What's staggering to me is that with the new Voyager discoveries lately it feels like we're a bunch of stellar savages who just managed to release a buoy far enough into the ocean to feel the currents.
Let alone recognize another savage on a different continent who might be doing the same experiment.
It may be even worse, that different continent is on a different planet.
Space(time) is absolutely, mind-boggling massive. Everyone knows it's big but it hard to comprehend how big and why there could be many alien civilizations out there capable of broadcasting or detecting but never intersect in any way because the detection windows of any 2 civilizations don't line up.
The Milky Way alone is ~150000-200000 light years across. Humans have been civilized for only some tens of thousands of years, and capable of sending and receiving signals for a mere century. Imagine that even at the speed of light the entire history of civilized life on Earth might come and go many times before something reaches us, or before the probe comes back.
There's no Earth-bound or common sense analogy that can convey this kind of vastness and emptiness.
I remember reading somewhere that due to the differing pace of evolution and technology advancements, any intelligent living aliens we meet are almost certainly going to be gods or cavemen. I can't find the reference.
It's from Arthur C. Clarke: "If one considers the millions of years of pre-history, and the rapid technological advancement occurring now, if you apply that to a hypothetical alien race, one can figure the probabilities of how advanced the explorers will find them. The conclusion is we will find apes or angels, but not humans."
Old-school angels were just as likely to rip your face off as serve you tea and cookies. Read the older Abrahamic texts, and it's clear that to encounter an angel was often a terrifying experience, even when it went well.
Obviously their marketing department has given angels quite a rebranding over the last thousand-odd years, but still...
Angelic doesn't imply good, just being sufficiently advanced enough to seem like magic (to use another Clarke quote.) Demons are technically angels after all.
Given the age of the Milky Way, a civilization using even slow sub light travel with generation ships or autonomous probes could have colonized the entire galaxy many times over. Why has no one done that? Hence the paradox.
Not sure why it was downvoted. Many people have looked into this. https://gtocx.jpl.nasa.gov/gtocx/competition/ Even entire competitions to find optimal colonization methods. Could take 90M years with measly future human tech. Age of Milky Way is 13.5 Billion so even conservatively you could indeed colonize the galaxy many many times over in that time.
There are problems of resiliency and energy storage that could be more or less fundamental problems. It could take millions if years of technological civilization to produce a machine capable of sustaining life for the hundreds of thousands of years necessary for interstellar travel, and civilizations may tend to collapse for various reasons before reaching such technological peaks.
It's also entirely possible that we are the first, or one of the first, technological civilizations in the galaxy. Given how little we understand about the appearance of life, the emergence of multicellular life from single cell life, and the emergence of intelligence from multicellular life, there's not way to put an estimate on these probabilities.
Think about the fact that in 3.5 billion years there hasn't been any new abiogenesis on the only planet in the universe we know for sure can sustain life, and in this billion years a single life form has ever evolved from a single-cell to multi-cellular life, aren't the priors pretty decent that life is an extremely rare phenomenon? Given the fact that the Milky Way is somewhere around 13 billion years old, how often can we expect a once in 3.5 billion years event have happened?
I don't know why this got down-voted. The milky way is 100K light years across. It's 13.5 billion years old. It's entirely possible to blanket the whole galaxy with probes, without even getting into self replicating probes.
It could be that none of them have seen any point in doing so.
Generally on Earth colonization has happened in order to provide a tangible economic benefit to those supporting the colonization effort. With someplace that you can only travel to and from by slow generation ship its hard to find any such economic benefit in having a colony there.
I'm fairly confident we'll eventually find that our form of life is the result of intentional or unintentional colonization of Earth.
If you look at how quickly life began after the oceans settled out, then look at precisely how complex even the most primitive forms of life are (in terms of likelihood of stochastic construction to the point of sophistication to support evolutionary mechanisms) it seems incredibly unlikely that we originated here.
Yes, I know the paradox. It's simple. It's too simple.
It has huge assumptions. Namely the assumption that the current problems to colonization can be solved in a cost-effective manner.
The longest continuous length of time spent in what limited space flight we have is just under 440 days. Not to mention, all of it was spent in low Earth orbit. Once we go beyond that, we lose all protection from the Earth's magnetosphere.
Then there's also the loss of bone density due to lack of gravity. 1% per month is nothing to sneeze at.
We are not built for space travel. We are built to inhabit this planet. We have evolved to the conditions here.
And before you say that the generation ships will just fake gravity and have appropriate shielding. Where do you get that assumption? We can't fake gravity. We have a space station where they take 10 times the radiation as here on Earth because we can't even realistically shield that.
And then we get to "autonomous probes", the great handwave of people who think they can cleverly sidestep the "humans aren't built for space" issue.
Who builds them? For what purpose? What's our expected return? How can you justify the investment in time and resources to shoot into space, with absolutely no hope of even knowing there's a chance for a return on that investment until generations later, a probe that can at best return data.
And then there's the issue of it being an autonomous probe. Two words that hide a lot of other problems. A lot of other assumptions. One being that we'll have created an intelligence capable of running this thing.
In other words, the Fermi Paradox just assumes that all of these incredibly hard problems can and will be solved and that the solutions are logistically viable.
Basically there is not need and motivation for humans to colonize anything outside the Earth. It's just too far, too expensive and too uncomfortable.
Humans evolved specifically to live on Earth, to live somewhere else, they need to be severely altered. Now you just seeded civilization of another species, that might turn out to be confrontational or outright hostile. Why would you do that?
Too see how well this works out on the local scale see colonization of Americas.
> Basically there is not need and motivation for humans to colonize anything outside the Earth. It's just too far, too expensive and too uncomfortable.
There is definitely motivation. Some people want to colonise Mars. Not everybody, but likely enough people to make it happen. Elon Musk wants to make it happen, and while there is no guarantee he'll get his wish, I think he has a decent chance of succeeding.
And establishing a permanent base on the Moon probably falls into a similar category. Moon has certain attractions over Mars – e.g. much more feasible target for space tourism, as a near-Earth testbed for developing technologies that may then be deployed to more distant parts of the solar system.
If the US (or a US-led multinational consortium excluding China) establishes a permanent base on the Moon and on Mars, that would increase the likelihood that China would do it too, in order to prove themselves equal to the US. (In principle other countries might feel the same urge, but China is possibly the only country who feels that urge strongly enough, and has sufficient resources, to actually pull it off; the US policy of excluding China from space ventures also gives China a motivation that does not apply to many other countries with which the US is willing to cooperate.)
Whether there is a "need" – the boundary between "wants" and "needs" is a value judgement. People who want to colonise Mars likely have different values from people like you who don't see it as worthwhile.
It's certainly possible that we might visit Mars, but colonizing it just isn't possible within the foreseeable future, certainly not within Musk's lifetime. We're not even close to having the technology necessary to survive that kind of journey and the engineering, logistics and medical science required to actually start a colony is far beyond anything we are currently capable of.
I personally love space and aviation stuff. But, as economies become more efficient and global, it’s increasingly unlikely that it will be possible to finance such projects. See: people haven’t been on the Moon for 50 years, Concord haven’t
flown for 20. Both projects have been financed through relatively undemocratic, non-market means.
> Basically there is not need and motivation for humans to colonize anything outside the Earth.
Our current gas emissions would disagree.
Also, asteroids, gamma ray bursts, curiosity, sheer ambition, etc, etc.
The thing is: we don't need to convince all of mankind to colonize another planet. All it takes is a few people. Crazy rich Mr. Musk is one example. He may not be able to achieve it, but maybe all we need is a few other Musks in the next generations and suddenly we'll be in other planets.
If Musk sent out a generation ship he'd die onboard and his grandchildren would turn the ship around to visit the mysterious alien planet they've heard tales of known as "earth".
I don't see any scenario where a generation ship can plausibly be expected to colonize another planet.
While at first it might seem that Mars or any other planet is the solution to our environmental problem, the easiest solution to the problem would be fixing this planet. Colonizing Mars would take up so many resources that fixing Earth might be more cost-effective.
Going fast in a straight line with conventional rockets is achievable, just not very timely.
Bending spacetime enough to make a difference — even just to the time taken between here and Alpha Centauri — is beyond any known mechanism humans could build, even in principle, using the total resources of our entire solar system.
(Using unknown mechanisms: perhaps, but they’re unknown)
> Going fast in a straight line with conventional rockets is achievable, just not very timely.
A constant-acceleration spacecraft could reach the opposite side of the galaxy in 24 years ship time. (That'd be over 100,000 years of Earth time, however.)
Conventional chemical propulsion don't have high enough impulse to do that. Possibly some kind of nuclear or matter-antimatter propulsion could?
> When it comes to [high thrust, high specific impulse] propulsion systems we might actually be able to build in the near future, the list includes Orion drives, Zubrin's nuclear salt water rocket, and maybe Medusa.
There have been many studied variations of Orion. Atomic Rockets cites hypothetical Isp between 3,000 and 12,000 seconds. Vehicles with delta-V of up to 100,000 m/s have been proposed. These could definitely be built, and would definitely work, but would require constructing, co-locating, launching, and detonating thousands of 5- to 15-kiloton nuclear explosives.
Medusa is basically Orion crossed with the image of a sailor blowing into their own sails. A huge parachute is deployed in front of the spaceship, and the nuclear explosives are detonated between it and the bow of the spaceship. The parachute can capture more of the explosive output than Orion's pusher plate can, it weighs less (because all of its members are in tension), and it can use its rigging's elastic properties to dampen the intermittent thrust, as opposed to Orion's (heavier) hydraulic dampers. The proposal study for Medusa (which assumed thirty 25-kg explosives) came up with an Isp of 106,220 seconds, and a delta-V of 4775 m/s.
The Nuclear Salt Water Rocket assumes plausible (but completely untested, so maybe impossible) continuous nuclear fission in a stream of uranium-salt-y water being sprayed into the combustion chamber. Assuming that this can be made to not blow itself up, 20%-enriched salt nets a theoretical Isp of ~7,000 seconds, and 90%-(weapons-grade) enriched fuel, with somewhat more optimistic efficiency assumptions, has a theoretical Isp of ~400,000 seconds and a delta-V of 10,000,000 m/s.
There are also lots of other currently-less-plausible proposals for high-power high-efficiency rockets. (Many of them assume things like efficient proton-proton fusion, which might be possible, but we have no idea how to do it.) Atomic Rockets is a great website for reading about these.
My takeaway is that it's almost certainly possible to build spaceships that can travel at >0.01c, but it would take a great deal of resources organized by a society that is more trusting and responsible than we are now. After all, any vehicle with that kind of power is also an equally powerful weapon.
Everything would run out of fuel over that distance if you were constantly accelerating ahead [0], but you don’t need to constantly accelerate in space.
[0] spinning is accelerating, and you can do that forever, but it won’t help you get anywhere
We still need to leave a heck of a collection. On a living, evolving planet if all civilizations are gone the signs get wiped out pretty fast in geological time (geology, weather), and in space the signs are usually traveling in the emptiness with little chances of being spotted. The best probes will eventually fail and will just add to the countless objects floating never to encounter anything.
I know it sounds depressing but I keep getting reminded of this [0] when thinking of loneliness in the universe. It's the most apt description I came across in recent memory.
On the other hand, large objects made by us on the Moon could last for 100's of millions of years. Especially if the object was designed to last that long.
> Humans have been civilized for only some tens of thousands of years,
That's giving humans a lot of credit. Civility has been regressing. I would be embarrassed for another civilization to find us now. Sure, we may have more technology and scientific understanding, but how we treat one another needs another world than civil.
"...first use in English is attributed to Adam Ferguson, who in his 1767 Essay on the History of Civil Society wrote, "Not only the individual advances from infancy to manhood but the species itself from rudeness to civilisation".[14] The word was therefore opposed to barbarism or rudeness, in the active pursuit of progress characteristic of the Age of Enlightenment." [0]
“... in the anthropological sense of the word.” -me, just recently.
If you are wondering where we might find a definition matching that sense, try the first sentence of the article you linked:
“A civilization (or civilisation) is any complex society characterized by urban development, social stratification, a form of government and symbolic systems of communication such as writing.”
Given the relative age of planets and stars, other alien "civilizations" would be hundreds of millions or Billions of years older than us.
The notion that we'd all be roughly at the same level of advancement is statistically impossible pop-sci-fi fantasy.
In my opinion, it's unlikely that they are even organic individuals anymore. Even the separate alien "entities" might have a process of merging once they achieve a certain advancement.
> They've been around longer than we have and take up more of the planet.
It looks like that to us, because our influence is visible over 80+% of the ground, but there's fungus IN us and covering more surface area than you can see. Imagine anywhere there's water (including from the air and including the oceans), there's fungus over a % of the land and organisms that you can see with a microscope. Fungus influence covers far more of the surface.
Yup, life as we know it wouldn't even exist without their decomposition abilities. Dead stuff would pile up, nutrients wouldn't be recyled, beer wouldn't exist. A world without beer just wouldn't be worth living in.
Fungi are very much overlooked, their role in forests alone is amazing let alone everything else they do.
If someday, some scientists discovered some kind of conscious fungal intelligence, i would not be surprised.
In some ways, then, we are 'alone'. Sure, there may be intelligent life out there, but the vast differences in biology combined with the likely vast differences in technology will render us 'alone' all the same.
Just like a goldfish in your apartment. To you, you are alone, goldfish don't count as company. And to the goldfish, it is alone, as humans don't count as whatever a goldfish thinks a friend is.
Using some rough numbers like the distance between NYC and London vs the distance from Earth to Alpha Centauri the equivalent would be saying that Voyager 1 is about 1.8 Miles into a 3470 mile journey (from NYC to London).
This is a fun story for a Friday evening. If we peg the beginnings of intentional electromagnetic emission from our planet at 1900, then by 2226 all of these stars will be able to "receive" or potentially detect, non-random emissions from the planet which will scale exponentially both in power and in frequency.
Those stars that are currently between 50 and 70 light years away will be experiencing our "golden age of television" about now.
Perhaps it would be useful to have a SETI project that focused on EM emissions to see if any of them have started transmitting. It would be hilarious if the first reception from an alien civilization was "Who shot JR?"
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Given that life only appeared once on earth in 3.5 billion years on Earth, the Milky Way is around 14 billion years old, we don't really have a good reason to believe there were more than a handful of abiogenesis events in the history of the galaxy.
Of course, its possible this is completely wrong, perhaps the Earth was completely unlucky, or perhaps there have been many abiogenesis events and they have just failed for whatever reasons.
Is "life only appeared once on earth" an accepted fact at this point? There was clearly at least one occurrence that led to a subsequent successful reproductive pattern from which we evolved, but prior to that, or alongside that, it strikes me as pretty unlikely that we would be able to discover other fleeting abiogenesis events.
We just discovered new salivary glands in human heads. Organs. Not microscopic ones. They are in our actual heads that we are walking around with and we just found out about it like a week ago.
So, forgive me if I am a little skeptical of our ability to find hard-to-find things. Some stuff is... hard to find.
No. We have a Last Universal Common Ancestor, but that says nothing about whether or not there were other independently-formed branches that were competing at the time.
My personal opinion is that life under early Earthlike conditions was/is almost a guarantee. There is compelling evidence that life already existed in and survived the Late Heavy Bombardment- that's very early in our planet's history. If it was truly a rare event that sparked things off, I would expect it to have occurred much later in the planet's history.
> My personal opinion is that life under early Earthlike conditions was/is almost a guarantee. There is compelling evidence that life already existed in and survived the Late Heavy Bombardment- that's very early in our planet's history. If it was truly a rare event that sparked things off, I would expect it to have occurred much later in the planet's history.
That is valid of course, but in the absence of evidence of its existence, the default assumption should be its unlikely.
Hmm, I'm not sure that that's correct. If you build an apartment block and it catches fire the week afterwards, then it's perhaps not reasonable to expect that if you build another one to exactly the same design it will never catch fire. At that point you might want to be reviewing your wiring plans.
That life showed up so early says... something. If life showing up was so fantastically difficult, we would arguably expect it to be later in geological time.
Sure, but if you look at an extremely old building and find signs of fire only from its very early age, it's somewhat strange to say that it was very likely to catch fire.
Still, until we find such life, the default assumption should be that it doesn't exist, and so that abiogenesis is an extremely unlikely even, even on Earth.
I imagine it's much harder for life to develop a second time once there's already life present. So I'm not sure how that affects your 3.5 billion time window. Prior to life appearing on Earth, the planet's conditions may not have been suitable. It may be that life appeared as soon as possible once the conditions allowed for it and that life developed to become so good at taking up available resources needed for life that new instances of life could not come about.
That only makes sense if we imagine life appearing in a primordial pool. But if abiogenesis were a common event on Earth, life should have formed all around, at distances far too large to immediately consume other proto-life forms. I also find it hard to imagine that, had this been a common event, a single strain of life should have resisted all the way to today.
Of course, until we manage to reproduce abiogenesis or find other examples of life, we won't know for sure. But I would say the theory with the least amount of assumptions right now is that life only appeared once in Earth's history or at least in one single relatively small place.
Why would there be multiple abiogenesis events? It seems once life evolves it can survive a lot and has all extinction events. The fact life occurred almost immediately after it formed suggests abiogenesis is common and more the rule as opposed to the exception. Multicellular life on the other hand could be much rarer since it took billions of years to happen.
If abiogenesis is common, we should expect it to keep happening everywhere around us. We should have noticed at least a few instances by now, given that we have been trying explicitly to produce it.
So at the very least, we can say that the conditions for the apparition of life and the conditions for the proliferation of life seem to be quite different.
Also, given the amount of isolated biomes on earth, if abiogenesis had ever been a common occurrence, i think we should expect for there to still exist some survivors of those other events.
The entire planet is coated with bacteria and bacteriaphages. It's entirely possible that any new life created through abiogenesis is almost immediately outcompeted by evolved microbes.
In today's world, perhaps, but it must have taken vast amounts of time until the first bacteria covered the planet. If abiogenesis were a frequent event on the early earth, there should have been plenty of space for more than one lifeform to survive before life became ubiquitous. And of course it's possible, but it shouldn't be the default assumption either.
What would abiogenesis even look like today? Some random molecules bouncing together in just the right way and spontaneously forming some organic compounds. And then a bacteria comes along and eats it, or it encounters the huge concentration of environmental oxygen and reacts.
Going from inorganic sludge to life isn't "an event", it's multiple events over millions of years until the right chemicals get together and form something that can reasonably be called "a thing" that can even be alive. It only makes sense for that process to have happened once, because the resulting life would have outcompeted any future proto-life.
Sure, that's a plausible account. However, they would only compete if they appeared in a pretty small geographical area. That still leaves it as being a relatively singular event. Maybe much more than once in a few billion years, but still much rarer than many seem to assume.
I would also note that we don't really know of any mechanism that would require millions of years for chemical reactions, or any equivalent of the theory of evolution that would work for hypothetical complex organic substances. Not to say that either is impossible!
> Given that life only appeared once on earth in 3.5 billion years on Earth
So, one theory is that once life shows up it tends to suppress protolife.
If it is hard for life to show up, then it is arguably very suspicious that it apparently did so so soon (in geological time) after conditions were suitable for it.
I always wondered if they could see us, would they recognize us as something to care about? I see ants on my porch, but they don't really matter much to me.
Idk, there are still people that study ants. Both professionally and as a hobby. Just because you don't care doesn't mean someone doesn't. I don't know why the same wouldn't be true for aliens. Unless those aliens are ant like (hive mind...ish)
What percentage of ants that exist are studied? They absolutely study some, but the vast majority of ants won't ever be acknowledged by a human. That seems like a relevant factor here if the assumption is that humans are like ants in both interest level and commonality in the universe.
Not to mention there are endless number of nature documentaries on Ants. If ants were not interesting then the National Geographic channel wouldn't have ant documentaries as often as they do.
I'm not sure I like this line of reasoning because it implies that the ants aren't aware of us. Certainly they are in some cases. Ants are able to physically perceive us. So if aliens aren't using some means of passive remote sensing to study us then I don't see why we wouldn't also notice them (though they may have good reason to not use active means). Sure, the ants aren't aware of what why we're hanging out around them, but they are aware of us.
When you live to be a billion, you probably study ants just to have something better to do than bitch about joint pain.
And having seen many, many, many ant hills, specific ones with slight odd variations unnoticed by people who are merely a million years old would stand out like a flashing neon sign and you would be all "Hello! What, pray tell, is this?!" while everyone looked at you funny because they lack context.
Most ants are benign. Some ants will eat your house. We have the technological capacity to make our own planet uninhabitable to humans and perhaps to any kind of life if we tried hard enough. We could probably do pretty nasty things to planets in other star systems if we were sufficiently motivated to do so and weren't in any great hurry.
An advanced alien civilization might see us not as threatening per se but rather as a potential problem they have to manage somehow and not just ignore.
If the planet is in the habitual zone for a given star with H2O then there is a biological chance some form of life exists. The evolutionary cycle for advances species development on the planet is the question. The human race did not evolve in a few million years. If there is a living advances species they could be very primitive compared to humans or much more advanced. There are so many variables that even science has not fully developed to come up with a plausible answer.
I'm pretty convinced at this point that it's incredibly unlikely that there's anyone around us to hear us. A lot of people have put a lot of thought into this. I'd suggest starting here [1] for an overview.
Indeed. It seems incredibly unlikely that another civilization would arise so closely in time to our own that it hasn't either collapsed or expanded to fill the galaxy well before our own development.
According to a talk I went to we don't have the tech to pick up our own signals. In other words, we started putting out singnals ~100 years ago with radio and then TV. If we were even at Alpha Centuri, our current equipment could not pick up those radio/tv signals.
my sci-fi perspective is practically on the side of charitable, but in essence more like disinterest.
in less than a century we went from heavier than air flight, to satellites, moon landings, mars probes, et al. and now we're talking seriously about terraforming mars and becoming interplanetary? it could turn out to be ~150 years from the invention of the lightbulb to people on mars.. insane.
another century or two of progress and that spacefaring civilisation, and their tech, will look nothing like 99.9% of the speculation. and may even look nothing like us lol.
so given the amount of time it takes for a ball of dirt to churn out meat computers, and how long it takes them to start making neil armstrong figurines. it would be reasonable to assume that all the other aliens are a few years ahead or behind us.
it is not easy to picture the kind of mind bending spaceships they might have because, for example, for us they are still being thought of as spaceships.
ex. you have to really think about what the internet is to not take the logical route and say that it's just copper, fancy glass and radio-waves.. it's actually extremely weird and magical. we have loads of stuff that is incomprehensible to our ancestors, and it's just going to keep going.
of course in this hypothetical universe, i assume that time creates consciousness and benevolence. which may not be the reality. but if it's true, and that advanced civilisations exist all around us and are enormous, magical realms of impossibility, then we will never see them because they are incomprehensible to us, and to them we are a curious entity which share some similarities to their own history – if that's even something that they still posses.
Unfortunately, yes. The first thing we’re going to do as soon as we fine intelligent alien life is figure out how to kill it. And sadly we’ll have to assume they’re doing the same.
An no, settling Mars won’t help. If someone / something can launch an interstellar attack it can certainly attack more than one planet and moon.
I have a far more charitable theory. The vast majority of human and alien life would want to be friends (or at least just leave their neighbors alone). It’s the elites who desire to destroy each other.
I also have a less charitable theory: intelligent life just doesn’t exist. A thousand years from now we will have met dozens of sentient species, but the search for intelligent life continues :P
>“For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons.”
― Douglas Adams, The Hitchhiker's Guide to the Galaxy
Universe is huge. Wars on earth are waged over scares resources. If we are capable of reaching aliens would we really be incentivized to fight them while there are so many resources available elsewhere?
The amount of resources some society can gather increases with the square of time and linearly to its expansion speed.
But life around here has an habit of expanding everything (including resource usage) exponentially with time.
There is a mismatch here that you are implicitly claiming that is solved for every space-faring civilization. Many people explicitly make this claim, what is reasonable, but it's not good to keep it implicit.
In the early years, sure, no problem. But conceivably the pace of resource utilization will increase as well. Eventually they will conflict. Worse, greedy civilizations would probably be selected for.
And how long before random differences and exponential growth mean the other side gets an overwhelming power advantage? Historically in human societies, that is essentially never a good thing.
Maybe civilisations will merge. I just had my double LOR'xin with extra pumpkin spice. Later I will resume work on my ansible station for the Y'norxa-Wallmart Corporation… hopefully I can push some lines of lox-lang to production today.
Or just defensively. The US invaded Iraq because they might have had WMDs. Other planets might have WMDs too. And they might think we have WMDs. Doesn’t matter if any of the sides actually do.
This seems likely; both sides might see it as a prisoner's dilemma situation, where there isn't any basis for trust and it's safer to destroy the other civilization before they're destroyed themselves.
(I don't think Iraq was actually such a situation, but at least on the American side some influential decision makers may have believed that it was.)
On the other hand, you might have something more like a cold war situation, where both sides have the capacity to destroy the other completely or almost completely but not without an equivalent counterattack, and so both sides have much more to lose than to gain by striking first.
Habitable planets are the ultimate scarce resource. Once the earth is full we’ll have to find a way to move and there’s less than 5 good options in this solar system. In time they’ll be full too.
Not at all, first our population will never exceed 11 billion, and most developed countries are in a demographic crisis. There is no sign of this trend reversing anywhere.
Second, what does 'earth is full' even mean? We have vast swaths of 'useless' land, like arctic and desert. Cities/towns/anything cover like
1% of the world. It is easier to desalinate water / build cities and greenhouses in deserts than it is to move people to another planet. We could host a lot more people if we adopted some serious geoengineering and built greenhouses /ate less meat.
Thirdly, travel to another star system requires insane amounts of energy, and could only be done by civilisations that already have enormous space infrastructure and industry. In which case you build habitats like we build skyscrapers, you can terraform, etc. In that case you don't need or want to ship billions of people to another star system.
> Habitable planets are the ultimate scarce resource.
Are they? That was once a common belief, but recent results in extrasolar planet searching would tend to contradict it, or at least cast it into serious doubt.
> Once the earth is full we’ll have to find a way to move
Will we? It's quite possible we'll see humanity's maximum population within the next century. Malthusianism didn't really survive contact with modernity; it turns out that most people don't particularly _want_ to have fifteen children, and as countries develop their population tends to become self-limiting. Wholesale emigration off earth feels like a very unlikely solution to population pressure, especially given that society seems to be automatically solving it.
And if we have the energy to lift billions of people off earth, we also have the energy to massively increase population density. Food, in particular, is ultimately largely a question of energy; we typically grow it in fields today, but given super-cheap energy there are other options.
If we've got the technology to travel between stars, we've probably also got the tech to leave planets behind entirely, or to terraform, or to adapt ourselves to conditions.
The only logical path is to download our brains onto computers, which will happen before that point. Once that technology exists, that's the only form of life that will dominate. Robots, nano-machines and hyper-intelligences will blow easily damaged flesh with finite lifespans. Habitable regions would be massively expanded.
I'm recently (as in last night) starting to question the likelihood of life forming at all.
I'm wondering how well we've nailed-down just what life is and how well we grok it's origination process. Cursory reading suggests we're still working from educated theory.
There's gotta be a sci-fi book about this but what are the chances that another civilization already went through the singularity? Is that even possible? How would that change things?
I struggled with that too. Here's my mental model, which may or may not be relevant.
Imagine you're holding a penny directly in front of your eyes, between you and the sun. It can do a pretty good job of blocking the sun for you, because it's so close, but no one else is impacted.
Now move that penny a few hundred feet up. Now it's almost imperceptible, but far more people (technology permitting) are capable of spotting it.
Let’s say that you need to be within, say, 1 degree of the ecliptic. The height of that ring is much greater at 100 ly than at 1 ly, meaning more space for stars.
I was translating 'direct line of sight' as 'parallel enough to our ecliptic plane to see the Earth occluding the Sun'.
> Every star within 1000 light years is in a direct line of sight to every other star.
There could be space crap in between. - Of course I just realized something obvious. Along our PotE lies most of our solar system debris. Shouldn't that be obstructing alien views?
Excepting highly tilted orbits or unusually clean solar systems, how are we seeing exoplanets at all? Is there a sweet spot, just a bit above the plane, where observable solar occlusion still occurs?
> There could be space crap in between. - Of course I just realized something obvious. Along our PotE lies most of our solar system debris. Shouldn't that be obstructing alien views?
Space crap is a lot less dense than you might think. Generally speaking, flying through the asteroid belt edge on looks like... well, just flying through space.
Turn it around: the space crap doesn't really prevent us from getting good views of Jupiter, Saturn, etc. Right? And it wouldn't prevent us from seeing Mars or Venus if they were outside of the belt either.
The total mass of the asteroid belt is estimated at something like 5% of the Moon's, and a third of it is accounted for by Ceres alone. It's spread pretty darn thin.
The Kuiper belt is much more massive, but is spread out even more thinly. Same again for the Oort cloud, where the average spacing between comet-sized bodies is about the same as the distance from Earth to Saturn.
A favorite quote from a relevant reference work: “Space is big. Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”
I’m not an expert but I don’t think this is true. The dark streak in the Milky Way (the “Great Rift”) is actually dust clouds that obscure our view of stars.
Think of the zone they're talking about as a disk: the plane of Earth's orbit, extending out to the maximum distance where the transit is still considered detectable. Most of that disk's area is far off, towards the edge; little of it is near.
If you're at a horse race, is it easier to discern the horses are running in circles from the sidelines, or from the bleachers? How about an overhead drone?
This very instant? I suspect not well. But conceptually? Yes. If we made a space based telescope that could do IR-visible-UV spectroscopy with decent resolution/sensitivity we would be able to get some information about the chemical make up of the gasses on planets transiting their stars.
Much like the kerfluffle about phosphine on Venus, there are some compounds you just wouldn't expect from strictly geologic processes. Molecular oxygen comes to mind, but also some complicated shortish life time compounds would imply industry maybe. If we had /really/ good sensors we might even be able to spot the isotopic differences, it's been awhile since I've looked into the capacity for spectroscopy, but since the masses are different, the vibrational modes should be different, resulting in different spectra. We could conceivably spot if weird isotope distributions were in their environment, if it differed wildly enough from their suns make up you might be able to make the case that weird non-geologic nuclear reactions were taking place.
The reason the astronomy community is excited about the James Web Space Telescope is that it can do a few of these investigations.
My hypothesis is that, if given a (simulated) spectroscopical observation of Earth's atmosphere from a distance, astrophysicists would come up with plausible non-biological, non-industrial explanations for it.
Empirically, we've just had our first occurrence of astronomers not being able to explain a compound in a planet's atmosphere, and it's something much easier to deal with than a massive amount of oxygen.
I think they would settle on the opinion that any explanation would be about as interesting as life. But not fully settle on life.
Would fluorocarbons be detectable in a remote spectrogram of the atmosphere at the levels they existed in the earth's atmosphere? Would the depletion of ozone in the atmosphere be more visible?
From [0] it looks like CFC's peaked on the order of 1 ppb. Humans (perhaps) just detected phosphine at the level of ~20ppb in Venus's atmosphere through telescope spectral analysis [1], but that's on a very close planet that we've been staring at intently for 4000 years; presumably there are compounds present in smaller concentrations that we haven't seen yet. Is there a heuristic for the hypothetical minimum sensitivity relative to interstellar distances?
It's currently possible to detect the atmosphere of some exoplanets. The presence of oxygen would be a pretty good indicator that photosynthesis is happening.
I always thought maybe the reason we don't see life in the surface of other planets is because of security/defense reasons. Why wouldn't they be cloaked? Isn't it a bad defensive position to just live out in the open like we do?
(a) to the best of everyone’s knowledge it is impossible to hide your heat signature in space, let alone hide the shadow of a planet blocking the light of its star (metamaterial cloaks are far too frequency-specific)
(b) the biosignatures we’re looking for right now are anything out of chemical equilibrium, so a planet-dwelling civilisation would only hide from us if they wiped out their surface and ocean ecosystems at the very least
No, it is pretty horrible of a browsing experience with adblock turned off, a video pops up in the lower right, a gigantic banner pops up - for me it was Oculus Quest 2 purchasable at Best Buy - there was no question presented to me about Cookies as I am in California so that was strange, and now the data brokers have my whole profile yet again.
Let alone recognize another savage on a different continent who might be doing the same experiment.