Planetary 'autopsies' indicate worlds like Earth common in the cosmos | Hacker News Reader

Planetary 'autopsies' indicate worlds like Earth common in the cosmos

reuters.com

115 pointsweare138101 comments

A possible explanation of why we haven't found anything is because intelligent live once developed will quickly overload the ecosystem and start causing things like climate change and quickly make the planet inhabitable, this could all happen in less than 2 million years which is nothing on the cosmological scale.

There was running water on Mars and it's within the goldilocks zone. Probably Venus too, both those planets had stable conditions for the emergence of life for billions of years.

Once a species like humans starts spreading like a virus and taking over the ecosystem, it can easily go downhill very fast (cosmologically speaking).

I think that at this point we're pretty confident that there have never been any advanced civilizations on Mars. We'd see their chemical and isotopic residues.

Here's a good talk on filters: https://www.youtube.com/watch?v=k7fLNvpl0c8

Not an expert here, but after a billion years, what would be the detectable residues of such civilization could realistically be detected?

I mean everything made of organic material would be gone, and all constructions would have been turned to dust.

Not saying that there was anything ever in Mars or Venus in terms of intelligent life, but non-intelligent life what traces would it leave?

Likely radioactive substances that were once in large amounts with long half-lives

For example, we are now moving away from nuclear due to the dangers associated, so we only have it for less than 100 hundred years.

The half-life of uranium is 4.5 billion years. Let's say civilization of earth is wiped out and someone visits the planet a billion years from now.

Could they tell that there was something here just by the levels of uranium, assuming that say we only used it for 200 years before moving fully to clean energy?

A billion years is a long time. But if they came in a million, they probably could - if not from radioisotopes, then just from observing that the surface layer composition of metals doesn't fit any reasonable geological model. We dug up a lot of stuff, and while this initially concentrates them, as our works decay, they get dispersed into the environment, and I doubt a million years is enough for them to reintegrate back into the crust.

But wouldn't those substances be buried deep in the soil 1 billion years later? Or in the case of Earth with all the plate tectonics, entire plates could be already inside Earth's mantle.

>all constructions would have been turned to dust

I don't think that's true. There are detailed structured fossils and strata on Earth that are billions of years old, and our planet is geologically active with much more weather erosion.

> There are detailed structured fossils and strata on Earth that are billions of years old

Yes but that is not detectable from space, right? Also in Mars for example, without excavating specifically for fossils which I think hasn't been done yet, is there a way like certain geological structures that would remain intact after a billion years that would indicate life?

steroids

I suspect it's the other way around, really: it might be really hard to develop out of the early stages without hitting a reset button. Yes, we're destroying the planet at the moment and it remains to be seen if we learn quickly enough. However, the first cyanobacteria repeatedly caused global mass extinction events by poisoning the atmosphere with oxygen for over 800 million years until something evolved that could breathe that poisonous molecule[0]. That is almost one fifth of the entire age of Earth.

What if the odds that most planets are trapped in early development of life for the entire time that it can support life are just really really big?

[0] https://www.patheos.com/blogs/daylightatheism/2009/02/bands-...

I think this is also a likely cause, the odds that life even develops beyond the microscopic level, plus the fact that civilizations probably don't last that long combined with the scale of the cosmos and the light speed limitation means that it's unlikely that two civilizations even become aware of each other.

Still, I think it's a bit surprising that no signs of former life have been found so far in both Mars and Venus especially, and even elsewhere in our solar system like on certain moons.

There are definitely lots of hints that there is live in Mars, but not a smoking gun yet. https://en.wikipedia.org/wiki/Life_on_Mars#Possible_biosigna...

I always wonder how our own evolution affects our long term chances of survival as an intelligent species. Homo sapiens only exists 30K years and until recently survival was hard, making it an advantage to be intelligent. But our recent technological and medical advances make survival more and more easy so in terms of evolution, other biological features become more useful, such as for instance the rate of reproduction. So suppose we keep improving our life standard like we have been doing so far, how will humans as a species develop over the next, say, one million years?

I think biology itself provides us with some clues of what is likely to happen. There have been other species in the past that because of climatological or geological changes suddenly had a very easy time surviving. Take the Dodo for instance. What happened to them is that they gradually lost most of the survival features that they didn't need anymore. Perhaps this is the future of any intelligent life form and maybe this is why we don't detect any sign of them in the universe.

> Homo sapiens only exists 30K year

You meant 300k, right? The problem is, the human species is growing at an exponential rate, so if this continues and it's going to be hard not to, the damage tho the ecosystem can go very fast as there are processes that can also be triggered in an exponential manner.

For example, melting of the ice cap would cause not only ocean rise but a lot more heat staying in the planet as ice reflects a lot of it back into space.

Also, a temperature rise of 5 degrees would kill most phytoplankton, which is the main source of oxygen.

All of this sounds very catastrophic, but it might be somewhere in between a few centuries and a few millennia away, which is nothing on a geological time scale.

The current equilibrium that allows for human life on this planet is much more fragile than we think.

While I think we should reduce our footprint on our ecosystem, I doubt we could do enough damage to eradicate life by blowing away the atmosphere or using all oxygen and nitrogen that basically only carbon dioxide remains - not even with American cars.

The more probable scenario would be that humans destroy the foundation of their own food chain until the population starts to decline in a catastrophic manner. But that seems to be the case for any type of mammal that experienced a significant population grow.

Of course human with their adaptability would damage a lot of biodiversity in the process of "dying out".

The truth is that Mars and Venus are comparatively "shit" even while fitting some conditions as "worlds like Earth", even if their signatures while being swallowed by a white dwarf would be very similar.

But the article is true and there could indeed be a lot of other blue marbles given the size of the cosmos.

Due to the exponential rise of the human population, which shows no signs of slowing down, it might go quite fast.

There are many geological processes that get triggered in an exponential way and can radically change the ecosystem.

For example, melting a part of ice cap means less heat gets reflected back into space, meaning more heat that will further melt more ice cap, etc. a potential positive feedback mechanism that once triggered cannot be controlled.

Uninhabitable. Inhabitable is like inflamable.

Or maybe they also go the bellow replacement level population growth like we do know, and they never recover, they simply die out. The tough conditions that created an intelligent species are simply not there after that species changed its environment "for the better", the species cannot evolve fast enough to catch up with its capabilities and the species dies out. Maybe all intelligent life strives for comfort, but once comfort is achieved, it just kills of the species that created it.

The probability of no other intelligent life other than ours is near zero. The reason most question it is because we are relatively unintelligent, given we can’t even exit our solar system, and also see anything clearly in the next closest system.

No, they question it because there's no evidence that there's intelligent life elsewhere. Not only do we only have one known example of sapience in the universe, but only one example of sapience on a planet with over a million species of animals. As much as I admire crows, dolphins, and greater apes for their intelligence, they don't even come close to the intellectual capability of humans.

The fact that there are habitable planets out there gives us hope that we will find extraterrestrial life, perhaps intelligent, but to assert that there must be life out there is speculation. To say that those who question whether there's extraterrestrial intelligence is pure arrogance.

> only one example of sapience on a planet with over a million species of animals.

We're not so sure on that score:

https://siberiantimes.com/science/casestudy/features/f0100-s...

We are the only one in the boxes we have made. That does not mean there are not other boxes.

The anthropic principle goes both ways.

I've read this thought experiment somewhere -- imagine, you're locked in a cell and are given a set of lockpics, and you are told you have to pick the lock of the door and get out, or in 1 minute a neurotoxin is released that will kill you.

You have no idea how to pick locks, but you try anyway and you manage to open the lock in 10 seconds.

You are asked how tough do you think the lock was?

You reply "it was really easy, I have no idea how to do it, yet I did it in 10 seconds, easy!".

What you don't know is there were also another 1 trillion cells and you're the lone survivor -- the lock was incredibly hard to pick, with a 1 in a trillion chance of success, but to you, the survivor, without external information it seemed really easy, you were just incredibly lucky.

>Not only do we only have one known example of sapience in the universe, but only one example of sapience on a planet with over a million species of animals.

What's even crazier to think about is the sequence of events that happened before humans appeared on Earth. Perhaps humans wouldn't have appeared if dinosaurs hadn't gone 'extinct' the way they did. It was also not guaranteed that our species would survive as long as we did - we have some evidence that we've come close to extinction before. Furthermore, it took a very long time for civilization to appear and even with civilization around, we weren't really advancing significantly before the industrial revolution. Yet what was vital for the industrial revolution? A cheap, plentiful, and easy to use source of energy - fossil fuels. The reason we have so much fossil fuel is because nothing could break down dead trees for millions of years, so they were buried instead. That eventually formed into various fossil fuels.

The sequence of events that led humanity to the point where we could start exploring our solar system is crazy. Take plentiful fossil fuels out of the mix and modern society wouldn't exist.

We're not looking for just intelligent life. We're looking for intelligent life that has got to at least a similar level of development as us. I don't think that's something guaranteed at all for intelligent life. Perhaps there are dozens, thousands, millions of planets, where intelligent life evolved, for every planet like ours, where intelligent life got to the point we did.

Then there's also the fact that... time in space is a messed up fact. We could see evidence of life that was sent out 50k years ago (say a beam of light), but their whole race could be dead for a few thousand years and we'd never know until we set foot in their solar system.

Or there could've been life nearby that went extinct the minute we began fashioning our own tools out of stone and metals.

There could've been whole wars fought in space with the winners/losers going extinct before we were ever even formed through evolution.

Would be nice if we can ever explore all of the universe and figure out all those secrets, and see the archaeology of other races, but I don't know if we'll ever get there. Would be amazing if we did, to only find out that we are the only sapient species. How rare a thing that would be that we're the only ones to make it past the great filter.

Although the current state of affairs seems to be that we are hellbent on activating said filter and we‘ll be long dead (at least as a technological civilisation) by the time anyone else receives our current radio transmissions.

Nobody can ever receive most of our current radio transmissions. They drop below the noise floor just out of our stellar neighborhood.

True... but odds are also that IF civ's get near to Kardashev 1, there's a good chance they ALSO build AI's, which even if they died out, the AI would live on being synthetic and nearly immortal.

I think it's odd we don't see more synthetic ai type signs of life out there, at least.

I think if we do kill ourselves we might have AI before then to at least broadcast to the universe that we were here.

I just looking at the billion billion galaxies out there, what are the chances there is no life or even slightly intelligent given the physics and chemistry laws are the same in every planet.

Some scenarios:

1. ET life formed and vanished so quickly that they didn't even get to the stage where they generate electromagnetic signals.

2. ET life formed and got to generate EM waves, but:

- they're either too far from us that we haven't detected those waves yet;

- they only recently got to this stage and the signals they produce have not reached us yet;

- or both.

3. ET life formed way sooner than we did; figured out how to generate EM waves, and then vanished entirely. So, any signals of their civilization they must have sent out there have already reached earth, but before we began listening for such signals.

4. Then again, since there are practically infinite number of planets with habitable conditions for ET life, statistically speaking, we must have already received a signal from at least one of them.

Which leads me to this:

5. ET life doesn't exist, because the universe as we know it is most probably a simulation inside a computer and the computational resources can only render so many different objects at a time. (This is serious stuff, researchers have already proposed methods for verifying this: https://www.washington.edu/news/2012/12/10/do-we-live-in-a-c...).

(5) is not serious. It’s nonsense, and I wish people would stop bringing it up.

Can you say why it's nonsense? It's a speculation and can either be proved or discarded. I wouldn't do neither without proof.

It's essentially solipsism and there are strong philosophical arguments against it.

That's it in a nutshell.

Demanding proof either way is unhelpful as it’s not possible, but we can I think trim down the balance of probability.

Looking at our own universe, building a simulator for it inside itself looks like a non starter. We’re even detecting gravity waves from black hole collisions billions of light years away, that's how detailed the simulation would have to be. There’s no way to build a simulator with that level of detailed fidelity of a universe in that same universe. Imagine designing a computer chip to run a simulation of itself. Yes we run low fidelity weather simulations, but to simulate outcomes in our universe at a general level like that you wouldn’t need to simulate consciousness. In the same way that we don't think superintelligent AI would necessarily need to be conscious, the actors in a history simulation wouldn't need to be either. Our universe is too detailed to be a statistical simulation and too complex to be an accurate simulation. The parameters don’t make sense.

That only really leaves the possibility that the simulator is running in a dramatically more complex universe, so simulating ours would be relatively easy. But then, there would be almost infinitely many less complex universes they could simulate, why choose ours? The more complex the universe running the simulator(s), the more lower complexity universes there are available to simulate. As the number and complexity of universes available to run simulators goes up, the number of lower complexity universes (and the complexity of them) that it's possible for them to simulate also goes up, so the probability they will bother with ours probably stays steady at a very low prior.

How is 5 more nonsense than any of the other options?

You're assuming the others are also nonsense. Care to provide some reasons?

I don't pretend to know.

I bet if octopi didn’t starve themselves to death in three years, after reproducing, there would be much greater examples of their intelligence

Or maybe this is an example

The problem with octopi is that they're solitary, by nature and instinct.

The smartest human in history, with all the encouragement in the world, couldn't invent agriculture or ironworking from scratch if they were born a hunter-gatherer. Innovation means building on the work of hundreds of generations of the best and brightest. That can't happen if you don't regularly interact with other people. Every genius octopus is starting from a blank slate.

It sounds silly but also a lack of ability to make fire puts a dampener on things. No easily digestible cooked food. No ability to make metals.

Perhaps somewhere near an underwater volcano there is a technologically advanced octopus city waiting to be found?

Like Octlantis, but hotter, and with steel (“Cuttlefisheffield“?):

https://www.theguardian.com/environment/shortcuts/2017/sep/1...

If you were to encounter a crow out in the wild, it would be considered irrational to believe that it is the only crow out there in existence. The same goes as you scale up the chain, if you encounter one human in the wild, the odds are high that there is another human out there somewhere. The evidence that intelligent life exists out there is the fact that humanity exists.

I think it would be more arrogant to assume that we're somehow special or unique in what is an incredibly massive universe where we exist as mote of dust upon a mote of dust. Right now, humanity is in the stage of tossing messages in a bottle into an unimaginably vast ocean, while using a hastily built telescope attempting to see over the horizon.

This isn't to discount the incredible efforts of those people exploring the cosmos, but rather that to demonstrate just what we're working with.

Any citations for that number?

We simply don't know yet!

We have a good estimate for how many worlds there are out there, but without the probability for life to exist, it could just be we are the only planet in the entire universe that holds life/intelligent life.

Even if there are Earth like planets everywhere, we don’t know the probability that life appears spontaneously. Right?

How does this change our outlook if one assumes The Great Filter hypothesis? Does this lower or increase that such a filter would be behind us or before us?

technically it's not spontaneous. There are some thoughts out there that organic compounds can emerge from non-organic ones and, given enough time, "life" will emerge.

One of my favorite books on this is "Regenesis: How Synthetic Biology Will Reinvent Nature and Ourselves" by George Church. I have also seen arguments for this in "The Blind Watchmaker" by Dawkins that was published in 1986.

The Blind Watchmaker is mostly a book about evolution. Evolution does not explain origin of life, so it is not relevant here.

you are right that it’s mostly about evolution, but also touches on what may have given birth to life.

We do know the probability life appears is non-zero though, because it has happened. I don't know why all 9 steps to colonization can't be considered improbable, and therefore the filter be behind us and in front of us.

We don't even know all the steps between "Step 8: Where we are" and "Step 9: Colonization." Maybe a moon is required for it. Maybe materials not found on this earth are required for it.

I think we as a species have decided that colonizing Mars is possible. It might not be probable, but we can do it. We know how, we just haven't yet.

Humans just might be the first intelligent life. If the Milky Way was already colonized, some civilization made the first leap to another planet.

It's manifest destiny. We have to colonize the universe. It's our moral duty as an intelligent species to maintain awareness of the universe.

"Humans just might be the first intelligent life." is incompatible with the notion that life is common (which may or may not be true) - our planet is a bit older than the average (e.g. the examples in the article are suns/planets which have already gone through all the lifecycle that Earth will have eventually), so it's probable that we're the first intelligent life in the galaxy if and only if it's likely that we're the only intelligent life that the galaxy will ever spawn.

If there's no great filter before our current stage, then it's extremely unlikely that we're the first intelligent life in galaxy, and either there's a great filter after that or many civilizations have risen already (and have had more than enough time to colonize the whole galaxy a thousand times over at a relaxed, leisurely slow pace, if any of these civilizations wanted to) but we just don't see them for some reason.

Just because something is unlikely doesn't mean it can't happen. Furthermore, there could be something very special about Earth's position that makes it far more likely than we initially calculate. It doesn't make sense to dismiss theories as 'unlikely' when our degree of understanding of that probability is absurdly primitive.

"something very special about Earth's position that makes it far more likely than we initially calculate" - makes what far more likely ? Spawning life? If so, then that special factor, whatever it is, would simply be an example of a great filter behind us. I'm not saying that we can't be the first ones, I'm just noting that us being the first implies that we're alone in the galaxy.

To make that point perhaps more clearly, let's say that before and including us, our galaxy has had X planets like Earth. Whatever that X is (1 or 1000 or billions), the total number of such planets that our galaxy will ever have is less than 2X. That doesn't rely on any poorly understood theories, that doesn't rely on any aspects of how life or intelligence might form - the lifecycle of stars is well understood, the age of universe is well understood, and the future has less new stars and planets than the past; we're currently past the midpoint of star/planet forming and that's that, most of the planets that will ever exist in our galaxy either exist right now (most of them for longer than Earth) or are gone already.

So whatever the "dice" of a suitable planet existing and creating intelligent life are - if we're the first ones (and I'm not making a point whether we are or aren't, whether that's likely or not, that "if" is an assumption), if X rolls of dice resulted in just a single success - then the remaining less than X rolls simply won't suddenly roll a hundred more successes; if the total number of spawned civilizations until us is 1, then that means that the total number of spawned civilizations until end of the universe would be 1 or 2 - and if it's 2, then it would be a hit-by-a-lightning-while-typing-this level of coincidence is that second one happened to arise at the same insignificantly tiny moment in time that constitutes the existence of homo sapiens until now, just some tiny 100 000 years after us instead of some 10 000 000 or much more years after us.

OR, possibly, there are and will be much more civilizations than that - but then some of them have been long before us.

“if X rolls of dice resulted in just a single success - then the remaining less than X rolls simply won't suddenly roll a hundred more successes”

Mmhh.. not so sure you can conclude this. You assume all rolls of the dice are identical (same likeliness of all outcomes), but this ignores the fact that the universe is ever-changing from a particular state towards its inevitable fate.

Consider for instance the "pulse" of galaxies as they collide and 'ignite' their central quasars anew — this coincides with extremely harsh local conditions for said galaxy merger, which becomes likely very unhospitable to life. Conversely, when the jets calm down (mature) and winds recede, star formation kicks back up and a new galactic cycle begins until the next merger (if ever).

This mechanism alone could paint a very asymmetric past and future set of conditions (relatively to our rather 'calm' present, but it's actually a cycle). Some of these conditions would definitely affect life (for instance, during its active phase, we suspect that a galaxy's quasar might be strong enough to blow away planets atmospheres).

There's just too many unknowns at this point. Drake's famous equation was actually meant to expose this fact (he actually knew it was flawed/impossible to solve, but felt it was a meaningful thought experiment, iirc).

Exactly! You can only extrapolate statistical observations to identical scenarios but we know that every aspect of this universe has a great degree of variation and is anything but uniform. Statistics breaks down when you cannot ensure uniformity.

Most people's understanding of the complexity of a single-celled organism is absurdly primitive too.

> our planet is a bit older than the average

But our galaxy and solar system is relatively young compared to the universe. Plus the universe is massive. There's approximately 10 billion galaxies in the observable universe with and average of 100 billion stars per galaxy. At that scale the processes that created life on Earth would have happened countless times before. The building blocks for life are common in the universe but weren't common on the early, inhospitable Earth. It was brought to our planet from comets which is where the Earth's water came from.

https://helios.gsfc.nasa.gov/qa_star.html#howmany

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

I'm not an expert, but didn't it take quite some time for stars to create heavier elements like iron, go nova, spread the star-stuff across the Universe, and then repeat until we have the current mix of light/heavy elements?

Combine that with:

* The fact that life on Earth was possibly dependent on life from other planets to form.

* Has had multiple near-total extinction events during it's time.

* We're outright dependant on fossil fuels left over from previous cycles in order to get to where we are now.

* Our own species have been close to extinction multiple times far before we reached our current technological level.

* Our own emissions most likely blends with the background noise and are probably not detectable that far out.

* It's taken us countless millennia just to get to the point where we're approaching a technology level that will allow a fraction of our population to scan parts of our closest galactic neighbourhood for disproportionately large signal sources that happens to be on the bands we find to be most convenient.

To me, it sounds like it's quite plausible that we could be amongst the first to spread on an interplanetary scale (assuming we actually manage to do that), or that something happens and we go back to pre-industrial levels, leaving the aliens on the next habitable planet wondering why the level of noise from group of stars a few hundred light-years away suddenly grew quieter.

"It's our moral duty as an intelligent species to maintain awareness of the universe."

Interesting justification for colonising the universe. If you were from another civilisation, more advanced, you could see humans as a bunch of parasites taking over planets and destroying other life and themselves in the process.

This grand justification of maintaining the awareness of the universe is a bit of a stretch.

If we want to colonize anything outside our orbit, we should start with solving our basic earthly problems. Like stop fighting for territory, power, money or to prove who believes in the right God(s).

But I guess it would make us an "advanced" civilization.

It's naive to presume that one problem doesn't beget solving the other. Humans, for example, almost to a tee, define ourselves in terms of others - tribal heritage I guess. How long do "nations" drawn on 2D boundaries survive once there's tribes which operate in 3D space on other planets, or spread out through the solar system?

Which is to say nothing of the riches that await us if we can solve orbital and deep space access problems. If you can get to Mars, you can get to a bunch of asteroids with enough gold and platinum to ensure only the rich will have things made of wood.

What riches are there to be found in space and brought back to earth to sell for economic gain?

I thought space flight is too expensive and unobtanium is yet to be discovered?

Who's to say country X won't nuke you out of the sky before you have a chance at mining those materials? Whether we like it or not, international politics will dictate the course of humanity when it comes to space, unless some isolated group manages to do it in secret.

Further, even if a group manages to secure trillions of tons of common materials for us today, who's to say it will be given out for free? If it is, well, maybe I want you to give my country a bit more of the share than other countries, or I'll take their share by force. Even if we emerge a united world after something like that, we may find that we've developed far superior technology that has no use for the materials you've acquired.

There are tons of real-world questions that have to be answered, and it doesn't matter if we don't have time to come up with a good one, because someone will pull the trigger first.

Exactly, who's to say?

The idea that all problems must be solved in some order is naive. There is no order. We don't know what the correct path to future desired social outcomes is, we have what seems to be within reach and we achieve it.

A few hundred years ago and you would have priests declaring the men who spend their leisure playing with wires and magnets, or looking at tiny things through looking glasses are wasting their time - clearly they should be working on getting more blankets and clean air to those suffering from disease!

> If we want to colonize anything outside our orbit, we should start with solving our basic earthly problems.

That doesn’t necessarily follow. In fact one could imagine that earthly problems will provide the stressors to spur us into action.

A worthy sentiment. Its part of why in most sci-fi scenarios where humanity has expanded off world it’s usually some variant of the technocrats left everyone else behind.

Lengthy as they are, Kim Stanley Robinson’s Mars trilogy novels are so interesting for challenging that idea, from the very first chapter.

I read a lot of science fiction, and I'm yet to find one example of "the technocrats leaving everyone behind". Could you provide one?

None of these examples will be new to you, but maybe my viewpoint is?

In one category I see the stories of Star Trek and The CoDominium, / The Mote In Gods Eye. Both sets of stories revolve around a militaristic society where, even though there are democratic societies on frontier planets and back on Earth, the only travel between worlds is governed by the ruling group of technocrats who importantly are the only ones with access to interplanetary travel. These aren’t closely tethered warships like we have today: Star Trek plots are notable for the authority, autonomy and power that individual captains and their cadre of officers have. It isn’t explored in depth but Mote implies the CoDominium, the ruling structure on Earth and other worlds, is organized the same way the space faring military is run. Societies with a large military running the country day-to-day are usually considered technocracies (contemporary Egypt, for example.)

In Dune, the Navigators — a separate species evolved from humans — exert the same kind of authority over space travel. The fundamental access to other worlds is in the hands of their technocracy, though the other unevolved humans whose stories make up the main plot lines do so in traditional feudal empires. Maybe Navigators have their own ways of deciding how to run things that shows they are decidedly not technocrats, but to the extent that they control travel between worlds makes them technocrat overlords to everyone else.

Space travel and society in Banks’s Culture novels is much more democratic. Individuals roam in their own ships and all different kinds of societal structures are free to exist in many species and places. However, the over-arching control is still in the hands of the benevolent Minds — sentient supercomputers with a moral code that still allows for some humans to be involved in decision making, but only those humans that have been selected for their elite knowledge and skills. While the Minds have all the power, the humans call a lot of the shots. Decision making by only the most learned and skilled is the hallmark of a technocracy.

Of the first three stories I can talk only about Star Trek, and there I'd be inclined to disagree. While the shows do focus primarily on Starfleet, the Federation that exists in the background is a proper utopian, democratic government, and the civilian activity in space is very large. So I never got the sense that technocrats left anyone behind; Starfleet is portrayed as a "military" run by pacifists, focused more on science and exploration than force projection (to the point of the fleet flagships housing lots of civilians with their families).

(As a teenager I loved this adventure and exploration focus; as an adult, I wish they had explored the Federation as a government and society a bit more.)

I haven't heard of CoDominium before, and The Mote In Gods Eye is on my todo list.

Come to think of it, I could sort of see the "technocrats leaving rest behind" in StarGate series, where most of the off-world activity, including bases on different planets, were actually run by the US military (later a cooperation of militaries and civilian agencies) in secret from the rest of the world.

Out of the relevant books I read, all featured either just human expansion (with no leaving behind happening), or alternatively remnants of humanity going out, with nothing salvageable left behind.

Re-reading your comment, I see you're focusing more on the "technocrats" aspect than "left behind everyone else". Honestly, having grown up watching Star Trek, I'm biased positively towards technocracy - but I guess it worked there because in the society the show portrayed, neither people nor organizations were dumb. Merit actually meant merit.

I think the Spacers in some of Asimov's stories are an example of this idea:

https://en.wikipedia.org/wiki/Spacer_(Asimov)

"Become a Nobel laureate, Olympic gold medalist and a critically acclaimed artist all together, before you learn to walk"?

The problems you mention reach to the very core of human group dynamics. Colonizing space is orders of magnitude easier than solving them. If and when we do solve them, it would make us an extremely formidable civilization.

500yr ago that kind of attitude got you a footnote in history.

The people who went all in on what was the new thing at the time have states, cities, islands and whatnot named after thing

Infighting didn't exactly put a damper on the Europeans ability to colonize the Americas and exploit everyone else in the old world. Once we have the technical capacity to colonize other planets I doubt a little infighting on Earth is gonna stop us.

I think it's the only reason.

We don't know. The confidence intervals on individual probability distributions are already wide and long-tailed but convolving them only makes the problem worse.

https://arxiv.org/pdf/1806.02404.pdf

The last years have given us two estimates of previously unknown factors in the Drake equation, that's why everybody is excited.

Yes, life could be very improbable to appear, but there is a counterargument to this hypothesis: on our planet, life appeared almost immediately once the crust solidified and oceans appeared.

If there had been a 3 billion years period, there may have been an argument that maybe we got very lucky it appeared at all, but we have fossils that are just 100 mil years younger than the apparition of oceans. And we keep finding older ones.

If life was a really rare occurrence that would mean we would have been lucky twice: that it appeared at all and that it appeared that early.

> Does this lower or increase that such a filter would be behind us or before us?

When so many things are unknown, it makes little sense to talk about probabilities. It removes a possibility for a filter behind us.

I still have doubts that evolution necessary leads to intelligent life. When I started getting interested into evolution, my main surprise was that there is no "optimal" unicellular life-form. Why isn't the earth covered by a green pellicule of photosynthesis-able cells that would be a Kardashev I organism without ever reaching intelligence?

I still don't understand why it did not happen. Evolution favored competition to optimality and the reasons are unclear. I would not be surprised that evolution in other ecosystems would result in one organism "winning" over all the others.

My personal opinion is that we will find a lot of life on other planets, but many will be unicellular and many will show an evolutionary process that is stuck in a dead-end.

I expect intelligent life to be rare, and that the "great filter" is that we will find things much more worthy of our time and energy than colonizing the universe or doing mega-engineering projects. Maybe we'll colonize a few star, build a Dyson star or two, but then we will discover that everyone prefers to spend time in another dimension, or in infinite pocket-universes. Maybe the real party is inside the black holes or the neutron stars and all the advanced civilizations are waiting for us to figure it out.

The idea that an intelligent species would colonize the universe assumes that it does not manage to handle its demography or views its growth as a good thing. I doubt that this is a rational conclusion once you reached the state of full automation.

Green unicellular life-form is perfect food and energy source same way as energy of sun is. Evolution does not stop if there are easy energy sources available everywhere.

Nature does not care if energy of sun is used optimally or not. It just cares if offsprings live or not.

I think it is very easy to imagine a local minima in which evolution would be stuck. Making a membrane far too hard to pierce could starve a predator into extinction instead of making it evolve.

If you reach a point where one organism developed enough mechanisms to resist simple predators and that their advanced predators die out, I think it would be impossible for evolution to get out of that dead end. I am not sure that getting unstuck is a universal feature of life.

Emergence of sexual reproduction, of multi-cellular organisms, are all very weird phenomenon that I think are risky to take for granted.

I mean, it feels like playing Conway's game of life: Often, when you start a random one, it all dies out. It often gets stuck in a position where just a few things vibrates. Some last longer. Others go on forever but are rarer.

My intuition (which can be dismissed without argument) is that life is similar: if the conditions are right, it may lead to emergent evolutionary behaviors that eventually can lead to intelligent life, but that's not the most common outcome.

> If you reach a point where one organism developed enough mechanisms to resist simple predators and that their advanced predators die out, I think it would be impossible for evolution to get out of that dead end.

Evolution works on the level of individuals. Even if you end up in a situation where you have only clones of a single organism populating whole planet, these clones will compete with each other. Because of different environmental conditions, random mutations and distances this super successful organism most likely will still undergo speciation.

But what if you have already reach optimal growth and optimal energy efficiency?

If you have ever played with evolutionary algorithm, you have seen that it is very easy for a system to just "win".

Want to optimize a thing that heavily depends on a mass/surface ratio? Oh, a sphere is the perfect solution. Evolution can't beat it.

Yes, maybe there can be various colonies of photosynthetic organisms competing over millionth of percents of efficiency for billions of years. That's what I call a dead end of evolution.

You should keep in mind degrees of freedom of whatever you were playing with as well as complexity of the fitness function. Simple optimization problems have simple solutions. Physical, sustainable self replication is anything but simple. As far as I know humanity is not able to engineer anything that would be self replicating to the point where evolution could kick in. We have limited success at reverse-engineering nature but that's about it.

> Yes, maybe there can be various colonies of photosynthetic organisms competing over millionth of percents of efficiency for billions of years. That's what I call a dead end of evolution.

I would call that a plateau, because that was the state of Earth for about one or two billion years.

I think overall we agree - transition from single cell life to current level of complexity is not an easy one. We are significantly more likely to find single cell life in the universe, than anything that would resemble animals.

But you should also remember that Earth was not uniform in space and time, photosynthesis does not work equally well everywhere and overall conditions change a lot over millions of years. So even single cell life will be damn complex and dynamic on a scale of planet and evolution.

If all the predators died out, then those defense mechanisms would become wasteful, and organisms that didn't have those defense mechanisms would be more efficient. That would open the door to the development of new predators. The situation you're describing is not a true equilibrium, in other words.

True, but in such case, defense mechanisms don't just disappear from the gene pool, they just get deactivated. The second time they are going to be much faster to re-evolve, making the disappearance of the second appearance of predators even faster.

The predators will never disappear in the first place.

The fewer predators there are, the more wasteful defense mechanisms are, and therefore the more disfavored they are by natural selection. The more predators there are, the more defense mechanisms are favored. The equilibrium is neither zero defenses nor 100% effective defenses against predation. It's somewhere in-between.

The predators get to evolve too, by the way. There's no 100% effective defense against all forms of predation.

Evolution does not get stuck because the environment is constantly changing. This shakes things out of local minima.

Take your shell example: The shell is made out of something, presumably abundant. If it becomes less abundant this species becomes vulnerable again.

"If".

What if the substance is abundant? I suspect (here again, just an intuition) that our planet is actually exceptionally good, not for life to appear, but for evolution to occur.

One theory of abiogenesis supposes that life started in hydrothermal vents, in conditions that are very far from what is considered "habitable" for the current life (very hot water, high pressure and, IIRC hard acidity)

Maybe these are the only conditions for life to start, but does not offer a lot of room for improvement. Maybe there is just so much things you can do to efficiently colonize interstices of volcanic rocks. But then you have a whole host of conditions offered to you: a gradient of temperatures and pressures, light, storms, changing currents, varied geology. And then later on, dry lands, of a varied range of temperatures.

If the conditions for abiogenesis and evolution to occur are very different, Earth could be unique in that aspect: how many oceanic planets on a stable orbit will still have days, tides, seasons, storms AND hydrothermal vents of the correct type to generate life?

And the year before that gave us Dissolving the Fermi paradox[1], which conclusively shows that the drake equation is not worth the napkin it's written on.

tl;dr: It is possible for both of the following statements to be true at the same time:

(1) The Drake equation gives a true estimate for the mean amount of extant civilizations in the galaxy, and that estimate is relatively large. (As in, much greater than one.)

(2) The probability of sentient life existing outside our solar system is infinitesimally small.

The reason for this is that the Drake equation gives a mean over all possible universes, with the solution space created by our uncertainty in the parameters. Since all of the parameters have more uncertainty in one direction than the other, the probability distribution is not symmetrical, and so the mean, mode and median are not the same. In fact, it turns out that when you do the math right, you find that essentially all of the probability mass in the Drake equation comes from the cases where almost every star has a civilization around it. Using our current best estimate numbers, and excluding the cases we can conclusively disprove because we are not already chatting with our neighbors at Proxima Centauri, P(we are alone in the galaxy) > 50%, and P(we are alone in the observable universe) > 39%.

[1]https://arxiv.org/abs/1806.02404

The Great Filter hypothesis assumes that a society that has the capability to expand and colonize would do so without exception and make its presence known to more primitive civilizations. That's a pretty big assumption. Just look at how ridiculous most futurism of the early 20th century already seems (both culturally and technologically), and then consider trying to relate to the continuation of human civilization after ten million years. When we try to envision the future, it is still rooted in the familiar. I suspect ten million years from now (if our society continues on that long in some capacity), just about everything will be so fundamentally unrecognizable (including the continuation of humans, if there is still a biological form at all) as to make relating to their intentions or even trying to identify whether they exist from afar with primitive technology futile.

There's more hard evidence of "pseudo-magical objects that don't seem to wish to be seen up close" here on our Earthly radar systems than there is of the actual conditions on planets in neighboring habitable zones to confirm or deny life and start establishing probabilities.

> The Great Filter hypothesis assumes that a society that has the capability to expand and colonize would do so without exception

It doesn't assume that. (Explicitly doesn't; that's step 9 of 9, with modern humanity at step 8.) It just observes that we have no evidence of extraterrestrial life spreading out from their home system and colonizing the universe, and discusses some possible reasons for that.

My physics isn't great, but why does it matter that these are white dwarfs?

The article says "researchers studied six white dwarfs whose _strong gravitational pull_ had sucked in shredded remnants of planets" and "if they stray near its _immense gravitation field_, they “will be shredded into dust, and that dust will begin to fall onto the star and sink out of sight.”

Isn't it the case that the gravitation field will be as strong as it was before the star died, or even weaker from blowing off its outer layers?

I think it may be that while the field is more or less the same overall, the star no longer occupies as much of it so planets can get closer in where the gradient is steeper (and the tides can then rip the planet apart, giving us the chance to see its contents)

White dwarfs are interesting because they make up almost all of the current or future outcomes of most stars in the milkyway. -> https://en.wikipedia.org/wiki/White_dwarf

The Roche-limit (the radius at which a satellite would be ripped apart) for the Sun-Earth system is at ~ 550000km. That's inside the current size of the Sun. So if the sun shrank a lot (white dwarfs are basically small, 'dead' stars which shrank to that size after the nuclear fusion stopped which had counteracted the attraction of the star's mass), Earth could actually be in such a low orbit and therefore fall apart due to the Sun remnant's attraction.

-> https://en.wikipedia.org/wiki/Roche_limit

Why would a decrease in the sun's radius cause a change in Earth's orbit? From those to articles it sounds like the mass of the sun will remain about the same, so the orbit should remain about the same. And less mass will cause the orbit to migrate outwards.

Shrinking of the star simply makes it possible to come within the roche limit without being inside the star. The inspiral would happen due to separate processes e.g. friction as the star sheds its envelope or due to interactions between multiple planets.

When the Sun enters the red giant phase, will the radius have expanded enough to consume the earth? I'm trying to remember if that was something my physics professor said years ago or if I heard it from someone less reliable and am merely attributing it to him...

Wikipedia says the sun is expected to expand out to roughly the orbit of Venus (consuming it and Mercury) and turning Earth into a blob of molten rock.

I am not an astronomer, but in terms of empirical evidence, for the longest time the only prior we had was our own solar system. Thus the natural best guess should have been that (at least for stars similar to our own) earth-like rocky planets near our size should be the most frequent occurrence.

Assuming there are intelligent species living in nearby systems(with not such advanced tech), it's unlikely that they can notice us unless we can control the light intensity of our Sun. Because that's the only object they're probably looking at.

So, to be clear, are they doing spectroscopy on the spectra of these white dwarfs? Do they have to be looking at it at the exact moment the planet gets shredded or do the chemicals they're looking for remain in the star's atmosphere?

James Web telescope will be able to do that. I hope that it gets deployed without issues because it would be able to provide strong indicators of extra terestrial life

From their paper (link in my other message):

"(White dwarfs) WDs are the remnant cores left behind when a star ejects its hydrogen-rich outer layers after the red giant phase. These remnant cores are ~0.5 M (solar masses) and about the same radius as Earth, are no longer powered by fusion, and slowly cool over time. Because of their high densities, and thus strong gravitational fields, elements heavier than helium rapidly sink below their surfaces, becoming unobservable. Nonetheless, spectroscopic studies show that the atmospheres of up to half of WDs with effective temperatures <25,000 K are “polluted” by elements heavier than He (3–5). The source of these heavy elements is exogenous, coming from accretion of debris from rocky bodies that previously orbited the WDs (6–9). We exploit this pollution to measure the elemental constituents of extrasolar rocky bodies."

So the answer is "the later."

The paper:

https://science.sciencemag.org/content/366/6463/356

The science here and although it's different, makes me think of the "I’m Convinced We Found Evidence of Life on Mars" article posted here a few days ago. If they are able to draw these conclusions with such limited data, I doubt they've missed anything obvious on the surface of Mars.

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