Astronomers Detect a Possible Signature of Life on a Distant Planet

This is unsettling. If we are not the only intelligent beings in the universe, it adds credence to the idea of a "great filter."

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

I think it would be cool if the conversation on this post could go more into detail about hycean planets instead of the pretty standard and played out one about the Fermi Paradox and Great Filters.

That stuff is interesting but I'd rather hear experts talk about less talked about stuff like hycean planets and detection methods of them and other bodies that are that size.

My greatest desire is to know why we don’t see any galaxy-sized colonies. A great filter would certainly be a fascinating response!

> While inspecting K2-18b, Dr. Madhusudhan and his colleagues discovered it had many of the molecules they had predicted a Hycean planet would possess. In 2023, they reported they had also detected faint hints of another molecule, and one of huge potential importance: dimethyl sulfide, which is made of sulfur, carbon, and hydrogen. On Earth, the only known source of dimethyl sulfide is life.

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Intriguing.

This is about dimethyl sulfide in the atmosphere of exoplanet K2-18b:

https://en.wikipedia.org/wiki/K2-18b

The NYT article reports a new study in The Astrophysical Journal and links to it, but the DOI is currently not found:

https://dx.doi.org/10.3847/2041-8213/adc1c8

I also don't see the article yet under their Latest Articles:

https://iopscience.iop.org/journal/0004-637X

Here are recent articles about K2-18b from Google Scholar:

https://scholar.google.com/scholar?hl=en&as_sdt=0,48&q=%22K2...

Well, it’s better than what I came here to do, which was to leave a snarky joke along the lines of, “Sounds like we just found another place we need to tariff.”

But in the interest of keeping the discussion productive, I’ll refrain from doing that.

The Great Filter hypothesis is based on an analogy with the European conquest of the globe in the 19th century. Little by little all the white spots on the map were first explored, then annexed. The (unspoken) parallel is that an advanced civilization would explore and conquer the entire galaxy. But even if a civilization could achieve interstellar travel capabilities, it is entirely possible that they colonize, let's say, only 80% of the galaxy, not 100%. Or maybe only 50% or 10%. If our solar system is in the complement of their zone, how would we know they are out there. How would we know there are aliens around Alpha Centauri, let's say. They could be busy living their lives, broadcasting in all the regions of the radio spectrum with abandon, maybe even nuking each other from time to time. And we would just hear absolute silence. The distances between stars are just so mind-bogglingly huge.

i don't see the connection. being the only intelligent beings in the universe (at the moment) lends credence to the great filter, and finding large numbers of other inhabited planets eliminates it, and in between why wouldn't it monotonically decrease?

It's absolutely amazing that we can even figure out molecules at that distance. I'm sure it's accurate but it's so sciency to me that it might as well be made up entirely. I can't begin to fathom that process.

My guess is any civilisation advanced enough to populate their galaxy knows that it's inherently pointless. Unchecked growth is the impetus of lesser lifeforms

Life is probably extinguished by machine intelligence before it gets the chance to.

Infinite expansionism is just one of a whole tower of assumptions that underlie the Fermi paradox. It’s a good thought experiment and does rule out certain scenarios with ET life but beyond that it’s a speculation.

The main scenario it rules out is one where intelligent ET life is common and we are late to the party. I feel like both those things can’t be true or we would see evidence.

I do find it fun to think about because it unfolds under scrutiny into such a vast tree of possibilities. But that same huge tree of possibilities makes it hard to say much.

One of my favorite wild speculations is that there is somewhere more interesting to go than space, and more accessible, and eventually whatever that is gets found before starships get built. What could that be? A traversable multiverse maybe?

That belongs to a subset of scenarios I call “positive great filters.” That’s where the great filter is a big success that renders space flight unimportant or uninteresting but does not result in extinction.

What about hyper-miniaturization. Maybe you can have something the size and scope of a galactic civilization without leaving home by folding your minds and everything else up into quantum states or hidden extra dimensions. Think a civilization of “sophons” (three body problem reference) with trillions upon trillions of minds occupying a few square meters of space and consuming a few hundred watts.

Yet another is some kind of remote sensing that lets you explore without physically moving, like a real equivalent to remote viewing. There’s a sci-fi novel called Blind Lake about this. Combine with miniaturized super efficient information processing and you could have superintelligences that explore everywhere and learn everything without going anywhere.

Lots of speculations and possibilities if you allow for the fact that we’ve only been doing science seriously for about 150 years and surely do not know everything.

Technically that is the only natural source, it can be made industrially with hydrogen sulfide and methanol, both of which are very abundant in the interstellar medium and on gas giants (Neptune has large clouds of hydrogen sulfide). The reaction is catalyzed by aluminum oxide, which also occurs naturally. On a world with an aluminum-rich crust, I could see dimethyl sulfide being produced in volcanoes. It was striking that this planet had thousands times higher concentration of DMS than Earth; maybe it has vastly more algae, maybe it's purely geological.

If life evolves on a planet with only oceans, no surface, imagine how much longer it would take to discover rockets that can leave the planet.

Like if there was no surface on earth, and only fish, there must be some very significant reason for advanced fish to even want to leave the water, let alone the atmosphere

If you haven't already, I recommend learning about Astronomical spectroscopy, which helped me get a toehold on how this stuff works: https://en.wikipedia.org/wiki/Astronomical_spectroscopy

I haven't read the paper but it's likely just some fancy spectroscopy: looking at the wavelengths that are absorbed. Each molecule has a characteristic pattern.

Those DOIs have a different prefix, I think it might be in Letters

https://iopscience.iop.org/journal/2041-8205

It's still not out yet though. Also journals are often rather tardy or just straight up don't register the doi at all and still put it on their site, but maybe this is an embargo thing.

edit - is it possibly this after publishing? https://arxiv.org/abs/2501.18477

That seems like a very landbased mindset. From a high level, what is an ocean but a thick atmosphere? I could even imagine an underwater culture would be quicker to explore because they would surely discover the surface of the ocean quicker than we discovered the concept of the atmosphere and that innately leads to the questions of whether the atmosphere has a "surface" and what is above it.

the idea is: if we do find life elsewhere, especially basic life, it suggests that getting to that stage isn't super rare. which means the great filter probably isn't behind us (like abiogenesis or single-cell to multi-cell jump), but possibly ahead of us - maybe in surviving long-term, avoiding self-destruction, spreading beyond one planet, etc.

finding life doesn't eliminate the great filter - it raises the unsettling possibility that we haven't hit it yet.

Greg Egan's Permutation City is a great sci-fi novel partly about 'positive filters,' as you nicely put it.

The argument you're referencing is usually about finding life on a nearby planet, e.g. on Mars. Nick Bostrom has articulated [0] this argument. But finding life on a distant planet lacks the same statistical power for instilling this existential fear.

[0] https://nickbostrom.com/papers/where-are-they/

Good point about the DOI prefix. I don't think it's that arXiv article, though, since it says there is no statistically significant evidence for carbon dioxide or dimethyl sulfide. This NYT article (and presumably whatever journal article it's based upon) reports high levels of dimethyl sulfide.

I wonder how oceanic life would be able to record information. If we assume that extraterrestrial oceans would have lifeforms similar to corals and barnacles, how would an aquatic civilization prevent written information from getting encrusted with biofouling or keep it from corroding away?

Of course. It'd be much worse if we found life on Mars than on a distant planet. In either case, the chances of humanity being ahead of the "great filter" are greatly reduced.

> The main scenario it rules out is one where intelligent ET life is common and we are late to the party. I feel like both those things can’t be true or we would see evidence.

There are a thousand scenarios where those things are true, e.g. the Zoo/Planetarium Hypothesis, but they tend to result in the conclusion that we're being somehow manipulated and can't trust our observations, so they're strongly disfavored on scientific grounds... Which does not rule them out.

what happens if you have lightning on a hycean planet?

there are so many ways to record things... for example https://en.m.wikipedia.org/wiki/Quipu maybe the need to keep it clean just makes it more important to a society...

It's only possible if the planet passes directly between its star and Earth, so we can see sunlight passing through its atmosphere, and detect which specific frequencies of light got absorbed.

Maybe look for signs of chemistry that indicates industry? Teflon, by-products of steel-making, plastics, something like that? Signs of intelligent(?) life.

You're right, different authors too.

https://www.eurekalert.org/multimedia/1069012 uses the DOI in the article and says it's from

> A. Smith, N. Madhusudhan (University of Cambridge)

Here's another article on it https://www.bbc.co.uk/news/articles/c39jj9vkr34o

I think this is still under embargo, or hasn't quite been released. There's going to be some time required for visuals like on the bbc site.

> I can't begin to fathom that process.

It's basically "look at far away object with a fancy pair of sunglasses."

Because of quantum mechanical reasons, molecules can only absorb and emit light with very particular energy levels (which correspond to frequency/wavelength). So point your camera at an exoplanet and carefully record the amount of the light you see at different wavelengths. My guess is that it's based on IR spectroscopy, since there's a nice region of that spectra where you can "fingerprint" a molecule based on the peaks in absorption in that region (it's literally called the "fingerprint region").

> From a high level, what is an ocean but a thick atmosphere?

"Now you have two atmospheres."

Chemistry that indicates industry is signs of industry. In earth timescales, industry existed for effectively 0% of the time. Life existed for significantly longer though.

Even if there's life in lots of places, there may be no industry as we understand it anywhere else in the universe.

Overcoming water->land barrier seems comparable to overcoming land->air and air->outer space in the context of rocket launches.

There is also the issue that they will likely never discover fire and thus chemistry and metallurgy.

Ha. Ha ha. Nice.

What now? How do we confirm or disprove life there?

Existing telescopes?

Or do we need to design one quick, for Starship to take up next year?

I wouldn't trust Starship with a pair of cheap binoculars at this point.

And challenge chemists to produce these compounds abiotically ?

ALL of it? EVERY time? There should be some signs somewhere.

The last one did seem unreasonably rushed, for some reason.

Let's just hope debugging the next one distracts you-know-who from slashing any more climate science funding.

This is your daily reminder that if we do indeed discover life so close (~120 LY) to Earth, it's an incredibly bad sign for us. This is an exercise in Bayesian reasoning.

Imagine there are 2 planets in the Milky Way where life has developed. The odds are incredibly low they're next to each other, assuming a random distribution. So it's way more likely that there are more than 2. Imagine a sphere of radius 60 LY (120/2). Our Earth is the center of one. This planet is another. That's a volume of 10^6 LY^3. The Milky Way volume (from Google) is ~17T LY^3 so there'd be roughly 170M such spheres in our galaxy.

Now imagine if the odds of simple life becoming intelligent life that we could detect and could become spacefaring is 1 in 1 million. There'd be ~170 such civilization in the Milk Way.

We have absolutely no evidence of this So simple life is a lot less common, intelligent life is a lot less likely or, and this is the scary part, something tends to wipe out sentient civilizations and that's likely in our future.

In Fermi Paradox terms, we call this a Great Filter.

From TFA, they’re going to continue observing it with JWST to gather more data. New telescopes dedicated to detecting life are being built now - they were basically right behind dark matter in scientific interest.

They will also start to simulate hycean planets to see if these chemicals behave the same way there as they do on Earth to determine if there is some non-biological reason why they could detect this stuff.

Or everyone quickly discovers a better way of communicating, and the era of blasting out radio is a short one.

Taking it a step further, being an ocean dwelling creature could even be an advantage in space since they would more easily be shielded from radiation if they were enveloped in a large mass of water and g-forces might be easier on their bodies since they'd be less compressible.

But on the other hand: https://www.smithsonianmag.com/smart-news/fish-dont-do-so-we...

This still seems to be based on assumptions coming from our own history and situation. I don't know why some hypothetical species needs fire for chemistry or even metallurgy for that matter or why an underwater civilization couldn't eventually discover fire themselves. There is also the potential that our reliance on combustion based rocketry is actually a crutch preventing us further space exploration considering how impractical it seems for interstellar travel.

Looking forward to the John Michael Godier video that he'll inevitably put out about this.

To support this: Oceans are more conducive to exploration due to their natural currents and lack of mountainous regions or rivers which inhibit movement.

Like the comment below was getting at: if you are water bound, you are very unlikely to discover or become proficient with fire, which to us, as if now seems like a requirement to travel through space.

There’s also the massive weight disadvantage water has compared to “air”.

So no fire and have to travel with a water filled rocket instead.

But again maybe these are just land centered views.

Maybe you can just inject oxygen into the water that merely surrounds your head.

And maybe there’s a hydrogen power rocket that is more efficient than our fire ones.

https://arxiv.org/abs/2504.12267 matches the title ("New Constraints on DMS and DMDS in the Atmosphere of K2-18b from JWST MIRI") reported at https://www.eurekalert.org/news-releases/1080558, and it also matches the reported results.

> I can't begin to fathom that process.

I write about it in on page 5 of my coffee table photobook:

https://impacts.to/downloads/lowres/impacts.pdf#page=5

Land animals are more likely to develop hands. Hands wouldn't give a fish any advantage, because there is nothing to climb.

Building a rocket requires hands, and the type of intelligence that evolves only after having hands.

I don't think this is a great argument. Crabs and lobsters have claws which are almost hand like. And Octopus have tentacles, which can be highly manipulative. So those limbs must give those creatures an advantage even in water. It wouldn't be too much of a leap from those appendages to something as good as hands.

What about an octopus?

The thing we keep on neglecting to mention is that life on earth actually happened pretty quickly in the time scale of the universe. I can't remember but I think we're one of the earliest points for life in the "broad" time scale. I wouldn't be surprised if stastically we're some of the first intelligent life, or the first wave.

Starship test flights have to be rushed, because they can only test it in flight.

Before the last flight they static fired Ship 34 (the upper stage) for an unprecedented 60 seconds.

https://www.youtube.com/watch?v=x6Z7fnikKB8

But the new theory is flight 7 and flight 8 failed because of harmonic resonance developing after tanks (which big mass dampens resonance) emptying to a certain percentage. And you can’t replicate that on ground with full thrust and clamped down, or else the ship would take off, you can only test it during flight.

The test flights are relatively unimportant though compared to building up infrastructure like the launch towers in Texas and Florida. The goal is supporting +50 launches per year, so while at the moment launches are multiple months apart this will change rapidly when the second (third, fourth..) launch tower is operational.

Spectroscopy is cool! Basically whenever light shines through a thing, the thing can absorb or emit light, and that happens at specific wavelengths depending on what the thing is made of. You can get small spectroscope pretty cheap and play around with a bunch of hone experiments - a common lab project in class is putting salts in a flame and based on the spectra figuring out what atoms are in the salt. It's how we discovered helium must exist in the sun before actually finding any on earth. So basically we just do that, except on a planet that's far away. When it's between it's star and us, we look at the spectra of the light that goes through the planets atmosphere

On a related note, Birth-Death Formalism connects Jaynes' Prior Probabilities in a paper, "Do SETI Optimists Have a Fine-Tuning Problem?"

https://arxiv.org/abs/2407.07097

One of the authors posted an approachable video explaining how the ideas connect:

https://www.youtube.com/watch?v=b6-9Hq8dV_4

I mean, communication is insanely hard. If there's no way around the speed of light, life would still likely (slowly) expand across the stars, but it would be functionally impossible to continue to act as a unified civilization or colony across even a couple solar systems much less a whole galaxy

That's not taking into account that each solar system has its own set of circumstances, it could just be panspermia between earth and mars.

There’s no evidence yet, but we also haven’t looked very carefully or in very many places. And we only know to look for planetary life as we know it.

The middle of the galaxy could have a wildly different composition and habitat for life than the outer reaches where we are.

Time is also another factor. Maybe the galaxy is perfect for complex life, we just happen to be early on the timescale and in another billion years or two life will be clearly abundant everywhere.

For some perspective, if you take the size of the Milky Way (100k light years) and relate it to the size of NYC (~30 miles), then 120 light years ends up being ~190 feet in NYC, or less than a city block.

If you assume life is very likely then the Great Filter has to be an almost perfect filter to explain the Fermi Paradox. With fewer civilisations in the galaxy (<50) you might be able to assume that if 95% of them destroy themselves it would be unlikely we'd ever find life. If we assume 170 civilisations then the great filter would have to be something akin to a natural law.

My gut says that the Great Filter is real but probably doesn't filter more than 99% of civilisations. Were I to guess complex life is uncommon, and intelligent life very uncommon. The majority of planets which do develop intelligent life destroy themselves fairly quickly.

> Hands wouldn't give a fish any advantage, because there is nothing to climb.

The ocean floor has plenty of stuff to dig into, pick up, and manipulate, along with un-anchored things like mats of seaweed.

> Land animals are more likely to develop hands.

I can easily imagine sea-creatures making the same kinds of assumptions in reverse: "Sir Blub-blub, while this hypothesis of 'land' animals is indeed intriguing, they would undoubtedly be primitive, far less likely to develop intelligent grabbers. After all, there will be nothing worth grabbing but hard 'dry' rocks! They wouldn't even be useful for propulsion, given the intangibility of this 'air'."

Chemistry and reactions would absolutely still be a thing. Reactions happen underwater all the time such as the complex decay of organic matter.

The fire meta get's postponed until trapping air inside bags happens (could be seaweed/skin based bags).

Then you need to make a habit of collecting a bunch of air and trapping it and then can begin exploring chemical reactions in the air.

ex: take dead but not decomposed organic matter, dry it out in hot air bag (maybe cover the bag in black squid ink and float the bag of air in the ocean out in the sun's rays for day to warm it up.

Then eventually you need to have the insight to do friction based experiments in the bag with dried materials and then one discovers fire in a massive breakthrough not dissimilar to when humans created Bose Einstein Condensates for the first time in highly specialized environments.

Nothing here says "impossible" to me. I bet if whales had fingers to easily manipulate matter they might've already done all this by now.

Volcanoes can launch things into space. There are already systems that try to tap into it. So its possible in theory to trigger it underwater.

There's only the fact that we probably just CANNOT perceive extremely advanced civilizations.

An insect crawling around a 75 year old brick house that is covered in ivy and moss will have NO idea that the object it is walking upon is NOT part of it's natural environment. That brick house seems as natural to the environment as the grass, and trees, and rocks, and streams nearby it -- to the bug at least.

Similarly we take our telescope out and see what looks like a natural organic universe with organic galaxies and normal looking stars etc...

Because we don't have solar system sized brains and billion year life spans we are absolutely hopeless to realize that theres' a lot of massive artificial structures in this universe. We're too bug-like to even be able to perceive them from our natural environment.

*we do know of massive cosmic structures like filaments, voids, and the great wall. So it is possible we as humans are starting to notice the "house" in the woods since our theories of physics cannot really explain why these structures exist at these massive scales (we would expect uniformity at those scales). See [here](https://en.wikipedia.org/wiki/List_of_largest_cosmic_structu...)

I find myself believing less in the great filter. My comment here: https://news.ycombinator.com/item?id=43712645 explains why.

It would probably be useful for high speed travel. Speedboats can go a lot faster than submarines. Airplanes can go even faster, but they might be a bit impractical since they'd have to be full of water.

Also radio communications since radio travels much better through air than through water. Of course, they could just build antennas underwater and then float them above the surface to use them.

Navigating by the stars would be really useful, and for that you need to be able to see above the surface. I guess you don't need to go above the surface. A periscope would do the trick.

It might also be useful for energy generation. Wind power if the wind is stronger than ocean currents. Or solar because the light is stronger.

One thing that I haven’t seen discussed much in terms of galactic colonization is genetic drift, speciation and communication.

I believe there are simulations theorizing that galaxies can be thoroughly explored in 10M - 100M years.

But how would those species even communicate their discoveries across a 100k LY galaxy? The delay would render data inaccurate by the time it arrives. It seems challenging to persist in a common purpose for millions of years across vast distances.

And would they even be the same species on those timescales and distances? On Earth isolation leads to some unique physical and cultural evolutions.

"If life evolves on a planet with land, instead of only oceans, imagine how much longer it would take to discover boats and submarines that can travel on and under the water!" - Xenobiologists on K2-18b after detecting possible signs of life on the Sol system's third planet.

Earth had precious little land, if any, over the first billion or so years too. The crust takes time to differentiate and pile up into cratons.

Though in this particular case it looks like the planet is a gas giant, plausibly with a water ocean but without any higher density rocky/metal core to make "land" out of.

Maybe life already colonized everything within possible reach, made most of it inhospitable, and the remaining three survivor galactic empires sent an ark and some supplies to a small planet called Earth.

It isn't that simple. It took a lot of careful calibration to be able to determine the amount of ratio of materials from spectroscopy. This is what led to determining the Sun is mostly hydrogen.

extremely advanced civilization would be living around black holes because they are perfect heat dumps (they get colder as you add matter!) and would enable fundamentally better technology.

For traditional rockets, it's not so much fire, as it is the rapid expansion of matter and the force that it generates. Fire just happens to be the most convenient method for us.

There could be metals under an ocean that could be mined. An underwater civilization could potentially harness nuclear power.

While I agree that there is no logical reason that underwater organisms could not become highly intelligent or advance to the level of doing experiments with fire, it is clear that being underwater is an additional barrier.

As such, the number of intelligent underwater civilizations, that could get near our present level of advancement, would likely be significantly lower. Not impossible (because of how large the universe is), but some order of magnitude, less possible.

The middle of the galaxy is unlikely to be conducive to forming intelligent life simply because it's not stable enough for long enough.

In our part of the galaxy, the mean distance between stars is around 4-5 LY (at a guess) in terms of nearest neighbours and ignoring binary (and up) systems. At the galactic center it's a few light days.

We've had many events that have caused mass extinction. There are many more that could end all life as ew know it (eg gamma ray bursts, a sufficiently close supernova. We have ~10 stars within 10 LY of us. Imagine if that were millions instead. I find it hard to believe conditions would be stable enough for the millions or billions of years necessary to create and sustain complex life.

As for our galaxy being "perfect" this touches on a coupole of concepts, notably the Anthropic Principle. But again we return to Bayesian reasoning. If there was going to be 1000 spacefaring civilizations in our galaxy, what are the odds that we are first? And while the Sun is <5B years old, there are stars up to 14B years old. There's been a ton of extra time for civilizations to develop elsewhere.

Our generation time is probably too slow for us to be the first wave. I’d expect that title to belong to something that looks like a pile of snot on a table but under a microscope looks like a neural network.

It's never aliens.

Orcas could very well be smarter than us, but it is extremely unlikely they'll ever evolve hands to build tools - it would be a radical and crippling change in their skeleton with absolutely no evolutionary pressure to do so. Primates (and koalas) didn't evolve hands with opposable thumbs to build tools, we did so because our ancestors got pushed into the trees. And orcas really need their flippers to be good in the water.

A key limitation is that the early universe had virtually no heavy elements whatsoever, and it is far too fantastical to suppose there might have been life in the form of hydrogen-positron crystals or whatever. It took billions of years of supernovas for protoplanetary disks to include metals, complex organic molecules, etc, and perhaps even longer to make planets with enough chemical entropy to support life.

How high are you? :D

These compounds are easily produced in a lab or industrially (methanol + hydrogen sulfide + aluminum oxide as a catalyst). The only known natural source is photosynthesis, but the article mentions that vulcanism/etc is possible.

Their airplane doesn't necessarily have to be full of water, just like our high altitude (military) planes and spaceships do not have to be full of air. For convenience, yes, but just for survival you'd wear a protective suit with life support systems, just like we do. Edit: But I agree that they'd be impractical for convenient business and leisure travel for the average octopus out there...

I think the point is that they still seem too rushed (perhaps reckless is a better term), since these are causing serious problems for planes in the area and generating very nasty pollution - what if debris hits an airliner? Nobody's saying they have to get Starship 100% right the next time, they are human. But I am very concerned that SpaceX simply has bad internal testing and design, maybe inadequate computer simulation or telemetry, who knows. But the concern is they'll improperly judge Starship as good-to-go once it launches successfully, having somewhat blindly applied a bunch of duct tape without properly understanding the cause of the failures.

A lot of assumptions are made here about intelligent life with the great filter ideas. Intelligent life is not a fundamental phase of matter. It took a random walk over billions of years to end up there, with any point potentially leading to a deviation and entirely different outcome. Take the number of bacteria dividing over the last 4 billion years on earth to one and there’s your rate of intelligent life in the universe based on what we’ve seen on earth. Are there even that many planets or bodies in the galaxy for what a billion to the power of a billion to one odds or whatever absurd number this is?

This idea that can't perceive sufficiently advanced civilizations doesn't hold up to scrutiny. It comes down to energy and mass (ie resources). Both of them essentially necessitate a civilization becoming large. You can argue that not every civilization will be expansionist but those that aren't tend to get swallowed up by those that are, at least based on Earth's history.

So for energy, a likely path will be the Dyson Swarm, meaning a cloud of orbitals. Many mistakenly think a Dyson Sphere was a rigid shell around a star. It never was. There's no material, actual or even theorized, that has the rigidity to sustain that. Because of that confusion, many now prefer the nomenclature of "Dyson Swarm" over "Dyson Sphere".

Dyson Swarms have the advantage of creating incredible amounts of living room and solving energy needs with relatively low tech (ie solar). They can also be built incrementally. A cloud of orbitals that capture the Sun's energy with orbitals between Venus and Mars will (IIRC) have a mean distance between them of ~100,000km.

Why is this important? Because the only way to get rid of heat in space is by expelling mass or, more likely, radiating it away into space. You can reuse waste heat to some degree but it's not perfect (because thermodynamics) and you can't totally avoid radiating heat away totally anyway. The wavelength of such radiation is entirely dependent on the temperature. At any likely temperature, that means infrared ("IR") radiation.

So a Dyson Swarm around our Sun would stick out like a sore thumb with a massive IR signature. There's really no hiding it. And we're capable of detecting it.

Conversey, there's really no hiding from any civilization capable of such feats of engineering. Plus any such civilization would be capable of sterilizing the galaxy out of any competition.

Mass follows on from this.

Even still much of our evolution as complex organisms were far slower than our unicellular cousins. Bacteria have conquered every place on earth and humans have not. They probably took advantage of us to colonize the moon already. They have adapted a plethora of unique systems thanks the their ability to grow at log scale and rapidly adapt to any situation. The HN analogy would be a VC that could double the amount of potential startups it seeds every 20 minutes. Meanwhile over in the Homo genus only one subspecies has limped along to this day with severely diminished genetic diversity to boot in many large populations, with selective pressures probably not directly applied to maximizing intelligence in the species long term much less survival.

This all pre-supposes that evolution will lock alien organisms into a specific and static body configuration on other planets like it has done to organisms on Earth.

Is there any particular reason why an intelligent organism couldn't evolve to be able to grow and change its body into any arbitrary size and shape that it wanted to merely by thinking about it?

Perhaps aliens from another planet would consider our limitation as four limbed bipedal organisms to be absurd.

Why can't organisms chose to grow eight hands each with 16 opposable digits?

  Now imagine if the odds of simple life becoming intelligent life that we could detect and could become spacefaring is 1 in 1 million.

Why not assume the odds are 1 in 200 million, so that there's only one such planet in the whole galaxy and there's no Great Filter to worry about? It seems just as valid, except "200 million" is slightly less aesthetically pleasing.

We already know that human-type technological civilization is extremely unlikely, since the planet was full of somewhat intelligent bipedal dinosaurs for about 100m years, yet none of them seemed to engage in mining, large-scale construction, severely disruptive extinctions, nuclear power... (humans will leave a thick geological layer of concrete and pollution, along with plentiful unique minerals coming from slag, plastic, etc.)

I really have no patience for this sort of p(doom) nonsense. If you make up numbers you can come to any quantitative conclusion you want. Mildly tweaking totally unfalsifiable odds makes the Fermi "paradox" go away entirely.

Why is fire the only chemical pathway to metallurgy?

Can they not discover fire in underwater caves?

Can they not build underwater containers that hold the necessary materials to do chemistry, similar to what we do with bioreactors, flasks, beakers, and pressure vessels?

Anything that acts to lower the odds by 200x so that we're the only likely intelligence in the galaxy is the definition of a "great filter".

They could roll nodules near black smokers, and have fun with methane hydrates instead?

Also electricity be experiencing shocks from electric eels, or similar. Economic lighting by bioluminescence.

There will probably be a first, perhaps it's this one.

Why so complicated? There could be many 'mini-labs' in underwater caves, accidental discovery of inverse diving bell so to speak. With trapped gases of any sort, by whichever process(volcanism?) pushing the water out downwards, while unable to escape upwards. Ready to explore, and mess around with. Maybe even in something like free floating coral reefs. Or below the ice.

I don't understand why people fixate on Dyson spheres. Why would a Kardashev type 2 civilization rely on something that a type 0.7 civilization could come up with? Surely in the intervening 1.3 they could come up with something we can't. Dyson spheres are a type 0.7 imagination exercise. A type 2 civilization wouldn't just extend our technology - it would transcend it. Maybe they use dark energy, maybe they gather energy from simulations. We can't understand.

Vs. tentacles with claws and suckers(with nice sensors embedded). As in https://en.wikipedia.org/wiki/Cephalopod

But with a full water atmosphere in a space ship you would be way more protected from radiation :)

This argument is fairly dated now, we no longer need alien ruins to prove that humanity will probably destroy itself.

The detection of dimethyl sulfide on an exoplanet is an exciting development, ok. And DMS on Earth is almost entirely biologically sourced, but that doesn’t make it an exclusive biosignature. There are plausible abiotic pathways for DMS formation, such as in geochemistry we can’t know entirely about because we live on earth.

I’m not sure a journalist for this exalted American newspaper here knows anything about this and frankly the excited language of this article is dumb af. Probably because excited people keep paying for subscriptions to this trash.

It took my amateur self nearly 10 mins to ask around to qualified friends and research some counter ideas.

Actually, we're already past the peak of star formation in the universe. So the universe is well on its way winding down.. less and less stars are being created. We're seeing the universe more middle aged than especially young

https://www.reddit.com/r/space/s/0oVjIo0XMi

The article isn't overly excited imo. It clearly states nothing has been proven for certainty, which is in alignment with what you're saying.

> Astronomers Detect a Possible Signature of Life on a Distant Planet

> Further studies are needed to determine whether K2-18b, which orbits a star 120 light-years away, is inhabited, or even habitable.

It's not fair to call it "trash"

By using strings of pearls on fishbones. To the effect of something like this: https://en.wikipedia.org/wiki/Quipu

Or selectively breeding barnacles to make longlasting letters/symbols, or 'milking' their glue and put it on something to avoid being overgrown. Imagine an aquatic market for underwater fonts!1!!

“Remotely possible” sounds like a neat editorial compromise. A bit tongue in cheek. A pun. Fun.

Otherwise? Clickbait.

You could have just read to the end of the article and avoided wasting the time of your "qualified" friends:

> Other researchers emphasized that much research remained to be done. One question yet to be resolved is whether K2-18b is in fact a habitable, Hycean world as Dr. Madhusudhan’s team claims.

> In a paper posted online Sunday, Dr. Glein and his colleagues argued that K2-18b could instead be a massive hunk of rock with a magma ocean and a thick, scorching hydrogen atmosphere — hardly conducive to life as we know it.

> Scientists will also need to run laboratory experiments to make sense of the new study — to recreate the possible conditions on sub-Neptunes, for instance, to see whether dimethyl sulfide behaves there as it does on Earth.

> “It’s important to remember that we’re just starting to understand the nature of these exotic worlds,” said Matthew Nixon, a planetary scientist at the University of Maryland who was not involved in the new study.

The end of the article?

Thanks for making exactly my point.

> it's an incredibly bad sign for us.

No reason to expect other lifeforms to be as bellicose and destructive us humans.

It is literally in the subtitle. You are making a storm in a teacup here.

Good find. The DOI resolves and the article is up now too

https://iopscience.iop.org/article/10.3847/2041-8213/adc1c8

> While I agree that there is no logical reason that underwater organisms could not become highly intelligent or advance to the level of doing experiments with fire, it is clear that being underwater is an additional barrier.

Meanwhile, a few thousand lightyears away, some sort of talking crab is rubbishing the idea that industrial civilisation could arise on land; after all, they wouldn't even have access to hydrothermal vents! What would they do for energy, burn plants?

(I really think we're inclined to build a _lot_ of unwarranted assumptions into what industrial civilisation has to look like and how you have to get there, because it's what we did.)

But how many of those stars would have been suitable for life ?

A huge star that’s going to burn out quickly isn’t conducive to complex organisms

Also in a huge star there’s less material to form planets in the first place

Lol, that didn't take long: https://youtu.be/82cLukqLgME?si=7PJMoGsxf6Qtaz87

There's talk of 'forever chemicals' produced by everything we do. Is evidence of industry going to just disappear? Forever is a long time.

Unless there’s enough oxygen, it shouldn’t be a problem

That's not right, the great filter comes after the development of intelligence

I highly recommend reading Adrian Tchaikovsky's Children of Time series which explores this a bit.

I listened to the series, I enjoyed it a lot.

> Also radio communications since radio travels much better through air than through water.

There is https://en.wikipedia.org/wiki/Whale_vocalization which carries rather far, if not disturbed by humans.

This is why "forever chemicals" is a poor term for those pollutants. They take a long time to decay under natural conditions (kind of like nuclear waste) but they don't literally persist forever.

> As such, the number of intelligent underwater civilizations, that could get near our present level of advancement, would likely be significantly lower.

Unless of course, having opposable thumbs and >50 year lifespan and intelligence in the water causes you to go through a completely different developmental path than land based creatures. We just don't know.

A Great Filter could come before or after intelligence.

For example, predation could be a Great Filter. We made it past the threat of predation, but perhaps most life forms in the universe don’t. In this example, life could be pervasive in the universe but it’s optimizing for defensive attributes like speed and armor rather than intelligence. That could explain why we don’t see aliens colonizing the galaxy. With the Great Filter behind us, nothing would be stopping us from colonizing the galaxy ourselves, we just might be among the first to do it.

Putting the Great Filter in front of us postulates that many life forms have achieved our same accomplishments but haven’t colonized the galaxy. It could be because of doom and gloom scenarios like war, aliens, cosmic catastrophes, etc. Or it could be a beneficial Great Filter like enlightenment and the lack of desire to propagate and consume endlessly, or the ability to survive in deep space, leaving stars and planets untouched.

> This all pre-supposes that evolution will lock alien organisms into a specific and static body configuration on other planets like it has done to organisms on Earth.

It's pretty normal for organisms to have drastically different body configurations through their lives. e.g moths

Though I'm not aware of any that have choices to make in the process.

Edit: actually lots of organisms can "choose" to change their sex

And yet despite having vast quantities of the precursors, Neptune does not have detectable levels of DMS...

I agree. I made my argument, but think it's flawed now. Appreciate the responses.

or:

John Michael Godier's Event Horizon: JWST May Have Just Detected Alien Life at Exoplanet K2-18b

Episode webpage: https://podcasters.spotify.com/pod/show/john-michael-godier/...

Media file: https://traffic.megaphone.fm/APO8659624232.mp3

original source: https://arxiv.org/abs/2504.12267

>but that doesn’t make it an exclusive biosignature. There are plausible abiotic pathways for DMS formation, such as in geochemistry we can’t know entirely about because we live on earth.

I'm sorry, but this is ridiculous. You started by acknowledging that it is indeed exciting, that it is something we only understand to be produced by living organisms. I wholeheartedly agree with that. And so the plausibility of an abiotic alternative is the big question.

You suggest that there are plausible abiotic pathways, but I think that's where this all starts to go off the rails, because I don't think there are in fact plausible abiotic pathways. We absolutely should attempt to model such possibilities and should be extremely careful about assumptions before working that out. But the state of our knowledge thus far counts for something too and it would suggest that such a process is pretty rare or unique. And then it really goes off the rails because instead of an actual example, you suggest not any specific known pathway, but a kind of bizarre philosophical musing that maybe there's "geochemistry we can't entirely know about."

We most definitely are capable of modeling chemical processes even if they don't happen on Earth. And there sure as heck is no such thing as a principle that things beyond Earth's surface are things we "can't" know about. I truly can't stress enough how ridiculous an assumption like that is.

We know, for instance, that gas giants are capable of producing phosphine, even though that doesn't happen on Earth. We know that the moon likely has a molten core. We know all kinds of things about atmospheric chemistry of planets and stars, because even if the abiotic processes can't be witnessed directly on Earth, we know enough about the principles of chemistry to model them in new contexts with reasonably high confidence.

And that's before we get to the idea that such uncertainty about off-world chemistry can be treated as tantamount to evidence of known abiotic process. It's nothing of the sort, it's more like "who knows, maybe it's possible." We do indeed have to figure out if there are such things as an aviotic process, but just the idea that, hey, who knows, something offworld might be happening is nowhere near enough to count.

That last bit is the part I always think about. You could easily hide an entire civilization in space, and there’s a lot more “space” than “planet”

There are billions of engines sitting around the universe; might as well just use those.

The more advanced versions tend to simply use more radiative heat. they might arrange stellar nurseries, modify stars to be more efficient, or use black holes for engines, but even then you’re still just feeding them stars anyways.