher. So that's probably a filter. But not as big of one as the ones I listed.

Mentioned elsewhere in the thread:

Filter N: Even if life is complex it might not be likely to become intelligent enough to send signals and venture into space. It took quite a long time before we showed up.

But it comes back to the number of chances. To wit, there's approximately 200,000,000,000,000,000,000,000 stars in the universe. We might be that one in a 200,000,000,000,000,000,000,000 shot where it all came together to create life but it's rather improbable. Almost certainly is other life out there.

That's just counting the visible universe. We have no idea how much farther it extends!

That said, most of the visible universe is now unreachable due to the ongoing expansion of the universe. And life somewhere unreachable, even in theory, is not of that much interest to me.

My big one is multicellular life. Mitochondria are sooo weird.

Multicellular happened over and over again.

Mitochondria are weird, but we don't know that such organelles are necessary for life to become intelligent. And we don't know how weird that capture was. It is easy to make an argument for improbability. And it is easy to make it too extreme, like the absurd arguments that Creationists use against evolution.

That's a great list of filters. Thank you.

Do you happen to know books, movies, articles or other media that expand on this?

> We are actually running out of places in our history to fit a great filter.

Other than the obvious, which is the utter physical, technological, economic, political, biological, and statistical impracticality of interstellar colonization.

Probably, inevitable based on what sample size?

Techno-optimism. We didn't have planes, now we have planes. We rode horses and now we go to the moon. Therefore, anything you can possibly imagine is inevitable because "technology".

We will circumvent every possible logistical and physical barrier because of nebulous reasons.

It's a lot like that scene in Silicon Valley when Big Head is pitching a neuralink-esque device for a phone to the CEO and the CEO asks how long it will take and Big Head says "Soon, we just got to figure out how".

Like, no shit, the "how" isn't just the important part, it's the only part.

I am not convinced that self replicating machines spreading out between stars is possible. There's rather a lot that the machine has to be able to do on a destination planet to set up mines and factories etc before the first extra machine can be made,and it has to survive landing.

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