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> So if they were inhabited, what happened to them? Are they exactly at our level of development? Earlier? Hopefully. Because later poses some real big questions - does technology top out about where we are now - no FTL travel, no really big radio transmitters or stellar engineering? No probes to nearby star systems? Did they even make it past the nuclear age, or avoid wrecking their climate?

You get more than one chance. While finding intelligent life would be great, finding any life is nearly as great. We might not catch them at a comparable technological moment, but over 8 billion years, intelligent life could have come and gone many times. All we need are some biosignatures to confirm that something's out there, and exploration will kick into overdrive.

Actually if we find life on other planets that is bad news for us as a species:

https://www.technologyreview.com/s/409936/where-are-they/

> While finding intelligent life would be great, finding any life is nearly as great.

That would actually be worrisome. If we found and detected microorganisms on nearby planet e.g 12 light years away from earth, then that means we are probably headed for extinction.

The reason is the theory of the Great Filter. Given that we have not been able to observe any kind of activity outside of our solar system, it means that either life is rarer than we think or that entire civilisations go extinct pretty quickly.

If we find microorganism on a nearby planet, the logical conclusion is that life is not as rare as we think but evolved civilisation such as ours simply go extinct in a relatively short amount of time.

The Great Filter may be ahead of us.

Have we done anything that we'd be able to detect from 12 ly?

Our radio transmission bubble is far beyond 12ly. The question is how sensitive an instrument we'd need to detect it. IIRC, there are some pretty big bursts in ther along with the general noise.

There'd also be significant signatures in the composition of our atmosphere.

The window for detection at different power levels is probably quite small.

Very early radio would be somewhat weak. The middle phase of analog transmission probably has some higher power levels. The digital phase would coincide with rapid decreases in detectability.

That assumes every planet capable of supporting life a) has life and b) develops intelligent life. If only 1% of planets capable of supporting life develops life and only 1% of those develop intelligent life then it is extremely unlikely these two nearby planets would have any life at all. Even if you bump the odds to 10% or even 33% the odds are still against it.

For sake of argument assume we (or they?) won the lottery and intelligent life exists. Make an even larger stretch and assume that life is technologically capable, has been for 10,000 years, and didn't destroy themselves (achieving a stable population size and reasonable resource usage). Even then the odds are against us detecting any kind of radio transmissions.

I think you have a slight misunderstanding about the great filter.

If we found only microorganisms on the other plant that should indicate that the filter is behind us, life having died out on that planet before even reaching large scale organisms let alone technology.

If we find ruins of civilization and technology on the planet at either about the same stage as us or more advanced, then we can assume that the filter is ahead of us.

Not so. All we know from finding micro organisms (or any other form) is that the filter is after that stage. It may well be between micro organisms and us but that seems unlikely.

ok, assuming you mean that nuclear war is the threat to all civilizations (because once we advance to the point of developing nukes, eventually some asshole deploys them irrationally).. why isn't this a solved problem? I.e: create underground societies that are nuclear-powered and sustainable for centuries, and impervious to nuclear attack?

Not necessarily. Live != civilization, so just because many planets may have developed live (or obtained it via panspermia) but only very few (or one) have developed multi-cellular live (which even on earth is quite recent) and even less a civilization comparable to us humans.

I think there’s no technological barrier there, but cultural choice: if there’s no good economic reason to go to space (ie That has a high enough rate of return within a short enough period of time), we may just die out before doing any of that stuff. I think about that every time someone argues human spaceflight is worthless. I don’t think they’re wrong in the short-term, but the societal consequences are the same as if the entire species just decides to stop having children entirely because there’s no good economic reason to do so.

Especially thinking about this near the anniversary of Apollo. What if that was the greatest extent of human travel in space? To me, that’s so sad.

https://m.xkcd.com/893/ “The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space--each discovered, studied, and remembered by the ones who made the irrational decision.”

The note that it's an old star makes me worry though. If they're older than us, and habitable, were they inhabited?

Many dwarf stars have more solar flares than our sun, while their planets are closer. Teegarden's star is supposed to be very calm right now. I have no idea if that is likely to be true over most of the past 8 billion years. The amount of water they gather may be smaller, and their closer planets may not be able to retain water as well.

So if they were inhabited, what happened to them?

Let's say the origin of life is a million to one filter, and the successful development of sentience is another million to one filter. Those are actually pretty high odds for those two events, and the combination of those two togehter is enough to make it likely we're alone in the Milky Way.

One thing's for sure - if there's really 2 habitable planets, with liquid water, then we've got a hell of a target to point James Webb at when it launches - an infrared spectrum star should mean any plant life is well optimized to towards the redder end of the spectrum - we should see some type of chlorophyll.

Since most of the star's energy is emitted in the infrared, which is a more diffuse form of energy, does this limit the potential of photosynthetic organisms to gain a disruptive evolutionary advantage? (Maybe not. It's still free energy from the sky.)

> Let's say the origin of life is a million to one filter, and the successful development of sentience is another million to one filter. Those are actually pretty high odds for those two events, and the combination of those two togehter is enough to make it likely we're alone in the Milky Way.

I mean, not really? Doesn't the Milky Way have ~100 billion stars?

(million: 1)^2 * 100 billion gives an estimate of ~0.1 stars in the Milky Way that host life.

Indeed. But then developed it hitch hikes a ride on asteroids and spreads virally. See Dr Zubrin’s recent discussions https://www.centauri-dreams.org/2017/12/21/interstellar-comm...

>Let's say the origin of life is a million to one filter, and the successful development of sentience is another million to one filter. Those are actually pretty high odds for those two events, and the combination of those two togehter is enough to make it likely we're alone in the Milky Way.

The Drake equation has 7 terms. When it was first proposed, all but the first were complete unknowns. We're just barely starting to gather enough data to start tightening our guesses for the next two. The rest (which include the two you used) are complete unknowns. You say "those are actually pretty high odds", but by whose measure? There's exactly one data point to support that assertion, and right now that data point suggests that the odds are 100% (with an uncertainty also approaching 100%). We're still decades away from really having the data to assert anything at all about the presence of life outside of our solar system with confidence.

We should be able to make some approximations regarding sentience. If we only consider Homo Sapiens Sapiens, then yeah we only have one data point. If we consider other extinct hominid species, we have more. If we consider dolphins, ravens, etc - we start to have a fuller picture and can make some (at least slightly) informed estimates to that term

You're still extrapolating from a single life-creation event. Until we find a second planet that evolved life entirely separately from Earth, we have exactly zero meaningful information about the genesis of life. Without knowing what percentage of life is roughly similar to life on Earth, we have exactly zero meaningful information about how valid Earth-centric extrapolations are.

> Since most of the star's energy is emitted in the infrared ... does this limit the potential of photosynthetic organisms ... ?

I'm not any sort of biologist or chemist, so somebody please correct me if I'm wrong, but...

If you specifically meant photosynthesis by terran chlorophyll, then yes, I suppose it would be less effective. However, I could imagine photosynthetic life to evolve under those conditions that uses some other compound to capture and convert the energy.

Also to consider is the amount of radiation (light, etc.) available on the surface, which can be figured as a formula of the radiation emitted by the sun, distance from the sun to the planet, and attenuation of radiation by the atmosphere. Much of the light (and other energy) emitted by a sun does not reach the surface of a planet with an atmosphere. The particulars are, of course, dependent on the atmospheric composition, but generally I would expect infrared light, with longer wavelengths than visible light, to better penetrate the atmosphere and be more available to life on the surface.

> you imagine that - hopefully - the general progression of technology is forward.

I think this might be the key myth of our times. Our entire history is a blink of an eye along the timescales Earth normally changes on. But the last couple hundred years really takes the cake - within a couple human lifespans, we've gone from a lifestyle broadly recognizable to any human from history, to some kind of ravenous sci-fi techno-megamind with spaceships and robots. We should be scared - even on our human timescales things are changing rapidly. On Earth timescales, this is not a steady state but an event - a sudden, runaway, exponential, violent event.

We have such a short perspective that we are lulled into thinking of it as a "natural progression". But that's like jumping off a cliff and concluding the natural progression is freefall. We know this state of affairs cannot possibly last. Why keep pretending?

What I always find massively baffling is, that any transmitted and recorded history is less than 15,000 vears old.

First hints at sedentariness appear around the construction of Göbleki Tepe [1].

[1] https://en.wikipedia.org/wiki/G%C3%B6bekli_Tepe

However, biologically speaking we has Homo sapiens sapiensis are around for approximately 250,000 years.

That's ~6% of our biological existence where we suddenly went from running around, building like 3 stone-wood tools and wearing animal skins to communicating across the planet in real-time.

I totally agree. I have in the past gotten into online arguments with people who claim that this kind of exponential change will continue forever, and I just find it so baffling. The only explanation I can come up with is that this is a core ideological precept of our current economic system and people are just not prepared to challenge it. Like asking a medieval person to believe that god is not real. It’s seen as blasphemy.

> We know this state of affairs cannot possibly last.

Talk for yourself. I personally think this is just the beginning.

Your freefalling similitude has the big flaw of making completely unsubstantiated assumptions. For all we know, we might be elegantly diving into a pool, or having propelled ourselves onto an orbit where we'll forever spin - we just don't know.

Do we know that intelligent life is an evolutionary inevitability? Most of these discussions seem to assume that it is, but I haven't read any biologists mention this.

Or to take it a step further, whether it is inevitable that intelligent life will have both the capability and opportunity to make their presence known. Maybe some planets are full of superintelligent dolphin-like creatures that had their development stall because they didn't have the dexterity to manipulate tools to the extent that sapiens can. Or maybe there is intelligent life on a planet similar to Europa that never prioritized space exploration/communication because instead of an Earthlike atmosphere their planet is surrounded by miles of ice.

What we can infer from the gradual evolution of various species on Earth is that brains do seem to evolve larger, more complex, more efficient - though are often bottlenecked by other costs.

If you look at a snapshot of all life on Earth over tens of millions of years, the average brain size of dominant species has clearly increased.

Tens of millions of years is a pretty small snapshot to use. Brains have existed on earth for approximately 500 million years. Life for about 7 times that.

I don't think we even know that a planet that's had life twice as long gets twice as much evolution. The rate of evolutionary change is far from constant, and whatever factors affect that rate might be different on some other planet.

> Are they exactly at our level of development?

If so, then at just 12ly away, we could converse with them within (many of) our lifetimes.

What are the chances that would've already happened given how long we've been sending life made RF off the planet? A 24 year exchange isn't awful.

12 light years is a long way for a signal to go without attenuating into noise.

What about things like LIGO? It can detect changes in length corresponding to 1/10,000th the width of a proton. Surely communicating over RF with another planet should be within our reach, no?

Could we?

Despite stellar levels of energy being emitted, this star itself was only detected in 2003. We have to use the Deep Space Network to communicate with probes light-hours away.

I'm no expert so it very well may be possible, but 12 LY is still Very far.

It wouldn't be possible to send a message literally today, using existing structures. If we had a reason to, we could certainly develop and build new systems that could bridge the distance.

The main key difference is that the send/receive ends would be symmetric. DSN has to counterbalance the incredibly small size and power limits on the other end of its connections.

The odds of that are effectively zero. Over a multi-billion year development line, being within 100 years of one-another is effectively impossible.

They are either unevolved animals, or have already merged into the Great AI or whatever happens when intelligent species evolve.

in view of what you're asking about the development of technology, and whether or not civs tend to "peak out" around our current level, i think back to the drake equation* and the coefficients for the likelihood of intelligence evolving and the likelihood of intelligent life creating technology that emits detectable signs of that civilization (space infrastructure, dyson swarms, nuclear isotopes in atmosphere , etc). Those 2 being Fi and Fc.

Id like to share whata I think is one of the cheeriest possibilities:

- that earth-like planets are rather common (we have 3 such planets in the Sol system),

- basic life is less common but still pretty common (decent chance mars could have had life, maybe europa's sub-ice oceans has it now... conceivable at least),

- but what isnt super common is the development of human-level intelligence, and even less common is developing technology to the point we are currently at

- but (and this is the most cheery part) even though human-level intelligence and our current tech level is very uncommon, that once a species develops that level of tech, barring a catastrophic extinction event (DNA-hyper-plauge, mega-asteroid, all the nukes getting launched at once), that that life is likely to continue for a long time.

I say that last part because even with our current problems with the Anthropocene extinction and climate degradation, it's likely that humans will be here in 100 or 1,000 or 10,000 years.

Worst case could be even be so bad as humanity entering its first ever world-wide dark age (as opposed to regional dark ages) where higher technology is less prolific and more concentrated. Even given something like that that - which i think is neither a certainty or even a reasonable conception of the future - humanity would continue and 10 generations on our decedents would start something akin to a second Renaissance.

So what I'm getting at is once a civilization develops roughly our level of technology, it may be very durable even in the face of temporary disasters and darkness.

Now, as far as the fancy space tech you bring up, yeah, who knows... It seems like those tech have a big issue beyond Physics, which is the Fermi Paradox.

If say, Dyson Swarms were "possible" (they really seem like they should be... we could start building one now), then we should be seeing evidence of that all over the universe from those civs who've come before us and build them. That's scary to think about, that maybe we're the first life to get to this level in the universe. Then again, maybe advanced civs learn early to obfuscate the signs of their existence, or perhaps even use technology that we don't recognize / cant detect.

A great Youtuber named Isaac Arthur talks about both the drake equation and the futurist's existential bummer about the Fermi Paradox. Check him out if anything i bring up here sounds cool.

*Drake Equation is a simple(ish) way of plotting out how likely / many adv civs are out there based on the likleyhood of some conditions. From wiki - The Drake equation is:

    N = R ∗ ⋅ f p ⋅ n e ⋅ f l ⋅ f i ⋅ f c ⋅ L

where:

    N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);

and

    R∗ = the average rate of star formation in our galaxy
    fp = the fraction of those stars that have planets
    ne = the average number of planets that can potentially support life per star that has planets
    fl = the fraction of planets that could support life that actually develop life at some point
    fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
    fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
    L = the length of time for which such civilizations release detectable signals into space[

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