Not an original thought, but I wonder if the answer - or part of it - to the Fermi paradox is that we don't know all the ways it's possible for a planet in the Goldilocks Zone to be otherwise hostile to life.
Liquid water and.. chemistry leading to an ambient pH of 2 or 12.
Liquid water and.. radiation environment such that proto-RNA strands get immediately smashed to bits by high-energy rays.
Liquid water and.. bombardment every couple of million years with enormous asteroid.
Liquid water and.. 1800mph super-hurricanes.
etc.
The Fermi paradox seems to take for granted that complex multicellular life will eventually develop technological civilization, but there is no reason for that to be true. Orcas could very well be more intelligent than humans, but they are physiologically incapable of building tools. Human hands and visual processing were an evolutionary fluke that took tens of millions of years of natural selection, long before apes started using these adaptations to build simple tools. It is plausible that "bipeds with hands" will eventually lead to civilization: getting there is the hard part.
Put another way: birds are very intelligent bipeds, but I am not convinced that the dinosaurs would have developed advanced technology if the meteor didn't hit. There has to be an evolutionary path to develop something like hands, which means either sprouting extra arms or compromising a claw / leg / wing. Perhaps that path shows up, perhaps it doesn't - maybe there are fossils of raptor-like dinos with unusually dextrous claws. But without hands, even superintelligent animals cannot reliably make fire, build ropes, sew leather, carve stone, etc etc.
Pterodactyls when on the ground are believed to have been quadripeds that walked on "hands" with finger-like appendages[0] hence the "Dactyl" part of its species-name. They perished agter the meteor. More up-to-date, I believe Bats have a similar skeletal feature in their design.
Cetaceans have finger-like skeletal features in their flippers.[1]
I've often thought about how likely it is there are intelligent and sentient civilizations that are content to their planet, or bounded to it by - as you mentioned - physiological constraints. I never connected that to "you probably need hands or something very closely approximating a hand" but it makes perfect sense.
Hands, or tentacles, or a really long snout. There appear to be a variety of appendages that can be rather good at manipulating the environment for the users purpose.
Forgot also swarms of many cooperativing organisms. Ants appear quite adapt at manipulating things to a degree.
Intelligence is such a bewildering fixation too when you think about it for ourselves. Due to science fiction writers and our insistence on anthropomorphisation we assume we will be forming treaties aboard an alien ship meanwhile we have yet to communicate let alone form a treaty with any other form of life just here on earth. The hubris is massive and it invades even the scientific community to a degree. Whoever put that human pictograph on voyager evidently did not consult an evolutionary biologist nor a statistician, probably watched an episode of Star Trek.
I wonder what the likelihood is of big leaps forward there, in terms of communicating with other intelligent Earth life.
As in, will our ability to wrangle vast amounts of data and characterise it gives us enough insight into what whales are saying to one another that we might be able to start asking them questions?
It doesn't seem absurdly far-fetched at this point. But they're probably even more pissed at us for the last couple of centuries' behaviour than the various Indigenous peoples we Westerners have screwed over.
The hard part is that it goes two ways. Most animals are adapted for interactions within their own species. A seagull is adapted to react a certain way when another seagull screams the same way we smile when someone laughs or get a sense of panic if we hear someone shriek. A seagull has no concept of our behavior really beyond if we move at it in a threatening manner like other potential predators. The most you can do is probably some simple conditional learning akin to dog training considering seagulls in recreational areas have associated beachgoers with potential food source already.
Why might a whale speak back to us? Maybe it we chum the water when whales make certain noises they will begin making those noises and expect chum. I wouldn’t call that communication as people expect it to be with ET however. A primitive form of trade perhaps.
Whales are unusual in that they use complex sound for beyond visual range communication, and they may (emphasis may) be intelligent enough to treat our proxy sounds as an attempt to recreate their own and respond in kind.
I doubt we'd get much out of a seagull or even a cat. They don't seem to communicate much. Whales however seem to be able to "speak" over long distances and emit long phrases in which individuals are identified by something like a name. There's a lot more to work with there than even most mammals.
Even if you had human-like civilisations, they might simply opt for a simpler but more sustainable way of life, like many ancient civilisations which have been eradicated by more uncivilised ones.
There’s no evidence that societies based on our technological direction last more than a couple of centuries. Maybe societies with nukes and rockets always kill each other, and Mayan-like societies thrive for far longer periods without ever reaching outer space.
Maybe Earth is rare in that most life evolved in a way that locks in morphology.
It's entirely possible that it's far more common place for intelligent life to evolve in a way that allows that intelligence to direct the growth of an arbitrary body shape to solve arbitrary tasks.
But there are also 7500 known exoplanets within a few tens of thousands of light years of Earth. There are almost certainly multiples more than that we cannot see.
The "Goldilocks Zone" is also highly anthropomorphised: there are extremophiles that live in all sorts of crazy environments on Earth.
I'm coming around to the Dark Forest theory, personally, as terrifying as it is.
> I'm coming around to the Dark Forest theory, personally, as terrifying as it is.
Perhaps it's just that advanced technology is extremely rare given another comment's supposition that there could be other intelligent life, just unable to make advanced technology, or along those lines: if they have the appendages to do so, maybe their environment doesn't have the resources.
If you couple the above with the idea that FTL communication/travel is difficult or impossible, then it could take a long time for us to find evidence, and maybe by then we'll be extinct due to natural causes or devices of our own.
Or maybe there's some theistic evolution component and we are the only species in the universe with divine providence.
It seems to me that it would be impossible to prove or disprove any of those possibilities unless we actually discover extraterrestrial advanced intelligent life.
(And even then, who is to say that God didn't create Edens on other worlds? So meeting aliens still might not disprove any divinity.)
> the idea that FTL communication/travel is difficult or impossible
Not just FTL. My hypothesis is that any type of substantial interstellar travel is going to be so enormously expensive, complicated and time consuming, an advanced civilisation will only do it once in a billion years. In the form of mass exodus when there are no more habitable planets in their system or their star is going nova. As this never gives exponential growth, it is enough to resolve the Fermi paradox.
But that's simply not the case. We likely very close to the technology needed to get tiny objects to a decent fraction of lightspeed using laser arrays. Assuming genuine AGI is possible and miniaturisation continues, there's no physical reason a digital intelligence couldn't rapidly (on interstellar time scales) colonise the galaxy.
Okay, let's say I grant your two extremely optimistic assumptions. Then what? You can send a bunch of tiny sentient brains hurtling through the universe. They will have a very high chance of hitting interstellar dust and turning into a blob of plasma before they reach the target solar system. They also have no way at all to slow down once they reach the target system.
Interstellar travel requires not just being able to accelerate to incredible speeds, but also to carry enough energy and reaction mass to slow down again to (essentially) zero.
A really simple answer to the Fermi paradox is that we're the first, or in the first wave, of intelligent species, and it's just too early for the light from the others to have reached us yet. We're not just looking into the distance, we're also looking into the past. Life is less likely the farther we look.
It took a long time for the universe to create the conditions for a solar system like ours to exist in the first place, and why would have this happened so much faster elsewhere? The trend towards higher entropy/complexity is like a universal clock.
The universe might look big, but our view of it is not homogeneous. We wouldn't even see ourselves if we tried to find us, unless we were a close neighbor.
IMO the dark forest hypothesis leads to fun books but makes little sense. If a civilization is capable of the unimaginable feat of interstellar travel, surely their basic needs are well met and they aren't driven by base animal instincts anymore. They can probably engineer their own psyche. We humans will soon hit a population peak too, no exponental growth on the horizon.
Also, I don't think the timescales make sense at all. It took 200 years for industrial civilization to develop, maybe 200 more for us to travel the stars, but it takes billions of years for intelligent life to develop. I don't think there could ever be two comparable civilizations emerging at the same time, close enough to one another to compete for resources. Either the aliens found Earth millions of years ago and prevent us from ever existing, or there aren't any aliens closeby.
If you want an optimistic outlook on the far future which I think more plausible, read "Diaspora" by Greg Egan.
There's the question of motivation. It seems possible that an advanced civilization could gravitationally disrupt a small planet like mercury, turn it into solar collectors and particle accelerators and create multiple-ton quantities of antimatter and use that for interstellar travel, but they would likely choose to do something else with those resources.
People have a hard time thinking on a timescale of half a lifetime, never mind a lifetime or several lifetimes. The realistic version of the Bussard ramjet is not that you aim for c=0.1 or more, but rather with D-D fusion you can make hops of 1,000-10,000 au to Oort cloud bodies, you could possible gravitationally disrupt an object like Pluto and turn it into little ringworlds or other colonies. It might take people like that 10,000 years to make it to the next star but if they can make a comfortable lifestyle along the way why would they bother? And why would we even care enough to send them out on such a quest?
Even colonizing Mars is problematic in the sense that it's inconceivable that you could bring anything back from Mars that would give us flatlanders any economic incentive to do it. It might be a gift to a population of a billion or so people that will live there, but profitable to us? No way.
So even if you could colonize the galaxy with Von Neuman probes, it won't happen in your lifetime, your children's lifetime, etc. Our civilization might not be there to get the data from the first probes to reach other stars and the more steps removed the more the probability drops. Still there's just that tiny probability of a 'dark forest' scenario where somebody finds one of those things and decides to do something about it.
> If a civilization is capable of the unimaginable feat of interstellar travel, surely their basic needs are well met and they aren't driven by base animal instincts anymore.
That is a bit like saying a human isn't driven by base instincts because we are so large and advanced compared to amoeba. We have concerns and options that are so far beyond the amoeba's comprehension that it makes no sense to even talk about an amoeba comprehending. And yet we are still driven by the same basic resource-acquisition logic as any microbe. Being more advanced again is unlikely to change that.
Although I do agree that the Dark Forest hypothesis seems unlikely. It seems more reasonable to suggest that gravity wells and interstellar distances are a barrier that cannot be economically overcome, so intelligent life is bound to its own rock and eventually dies there. Then the odds just favour us not detecting life out there in whatever time period we've been looking.
That is if you assume the aliens will board a ship with conventional forces and enact a human style invasion.
Now what if the alien was not even sentient. A giant configuration of some structure of chemistry just floating through interstellar space, catalyzing reactions when inputs are met, lying in wait otherwise. It might not “die” in the sense that any other mass of atoms doesn’t “die.” When faced with some input it might swell up in size, divide and diffuse elsewhere. Akin more to a random chemical interaction among a few molecules in pure solvent than life as we know it.
Chemical structures like this could potentially be the wildfire patrolling the universe for fuel vs some spacefaring roman empire.
One might argue encountering something like this would be more akin to a natural catastrophe (like a killer meteor) rather than an alien invasion.
Stephen Baxter wrote a novel in which galaxies would be regularly wiped out by a natural phenomena, and that explains why there are no aliens in his universe. It's "Manifold: Space" if you're interested.
Life as we know it is just chemical reactions occuring within some membrane or walled environment. I don’t see why that definition couldn’t be extended to self sustaining chemical reactions that aren’t bound by a membrane or wall structure. The purpose of that membrane or wall is to just establish favorable conditions for the chemistry within the cell. If conditions could be established without such a membrane there wouldn’t be a reason for it. If reactions were energetically favorable across a wide spectrum of conditions there wouldn’t be a need for it either.
There are some that consider fire to be a form of life. I don’t think that is such a wrong idea if we are to consider how wide the scope of possibilities are in the universe.
Extremophiles don't tend towards complexity, though.
And if each common variable has, say, a 10% range in which complex life can occur, you don't need that many to start reducing probability a lot.
- Orbital stability?
- Tidal and seasonal ranges?
- Magnetic fields?
- And the big one - properties of our Sun & solar system that make it different to others of a similar age? For example, are there galactic-scale properties that affect the surface environment of planets on a long enough time-scale, so that, just as Earth exists in the habitable zone of our Solar System, there is a relatively narrow galactic habitable zone?
All the more reason though to get some telescopes built that can glean more detailed information on exoplanets. We might be in for another shock like the Mariner probes, or it might be 180 degrees the opposite.
> I'm coming around to the Dark Forest theory, personally, as terrifying as it is.
If you're silent with the intent of remaining hidden, then that behavior must have been learned. Either you evolved from a prey type of species, or a non-apex predator.
It would be strange of humanity is the only apex-ish predator intelligent-ish life form in the universe that blasts signals into space without consideration of who might hear them.
We don't have telescopes capable of receiving accidental emissions from Earth (say television) at interstellar distances. It seems reasonable that you could use the gravitational lens of a star to do so if you could launch a probe to 800 au for each and every star system you want to monitor.
As we transition to digital technology, our transmissions look more like broadband noise as opposed to having a strong carrier wave, cellular communications in 2025 are far less visible than, say, television broadcasts of 1975.
Deliberate attempts to communicate with other intelligent life are quite forlorn. This message was sent to a globular cluster 25,000 light years away
There a few 100,000 stars there, somebody there would have to be looking at our sun in particular at the right time, then it would take at least 25,000 years to get a message back to us, in which case it is likely that we'll be extinct, collapsed back to hunter-gatherers, or maybe advanced but forgotten that we sent the message or don't care anymore.
> If you're silent with the intent of remaining hidden, then that behavior must have been learned. Either you evolved from a prey type of species, or a non-apex predator.
Or you learned it in a non-evolutionary way, through logical reasoning.
No it is not necesarily learned. Even among species on earth a lot of behaviors are not learned but inherent. In other words, selection acts on a spectrum of behaviors and those with some fitness advantage you are likely to see more frequently in the next generation of offspring, extending until lineages of that offspring with that behavior are potentially all there is.
A dark forest planet need not learn to be a dark forest planet in the same way an earth colored beetle need not learn to perfectly mask itself against the dirt from a bird; the fitter mutation given the context of the environment won out.
Things can hide in bigger depths with little to worry how surface of some massive ocean behaves.
There are proper life filters but this isnt one of them. Folks just have to stop looking at survival and evolution in terms of 'if we dont have this pleasant spring stable situation life is doomed and has no chance'.
Challenge breeds adaptation, thats how our ancestors made it, environment was brutal and extremely hostile. Didnt matter, not for us at least.
I have memories of asking adults how many planets in the universe we know of at a time when the answer was 10 because we had just discovered the first exoplanet (and Pluto was still considered a planet) and laughing when they would give answers in the thousands or millions.
It's twenty times closer to its star than the Earth; the intensity of its starlight is hundreds of times brighter. Hot enough (1,400 K) to melt gold.
I don't understand the details, but in some sense it has to be an atmospheric heat engine between the day and night side of this planet. (Its rotation is tidally locked, so they are permanently distinct sides).
there is a good chance that the "measurement" is recording some other phenominon, as this can only be an interpretation of albedo changes, and could be the signal from say, low orbiting small moons
or a planetary ring,atmospheric electrical discharges
in any case, it is most definitly not an actual wind speed measurement, plus strictly speaking "wind" can only happen in air, and this, again, can only be something else, with the use of the term "supersonic" not even remotly applicable, unless of course its of the football field per second type of calculation standard
This isn't measurement of albedo changes. It's measurements of spectra that exhibit Doppler effect, which permits measurement of wind velocity. From the abstract:
"We studied the transmission spectrum of the hot Jupiter WASP-127 b during one transit in the K band with CRIRES+."
They acquired spectra for H2O and CO with hi-res transmission spectroscopy as the planet transited its star.
I don't understand. How can wind be supersonic? Isn't wind essentially a super-low frequency sound? Well, ok, not exactly, but still, it moves pretty much like sound. For it to be supersonic, air mass behind needs to move faster, than air mass in the front of it can be pushed, which seems kinda self-inconsistent. It doesn't make any sense.
I think wind is not like a sound, it's the bulk movement of the air itself instead of the propagation of a pressure wave (where there could be no average bulk movement). That's why wind can be different speeds and sounds are always the same speed (in the same air...)
Are not super storms raging for hundreds of years on Jupiter? What we can observe from earth are mostly giant exoplanets, not unlike Jupiter. Thus, I expect "normal" exoplanets are more like Mars and Venus. And who know, some could be very much earth-like!
Where they spell out a formula for the speed of sound in this type of planet given some assumptions. It's beyond my understanding, but I thought it was pretty cool. Section 4.4 if you want to have a look.
Very cool! Isn't it amazing what happens when you don't assume bad faith or incompetence on the part of the researchers? You have to like a paper that has a section discussing the precipitation of vaporized iron out of a planets atmosphere...mindblowing. Of course, that means doing a little homework to actually understand what they already know and avoiding the lazy "me and my preconceived notions and lack of domain knowledge are here to tell you why your wrong".
You can simulate the speed of sound based on atmospheric makeup and temperature. That said, 9 km/s is probably going to be supersonic in most media (for reference, the speed of sound in most metals is several km/s).
Not an original thought, but I wonder if the answer - or part of it - to the Fermi paradox is that we don't know all the ways it's possible for a planet in the Goldilocks Zone to be otherwise hostile to life.
Liquid water and.. chemistry leading to an ambient pH of 2 or 12. Liquid water and.. radiation environment such that proto-RNA strands get immediately smashed to bits by high-energy rays. Liquid water and.. bombardment every couple of million years with enormous asteroid. Liquid water and.. 1800mph super-hurricanes. etc.
The Fermi paradox seems to take for granted that complex multicellular life will eventually develop technological civilization, but there is no reason for that to be true. Orcas could very well be more intelligent than humans, but they are physiologically incapable of building tools. Human hands and visual processing were an evolutionary fluke that took tens of millions of years of natural selection, long before apes started using these adaptations to build simple tools. It is plausible that "bipeds with hands" will eventually lead to civilization: getting there is the hard part.
Put another way: birds are very intelligent bipeds, but I am not convinced that the dinosaurs would have developed advanced technology if the meteor didn't hit. There has to be an evolutionary path to develop something like hands, which means either sprouting extra arms or compromising a claw / leg / wing. Perhaps that path shows up, perhaps it doesn't - maybe there are fossils of raptor-like dinos with unusually dextrous claws. But without hands, even superintelligent animals cannot reliably make fire, build ropes, sew leather, carve stone, etc etc.
Pterodactyls when on the ground are believed to have been quadripeds that walked on "hands" with finger-like appendages[0] hence the "Dactyl" part of its species-name. They perished agter the meteor. More up-to-date, I believe Bats have a similar skeletal feature in their design. Cetaceans have finger-like skeletal features in their flippers.[1]
[0] https://duckduckgo.com/?q=pterodactll+walking+&t=newext&atb=...
[1]https://duckduckgo.com/?q=whales+used+to+have+hands&t=newext...
I've often thought about how likely it is there are intelligent and sentient civilizations that are content to their planet, or bounded to it by - as you mentioned - physiological constraints. I never connected that to "you probably need hands or something very closely approximating a hand" but it makes perfect sense.
Hands, or tentacles, or a really long snout. There appear to be a variety of appendages that can be rather good at manipulating the environment for the users purpose.
Forgot also swarms of many cooperativing organisms. Ants appear quite adapt at manipulating things to a degree.
Intelligence is such a bewildering fixation too when you think about it for ourselves. Due to science fiction writers and our insistence on anthropomorphisation we assume we will be forming treaties aboard an alien ship meanwhile we have yet to communicate let alone form a treaty with any other form of life just here on earth. The hubris is massive and it invades even the scientific community to a degree. Whoever put that human pictograph on voyager evidently did not consult an evolutionary biologist nor a statistician, probably watched an episode of Star Trek.
I wonder what the likelihood is of big leaps forward there, in terms of communicating with other intelligent Earth life.
As in, will our ability to wrangle vast amounts of data and characterise it gives us enough insight into what whales are saying to one another that we might be able to start asking them questions?
It doesn't seem absurdly far-fetched at this point. But they're probably even more pissed at us for the last couple of centuries' behaviour than the various Indigenous peoples we Westerners have screwed over.
The hard part is that it goes two ways. Most animals are adapted for interactions within their own species. A seagull is adapted to react a certain way when another seagull screams the same way we smile when someone laughs or get a sense of panic if we hear someone shriek. A seagull has no concept of our behavior really beyond if we move at it in a threatening manner like other potential predators. The most you can do is probably some simple conditional learning akin to dog training considering seagulls in recreational areas have associated beachgoers with potential food source already.
Why might a whale speak back to us? Maybe it we chum the water when whales make certain noises they will begin making those noises and expect chum. I wouldn’t call that communication as people expect it to be with ET however. A primitive form of trade perhaps.
Whales are unusual in that they use complex sound for beyond visual range communication, and they may (emphasis may) be intelligent enough to treat our proxy sounds as an attempt to recreate their own and respond in kind.
I doubt we'd get much out of a seagull or even a cat. They don't seem to communicate much. Whales however seem to be able to "speak" over long distances and emit long phrases in which individuals are identified by something like a name. There's a lot more to work with there than even most mammals.
Well most science fiction writers have to be mediocre, by definition.
There are some really intriguing works out there but they are very few and far inbetween.
Even if you had human-like civilisations, they might simply opt for a simpler but more sustainable way of life, like many ancient civilisations which have been eradicated by more uncivilised ones.
There’s no evidence that societies based on our technological direction last more than a couple of centuries. Maybe societies with nukes and rockets always kill each other, and Mayan-like societies thrive for far longer periods without ever reaching outer space.
Maybe Earth is rare in that most life evolved in a way that locks in morphology.
It's entirely possible that it's far more common place for intelligent life to evolve in a way that allows that intelligence to direct the growth of an arbitrary body shape to solve arbitrary tasks.
But there are also 7500 known exoplanets within a few tens of thousands of light years of Earth. There are almost certainly multiples more than that we cannot see.
The "Goldilocks Zone" is also highly anthropomorphised: there are extremophiles that live in all sorts of crazy environments on Earth.
I'm coming around to the Dark Forest theory, personally, as terrifying as it is.
> I'm coming around to the Dark Forest theory, personally, as terrifying as it is.
Perhaps it's just that advanced technology is extremely rare given another comment's supposition that there could be other intelligent life, just unable to make advanced technology, or along those lines: if they have the appendages to do so, maybe their environment doesn't have the resources.
If you couple the above with the idea that FTL communication/travel is difficult or impossible, then it could take a long time for us to find evidence, and maybe by then we'll be extinct due to natural causes or devices of our own.
Or maybe there's some theistic evolution component and we are the only species in the universe with divine providence.
It seems to me that it would be impossible to prove or disprove any of those possibilities unless we actually discover extraterrestrial advanced intelligent life.
(And even then, who is to say that God didn't create Edens on other worlds? So meeting aliens still might not disprove any divinity.)
> the idea that FTL communication/travel is difficult or impossible
Not just FTL. My hypothesis is that any type of substantial interstellar travel is going to be so enormously expensive, complicated and time consuming, an advanced civilisation will only do it once in a billion years. In the form of mass exodus when there are no more habitable planets in their system or their star is going nova. As this never gives exponential growth, it is enough to resolve the Fermi paradox.
But that's simply not the case. We likely very close to the technology needed to get tiny objects to a decent fraction of lightspeed using laser arrays. Assuming genuine AGI is possible and miniaturisation continues, there's no physical reason a digital intelligence couldn't rapidly (on interstellar time scales) colonise the galaxy.
Source - https://breakthroughinitiatives.org/initiative/3
Okay, let's say I grant your two extremely optimistic assumptions. Then what? You can send a bunch of tiny sentient brains hurtling through the universe. They will have a very high chance of hitting interstellar dust and turning into a blob of plasma before they reach the target solar system. They also have no way at all to slow down once they reach the target system.
Interstellar travel requires not just being able to accelerate to incredible speeds, but also to carry enough energy and reaction mass to slow down again to (essentially) zero.
A really simple answer to the Fermi paradox is that we're the first, or in the first wave, of intelligent species, and it's just too early for the light from the others to have reached us yet. We're not just looking into the distance, we're also looking into the past. Life is less likely the farther we look.
It took a long time for the universe to create the conditions for a solar system like ours to exist in the first place, and why would have this happened so much faster elsewhere? The trend towards higher entropy/complexity is like a universal clock.
The universe might look big, but our view of it is not homogeneous. We wouldn't even see ourselves if we tried to find us, unless we were a close neighbor.
Possible, but in terms of the galaxy vs evolutionary time, we're not looking very far into the past.
The Milky Way is of the order of 100K light years, which for evolution is the blink of an eye.
IMO the dark forest hypothesis leads to fun books but makes little sense. If a civilization is capable of the unimaginable feat of interstellar travel, surely their basic needs are well met and they aren't driven by base animal instincts anymore. They can probably engineer their own psyche. We humans will soon hit a population peak too, no exponental growth on the horizon.
Also, I don't think the timescales make sense at all. It took 200 years for industrial civilization to develop, maybe 200 more for us to travel the stars, but it takes billions of years for intelligent life to develop. I don't think there could ever be two comparable civilizations emerging at the same time, close enough to one another to compete for resources. Either the aliens found Earth millions of years ago and prevent us from ever existing, or there aren't any aliens closeby.
If you want an optimistic outlook on the far future which I think more plausible, read "Diaspora" by Greg Egan.
There's the question of motivation. It seems possible that an advanced civilization could gravitationally disrupt a small planet like mercury, turn it into solar collectors and particle accelerators and create multiple-ton quantities of antimatter and use that for interstellar travel, but they would likely choose to do something else with those resources.
People have a hard time thinking on a timescale of half a lifetime, never mind a lifetime or several lifetimes. The realistic version of the Bussard ramjet is not that you aim for c=0.1 or more, but rather with D-D fusion you can make hops of 1,000-10,000 au to Oort cloud bodies, you could possible gravitationally disrupt an object like Pluto and turn it into little ringworlds or other colonies. It might take people like that 10,000 years to make it to the next star but if they can make a comfortable lifestyle along the way why would they bother? And why would we even care enough to send them out on such a quest?
Even colonizing Mars is problematic in the sense that it's inconceivable that you could bring anything back from Mars that would give us flatlanders any economic incentive to do it. It might be a gift to a population of a billion or so people that will live there, but profitable to us? No way.
So even if you could colonize the galaxy with Von Neuman probes, it won't happen in your lifetime, your children's lifetime, etc. Our civilization might not be there to get the data from the first probes to reach other stars and the more steps removed the more the probability drops. Still there's just that tiny probability of a 'dark forest' scenario where somebody finds one of those things and decides to do something about it.
> If a civilization is capable of the unimaginable feat of interstellar travel, surely their basic needs are well met and they aren't driven by base animal instincts anymore.
That is a bit like saying a human isn't driven by base instincts because we are so large and advanced compared to amoeba. We have concerns and options that are so far beyond the amoeba's comprehension that it makes no sense to even talk about an amoeba comprehending. And yet we are still driven by the same basic resource-acquisition logic as any microbe. Being more advanced again is unlikely to change that.
Although I do agree that the Dark Forest hypothesis seems unlikely. It seems more reasonable to suggest that gravity wells and interstellar distances are a barrier that cannot be economically overcome, so intelligent life is bound to its own rock and eventually dies there. Then the odds just favour us not detecting life out there in whatever time period we've been looking.
That is if you assume the aliens will board a ship with conventional forces and enact a human style invasion.
Now what if the alien was not even sentient. A giant configuration of some structure of chemistry just floating through interstellar space, catalyzing reactions when inputs are met, lying in wait otherwise. It might not “die” in the sense that any other mass of atoms doesn’t “die.” When faced with some input it might swell up in size, divide and diffuse elsewhere. Akin more to a random chemical interaction among a few molecules in pure solvent than life as we know it.
Chemical structures like this could potentially be the wildfire patrolling the universe for fuel vs some spacefaring roman empire.
One might argue encountering something like this would be more akin to a natural catastrophe (like a killer meteor) rather than an alien invasion.
Stephen Baxter wrote a novel in which galaxies would be regularly wiped out by a natural phenomena, and that explains why there are no aliens in his universe. It's "Manifold: Space" if you're interested.
Life as we know it is just chemical reactions occuring within some membrane or walled environment. I don’t see why that definition couldn’t be extended to self sustaining chemical reactions that aren’t bound by a membrane or wall structure. The purpose of that membrane or wall is to just establish favorable conditions for the chemistry within the cell. If conditions could be established without such a membrane there wouldn’t be a reason for it. If reactions were energetically favorable across a wide spectrum of conditions there wouldn’t be a need for it either.
There are some that consider fire to be a form of life. I don’t think that is such a wrong idea if we are to consider how wide the scope of possibilities are in the universe.
Extremophiles don't tend towards complexity, though.
And if each common variable has, say, a 10% range in which complex life can occur, you don't need that many to start reducing probability a lot.
- Orbital stability? - Tidal and seasonal ranges? - Magnetic fields?
- And the big one - properties of our Sun & solar system that make it different to others of a similar age? For example, are there galactic-scale properties that affect the surface environment of planets on a long enough time-scale, so that, just as Earth exists in the habitable zone of our Solar System, there is a relatively narrow galactic habitable zone?
All the more reason though to get some telescopes built that can glean more detailed information on exoplanets. We might be in for another shock like the Mariner probes, or it might be 180 degrees the opposite.
> I'm coming around to the Dark Forest theory, personally, as terrifying as it is.
If you're silent with the intent of remaining hidden, then that behavior must have been learned. Either you evolved from a prey type of species, or a non-apex predator.
It would be strange of humanity is the only apex-ish predator intelligent-ish life form in the universe that blasts signals into space without consideration of who might hear them.
We don't have telescopes capable of receiving accidental emissions from Earth (say television) at interstellar distances. It seems reasonable that you could use the gravitational lens of a star to do so if you could launch a probe to 800 au for each and every star system you want to monitor.
As we transition to digital technology, our transmissions look more like broadband noise as opposed to having a strong carrier wave, cellular communications in 2025 are far less visible than, say, television broadcasts of 1975.
Deliberate attempts to communicate with other intelligent life are quite forlorn. This message was sent to a globular cluster 25,000 light years away
https://en.wikipedia.org/wiki/Arecibo_message
There a few 100,000 stars there, somebody there would have to be looking at our sun in particular at the right time, then it would take at least 25,000 years to get a message back to us, in which case it is likely that we'll be extinct, collapsed back to hunter-gatherers, or maybe advanced but forgotten that we sent the message or don't care anymore.
> If you're silent with the intent of remaining hidden, then that behavior must have been learned. Either you evolved from a prey type of species, or a non-apex predator.
Or you learned it in a non-evolutionary way, through logical reasoning.
No it is not necesarily learned. Even among species on earth a lot of behaviors are not learned but inherent. In other words, selection acts on a spectrum of behaviors and those with some fitness advantage you are likely to see more frequently in the next generation of offspring, extending until lineages of that offspring with that behavior are potentially all there is.
A dark forest planet need not learn to be a dark forest planet in the same way an earth colored beetle need not learn to perfectly mask itself against the dirt from a bird; the fitter mutation given the context of the environment won out.
The oxygen in our atmosphere has been prominent for millions of years, highly visible.
Anyone who is curious is already here, or has been here.
Things can hide in bigger depths with little to worry how surface of some massive ocean behaves.
There are proper life filters but this isnt one of them. Folks just have to stop looking at survival and evolution in terms of 'if we dont have this pleasant spring stable situation life is doomed and has no chance'.
Challenge breeds adaptation, thats how our ancestors made it, environment was brutal and extremely hostile. Didnt matter, not for us at least.
As with black holes, in my lifetime exoplanets have gone from being conjectural-but-likely to scientifically rich observable phenomena. I love it.
I have memories of asking adults how many planets in the universe we know of at a time when the answer was 10 because we had just discovered the first exoplanet (and Pluto was still considered a planet) and laughing when they would give answers in the thousands or millions.
> Reaching speeds up to 33,000 km/h, the winds make up the fastest jet stream of its kind ever measured on a planet.
Great planet for sailing!
Woah how’s that even possible? How does the fluid pick up so much kinetic energy? I’m not saying they’re wrong, I’m just fascinated.
It's twenty times closer to its star than the Earth; the intensity of its starlight is hundreds of times brighter. Hot enough (1,400 K) to melt gold.
I don't understand the details, but in some sense it has to be an atmospheric heat engine between the day and night side of this planet. (Its rotation is tidally locked, so they are permanently distinct sides).
The gas is probably mostly hydrogen. Hydrogen accelerated through a thermal rocket can reach 10 km/s or more.
I guess a gas giant means there's super strong electro-magnetic field.
Possibly solar radiation?
Wow, that's 9km/s. In comparison, objects in Low Earth Orbit travel around 8km/s.
there is a good chance that the "measurement" is recording some other phenominon, as this can only be an interpretation of albedo changes, and could be the signal from say, low orbiting small moons or a planetary ring,atmospheric electrical discharges in any case, it is most definitly not an actual wind speed measurement, plus strictly speaking "wind" can only happen in air, and this, again, can only be something else, with the use of the term "supersonic" not even remotly applicable, unless of course its of the football field per second type of calculation standard
This isn't measurement of albedo changes. It's measurements of spectra that exhibit Doppler effect, which permits measurement of wind velocity. From the abstract:
"We studied the transmission spectrum of the hot Jupiter WASP-127 b during one transit in the K band with CRIRES+."
They acquired spectra for H2O and CO with hi-res transmission spectroscopy as the planet transited its star.
https://www.aanda.org/articles/aa/full_html/2025/01/aa50438-...
I don't understand. How can wind be supersonic? Isn't wind essentially a super-low frequency sound? Well, ok, not exactly, but still, it moves pretty much like sound. For it to be supersonic, air mass behind needs to move faster, than air mass in the front of it can be pushed, which seems kinda self-inconsistent. It doesn't make any sense.
I think wind is not like a sound, it's the bulk movement of the air itself instead of the propagation of a pressure wave (where there could be no average bulk movement). That's why wind can be different speeds and sounds are always the same speed (in the same air...)
The speed of sound on earth at sea level
Are not super storms raging for hundreds of years on Jupiter? What we can observe from earth are mostly giant exoplanets, not unlike Jupiter. Thus, I expect "normal" exoplanets are more like Mars and Venus. And who know, some could be very much earth-like!
> Reaching speeds up to 33,000 km/h
Feels a bit unrealistic since that would be orbital speeds at least with earth gravity.
> Reaching speeds up to 33,000 km/h
That's ~10x speed of a bullet!
> WASP-127b, a giant gas planet located more than 500 light-years from Earth.
How do you define "sound speed" on a gas giant?
As a layperson I thought that was odd choice too and would be an Earth-centric measurement, but the paper on which this article is based references this paper: https://iopscience.iop.org/article/10.3847/1538-3881/ac51d2
Where they spell out a formula for the speed of sound in this type of planet given some assumptions. It's beyond my understanding, but I thought it was pretty cool. Section 4.4 if you want to have a look.
Then back to the article paper: https://www.aanda.org/articles/aa/full_html/2025/01/aa50438-...
> Using their formula we obtain sound speeds of the order of 3 km s−1 for WASP-127 b.
Very cool! Isn't it amazing what happens when you don't assume bad faith or incompetence on the part of the researchers? You have to like a paper that has a section discussing the precipitation of vaporized iron out of a planets atmosphere...mindblowing. Of course, that means doing a little homework to actually understand what they already know and avoiding the lazy "me and my preconceived notions and lack of domain knowledge are here to tell you why your wrong".
You can simulate the speed of sound based on atmospheric makeup and temperature. That said, 9 km/s is probably going to be supersonic in most media (for reference, the speed of sound in most metals is several km/s).
What, in this context (and most likely all), does outside our solar system actually mean?
It means a planet orbiting a different star than our Sun, aka an exoplanet.
Like 500 light years away, as opposed to 500 a.u.
Some more context:
Sun -> Pluto distance is average of 40a.u.
500a.u. is 0.0079 lightyears.
Nearest star to us is ~4.5 Lightyears.
This exoplanet is ~520 lightyears away.
Thanks for the perspective.
That's somewhat of mind boggling concept to appreciate!