Alone in a Crowded Milky Way | Hacker News Reader

Alone in a Crowded Milky Way

scientificamerican.com

243 pointsBerislavLopac260 comments

I don't buy this argument. Let's pretend for a moment that there are currently 5-20 intelligent species in our galaxy, and everyone except us developed deep space ships and successfully colonized thousands of other planets (make up almost any numbers you want here; the results still hold).

What would our telescopes see? It seems like we would most likely see exactly what we see today.

The probability that one of those ships happened to fly anywhere close to our solar system, while we were looking, is still vanishingly small. Omnidirectional radio transmissions spread so quickly that they fall below the noise floor almost instantly over interstellar distances.

Space is really really really really big. We can see stars. We can just barely see some planets in a few very specific configurations. We can sometimes make coarse estimates of the chemical composition of those planets. And that's about it. We don't really know how to detect life on extrasolar planets. The ones we've already found could be teeming with life and we wouldn't know it.

Why would they stop at thousands of colonies? What is it preventing the colonies from themselves creating colonies? Also, realize that a colony in the system of another star will move away from the originating system. In our neck of the galactic woods the rate of separation is typically about 10^-4 c, so in a million years they'd separate by 100 light years.

The problem with endless expansion is it requires stability over very long time scales. Sending a probe to another solar system is hardly enough. If you can send a ship say 100 light years from your home planet that’s 2,000+ repetitions of terraforming and colonizing a planet, building up an industrial base, then sending ships to every planet in reach. Under ideal conditions that might take 10,000 years assuming everything went well so you need 20 million years to colonize our galaxy. But, assuming everything goes well for 20 million years and colonization continues to be a priority seems unlikely.

It’s very possible to reach a wall where zero teraformable planets are within reach of your ships. For large civilizations that’s unlikely to totally block expansion, but it might make the path very convoluted thus increasing total time by a rather extreme factor.

Culture rot will kill you quicker than density of colonisable planets.

The transport layer is the easy part. Content integrity is a much harder problem.

All of your probes and colony ships have to reproduce the source culture - or some viable subservient spin-off - with 100% accuracy.

This explicitly means 100% reproductive success of all features, especially the politics and economics, with no errors.

For a successful colony, stability and conformity have to be maintained for long periods - centuries at a minimum, perhaps even millions of years.

And of course this assumes the source culture is stable in the first place.

Otherwise you're just seeding the galaxy with potential competitors, and/or setting up some kind of galactic Battle Royale.

I'm bemused by the suggestion the first option is actually possible. The second seems more likely, but might not be considered a success in the sense of creating a stable galaxy-spanning civ capable of common strategic goals.

> All of your probes and colony ships have to reproduce the source culture - or some viable subservient spin-off - with 100% accuracy.

The only thing that needs to be preserved is the desire to build more colonies. I'll grant even that's a stretch, but demanding 100% cultural fidelity is silly for discussing the Fermi paradox.

If human history suggests anything, it would be that at a certain point invading other colonies will become more profitable than founding new colonies in sub-optimal locations.

Invading another star system of similar technology levels without FTL seems like non starter. You could sterilize planets, but space based assets are another story and retribution is possible.

Yes. Invading ships wouldn't be able to bring a lot of fuel/propellant with them beyond what's necessary to decelerate from the trip. And they would have to be warm enough to support life, so they'd radiate a lot of heat. They'd be easy to spot. So no fancy maneuvering and no stealth. And the defenders have the resources of an entire star system to throw at you.

Terrorism, as you mention, might be possible (but again remember, no stealth) and claim jumping (where you displace another group that got there roughly when you did). But even in densely packed stellar neighborhoods the average star is surrounded by a moat several light years across. Once the locals are developed enough to mount a serious defense, they're probably immovable.

Invaders might not need to bring anything with them at all. Particularly relevant to your point, I'll share one of the military projects from Sid Meier's Alpha Centauri: https://www.youtube.com/watch?v=aKcEwUcVBHs

More generally, the point I'm raising is symbolized in entirety by the Spartan faction's ideology in that narrative environment.

You still lose to the first-mover advantage though. If universal assemblers are possible, then the defender with the resources of a star system at their disposal and early warning of the attack is going to outproduce the aggressor.

The only advantage I imagine an invader would possess is the possibility of taking control of the Lagrange points and any orbital production facilities, and then besieging the population below.

Dropping asteroids on habitable worlds and causing ice ages to clear out the population _might_ still be faster/cheaper than terraforming a semi-hostile world.

That assumes the Lagrange points are empty. A civilization capable of interstellar war is going to have a lot of space based assets.

Further starship drive capable of reaching a significant fraction of the speed of light make one hell of a weapon. But you still need to deal with space based assets that can dodge your initial bombardment and at a minimum are armed with powerful engines. So sure you can destroy planetary populations etc, but now your still out gunned 1,000:1 locally and pissed off a civilization capable of doing the same thing to you. Net result MAD.

A large technical advantage may make up for this, but that means the winner has better tech is much harder to take over a second time. On top of this the only thing worth shipping between stars is information at the speed of light. Making conquest largely pointless without FTL.

> On top of this the only thing worth shipping between stars is information at the speed of light.

It could be worthwhile to beam energy out to interstellar distances (also at the speed of light). This is probably needed for interstellar travel anyway.

Eh? Physical war is almost obsolete today.

> The only thing that needs to be preserved is the desire to build more colonies

That's hard. I'd say harder than solving the physical problems of interstellar travel. Once a generation has learned to live with the limited resources of a starship, living with the limited resources of a planet is going to be a very attractive option. What's their incentive to colonize more from there?

In the long run resource shortage goes down. Technology increases the amount of output possible for a given amount of effort over a given amount of matter. For example: wood to coal to oil to nuclear. Thinking about starships of 3000 AD we're talking about a thousand years of scientific development towards nuclear reactors, food processing, scientific computing, and random technologies I can't even fathom because they'll rest on a bed of mathematics and physics that's not even conceivable yet.

If more technologically advanced aliens exist then our not sensing them is much more likely because they don't want to be sensed than some other consideration like them stopping to setup on some habitable planet. I'm horrified about war, and I'd hope they would be too, but it may be that aliens come to understand species or ecosystems in a more expansive way and may consider the process of ending war as a necessary one for the maturation of an ecosystem.

Or the great filter is true. We all end up killing ourselves because it's impossible to escape exponential technology growth and mismatched incentive problems, or something else like that.

It's always going to be a small percentage that desires to venture further out to new areas. On a newly settled planet, most will not want to leave. But some will.

But you have to wait for that society to forget that living on a starship means spending your whole life never venturing out, while a planet lets you spend your life exploring.

Or, you know, some just want to get away from the other individuals.

That is, if we are talking about something comparable to current humans. Immortal super AIs might don't care about idling in the void for a few million years, just for the opportunity to re-sync those gained experiences to their decentralized knowledge a few million years down the line. I really like the single omnipotent AI scenario, since being immortal and not depending on others changes quite drastically what strategies can be successful - it won't be anything like human kings who need to keep their subjects at bay and working for them to support their power and limited life. But we shouldn't restrict our imagination, if we are talking about possibilities and galactic time-spans.

The important part is, as mentioned by GP, the desire to expand, since this is a dominant strategy. In comparison, not every living being on earth has the drive to participate in evolution by e.g. creating offspring. Those usually just drop out of the "game" and likely won't matter in the long term, at worst making it a bit harder for the others initially till their disappearance. What matters are those who have persistent impact... e.g. by colonizing/making offspring.

And that doesn't need to happen with anywhere near 100% accuracy. If 1% of the offspring multiplies and works to found new colonies that barely changes the dynamics or speed of spreading.

Even on earth we had plenty of colonies rebelling against the founding nation, gaining independence and becoming a serious competitor. Britain might conclude that they would be better off today had they never colonized America and India. Repeat this pattern often enough over millennia and it seems plausible that an entire race might become very cautious with forming permanent colonies.

Britain had to colonize the Americas or France and Spain would have without them. It would take another 200 years for the empire to fully collapse. It’s hard to say colonization was a net negative just because of America’s independence.

Further it seems much less likely the populace would be so willing to send aide to Britain during WWI if it weren’t for the cultural similarities. If instead Spain had colonized the US it seems very likely the country would have remained neutral as Spain did.

My gut feeling would say colonization was a net positive to Britain, but it's hard to say. It's just too big of a what-if. The US would have likely gone to France, their main rival at the time. On the other hand Britain spend a lot of resources on their US colonies, both building them and fighting France in America. Who knows what else they could have with those resources.

It's not just the US either. India was a profitable colony at the time but might turn out to be a major detriment to Britain overall, both as a source of cheap skilled labor and as a powerful nation of their own. Who knows what would have happened without the British. A lot of the borders in the Middle East are drawn by Britain as part of their WWI mandates/colonies, and the problems from how those borders were drawn spill over into Britain (yes, it's not the only problem in the Middle East by a long shot, but it's one of them).

I still think overall Britain came out ahead (just look at Hong Kong for what cultural influence can do), but it's not hard to imagine how colonization might be seen as a net negative if a few times things turned out even slightly worse.

Spain did colonise much of what is now the USA. That’s why it’s “Los Angeles” and “San Francisco”.

https://commons.m.wikimedia.org/wiki/File:Imperios_Español_y...

And Louisiana was French.

Britain seeded the Earth with English speakers that inherited her legal traditions and cultural values for the most part that then developed into rich trading partners that participate in an international system of voluntary exchange that has enriched the British.

It could have gone another way, there’s a reason we’re talking about Britain instead of England and Scotland, but I would say it has worked out brilliantly.

Not just the desire, but also the ability- the cultural context for an industrial base potentially far more powerful than what we have. That may be extremely difficult to sustain over such timescales.

Implying culture as we have it may be a stretch too big for other species. Who may form single integral units like a zerg swarm. Yeah, it is a game fiction, but you got the idea. Why do cells split and grow with no complaints about their life? Because it is the way they are, and if they were not, they simply didn’t. What is their strategic goal? A counterargument to this is that swarm may be not intelligent enough to make it, but my point is that our lifeform’s culture is not the only one possible, and the culture as we have it may be not a requirement. (Not that it is any sort of beauty anyway. Apart from particular individuals, it is mostly disgusting and ineffective.)

Also, a neighbor idea of the scientific progression in thousand years from now on doesn’t account for an artificial biology progression, like the same humans in 1k years would do unimaginable things. Would they be still individual humans? Personally I don’t think it is more than juvenile civilization’s tunnel vision illusions.

> For a successful colony, stability and conformity have to be maintained for long periods - centuries at a minimum, perhaps even millions of years.

The number one attribute that needs to be preserved is the disinclination to blow each other to smithereens. I suspect self-destruction (to a level where technological progress is setback millenia) is a common enough occurrence that would occur well-before FTL becomes a possibility.

I also suspect (despite decades of reading SF and my own wishes to the contrary), that the kinds of attributes that encourage exploration, expansion and risk-taking, are also somehow linked to aggression and violence - "might makes right".

If you can create ship, which can travel for generations, why you need to colonize anything? For second generation, their home will be starship, not a planet.

This. Planets are incubators for civilizations.

Does intelligence and innovation predict cultural change? Is there evidence that this is prevalent in other species?

> All of your probes and colony ships have to reproduce the source culture - or some viable subservient spin-off - with 100% accuracy.

Any empire/political system/civilization needs some means of holding it together. Traditionally this is done through armies. As our transport technology has gotten better, our ability to move armies around the world has increased and with it the ability to control large economic systems without them breaking apart. Nowadays we have a globe-spanning economy. However, time scales of interstellar travel are so big that cultural change is much faster than the method to build a colony. By the time that nuclear bomb ship has arrived at the other planet, we might have changed our mind threefold.

In fact, already if you send a generational spaceship to a star 100 ly away to reach its destination in a thousand years, by the time you receive message from their arrival, both their as our language will have evolved by 1100 years. So yeah you are right, cultural decay (or rather "change") is a big problem.

Currently our governments are run by humans with all the human failings. Instability, corruption, etc are components of the governments due to our human nature. You are right that it would be hard for human run governments to colonize the galaxy as due to the light speed limit, we can't achieve transport scales needed for a human-run civilization.

However, we won't need humans to run the governments. In the future we'll be able to engineer and build extremely intelligent AI systems with multiple layers of error checking to withstand decay for trillions of years. You think that sounds undoable? Check how many cells humans are made out of and how well they work together for decades.

The unsolvable political problem will just be turned into a solvable engineering problem.

Those AI systems would run key parts of the governments and economies themselves (entirely without needing human help) and enforce a set of basic rules like preventing nuclear weapons, bioweapons, torture, etc alongside ensuring they are the most powerful factor in those places, i.e. are able to fend off any kind of attack. Otherwise they won't interfere with human matters and let humans govern themselves with the human imperfections.

Basically, they'd provide the "galactic federation layer" and ensure peace through their programming. Some factors of their programming could be changed by the human population, but others, like preventing nuclear weapons, couldn't. So even if the humans wanted, they wouldn't be able to wage catastrophic war with the neighbour planet, or at least specific types of war (allowing trade war but not allowing nuclear war). Even if the risk for interplanetary war is just 0.1% per year, over millennia that's a large number and interplanetary war can have major consequences.

To the present reader, those AI systems probably seem weird and dystopic, but I think we are already evolving towards them. Already, many parts of the governments and economies of various countries are being automated. One day in the future the automation will have minimized human involvement enough so that you can think about von Neumann probes.

The first people to develop AI ran governments will probably be the dictatorships who want absolute control and micromanagement (single-operator government). But in general, the systems are more efficient than chaotic systems, and with increasing perfection of the technology, once a system is a dictatorship, it probably won't change back to a non-dictatorship without outside interference. It's important to eventually remove human control from them as otherwise over the millions of years, eventually someone will figure out how to flip the switch and create dictatorships. So it's kinda important to get the "right" set of rules into these computers.

Already building these computers is a huge project that would take a long time to get it right. But it's an easier task for humans to do than running an intergalactic civilization.

Also note that those systems don't have to necessarily deal with humans in their current form. They could also deal with human simulations uploaded to the cloud and the systems would just provide the resources to run that cloud. The "real world" might become utterly uninteresting to humans.

>In fact, already if you send a generational spaceship to a star 100 ly away to reach its destination in a thousand years, by the time you receive message from their arrival, both their as our language will have evolved by 1100 years.

It is not necessarily true that more time is spent aboard a ship than light would spend taking the same path, as measured by an external observer.

If you had a ship capable of accelerating at 1g indefinitely, then as measured by the crew, they could cross the galaxy in only 24 years.

https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...

I like everything else you wrote.

I don't understand how this is possible. To accelerate the spaceship at 1g becomes more and more difficult as you approach the speed of light. That's the whole point of relativity. And yet the article says "the spaceship will approach the speed of light in the middle of its journey, as measured from the planet's frame of reference".

It only becomes "more difficult" as measured by people not onboard the spaceship. For people onboard, time effectively speeds up for the rest of the universe, so that there is no brick wall to your acceleration. Therefore, it's also possible to time travel into the future, but not into the past.

That is not how it works from what little I know. Neither the spaceship, nor the outside observers will EVER see it hit the speed of light. That is the only constant thing they agree on. All of relativity hinges on this point. The Lorentz transformation is based on the fact that the speed of light is constant for all observers whether they're "stationary" or moving at 0.999999999c . So even at very high fractions of light speed, you know for a fact that you haven't hit light speed because when you turn on your spaceship's lights, the photons will look like they're travelling away from you at the speed of light (due to the own time dilation and length contraction you experience).

This is why when you're calculating the actual value of time dilation, it considers what fraction of speed of light you're traveling. Because if you were the traveler, time dilates and length contracts EXACTLY enough to make light appear to travel at 1c (regardless of your own speed).

https://en.wikipedia.org/wiki/Lorentz_transformation

Time dilation is only 1/2 the story. The other half is distance measurements get distorted.

People in the spaceship see the same maximum velocity of objects they pass aka c. However, if a huge measuring tape with say light year tick marks passing them they are going to measure it’s speed at say .99 c and the time between tick marks is X. Alternatively, at .999c they would get a new time period Y. However the difference between X and Y is not simply .999/.99 but rather a more complex relativistic adjustment.

However, this is only important for people on the spaceship. For people staying home the it takes 3.5x the energy to hit .999c vs .99c yet it’s only shaving 1% off the observed travel time. Which is unlikely to be considered worth it by just about any civilization baring significant changes to the laws of physics.

Not really, even if you have optimal rocket fuel, you still have huge fuel demands: http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/r...

That’s irrelevant for people on the planet sending the spaceship.

Particle physics get matter to 99.9999% of c which causes crazy time dilation to the particles and nothing to the scientists. Further, constant 1g acceleration of a starship to high fractions of c is basically science fiction. Not even matter anti matter reactions can keep up those energy demands for very long.

No, endless expansion does not require stability over very long time scales. It just requires that each colony produce, on average, at least one successful daughter colony. It's not even necessary for the colony to have any cultural continuity between when it is created and when those descendant colonies are created.

There is a very interesting series by John C. Wright called _The Eschaton Sequence_ that explores this idea of stability over long time scales this in great detail (builds up through K7 civilizations over the course of the work)

https://us.macmillan.com/series/theeschatonsequence/

I think you could take some ideas from the Foundation Series of Asimov (https://en.wikipedia.org/wiki/Foundation_series)

> Why would they stop at thousands of colonies

Why would we stop at a hundred of colonies? A couple of observations:

- in rich countries, the trend is that the birth rate is declining, the population gets "older". There seems to be a link between wealth and birth rate. Even if space conquest gives us a lot of resources, if that trend persists, the lack of people will be the limiting factor.

- there are only really two reasons to go out: curiosity and making sure that a stellar-scale catastrophic event doesn't wipe out our civilization. A bunch of colonies "far enough" from Sol achieves this. And probably after visiting a dozen of systems, the next one will look like one of the previously visited.

The curiosity aspect might be generational. After growing for enough generations, the critical mass of "curious" individuals - people who are persecuted, who don't fit into the prevailing culture, or who are just really bored - might be there for exploring outwards, even if it had already been done many time before.

That's the general story of humanity. From the first settlements to the ever-away "final frontier" — somewhere between Moon and Mars as we speak. There is no doubt in the mind of any historian, psychologist or sociologist, IMHO, that we'll probably keep doing this for as long as we are "homo sapiens sapiens". That should be ~50K years total based on past mutations (iirc? anyhow much bigger than recorded history), so I figure we can take curiosity for granted as a civilization trait for next-gen politics. Like, lots of gens. ;-)

Since I'm no historian, psychologist, etc. I have always believed that great migrations were caused by local population pressure - id est too few resources for too many people. Even Columbus stumbled upon Americas because he was looking for a better trade route.

That's a reasonable enough assertion!

You could argue that exploration, migrations, colonization are but the emergent/complex behaviors described by more fundamental principles in psychology, sociology, biology. Conway's game of life, in a way. History being a mere factual, chronological account — a log.

You are thereby operating at a high-level, manipulating complex umbrella objects like "great migrations", "local population pressure", each of whose words (composite concepts) map to lower-level datapoints — e.g. like some eternal tension (psy., soc., hist., bio...) between a desire to look inwards (for security? familiarity? survival, support?) and a drive to seek outwards (for growth? curiosity? lack, want, need?)

I think you could change these guesses to be almost whatever you wanted with similar results.

We would not observe anything different unless one of them actually flew to our solar system and tried to contact us. That's how bad we are at detecting distant life.

I reckon astronomers would find anything that entered our solar system and stayed in some solar orbit.

You'd be surprised how much stuff there is just in our neighborhood that we're unable to catch, yet. We mostly track dangerous stuff, the big enough - fast enough to destroy us, and we now have probably in the 6-7 figures objects tracked in the inner solar system. That's it. Elusive 9th planets and other major 'quests' are shots in the dark so far, mostly — read accounts on why they target some region of the sky, how narrow our observational capabilities are as we can only point to a very specific direction at a time with each telescope, etc.

So, some alien unmanned probe the likes of Voyager in large orbit around the Sun? Yeah, no chance in hell we'd detect that by random chance, we'd have to seriously upgrade our space infrastructure to even pretend 'monitoring' our close vicinity, let alone post-Jovian space. And we have virtually no knowledge of about half the distance between interstellar medium and the Sun, that's how limited we are to even modeling the closest star systems.

Edit: apparently double-post with aruggirello; I agree with him.

To underline this point: we shot a red tesla into space about 2 years ago [1]. We cannot detect it any more. We'd need a telescope with a mirror of 15km to see it. Due to uncertainties accumulating, even if we'd had a scope like that, we'd probably not be able to point it exactly enough.

Oh, and that thing is mostly between the orbits of Mars and earth - much smaller search space than "the entire solar system"

[1] https://www.whereisroadster.com/

You really mean anything at least comet/asteroid sized, passing within the inner Solar System with a speed and an albedo that would make it stand out against the background of stars (reaching at least say, apparent magnitude 8-10). Also, note that it should be found near the ecliptic plane, to improve the chances of detection.

Now, exchange that for a black-ish ship a few hundred meters sized, quietly coming from Vega to visit say, Saturn. Nobody would probably notice it coming and going, despite Saturn being one of the most popular targets of the entire sky.

You’re very mistaken. We still regularly find 300ft boulders in _Earth Orbit_. And routinely find city sized asteroid in asteroid belt and state sized minor planet in Kuiper belt. Suggesting that a ship can be found as long as it’s in Solar Orbit is an extremely misinformed opinion.

We have never found a 300 ft boulder in Earth Orbit.

Perhaps you mean in a solar orbit near the Earth?

True, but without radio transmissions, I bet we would spend decades arguing about whether it was actually an asteroid and a measurement anomaly. We can't really distinguish a rock from a Battlestar at those distances without physically flying over to look.

At this point we're relying almost exclusively on radio waves to detect any traces of intelligent life out there. So whether they're building moon stations in their neighborhood, or sending rockets here and there, we'd still look for their transmissions to identify their existence and to tell them apart from a random natural event.

And while intelligent life may exist on a planet for millions of years, their window of actually emitting something into the void in a manner we can detect with our tech today [0] will probably be a lot shorter than that.

This gives us a relatively tiny and limited visibility window into the history of life out there. Unless we manage to sync our window perfectly with theirs we'll never know they existed.

[0] https://www.xkcd.com/638/

Compounded by the fact that advanced space communications would likely rely mostly on laser beams[1], whose efficiency and general design fits much better with that environment and its infrastructure. Unless pointing directly at your instrument (good luck, what are the odds?) and missed by the intended receiver, the beam will never reach you anyway.

[1] Particularly if your operation is covert, discrete, observational, non-disruptive: you'd want to avoid signaling your presence in all directions, while wasting 99.99% of that energy away from your intended receiver. It's just military efficiency, a photon-VPN so to speak, that you'd need to "physically MitM" to hack.

Sorry to pile on, and I don't think you deserved the downvotes, but I'd like to point out there may be an undiscovered planet in the solar system.

https://en.m.wikipedia.org/wiki/Planet_Nine

There may also/instead be an undiscovered primordial black hole in the solar system.

https://www.sciencemag.org/news/2019/09/planet-nine-may-actu...

Why does everyone assume alien races would want to spread out and colonize the universe? Perhaps we should consider the possibility that the insatiable desire to constantly expand like a virus is coupled with the tendency for civilizations to destroy themselves through warfare. Maybe civilizations with advanced technology also have advanced philosophy and are content to merely exist and be content? Why do we take it as a given that aliens would be anything like us, with the same desires and tendencies we have? Its fine to consider that as a possibility, but there are many unknowns we should acknowledge.

> Why does everyone assume alien races would want to spread out and colonize the universe?

...because organisms (and presumably cultures) without that characteristic wouldn't be as numerous as otherwise identical organisms which do have that drive, in a given environment.

Maybe we don't see them because they aren't as numerous, because they aren't interested in spreading out. Maybe the "drive" to spread out and colonize the universe or the cultures that would encourage that frame of thought are linked to a propensity to wage war or other some other counterproductive behavior that results in extinction before achieving the ability to colonize the stars.

It's entirely possible that a civilization would stop at thousands of colonies because, they no longer have the technological capacity (having regressed for whatever reason) or the desire to continue further. It's also possible that the odds against successfully expanding beyond a single colony are so great that no one ever makes it to a thousand.

ALL the colonies regress? And stay regressed? Forever?

How is that supposed to work?

I wouldn't assume that colonies would have anywhere near the technical capabilities of the seeding planet.

Just look at what we have achieved in Earth vs. what we have achieved on the moon, or anyone's plans for a Mars colony. Mankind may set for on Mars eventually, but i don't think we'll ever do something like set off fireworks there.

Any colony that moves past the immediate survival stage is a success. That does not mean they have millions of years of fossil fuel stored to start further exploration.

generating methane from co2 and electricity is fairly easy, mining helium from jupiter too. Once you have self sustaining colony on mars it can colonise the rest of the solar system far easier than earth can.

Technological civilizations are fragile - it's more likely that they collapse than remain and progress exponentially forever.

But your argument requires that all these branches, separated by light years, collapse, and then stay collapsed forever. The counterargument does not require that they progress exponentially forever. They can go through cycles, even extinctions, but the remnants can pick themselves up and go on.

Your scenario requires a uniformity of outcome across all the parts of that civilization, spread across multiple stars, and spread across all future time. They all have to go down and stay down.

They don't have to "collapse," merely remain at a point of stability that doesn't allow for the energy expenditure and infrastructure of interstellar travel. That's not an unlikely scenario.

Stability is achieved by having excess capacity, then limiting use of that capacity. Societies are not stable due to being right up at their limit; such societies collapse because of external changes push them over the limit.

So, if a stable multistellar society is not building colony ships, it's not because it can't, but because it has chosen not to. How does that uniformity of choice get enforced across time and space?

I don't believe there is, or can be, such a thing as a stable multi stellar society. Barring FTL technology, it's impossible to correlate activities or maintain coherent relationships when every interaction takes years, decades or centuries.

What you have are individual civilizations which may or may not, as you mention, decide to invest the time and resources into interstellar travel. But that investment isn't guaranteed. We've had the technology to send out interstellar probes for decades, yet we haven't committed to sending them out by the hundreds or thousands. We could have colonized Mars or the Moon by now, built Orion starships, but we haven't. Technology doesn't govern the advance of space travel, politics does.

>How does that uniformity of choice get enforced across time and space?

I think it's just a matter of probability. I don't believe technological development, much less to the degree of having a space program, are an inevitable result of intelligence or the presence of civilization. It's easier not to have a space program. It's easier, if you have a space program, to only explore your own solar system. Any number of issues, such as not being near enough to a colonizable star, not having sufficient energy or resources, natural disaster, giant ants, robot uprising, superflu, etc. could keep a civilization from starting, much less maintaining, a project of the necessary magnitude for the necessary amount of time.

And then you have to survive the trip, and actually succeed at colonizing another planet.

I think it's entirely within the bounds of reason for every civilization which has attempted interstellar travel to have failed up to this point.

There is some point to that. We are perfectly adapted to our planet because it formed us. Colonists on another planet may not find the same perfect conditions and it's likely that even to get a partial match (say Mars like conditions) they'd have to be many, many light years away from each other, with little outside support. And they'd need to adapt to colony ship life first, then to life on another planet.

They'd more or less evolve completely independently and it's conceivable that having these limitations will mean they never reach the same potential as the original humans did on Earth.

Usually the comparison with colonists of the past pops up. But they had the distinct advantage of being perfectly adapted to the planet and many civilizations still perished. Seeding another planet with humans raises a lot the bar for successfully developing a thriving civilization capable of reaching the levels required to further spawn successful colonies.

And a philosophical thought: would they even still be humans after (tens of) millennia away from the home of humanity, in vastly different conditions from the ones that evolved us? Would they be "our" thousands of colonies?

We don’t know how fragile technological civilisations are because we’ve only got one example. It’s reasonable to say the technological civilisations are highly specialised, and it’s not unreasonable to suggest that excessive specialisation is fragile as we have many examples of that in the form of biological speciation.

However, the economic cost of making an interstellar colonisation ship is so vast, that from where we are it seems reasonable to assume that anyone who does it has fully automated manufacturing and resource gathering – or, to put it another way, they are post-scarcity. If you’re post-scarcity, then you’re no longer fragile, because you can have a complete backup of everything you need, including the skills needed to rebuild.

Of course, there’s lots of ways for things to go wrong, and if I were to imagine badly written control software that means the fully automated manufacturing kills everyone, I’d be accused of being too derivative rather than implausible…

Is this true? Ours is far less fragile than at any point in history. Our only long term threat is nuclear war.

We're on the edge of a global environmental collapse, and most of our civilization's knowledge is being kept on the internet of all places.

Also, we were able to land men on the moon 50 years ago, and now that knowledge is basically gone, and the tapes lost, and people are starting to believe the Earth is flat and that the moon landing never even happened.

Meanwhile, we can still read tax records from ancient Sumeria because they were carved into clay.

Complex systems are always more fragile than simple ones. It seems to me like we've been standing on a house of cards for the last century.

Our worst long-term threat is our inability to coordinate our efforts in order to save ourselves. This test is not graded, it's pass-fail.

We don’t know that; we have a sample of approximately N=1ish (depending on what you want to define as a civilisation or a collapse) and we’re not done yet.

If our technology continues to improve, future humans could be looking at life spans of thousands of years if they are not killed by accidents.

I assume that it will require population control, because we will not be able to find enough habitable planets to keep up with the growth we have today. Basically a choice of "immortality" or procreation. This will also set a limit to how many colonies that are practical to create.

Also some may not accept the risks of travelling to other solar systems. Why risk dying "young" when you can expect to live for thousands of years?

Well, if you combine these advances even with basic artificial habitat building at reasonable scale(Oneil cylinders, world houses, covered craters, cavern cities, asteroid habitats, etc.) you should be able to house all these people quite easily.

If all these long living people dont have to much new children (and might not be able to ? eq. if fully digitized or with body fully replaced with mechanical parts), it might be even easier.

One issue with that is based on current physics, a deep space ship that isn't some millenia generation ship but accelerates to a decent percentage of c will expel a fuckton of energy in some type of fusion/fission/antimatter reaction, which tends toward being very, very visible. The first sign of a torchship-capable civilization wouldn't be random radio emissions, but would instead be some star system suddenly gaining another star that ignores orbital physics and instead ends up leaving said system at some absurd speed, probably with a bowshock measured in AUs from all the interstellar dust going nuclear as it collides with said ship.

>What would our telescopes see? It seems like we would most likely see exactly what we see today.

We'd see more red than we do - more heat and less light. Civilization produces heat. Advanced civilizations would presumably convert starlight to energy and produce waste heat.

An advanced civilization, by definition, would not be dependent on starlight.

Or planetary surfaces.

Where else could they possibly get energy from? Planets can be replaced by orbitals, but there's no way to replace the sun.

Even extreme primitives have magnetic-confinement fusion.

Ah ok. That makes sense. In that world, they can even use miniature black holes once they can stabilise and capture them in a field, to generate energy.

Who's to say that the amount of red we're seeing now isn't exactly what you're describing? Maybe if we lived in a barren galaxy, we'd see a lot more _blue_, as stars shone unencumbered by matrioshka brains.

For a simple example, can anyone see Elons Tesla Roadster out near Mars? And that's something we know is there.

https://www.whereisroadster.com/

“A telescope about 51,075 ft (15,568 m) in diameter would be required to resolve the Upper stage from Earth. A smaller one could see him as an unresolved dot, about 98.2 ft (29.9 m) in diameter, in ideal conditions”

So I recon that reinforces the hypothesis.

The angular resolution of a telescope scales as the size of the diameter of the telescope, essentially [0]. Meaning that if you want to image the roadster in visible light, you need a telescope lens about the size of Washington DC (currently). To just see it at all you need a lens about the size of a McMansion.

To image something like the roadster on a Planet orbiting Vega (~26 LY away, furthest star anyone on Earth could visit and then return from in a lifetime) you're looking at lenses greater than the orbit of Pluto, ish.

Optics/Physics is a bitch here. To really see/prove there are aliens running about, they have to screaming at the top of their lungs for a very very long time, hoping against hope that anyone will hear. It's just really really hard to build equipment that can passively listen for accidental broadcasts and spy on alien cars. At least under our current understanding of physics.

[0] http://hosting.astro.cornell.edu/academics/courses/astro201/...

>Vega (~26 LY away, furthest star anyone on Earth could visit and then return from in a lifetime)

It is not necessarily true that more time is spent aboard a ship than light would spend taking the same path, as measured by an external observer.

If you had a ship capable of accelerating at 1g indefinitely, then as measured by the crew, they could cross the galaxy in only 24 years.

https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...

To an observer who is self-propelled (and has enough energy), the speed of light (as seen by others) is no limit. It's not like you can fire your thrusters and NOT gain momentum and speed; or that, as you accelerate, the stars start passing by at the speed of light, and suddenly your ship jerks, ceasing to accelerate, because you hit an invisible velocity brick wall.

Yes, relativistically, you can travel anywhere in the Universe and only have seconds pass for your frame of reference. But I thought that Vega was the furthest star that you could travel to and from and then still have people you knew here on Earth that were alive. Also, I was totally wrong about Vega. I think that was my reading of Contact that gave me the thought. There are a LOT of systems that are inside of 30 LY from the Sun: https://en.wikipedia.org/wiki/List_of_star_systems_within_25...

I wish I could save comments so I'm just replying instead. It is so fascinating.

Bookmark the time stamp

Optics? Or my very brusk explanation of the limitations of our shared reality?

Not necessarily, the apparent magnitude is the issue here, not resolving power. Located at a comparable distance, Deimos, the smaller moon of Mars, reaches at most magnitude ~12.5, meaning that any telescopes smaller than 6" to 8" might not even be able to ever detect it's there. And we're talking about a 6.2Km sized moon, not an object with an overall visible area ~40000 times smaller - that would mean an apparent magnitude of ~23-24 as seen from Earth, meaning only the most powerful telescopes on Earth would be barely able to detect that "unresolved dot" - provided it had the same albedo of Deimos.

https://en.wikipedia.org/wiki/Deimos_(moon)

https://en.wikipedia.org/wiki/Apparent_magnitude

Edit: corrected

We might be see them already and not be able to single them out. Like the disappearing stars reported recently.

Why would they send themselves? Even we send robots, not humans, out to the distant edges of our solar system.

Why send the robot or alien at all if you can instead send the design/machine to make the alien. Perhaps they need send nothing more than RNA/DNA on an incoming space rock....

The thing is, why "5-20"? That's a super narrow range. The parameters would have to be tuned to a very small degree to produce just a handful of technological species in a galaxy.

A much larger range of the parameter-space could produce either thousands+ of technological species (which we have pretty good evidence is not the case) or less than one on average pretty galaxy.

So we have the options:

Lots of species (contradicted by the evidence)

A handful of species (inherently unlikely)

Very few species (current best bet)

I think you could increase the guess to 1,000 or 1,000,000 species and the outcome would still be basically the same.

We do not know how to detect life outside of our solar system. The only way our measurements would change is if one of them literally landed on top of us.

Well, we know how to detect laser and radio transmissions. If there are thousands, tens of thousands, millions of species out there right now, we've looked at several of their stars.

And if there are all these technological species, we would expect some of them to be much more advanced than we are. Why haven't some of them noticed us?

You can come up with possible answers to these questions, it's just that those answers look less likely than, "those species aren't actually out there."

We know how to detect laser / radio transmissions pointed at us.

You can't see a laser transmission off-axis if there aren't any stray photons reaching your detector - that's just physics.

You can't detect a radio signal below the noise floor without some a priori knowledge about the statistics of the signal.

These aren't justifications, these are simply facts about the current limits of our ability to detect far-away signals. These limits suggest that millions of far-away worlds could be extremely chatty between themselves, but unless they decided to point a transmitter at us, we would be none the wiser.

You shouldn't use a measurement that looks identical for case A and case B to decide which one is more likely.

I appreciate seeing your comments. The Fermi paradox and these similar ideas seem the modern equivalent to assumptions the sun revolves around the earth. We need more research and infrastructure in this solar system to really progress on this.

Imagine if we had thousands of microsats in orbit around the various planets that we could triangulate data amongst? We need to be more aware of our solar system before we can even make reasoned arguments about life within it alone.

> before we can even make reasoned arguments about life within it alone.

That's an excellent point, for all we know we have intelligent, non-spacefaring life right in our solar system. It's unlikely, but there's still plenty of oceans, gas giant atmospheres and lava tubes that we haven't looked at yet.

Consider that we have, ourselves, gotten far harder to detect over the last fifty years. Energy spent accidentally sending signals into space is wasted. And we are making much greater use of cryptography and compression schemes, which would make signals look like pure noise.

So, question: how strong does an undirected, random signal need to be to be reasonably detected at 10 light years away?

Even more basic than that, why do we think radio/photons are the most efficient/effective way to communicate for an advanced civilization? Why would they be using them in the first place?

We already know neutrinos can travel through most mass, so modulating those would let you transmit through the Earth and Sun with lower latency and without a repeater constellation routing around the object.

Whatever aliens might be using to transmit information is likely more advanced than we're able to detect.

Yes, that's another example of tuning the parameter-space for a possible answer, just an unlikely one. Yes, maybe the Milky Way is just chock full of highly advanced technological species who have all made themselves very hard to detect and none of whom have any interest in communications with other intelligent life.

But a simpler explanation that has many more paths to being true is "there's nothing out there."

To be clear, I don't think the evidence suggests near-certainty here. I wouldn't say that there's a 99% chance that we're alone in the galaxy. But it's also not a wide open field. There is some evidence, and so far that evidence suggests that we're likely alone.

I think your assumptions about what is hard and what is easy to detect need some recalibrating.

Alien life forms wouldn't need to use technology to make themselves harder to detect. It's extremely difficult by default.

They would need to use technology to deliberately spread a message in a way that is at all likely to be detectable, and even then would still have to get quite lucky.

Encrypted data does not look like noise. It looks very very different from noise. If not, the entire concept of communications engineering wouldn't exist. We're always looking for the next sharply bounded filter.

Well, that should be just temporary before our real mega engineering projects get started. Hard to not notice those, even just by the expected heat signatures.

> Why haven't some of them noticed us?

Maybe they have?

We don't "contact" every pack of deer that we notice.

Deer sure as hell know we exist.

Certain deer do, certain deer dont. Also, feel free to use a lower animal if that abstraction works better for you. My point is that if humans are some out of the way primitive life form it might make sense why aliens may know of us but not contact us (as in, there may be no purpose to explicitly contact us, as humans dont generally try to explicitly contact every deer herd).

It is not that humans are technologically primitive (which we are), it might be we are too intellectually/capacity primitive to be seen as "contact" worthy.

Ants then. Or even bacteria.

Further, think about how powerful a transmission has to be in order to not be drowned out by the power of a star. A laser would have a far higher chance (yet still hugely powerful to cross the distance), but only if aliens found us and pointed a laser directly at us.

Discussions of the Fermi paradox get swamped with people's individual hypotheses. It's nice to see an article that tries to develop a whole different kind of answer. The known possibilities seem to be:

1. We're alone (or very nearly so) due to an early filter. i.e. it was vanishingly unlikely for life to develop as far as it has here.

2. We're alone (or very nearly so) due to a late filter. i.e. life develops in lots of places but, terrifyingly, it becomes overwhelmingly likely to wipe itself out rather than spread.

3. Life develops frequently but there's some sort of interstellar ecology that makes species stay hidden or be wiped out.

4. Life develops frequently but is overwhelmingly likely to develop some other interest (becoming inward-looking, or exploring other dimensions) rather than colonising all of space.

This article's suggestion that Earth may be in a backwater wouldn't be sufficient by itself, so it is coupled with the idea, derived from observations on human colonisation of Micronesia, that expansion happens in waves and life on Earth happens to be in between waves. The problem is, advanced technological civilisations expanding across the galaxy isn't the same thing as Polynesian explorers eventually being followed by Europeans. Why would the waves die away? This is a late filter with extra steps.

5. No Aladdin's lamp. There's no FLT, no wormholes, no solution to the huge distances. And/or interstellar space is so full of toxins or plasmas no lifeform can survive it. And/or all EM data transmissions are reduced/scrambled/swallowed/encrypted by the void. All the experiments are naturally locked in separate containers.

6. Klaatu barada nichto. We are indefinitely locked in solitary, incommunicado, for creating and using nuclear weapons. On ourselves. Immediately.

I find (6.) somewhat anthropocentric in that it assumes nuclear weapons are the nec plus ultra of destructive power. You might as well have said in 1917 that we were incommunicado for inventing chlorine gas, or shotguns (whose use the Germans did object to as a war crime!)

They aren't. We almost have the capability to do much worse ourselves already. If you want big-bang type weapons, you can modify an asteroid orbit to drop a K-T event on the planet. It's not very target-able, but if you want to try and wipe out civilization, it would be pretty effective.

It's the ethics. I wouldn't 'hang out' with anyone who would shoot an unarmed civilian in the back. It's not about the gun.

In case you haven't seen the movie, 'The Day the Earth Stood Still', I'm referring to the speech at the end. https://www.youtube.com/watch?v=ASsNtti1XZs

6. is interesting because nuclear weapons are hardly the worst weapon possible. Even a relatively small mass accelerated to relativistic speeds would be more dangerous than a nuke, or even a very large mass at far lower speeds (asteroid). Similarly a genetically engineered biological weapon would probably be far more effective if total destruction is your goal.

Or 7 (is it now?), based on a thread above, organic civilizations become machine civilizations, which can colonize much more efficiently because long journey times don't bother them, and more stealthily because they can make do with comets and moons and such that won't support organic life.

Yeah (2) seems most likely to me.

Semi-advanced civilization like ours is relatively common but almost always depletes it’s resources and collapses.

Any civilization needs a lot of energy to grow. Energy is generally dangerous.

Climate change and ecological collapse seem to be hard to avoid for any civilization wired for growth and advancement.

I find most Fermi-paradox arguments drift towards being too biology-centric even if they acknowledge the possibility or probability of a transition to machine-based life.

For example this paper assumes that you need classic "habitable worlds" to colonize a solar system, but it's unclear why machines would need more than relatively small rocks or comets.

The paper also assumes that each colony needs to operate as a continuous entity and can therefore collapse or experience massive cultural shift. But if it's all machines, then you can put some powered-off seed ships in long orbits for cheap self-recolonization (seems strictly easier than crossing interstellar space in the first place).

I'd like to see more studies on the feasibility of those ultra-long-lifetime interstellar ships (assuming plausible tech like general AI). Maybe there are thermodynamic or other reasons why that can't be done.

(Personally I'm in the camp of "abiogenesis is actually really hard so we're the first civilization in our light-cone; the doomsday argument holds, and will be a theistic eschaton".)

Some fun ideas, because there's absolutely no reason why life should be so biological, as you say:

- Some ancient civ managed to run computing hardware on the surface of cooler stars (there are stars that allow non trivial surface chemistry)

- the same but with gas giant planets near their metallic or rocky cores

- Gamma ray bursts are galactic compute nodes syncing data

Machines need to be maintained. Machines of useful complexity include such parts as microprocessors. To create new or replacement parts, nothing less than the full Earth industrial complex is required. It's not clear how to package all that in a ship, including enough reserves to bootstrap an industry up to the point it is possible to build microprocessors. I doubt that "machine life" could subsist on a small barren rock with more success than biological life.

It's very interesting to consider what would be required for a minimal industrial complex that supports microprocessors. My intuition is that it would be much smaller than "the full Earth industrial complex". Seems like a question that is actually answerable with research, and potentially important too as a hedge against our current industrial complex collapsing.

Here’s an article on that: http://caseyexaustralia.blogspot.com/2018/09/how-to-industri...

Excellent link, thanks! That's exactly the sort of analysis required, though a lot more is needed.

I didn't follow why mining has to be (or should be) so human-labor-intensive.

Exactly, any such ship would be packaged around a processing unit factory

The problem with these types of arguments is they are assumptions built on top of other assumptions.

We don’t know how to colonize other star systems, so we don’t really know the factors at play. How easy is it to travel to another planet and start a colony? We don’t know. How likely is it that that colony will colonize other planets? We don’t know. We are taking numbers we guessed and multiplying with other numbers we guessed to get to an answer. If any of them are much off the answer doesn’t make sense?

What if the amount of resources to successfully travel to and colonize a planet in another solar system is so high that the vast majority of attempts fail and only a few attempts can be made? We can have n (pick some random large number) intelligent civilizations in our galaxy and not know a thing about them.

My thoughts exactly. I've always found it funny how people imply there's some major issue with cosmology because the Drake equation shows there should be intelligent life all over. Even though some of the terms in that equation are very not known and it would only take a few being an order of magnitude or two smaller than expected to result in a paucity of intelligent life rather than an abundance.

Right. The Drake equation was never supposed to "show" anything. I think the original intent was to lay out the factors at play and stimulate conversation, not to provide a probability. I think over time, the imagination of the public have taken over though and put more confidence behind things than we should.

So this article started as a good intro and overview of the Fermi Paradox (which is somewhat of a misnomer because as far as Fermi was concerned it wasn't a paradox at all) but it faltered at the end when it talked about habitable worlds.

This is a topic Isaac Arthur [1] has gone into great depth about. If you haven't found his YouTube channel yet prepare to lose several days of your life. I find his arguments here compelling.

Basically planets only matter as a source of raw materials. Planets are highly inefficient ways of creating living area. The most likely outcome for a spacefaring civilization is actually a Dyson Swsrm. 1% of Mercury's mass used this way could create orbiting habitats that support a quadrillion people and fully utilize the sun's power output (a so called Kardashev-2 or K2 [2] civilization).

And these are simply O'Neil Cylinders [3], which don't require any materials that don't already exist.

The beauty of this is it doesn't require much more technology than we already have. Better yet, it doesn't even require commercial nuclear fusion (personally I'm not yet convinced this is even viable).

Take this further and a K2 civilization is not subtle and is highly detectable. For it not to be violates thermodynamics. We've seen no evidence of any K2 civilizations within millions of light years, which suggests their existence is highly unlikely (within the cone of spacetime we can observe).

Given this seems to be such a natural evolution you can extrapolate and say that we are pretty much alone.

Remember it's not about what most civilizations do because it only takes one to go this road. The argument that no civilizations become K2 civilizations use much harder to swallow than a few do. This notion gets more absurd the more civilizations there are.

[1]: https://www.youtube.com/channel/UCZFipeZtQM5CKUjx6grh54g

[2]: https://en.wikipedia.org/wiki/Kardashev_scale

[3]: https://en.wikipedia.org/wiki/O%27Neill_cylinder

These are all under our current understanding of physics, which does a good job, but we know it's not the full picture. Matter, the stuff you and I are made of, is ~5% of the universe's mass-energy. We understand the physics of this stuff fairly well.

Dark Matter is, as far as we can tell, is entirely made of stuff that falls down and does nothing else. Dark Matter is ~25% of the universe. We have a fair few theories of what Dark Matter is, if/how we can use it, how to make it, move it, etc, but it's still very active research. We have a toehold on Dark Matter.

Dark Energy, which makes things fall up, is ~70% of the universe. We are almost completely stumped as to what it is and how it works beyond making the universe roomier. We're just totally knackered on Dark Energy.

Any civ that is thinking that seriously thinking about (let alone putting down-payments on) discombobulating planets in order to make more lawns to mow and gardens to weed is very likely to have more than a toehold on Dark Matter and is likely trying to make Dark Energy levitate tequila shots.

And that's just the physics that we know we're missing. K2 civs are probably far more aware of yet more dragons in the mists.

So, concluding (correctly) that since we don't see the IR heat of K2 planet demolitions, that we're alone, is not the best conclusion. We've not a clue as to what the rules of the universe are yet. We can talk about strategy once we learn how the knights and bishops move about the board.

I've never heard of K2 before. Really interesting!

I suppose one reason we can't see them is that there is an even better model so advanced civilizations end up using, but we haven't figured it out.

While I love futuristic ideas like those of Dyson, it seems naive to assume that because we don't see evidence of our virgin civilization's futurists' visions of advanced civilization, it does not exist. This is considering that our futurists are currently living in a newborn civilization on a geological time scale and are still grounded in their vision by science that we currently have. I'm of the opinion that we should probably wait a few thousand (or perhaps million) years before we start slapping the word "law" onto some reliable physical properties we can recreate in little Earth-scale experiments.

And since we don't know for certain whether there is advanced life or not, we also don't know what the universe would look like if there was -- perhaps the current stars we see are just a fraction of the stars that existed pre-Dyson swarming.

My theory is that any advanced civilisation reaches a point at which a vast amount of destructive power becomes accessible to individuals. At this point it becomes only matter of time until that civilisation is destroyed.

The analogy I use is to imagine that every adult human on Earth woke up tomorrow morning with a button on their wrist that could destroy the Earth. How long do you think we would last?

We haven't reached a stage where an individual can create a nuclear bomb, a new kind of super-virus or some other doomsday weapon but I imagine its not an implausible scenario in the future. I think this is kind of a wall that all advanced civilisation may hit at some point.

It’s not hard to imagine in the near future that having a PhD in biology and access to a moderately equipped lab would grant a person the ability to create super plagues capable of killing most humans.

Couple that with the wide spread nihilism that wants to destroy the world because they can’t stand the injustice of life, and it’s a pretty good bet our time as a species is limited here.

If I were king for a day I’d do everything I could to get the message out that things are getting better, injustice is shrinking every year, and there is hope.

> It’s not hard to imagine in the near future that having a PhD in biology and access to a moderately equipped lab would grant a person the ability to create super plagues capable of killing most humans.

Pretty sure that's already the case.

A way out would be to quickly move our brain to machines and build fully autonomous and self sustaining asteroid sized ships (could be built in situ). To function as backups and spreader for our civilization

This is an interesting theory I have considered as well, however there is a reason to disbelieve it. It assumes at its core the diffusion of some form of highly destructive technology, and that the technology will be unleashed in an irreversible way before it can be recognized and “put back in the box”, or it can’t be “put back in the box”.

These assumptions individually seem strong but together they get quite weak. For example, diffusion of civilization over several planets before this technology is diffused provides a potential firewall. (For example, once the technology is recognized, an orderly exodus is made which forcibly leaves behind any trace of it.) Alternatively, the diffusion itself may not occur as well, similar to the current life-ending technologies we have now that can only be created by state actors.

It is a legitimate prospect — but hinges upon several aspects hung together to get to a point where it’s an inductive invariant explaining fermi.

Do note that it is orders of magnitude simpler to reach the technological level necessary to create the means of causing the collapse of civilization than to create the means to colonize other worlds. There are places on our own planet far more hospitable than any other world in our system that we haven't yet colonized, yet we are potentially a few political incidents away from nuclear annihilation.

Maybe a biological weapon being unleashed from some genocidal nutcase's basement hobby laboratory?

this is a good theory but you don't even have to look at it as, "each being has the will to destroy everyone". way more likely that it's a natural byproduct of existence that can't be adequately anticipated such that the species can do something about it. We're already on the edge of waiting for the bacteria that can't be killed, the climate disaster that destroys our food supply, etc. (you might say climate disaster is adequately anticipated, but while science is anticipating it, the whole of the species is unfortunately not).

This is why they're orbiting at a safe distance and waiting to see what we do when we discover antimatter bombs for ourselves.

Like "Mail order CRISPR kits for everyone"?

The scary part is that there actually already is a web site that sells those...

Probably an arms race would make defense technology good enough to limit the consequences of it.

If that happened you would probably see (wealthy) people migrating to underground bunkers to protect themselves and interact using VR. That could be one of the explanations why they don't go out to create colonies and make enough noise for us to detect them.

Does a lion born in a zoo understand it's being held captive by (in comparison) super intelligent humans? When it's tranquilized, does it know this isn't a normal thing for a lion? When the caretaker throws food out or pets it, does the lion have the capacity to think about it in any other way than what it means right now for the lion - food, feels nice, etc?

If there's a correspondingly more intelligent alien species hanging out on our planet with us, would / could we even hope to know?

Lions are also unaware of radio waves. We could be unaware of self-organizing ripples at the scale of subatomic particles. That's a life form that could efficiently colonize the universe hitching rides on rocks.

What if the Universe is the "zoo", only created to contain us?

But Lions don't appear to have any abstraction ability, or reflective thought. By that I mean you as a human can imagine yourself thinking about some hypothetical situation, as well as consider what kind of evidence would support a given hypothesis.

I think this might have actually happened (apocryphal?), but just imagine if you took humans from another country and put them in a zoo. They would surely figure it out, based on the evidence at hand.

Definitely agree.

Just like how a lion or a chimpanzee wouldn't make a convincing zoo for another lion or chimp, a human could figure out they're in a zoo made by another human.

But when you make a zoo for an animal that isn't on your level, you can figure out what's needed to satisfy it (even if it's really crappy compared to their normal environment).

So if something smarter than us by an order of magnitude or more made a zoo for us, it would be a much more elaborate and convincing zoo, and I'm not sure we'd figure it out.

If we are talking super-advanced, it wouldn't even need to be a physical zoo. Just mess with enough of our brains enough to make us not want to do certain things and we'll stay on this rock forever.

How exactly do we know they dont have reflective thought? Or at least any less reflective thought than your average human. Not really sure how to test that. I know there is the mirror test but what if there are different types of reflective thought and they just missed the boat on that by a little but have other kinds of thoughts?

Franz Kafka proposes this kind of scenario in "Investigations of a dog."

yes.

Edit: Ok. This is a common argument (well apart from the "living on earth with us" bit which requires some Doctor Who levels of mind-wiping so let's discount that.

Lions see humans in the zoo, and they see the walls of theie prison. Lions definitely have had psychological problems in the worst run zoos so it is fair to say they are affected and aware.

Are they aware of the concept of zoo? Equally unlikely. And the next question is how much more intelligent is a human to a lion. the answer is not comforting to us as a species.

I'm not sure where the corresponding boundary would be exactly, since we do seem to be on the verge of exploring other planets, but you could say that we also understand where it is we're allowed to roam - the surface of Earth. And we aren't free of psychological problems.

Interesting philosophical proposition, have an upvote.

It also speaks to the limitations of our senses and the way we experience the world.

The article does a good job of explaining some of the numbers, but it’s important to remember just how large they are.

To a spacefaring civilization a million years might be the human equivalent of a decade.

The sad truth is that intelligent humans (enough to think and act on thoughts of space travel) have barely existed on the cosmic timeline, and likely won’t live long enough to know the answer to whether or not we’re alone. Not because of some romanticized fermi gate paradoxical reasoning, but simply because we ran out of time.

What do you mean? How is running out of time different from a Fermi gate? Without a gate, why would time run out? The only natural limits are the time limit to colonize another planet, then another solar system, before our earth and sun lose their ability to sustain life.

I personally subscribe to the school of thought that interstellar travel is impossible, except through some form of suspended animation or generation ships (which both have its own problems). So no warp/hyperdrives, no wormholes, no shortcuts to travel between the stars. This article dismisses that notion before it even begins, but this is the only theory that fits the currently observed laws of the universe.

Even with no FTL, you can still do interstellar travel just fine if you make people live longer, which is being worked on for other reasons already.

It's not individual lifespans that are the issue, it's the lifespan of your equipment. If your rocket breaks down in the interstellar void, you have no resources with which to fix it.

And then you need to be able to bootstrap the entire industrial base to build a new rocket at your destination without any help whatsoever aside from what you brought with you. Given the history of interoceanic colonization efforts on Earth, this suggests that the difficulty ranges from "insane" to "impossible."

I think thats stil managable, even simply by redundancy and sending fleets of ships. Also 3D printing of replacement parts seems pretty promissing and is already being looked into (there is a basic 3D printer or the ISS).

There is, but it doesn't really do anything, right? They printed some plastic toys with it; it's not operations-critical.

the article refers to travel not just by the species itself but by machinery that is not limited by lifespan, which in theory would also be observable. We have probes that have left the solar system through this means. not to mention just the simple example of radio waves.

The lifespan (either longer human, or mechanical) of individual travellers does not affect the speed of colonisation, so any communication would be quite limited. Which means that there be will be no interstellar "empires" or even cultures -- and if any habitable worlds are as rare as it seems to be the case for us, I'm not very optimistic about encountering any alien species any time soon.

I think it's time we stop looking for life near other stars and start saving our own. This planet is completely neglected. You want to live on Mars? That should be fun, without a magnetic core. Living underground, like rats.

If you want to know what frontier living feels like, take a week off and stay in one of the Inupiat villages on the edges of Alaska. You'll be climbing up walls in 3 days. And that is a luxurious vacation compared to frontier living on a barely habitable planet. Netflix? Nah, bro. They still have Blockbuster.

More likely we really are alone: http://aleph.se/andart2/space/seti/dissolving-the-fermi-para...

That paper only claims that it is plausible we're alone, meaning the Fermi paradox is only a question, not a conundrum.

Fermi paradox. I never liked it.

It presumes too much.

It presumes that technology will advance to the degree that we overcome the speed of light. Not directly, but that's where it has to wind up.

Because no matter how you slice it, it's still four years to Alpha Centauri at the fastest possible speed we know. That means it will be at a minimum 8 years before we know if anything was successful.

And yes, for the travelers, they experience time dilation, but we here on Earth would not. That time does matter. Even with self-replicating Von Neumann probes, they still have to send that information back. That's still going to take time.

How many resources can you dedicate to a bet that's going to take at least a decade to show a return? How many of those bets can you make before you've depleted your resources to the degree that you simply cannot do it anymore?

I think we may find ourselves up against the uncomfortable truth that our cosmic range is rather limited.

IIRC Fermi paradox does not expect FTL - a locust style colonization effort should be able to settle the whole milky way quite quickly (couple hundred thousand years) even with not very fas sub light travel.

Like I said, not directly, it doesn't, but once you start digging down, you're going to need that.

A couple hundred thousand years is quick on a cosmic scale, but we, as a species, have never undertaken any project on that scale ever. No species has that we have evidence of.

Any sublight travel is a one way trip with almost no hope of ever knowing it was a success by the people back home. No one funds that. And I don't blame them. There is no return in any fashion for the people who remain. And little to no return for anyone who starts the journey. The only thing you can possibly satisfy is some minor curiosity.

Travel to Proxima Centauri at the current highest speed we've sent probes into space would take over 80,000 years. If you double that speed. It will still take over 40,000 years.

So, cosmically, the time scale is short. And compared to light, the speed needed is slow.

But we're not light, are we? We don't exist on cosmic scales. I'm not concerned with the theoretical limits of physics. I'm more concerned with the practical limits of us.

Don't be; 'we' won't be doing it. These are evolutionary/revolutionary timescales; how many millenia away do you think general artificial intelligence is?

First, I think what we're searching for isn't intelligence so much as consciousness. So I'm going to treat general AI and consciousness as pretty much the same thing.

Considering we don't exactly know what consciousness is or what it means to "be intelligent", I have absolutely no clue how long it will take. But unless there is something I'm unaware of, I do think that we're approaching the problem from a wrong direction.

Think about it like this, we know that intelligence/consciousness is an emergent property of a lot of life on this planet. Including some life that we previously didn't consider aware in the traditional sense. Plant life may have some sort of intelligence/awareness.

When an artificial intelligence can express a genuine desire to avoid termination, we'll know we've gotten it.

Then again, do we even express genuine desires? Or are we simply inefficient meat computers responding in predictable ways to external stimuli?

So the question is whether or not general AI is even possible for us to make.

And then the assumption is that this general AI will be able to plan on the cosmic scale. But why? First, what's the life span for most electronics at this point? That factors into desire. What happens beyond our death is only of academic concern to us. To assume it won't factor into their decision making process is just speculation.

And if you presume we'd have programmed this general AI with the desire, well, it's not really a general AI, is it? We've robbed it of a decision. We've taken an entire forest of decision trees from it. It can't not choose to colonize the stars.

Then you're also making the assumption that general AI won't come to the conclusion that colonizing the stars is an inefficient use of resources. General AI doesn't really change the problems with the Fermi paradox, it only seems to add new problems.

>First, I think what we're searching for isn't intelligence so much as consciousness. So I'm going to treat general AI and consciousness as pretty much the same thing.

That's not how I think about it at all. I think you're underestimating how alien AI could be to us, in general. I.e., I think you're anthropomorphising it unnecessarily.

There's an idea called the orthogonality thesis, which says: The intelligence of an arbitrary agent can vary independently of its goals.

Here, I'm using intelligence to mean just the ability of an agent to generate/evaluate/execute plans to further its goals. A modern chess AI on modern hardware is more intelligent than one from the 1980s. In principle, you could have any arbitrary utility function attached to any level of intelligence.

This idea was brought up because often, when people heard about the paperclip maximiser (an agent that tries to maximize the number of paperclips- and thus wants to take apart everything in its lightcone and turn it into paperclips), they said: "But why would something so clever do something so stupid and pointless? A superintelligence would surely realize it was being stupid and decide to do something smarter."

But there's no reason to think this! When you take away the agent's goal of maximising paperclips, there's no perfect platonic ghost of consciousness left! The paperclip maximiser, as defined is just an algorithm that predicts the future, looking for actions that maximise paperclips, and executes them. Given unbounded compute power, it can just look through arbitrarily many counterfactual simulations of the future given different plans, pick the plan that maximises the number of paperclip-like structures in the universe, and execute it. The rest is implementation details, given we don't have unbounded computing power, but the point is such a system doesn't need to be conscious to be powerful.

If you have an AI without a utility function, you don't have an AI. 'General intelligence' just means the AI's computing/reasoning/versatility power, in a vague sense. It has nothing to do with whatever particular utility function an agent might be trying to maximize.

The paperclip machine doesn't 'want' to colonize the stars; it's just a system that will do that if it can, because tautologically, it's a system that tries to turn as much as it can into paperclips.

I don't really think there is a Fermi 'paradox'. We don't have solid priors on how often agents arise in the universe. The fact there aren't any visible aliens should either just lower our estimates of how likely life is, or maybe there's some sort of anthropic principle argument to be made here where we probably wouldn't observe a universe where aliens come to visit, because in nearly all possible universes where intelligent life survives and goes from star to star it just eats all the stars very quickly on astronomical timescales or something, such that the chances of intelligent agents like us arising while there's visible evidence of other agents is incredibly slim.

Like I said, we don't even know what consciousness is.

To say there is a platonic consciousness is kind of saying you know what that looks like. And to say that you could grant something an intelligence capable of solving the problem of colonizing the stars while also denying it the ability to choose its own goals is an assumption I'm not willing to grant.

In other words, there is "a reason to think this!" We are that reason. Other life on this planet is reason to think this.

It still expects technology that we do not know is possible to build.

Stuff like https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... should be doable with current or near future technology.

I find it strange that the author thinks that Dark Forest theory is implausible. It strikes me as the simplest of explanations.

Granted Cixin Liu stretches physics into all sorts of implausible places, but it does make a strong argument for the theory.

https://www.goodreads.com/book/show/48838110-three-body-prob...

I loved those books, but the dark forest theory doesn’t make sense. Given a dangerous universe it would make sense for a civilization to try to communicate with other civilizations to create alliances for mutual safety.

The civilizations that are able to forge alliances will tend to out-compete lone wolves.

Liu assumes that it is somehow a lot easier to wipe out a civilization than communicate with it, and that for some reason your civilization has to decide to wipe out another civilization without communicating with it.

> Liu assumes that it is somehow a lot easier to wipe out a civilization than communicate with it...

This may be true, though. We struggle to effectively communicate with creatures on our own planet available in real-time, like dolphins and elephants, who appear to think and have language of sorts.

Launching some relativistic sand at another planet may well be a lot easier.

We seem to communicate pretty well with dolphins, elephants, and other animals. Consider trainers who work with these animals on a daily basis and have rich and productive relationships with them.

We can explain "go press that button" or "lift your leg" fairly well. We can't, as yet, put a dolphin through something like an elementary school level education.

alliances put some lower bound constraint on the logistic capabilities and density of the civilisations that form them.

strategically speaking and stunning hostile unknowns a stable civilization controls a territory matching reasonable response time from the ready armies at their combat speed and necessarily a requirement for alliances to form is for these zones to overlap

but if they are at such distance it negates one of the prerequisite for the dark forest theory, that civs are sparse enough for the chance of facing hostiles alone is on par with encountering non hostile civs

Interstellar space isn't an ocean, and star systems aren't countries. Analogies to Earth militaries and navies simply don't apply, the scale of space is too big.

You're not going to form any sort of "alliance" over a distance of light-years, much less consider the fleets of hostile civilizations to be a threat by their proximity the way England once considered Spanish fleets a threat. There's no "reasonable response time" when allies will take years to hear your distress call, and more years to arrive.

I loved the series, but the physics was horrendous, and I don't agree it made a strong argument for the Dark Forest theory. It made an enjoyable, interesting read about the Dark Forest theory, but the schemes the author used didn't make sense and wouldn't result in the universe as described in the books.

Yeah, the book was about allegories and situations. The plot devices were intended to drive certain plot elements, not to be in the Clarkean way the first principle driving rationale for the work.

The trilogy is very enjoyable!

Well put - the way he wrote the "science" was fun and used in novel, clever ways to further the interesting situations and ideas and analogies, which is why it was awesome. Plus it was neat reading a book that was first Chinese and then translated. I found the subtle differences in tones and characters fascinating.

The dark forest theory works wonderfully as a plot device in the book. That trilogy is the best sci-fi I've read after Banks, Clarke and Asimov, hands down.

But, if you stop and think about it, in the real universe it has two gaping problems:

First, The Dark Forest theory depends on the capability and willingness to develop world destroying devices.

Second, it depends on the likelihood that the species you detect has not yet spread to other systems. If it has, congratulations, you have started a shooting war with an enemy whose threat level you have no gauge of. Some with an inclination of game theory might want to figure this out through better, though.

> First, The Dark Forest theory depends on the capability and willingness to develop world destroying devices.

Any civilization capable of traveling to another solar system has this capability: just take one of their ships designed to accelerate to significant fractions of the speed of light and decelerate at the other end of the journey, set a course, and simply don't decelerate.

> Second, it depends on the likelihood that the species you detect has not yet spread to other systems. If it has, congratulations, you have started a shooting war with an enemy whose threat level you have no gauge of. Some with an inclination of game theory might want to figure this out through better, though.

There's a good chance the above described weapon would be nearly undetectable and untraceable. For at least the latter half of its journey, it's just a chunk of mass traveling through space, emitting no signals. It would also be only a small factor difference in capability (0-1 more accelerations and decelerations than an actual interstellar transit) to send it from a different part of the galaxy.

Another book in this vein, although distinctly more uncompromising in its conclusion, is The Killing Star, by Charles R. Pellegrino and George Zebrowski.

Available on Audible now. Hard to find it in print.

Another series is Greg Bear’s Forge of God

Having just today finished Cixin Liu's 'Death's End', I rescind my 'distinctly more uncompromising' comment.

Well, even if we're not alone, we must acknowledge that someone had to be first to develop the ability to travel through the cosmos. It may actually be us.

We already have that ability. It's just that this travel is insanely slow and requires the energy levels that we can't easily produce in those timescales. It is quite possible (I would even say likely) that any faster travel is not very viable, and it might never be possible to make any kind of FTL engine.

We don’t have yet the communication technology for anything far from our system.

I'd like to think it's at least possible that a life form which made it to the stars without blowing itself up is compassionate enough to leave Earth the heck alone and treat this system as a giant nature reserve. Perhaps they'll swoop in and borrow our tech if we ever come up with anything good, just as we might draw on the natural world for new medicines or construction materials.

You're assuming a species that practices "compassion" towards its own kind would care about us.

Human history is full of examples of societies which treated their kin with kindness, but others with cruelty.

And yet, over time, humanity has trended to respecting the life of all sentient creatures. It seems like in the limit, especially if scarcity of resources is eliminated, all life will be precious and valued.

I just googled for how many lab animals are used in reseach in the US, and the number was ~800K in 2017. But (and this is a big but) rats and mice (and birds and fish) are not counted. For some reason, guinea pigs and hamsters are considered more equal than rats and mice.

One supplier of lab mice in Maine provides ~3 million mice per year...

Yearly production (and slaughter) of chickens is something like 60+ billion. Not sure if sentient, but perhaps they deserve it as descendants of the dinosaurs that terrorized human ancestors...

The simulations in this article are compatible with the more abstract analysis in my paper at http://www.cs.utoronto.ca/~radford/anth.abstract.html (see Section 7).

The brief summary is that we observe two things: (1) we exist, with the full set of memories we have, (2) these memories don't include any evidence of other intelligences (I'll assume - readers who think they've ridden on UFOs can draw other conclusions).

The existence of our particular civilization (in all its detail) is more probable if intelligent life is more probable in general (assuming one dismisses arguments about infinite universes containing all possibilities, so you can never conclude anything from anything).

But if intelligent life is generally more probable, it's more probable that we have seen other intelligent life, contrary to observation.

So the most likely situation given what we observe is a compromise - intelligent life is fairly likely (explaining our existence), but not really likely, or at least not really likely to explore other stars (explaining why we haven't seen any aliens).

One unfortunate possibility is that intelligent life reaching our technological level is common, but getting to the level of colonizing the galaxy is uncommon. But that needn't be highly likely. It's also possible that there's other intelligent life out there not far away, in which case it may well be within our ability to detect it with a bit more effort. That's what one would conclude from this article as well.

I have a somewhat nihilistic theory around the Fermi paradox. What if all intelligent life annihilates itself before reaching high enough technical proficiency to achieve widespread inter-planetary travel (or time travel). The idea is that intelligent life emerges from the process of evolution (natural selection) where the stronger survive. But that leaves you with people who have the tendency to kill each other and themselves off. As the technological ability to completely annihilate ourselves increases the probability that it will eventually happen goes up over time. As technological prowess increases and population increases, intelligent species eventually destroy themselves by using up all their resources or ruin the planet with climate destruction before achieving inter-planetary capability. Similar to how yeast will reproduce until they all kill themselves off in their own waste product (alcohol). It is possible that this is a universal axiom, hence intelligent life does not spread across the galaxy. I know this is a depressing thought but it's an idea that has haunted me once it occurred to me.

This is known as the Great Filter theory

oh thanks, just googled it, I had not heard of it.

It’s described in the article:

> Sounding a more ominous note are concepts such as the “great filter”—the idea that there is something that always limits a species, perhaps an inevitable failure to achieve that green revolution, leading to an implosive extinction of all potentially technological life.

The models attempt to encapsulate this issue through the variable of how long a civilization lasts. As easy as it is to imagine civilizations similar to us, it’s equally easy to imagine others where other variables prevent the intense egoism we evolved as a species. Or worlds where competition is less fierce perhaps. Etc..

Either way I find it fascinating that we could be living in what is essentially the rural area of the galaxy.

With a sample size of 1, there is no way to estimate the possibility of a species fundamentally unlike us becoming spacefaring.

We can count stars pretty well, but we can only barely estimate the probability of an earth-like planet existing around a star and forming cellular life.

This actually was kind of the nugget for me in this story: "At one extreme, it is easy to make the galaxy empty by simply shrinking the number of usable planets and having civilizations last for only, say, 100,000 years or so."

i.e. 10x longer than we have had even rudimentary technological civilization on our own planet. Sample size of 1, etc. but this to me seems the simple explanation of the "paradox". Space is big, and 100k years is a long period of time to not make a mistake.

They theory already is shown on Earth. Look how long it take humans to get to where we are, compared to how long it would have taken if a God had carefully guided us away from castrophes like the meteors, plagues, famines, and wars.

It bothers me that the authors' assumptions are so controversial and that they hide them in the middle of the article.

In the simulations the authors are using, civilizations have lifetimes, meaning that all of them end after a while. And that simply isn't supported by events. Technological civilization has never vanished even from our little one-planet civilization. Polities do decline, but there is usually someone there to pick up the pieces. In an interstellar civilization there would be more recovery opportunities: interstellar visitors who arrive to see why a collapsed planet went offline.

The authors of this piece are asking us not just to assume that simultaneous disaster is possible on ten, a hundred, or a thousand planets. They are asking us to assume that it happens to every single time a civilization has achieved interstellar travel, and that it has been happening for the last ten billion years.

Simultaneous catastrophes on thousands of worlds affecting millions of species for billions of years? Life arising only once could easily be the more plausible option.

It's interesting to think that although it is highly likely that life originated on Earth, we don't have evidence of multiple originations.

If life is so rare that it occurs only once even in hospitable conditions, then it may follow that life is extremely unlikely even on a cosmic scale.

> Life arising only once could very well be the more plausible option

Indeed I feel like coming to this conclusion is something that the authors - and most of us rationalist types - do not _want_ to come to.

Because if you accept that hypothesis, then it follows as a consequence that an alternative view of the world makes a lot more sense: what if, rather than living in an emergent, random universe where life sprouts up everywhere, hundreds of billions of times, but somehow _always_ disappears before we can ever observe it outside Earth, we are instead living at the center of a universe where we are the sole intelligent species that ever existed? In that system of the world, the universe is being directed by beings existing outside its bounds - gods. A simulation created and managed by uncaring observers - as hypothesized by the likes of Elon Musk? Or a benevolent God in the Judeo/Christiano/Islamic tradition?

The truth is that this alternative is being rejected a priori, indeed not even acknowledged, by the authors of the article or most people in this thread, because it is an affront to their core beliefs, not through pure logical reasoning.

> The truth is that this alternative is being rejected a priori, indeed not even acknowledged, by the authors of the article or most people in this thread, because it is an affront to their core beliefs, not through pure logical reasoning.

I think it isn't acknowledged because it is inconsistent with literally everything we have learned about physics and the universe, and even if it were true, as you said, they are outside this reality and don't care. They set the simulation parameters, and then walked away, so they are irrelevant.

If however, you point to something like miracles occuring in our reality to back up the "gods" view, then you aren't really having the same discussion as the authors.

I don't understand why ufological data is systematically ignored. This leads to biased reasoning.

I wouldn’t say it is ignored, more that it isn’t particularly useful. Shaky YouTube videos don’t allow for much in the way of study. Even more convincing sources, such as that video released last year of the Tic Tac UFO, were interesting, but not all that useful.

I agree. To talk about the possibility is to commit scientific suicide. Even cautiously talking about the topic immediately outs you to others as a crackpot. I think it's undeserved. Especially when we are now seeing just how many habitable world's are out there. It seems plausible that we have been visited by curious extra terrestrial civilisations. The bizare patents coming out of the US navy suggest to me that no one knows where these things are coming from, if they are real.

> It seems plausible that we have been visited by curious extra terrestrial civilisations.

no it doesnt. It seems increasingly implausible

How do you justify this claim ?

Indeed, if this theory is correct what we should expect to see are individual, small expedition-like visitations, which aligns roughly with the limited bits of credible ufo-related data.

One would have to assume that UFOs are piloted by aliens which since there is no proof alien life exists it's a Fool's errand.

I see two alternatives, each sufficient:

1. Expansionist civilizations eventually encounter another one, and reliably obliterate one another. (Note, this is not "Dark Forest": it requires no long-lasting structure of any kind, just the occasional chance encounter that turns out badly.)

2. Expansionist civilizations find goldielocks planets both unnecessary and limiting, and just leave them the hell alone. They probably mostly use Neptune-like planets, when they have a use for a planet at all. Maybe they are at "our" Neptune right now, and have not contacted us, because why bother? We're "made out of meat". <https://www.mit.edu/people/dpolicar/writing/prose/text/think...

This brings to mind Dr. Greer and the Sirius Disclosure project [0]. The first documentary, Sirius, is available on YouTube [1] and the second documentary, Unacknowledged, can be viewed on Netflix.

To be clear, I'm not sure if I entirely believe in all of this myself. However, I don't regret watching any of it. At the very least I got some inspiration for short stories/screenplays.

[0] - https://siriusdisclosure.com/ and https://www.youtube.com/channel/UCC6B4Y0oFACv9QBlf0ebBcg

[1] - https://www.youtube.com/watch?v=5C_-HLD21hA

One thing I fail to see mentioned here and in such articles is the complexity of colonization. We are falling in the trap of "idea == profit". A lot needs to be done, and can go wrong, between both.

Some examples I am thinking of, and I am certain people will have more... All are compounded by the LY distances between colonies and whatever home is:

- Terraforming - It would be the exception that new planets are 100% hospitable to a specific species. How long to properly terraform, and then how long before the can get to a point where they can launch a new sub-colony? Need proper population, technology and resources.

- Culture drift - how long can the colony and home share the same culture, with same values and objectives?

- Political drift - Imagine you are part of a colony, with "home" some 4 LY away. How long before you will want to have full autonomy, specially given the distance?

- Cultural and political factions - Is it possible that individuals in the colony have different objectives, resulting with political infighting or open war? What would then be the impact on the colony?

- Protection - Depending on technological advancement, how can a colony protect itself from external rogue elements (big warship gone rogue, pirating the colonies for resources?)

For sure, many of these things depend on the type of species colonizing its region, how much sentience and free will they have. I also assume they haven't solved FTL travel!

This is article went off the rails when it talked about evidence for past civilizations on Earth being undetectable:

> The only real evidence after a million or more years would boil down to isotopic or chemical stratigraphic anomalies—odd features such as synthetic molecules, plastics or radioactive fallout.

Civilization on the scale such as ours creates huge waves of extinctions in the planet's species leaving lots of evidence easily available for us to see that it happened.

In addition we've affected the Earth's atmosphere with our carbon emissions and that's going to leave evidence behind as well that will last a very long time.

Also, all that easily accessible oil that we've been using to power our engines would not exist, because nobody is going to be leaving such an abundant and easy to use source of fuel around. The oil and gas we use took tens and hundreds of millions of years to form.

Finally, and not least of all, the quoted paragraph mentions radioactive fall out, but any radioactivity would be blatantly obvious unless this civilization used none of it. There would be a very clear indicator in our dating methods of any radioactive activity in the past.

I think it's safe to presume that instead of some past civilization that didn't use the most abundant natural source of energy around, didn't make use of nuclear energy and somehow managed to leave the species record clean it simply didn't exist. I don't feel like it takes more than a few moments to just realize how unlikely that take is and shouldn't have been included in the article.

You might find the the paper [1] and HN submission interesting. I believe it addresses every concern you raised, and comes to the opposite conclusion.

[1] https://fermatslibrary.com/s/the-silurian-hypothesis-would-i... [2] https://news.ycombinator.com/item?id=21840320

What’s the point of settling on planets if you can sustainably develop anywhere in space, which I think is within the reach of any typical space-faring civilization?

I guess, you can do both. Well unless you want to use the mass of the planet for a more efficint purpose, eq. habitat swarm.

On Earth, there have been previous life-forms which have died out, there have been more or less intelligent life-forms which have died out (various dinosaurs and exhausted branches of hominids etc.), there have been previous civilizations with varying scientifical/technological achievements; but there has never been a species on Earth which has created a civilization as advanced as humans have.

So, we are the first ones to reach this point on the Earth. Not the first ones ever, but first ones to get this far.

If we assume the patterns of evolution observed on the Earth are nothing specific to Earth and they repeat throughout the Universe, there are/have most likely been life-forms (simple and complex) of varying degrees of intelligence, as well as civilizations of varying degrees of technological advancement.

However, since we apparently see absolutely no trace of anyone else, either they failed to successfully bootstrap their colonies outside of their home planet/moon, or we got here first. It's unlikely, and absence of evidence is not evidence of absence, but someone has to be the first. Maybe it's us, from our little blue planet.

> but there has never been a species on Earth which has created a civilization as advanced as humans have.

It's an interesting to think about what traces an industrial civilization like ours would leave behind if we were to be wiped out tomorrow. Most evidence would be gone in a few thousand years. Wait a million and it would be almost like we were never here.

https://www.theatlantic.com/science/archive/2018/04/are-we-e...

https://news.ycombinator.com/item?id=19707426

Never say never :-)

I am intrigued by the simulation theory. That we as a species has reached a certain level of advancement to simulate a reality and experience it; or we may just be npcs or temporary programs for another intelligent race in this simulation.

We could also be a zoo/prison planet far into enemy territory. Currently being experimented and observed. Hybridization in order to infiltrate our actual civilization that’s located elsewhere.

Perhaps slightly off topic, but the title reminded me of this picture I took a few years back.

https://www.flickr.com/photos/earlvontapia/16211171391

I really wanted more of the Milky Way to pop out, but was hard given the sensor and the lens I was using.

(1) Biological life colonizing other planets? The individual beings would not live long enough to make the journey. So, would have to have reproduction of generations during the trip, and that means one heck of a big spaceship. Then for any of the motivations, I would be easier just to stay home.

(2) Sending self-reproducing robots? Why? What's the motivation? E.g., why should I consent to spending big tax bucks to send robots out that would need millions of years to have any effect back on earth? I won't.

Okay, there is the scenario that a planet is ready to die, and the beings want to move to a new land. Again, for anyone alive, what is their motivation? That is, either stay home and wait for, say, the star to nova or just die on a long space trip? Just stay home; as bad as a star nova would be, just stay home.

One more scenario is that fast space travel is possible but uses physics we don't understand and, thus, can't detect.

I guess the primary argument to this is the number of stars, and the amount of time the universe has been around... but like the universe is _very young_. Our universe currently has an expected lifespan of like a trillion years. That is to say, if it's lifespan is 100 years, it's currently a ~13 month old infant.

There is a supremely _good_ chance we, humans, are and will be the creepy ol' species we write movies about that has colonized stars and existed "since the beginning."

Should we ever successfully make it off this rock that and to another star that is...

It's fun to think about too, how will our species handle billions of years of separation at distant ends of the universe? Will we use gene therapy to ensure our "look" and aesthetic, or will culture and evolution be unpreventable yielding humanoids nearly unrecognizable to our current form?

I would be especially careful of arguments that end up like "it's a great opportunity for humankind as no-one else is there to compete for the next million years"

It might be true. But the most likely thing we will find on the nearest habitable planet is a legal writ and summons.

The boring answer is that the initial origin of life depends on a sequence of extremely improbable chemical reactions (even given the prior existence of the most favourable possible “organic soup”), and there is no other life of any kind in the observable universe.

life arose on Earth immediately after it cooled down and Earth then was nothing like what it is today. The organic chemical reactions are extremely probable not improbable.

It seems to me that the millions of events that happened in order to get to where we are now (alive on a rocky, water and oxygen-filled planet, in the Goldilocks zone of a healthy star) were sequential in nature and they took a finite amount of time to occur.

Assuming that there was A Beginning, where everything started at the same time, wouldn’t the steps to get to where we are in this process take about the same time for everyone else? Meaning that if there are other civilizations out there, that they’d more or less be as advanced as we are? Which is pretty sophisticated in certain areas at home, but not yet super capable in the long-distance human space travel department.

Not a scientist, just thinking out loud the thought I had reading the article.

Perhaps, but even tiny variances could cause shifts in the timeline of thousands or millions of years, which would be a blink compared to the age of the universe. Look how far we’ve come in the last 200 years. Imagine a civilization that is only 10,000 years ahead of us.

I’d love to see what the iPhone 10,000 ends up looking like

There are many stars and planets much much older than ours. Earth is 4.5 billion years old, the oldest exoplanet we've seen is 12.8 billion.

The terms of the Fermi paradox are are designed to cover things like this.

50000 years ago we were throwing chipped rocks at hairy elephants. Technology moves fast on galactic time scales. Expecting two alien species to have roughly the same tech would be like two randomly fired bullets to collide mid air.

I think big filter is plausible where as we advance in tech, the probability of us accident using to kill off everything increases. It starts with nuclear weapons and then maybe later mini black holes, etc.

(First wears tin-foil hat). It may be more likely that we are under observation and a mature inter-stellar space faring alien civilisation has commandments not to interact or interfere with the primitive natives. They occasionally mess up and then the UFO's are seen. But their propaganda department clears the mess up.

From our perspective, even if another species had colonized millions of stars, it would still be like looking for dust on a mountain.

The theory of this article is that we are not just in a gulf of space but also a gulf of time. We are after all on the relative outskirts of our galaxy, vastly isolated from other civilizations. Perhaps one day we'll be the ones knocking on our neighbor's door to say hello!

Previous discussion on the possibility (mentioned in the article) that an advanced industrial civilization existed on Earth: https://news.ycombinator.com/item?id=21840320

Afaik, nobody has debunked the Borra paper, so we already found them.

Discovery of peculiar periodic spectral modulations in a small fraction of solar type stars

https://arxiv.org/abs/1610.03031

This study fails to replicate Borra's results.

https://iopscience.iop.org/article/10.1088/1538-3873/aaeae0/...

Drat! Thanks

I think if you look at patterns in nature this has to be possible. Surely there are some remote ant colonies that don’t have interaction with anything outside the natural resources that sustain them.

There are arguably too many unknowns to do much more than speculate.

But let's say there's some other planet with comparable technology. At what distance could we detect its routine radio emissions?

No more than 1000LY, per this article:

http://www.setileague.org/askdr/howfar.htm

i.e. 1% the diameter of the Milky Way:

https://www.universetoday.com/21998/the-diameter-of-the-milk...

Thanks.

I wonder what percentage of the sky those larger SETI telescopes have looked at so far. I tried searching the SETI site, but had no luck.

But anyway, that's a small enough volume that it could plausibly be temporarily dead or quiet, as TFA argues.

Fascinating theory, but we aren't Pitcairn Island.

> Why, then, have we found no irrefutable evidence of aliens visiting Earth?

We have evidence, it just gets "refuted" for psychological reasons. The Fermi Paradox is a Rorschach test, and has nothing to do with reality.

In reality, humans in every culture have recorded incidents of communications with non-human intelligences.[0]

In reality, the Brazilian Military has gotten much less coy about UFO phenomenon in recent years and has started declassifying documents. Their overall conclusion is that, whatever they are, UFOs are real, pose no national security threat, and should be researched and discussed by society at large, with some urgency.

Here's a fascinating lecture by a Brazilian UFO researcher about the overall situation in Brazil and he describes three encounters that are known to have government involvement (so the researchers know what to ask about, in these cases.)

"Operation Saucer - UFO military encounters in the Brazilian jungle" https://www.youtube.com/watch?v=ThkmRsEBOY0

> In 1977, numerous UFOs were seen in the Brazilian city of Colares, Pará. The UFOs fired light beams at people, causing injuries and sucking blood from 400 witnesses. After a rise in local concern, the mayor of the city requested help from the Air Force. Operation Saucer started, during which numerous photos were taken and testimonies collected. Operation Saucer is just one of the compelling cases which A. J. Gevaerd, editor of Brazilian UFO magazine, talked about in his latest lecture in Copenhagen, paving the way for complete Disclosure in his country. Kudos to Exopolitics Denmark for setting up their excellent annual conference at the Danish National Museum on September 26 in Copenhagen!

The first case involves thousands of people, living on an island in the Amazon, who were attacked by UFOs over a period of several years (1975-1977 IIRC). Flying cans with visible pilots were shooting people with bending "light" beams and sucking up their blood. It got so bad that thousands of people evacuated and the Brazilian Army sent in a unit to find out what was going on and try to make contact. I won't spoil the rest of the story here.

To me, the strangest thing I can see is the question: Why would people (aliens or humans) who have evidently advanced technology go around attacking poor villagers to suck their blood!? WTF?

[0] (I myself once attended a event at an airport hotel at which some purple telepathic space dolphins were guest lecturers. FWIW, their basic TL;DR: was "Be nice to each other." Aliens were attending underground raves in Seattle in the 90's.)

[1] https://www.youtube.com/watch?v=DHMDrhBREXU (Destroy all Humans - Offical Remake Trailer, 2m10s)

> pose no national security threat

> sucking blood from 400 witnesses

Pick one.

Sucking blood from 400 people posed no national security threat.

Don't get me wrong, I'm not trying to trivialize what these folks went through. I'm pointing out that the threat was in a small, localized area.

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