[buran77]

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.

[theandrewbailey]

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.

[krapp]

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."

[0]http://www.projectrho.com/public_html/rocket/alientech.php

[kfarr]

I like that quote but lately feeling like advanced tech doesn't necessarily mean angelic

[nkoren]

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...

[julius_set]

Cue the plot of Doom Eternal

[krapp]

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.

[zabardasth]

> And she took on another heart—no longer minded toward earthly things—but ecstatically in the angelic dialect, sending up a hymn to God in accord with the style of the angels. And as she spoke ecstatically, she allowed “The Spirit” to be on her garment.

It seems that speaking to one would be quite a terrifying experience, especially if one were speaking in tongues.

[krapp]

When angels are described in the Bible, it's often in strange and abstract terms, beings with multiple faces, legs made of burning bronze, eyes where eyes shouldn't be, etc. As if the writer was having difficulty comprehending what they were seeing,much less finding language for it. And the first thing angels do when they encounter humans is tell them not to be afraid, because of course the logical and proper reaction to skyscraper-sized interlocking, burning, eye-covered wheels with multi-faced, multi-winged beings in the middle is bowel evacuating terror.

And of course, many of Lovecraft's eldritch horrors were simply aliens that were so alien that the mere sight of them broke human minds, and that were no more concerned for humanity than humanity is for a particular anthill.

That's probably what an actual encounter with an alien is going to be like for us. We'll try to understand why a living infinite-dimensional hypersphere made of flesh made of time whose eyes are our eyes all at once just showed up and "unfolded" our sun into a non-Euclidean shape we can't even describe mathematically without being driven slowly to madness, while it won't even know we were there.

[vmception]

The fermi paradox does convey this.

[bena]

Not well. It makes the assumptions that all of the problems with space travel are logistically possible.

[deeeeplearning]

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.

[deeeeplearning]

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.

[Retric]

The Milky Way lacked rocky planets early on, making that 12.5 Billion year age largely meaningless.

Which is just one of many bad assumptions in how people do these calculations. At a minimum you don’t get a straight path from A to B. Assuming any kind of limitation in distance traveled and your at the mercy of the distribution of whatever resource you need. Aka need rocky planets with liquid water, that’s likely going to be an very indirect path. Even just non binary star systems is significant. Further, assuming every trip is successful is again unlikely. How long you need to wait before the next trip is again a major qualifier.

For example, what happens if they first send a probe to verify habitability? Suddenly travel times more than double.

I have seen plenty of optimistic calculations that still add up to over a billion years before total colonization and sometimes much much higher than that. And that’s a billion years where expansion is a major priority at the frontier. Look at successful colonizations that don’t expand rapidly and again things keep slowing down.

[sliken]

One effect not considered in early considerations was the differential radial speed. So even the ability to seed planets 10 light years closer or further from the galactic core over a few 100M years results in expansion much more quickly than earlier models.

[thaumasiotes]

> For example, what happens if they first send a probe to verify habitability? Suddenly travel times more than double.

This doesn't seem like a good idea if their method of traveling is generation ships. What would be the point?

[mylons]

If you used the Von Neumann machine approach wouldn’t it not really matter if the planet was habitable or not?

[tsimionescu]

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?

[Baeocystin]

>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?

Any freshly-evolved life would have to compete with organisms that have already been honing their survival strategies for literal billions of years. There's no reason to think such a thing is possible, and the lack of it doesn't speak one way or another to the difficulty of it happening in a virgin environment.

[tzs]

> 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.

For a generation ship, are you referring to all the machinery that can maintain a balanced ecosystem of plants and animals and humans in order to provide food for the people during the trip to the new planet, and to make all the things needed to keep those people healthy during the trip such as medicine and drugs?

If so, there may be a way around that. Send all your colonists as frozen embryos or frozen sperm and eggs. Your ship only needs life support then to keep alive the people who run the ship. For food, don't grow it. Take it with you.

At first taking your food with you seems absurd, but if you had a food with the same caloric density as rice, enough of it to provide 2000 calories/day to one human for 100k years would fit in a sphere with a radius of 24.4 meters. So once your technological civilization figures out a way to preserve food such that they can make a rice ball equivalent with a 100k year storage life, a generation ship with a small crew becomes a whole lot more feasible.

For replacement crew throughout the journey, you can do a mix of using whatever kids the crew produces the old fashioned way and using kids produced from some of the frozen embryos/eggs/sperm.

I think technological civilizations will reach the point of being able to do this well before they are millions of years old. We aren't too far from being able to do it ourselves. We are probably farther out on the propulsion for the ship itself.

[natechols]

I'm always fascinated in the assumptions underlying some of these proposals, and how little thought they've given to the problem. For example, the complete disregard for the lives or autonomy of the "replacement crew", who are effectively treated as a consumable resource starting from childhood.

Science fiction set on generation ships tends to be extremely gloomy for good reason.

[sliken]

Seems a bit silly, you can buy a glass sphere with small closed ecosystem that can last years with indirect sunlight. Surely we can manage something that recycles astronaut poop/pee into something vaguely edible with the help of bacteria, fungus, plants, and algae. Sure some genetic editing (of humans, bacteria, fungus, plants, and algae) might be necessary. Even just some minor tweak like happened in the last 1000s of years to make humans more compatible with cows milk.

[jcranmer]

> a sphere with a radius of 24.4 meters

A more human-sized comparison is "100 average single-family homes in the US, all filled to the brim with rice". Or 60 ISSes, all filled completely with rice. Per person. And this is volume, not taking into account the weight of rice.

Minimum sustainable population size seems to be about 100 people, so consider how large a ship you'd need just to fit all that rice storage.

[tsimionescu]

I am referring to all of the machinery on the ship in general - whether it's life support systems, engines, monitoring/navigation systems etc. Even if you could take a ship to outer space, freeze it to ~absolute 0, and launch it on its trajectory, you still need a computer to allow it to warm back up and land at its destination.

Keeping a computer running in outer space for a few thousand or hundred thousand years is a gigantic engineering task, far beyond anything we could achieve today.

And of course, in reality its unlikely you could rely on a single computer system and on 0 propulsion. It's far more likely that you'll need life support, engines, complex medical equipment, cooling systems, lights, all sorts of mechanical parts that will need power, replacements, and that degrade in time, especially at such huge scales.

[eloff]

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.

[e12e]

You have to make an assumption about speed - it certainly won't be more than a tiny fraction light speed. Eg voyager appear to travel now at less than 0.00006 c (16 km/s). Than turns 100k light years into ballpark 150 M year journey (no it doesn't its 1.8 bn years as mentioned in reply) . Still possible to cross 10.000 times - but that would be a straight line. I suspect the distances will grow somewhat fractally if you want to swing by any stars? (ed: so, not really very likely at all)

[Baeocystin]

To traverse 100k light-years at 16km/s would take approximately 1.8 billion years. FWIW.

[eloff]

To imagine that voyager technology will define the maximum velocity of interstellar travel, a thousand years from now, ten thousand, a million, etc is short sighted. Maybe we never can exceed light speed, but we could get up to a reasonable percentage of it.

[sliken]

There's current projects on earth seriously working on getting probes up to 1% of the speed of light. Just a small/light weight probe, a solar sail, and a large (but feasible) array of lasers.

[mistersquid]

> Than turns 100k light years into ballpark 150 year journey.

Forgive my confusion.

If 100K light years is 100K years at c, how can

> 0.00006 c

yield 0.00150K (150) years?

[tzs]

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.

[jcims]

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.

[Osiris]

This is an interesting idea. Look at how religion explains the origin of life: A lifeform not from this planet, far more advanced than us, gave "the breath of life", and calls us their "children".

The vastness of this universe leads me to believe that it's impossible to dismiss the idea that there is an intelligence/lifeform sufficiently advanced as to appear to be a God to us.

[jcims]

Totally agree. Joscha Bach laid out a few interesting ideas around this at the end of a podcast.

If you have a few minutes start here for a broader context (starts of wholly unrelated but with some great concepts):

https://youtu.be/P-2P3MSZrBM?t=10084

If not, he drills into it here:

https://youtu.be/P-2P3MSZrBM?t=10400

[psychoslave]

That doesn't explain where the said intelligence /lifeform would come from itself, so what the point of such a theory?

[sliken]

I read a short story that explained the explosion of life on earth during a very short period on some alien that didn't follow protocol and dumped some poop.

[marta_morena_28]

Possible, but far reaching. There are other explanations:

* We are a computer simulation (hence there is no colonization, we are in an experiment)

* There are like 1,000,000,000,000,000,000 habitable planets in the universe. Just because something is "extremely unlikely" doesn't mean that it didn't happen to us. I.e. whomever this happened to, would ask himself that question. We may just be the ones it happened to.

Also: Why would they settle species from millions of years in their own past. If they wanted to colonize, they could start with their own life-forms.

Could be several things as well:

* We are a genesis project and they will simply come back later and settle in what we left behind (i.e. they let the ecosystem build for a few million years before trying out this settlement)

* They don't want to create competitors

* We are a population bomb, i.e. they just sent out billions of probes trying to populate any given habitable planet, and they couldn't just spawn themselves there and instead had to start from somewhere where a sustainable ecosystem would derive from

[35fbe7d3d5b9]

> * We are a genesis project and they will simply come back later and settle in what we left behind (i.e. they let the ecosystem build for a few million years before trying out this settlement)

Depressing fiction idea: our progenitors return, look at what we've done with the world, shake their heads and leave us to suffer.

[nn3]

Keep in mind that molecular evolution happens at a massive parallel scale. If there's some simple recipe for basic evolving life it is very unlikely that is not being hit in a few million years by a large number of molecules and then primitive cells.

And it's unlikely that there is only a single recipe. Most likely there are many (just on Earth all the others died out)

[bena]

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.

What if they're not?

[deeeeplearning]

You talk like this is all expected to be done by 21st century humans when in reality if there were civilizations out there capable of doing this colonization they would likely be millions of years our elders and its incredibly foolish to try to guess their intentions or the capabilities of their technology. Your view is painfully anthropocentric.

Just to add, there are plenty of valid criticisms or plausible solutions to the Fermi paradox but I think you've failed to identify a single one.

[bena]

You talk like this is all a forgone conclusion. Technology is not magic. Time is not a salve that solves all issues.

You say that my view is "painfully anthropocentric", but how?

It seems your only response is "but aliens". That is not good enough.

You want to say that it is foolish of me to try and guess their intentions and capabilities, but that's what the paradox does as well. It assumes their intentions are to colonize and their capabilities allow it. With no proof. The only life we have to base anything off of is right here.

And if you think I haven't identified a single valid criticism of the Fermi paradox, then I'm just going to assume you aren't aware of the criticisms.

I've basically touched on this one https://en.wikipedia.org/wiki/Fermi_paradox#Economic_explana...

So no, I'm not saying that just because it can't be done now, it can't be done ever. I'm saying the Fermi Paradox is basically saying "Once you solve these incredibly hard problems, this becomes easy."

I think the Fermi Paradox is phrased wrong. It should state that if it were possible to colonize the galaxy, it would have been done by now.

[ben_w]

> We can't fake gravity.

Yes we can, it’s a standard part of fairground rides.

(I’ll agree that the unknowns of space colonisation, and of the automation we’d need to be able to afford the infrastructure to even launch a serious effort, may prevent such colony efforts from happening)

[bena]

Centrifugal force does mimic gravity but it's not really something we can do at scale or even in space. When we're talking about a generation ship, we're talking about something a little larger than the Gravitron.

Not to mention, they work within Earth's gravity. Take a tube and spin it around you in space, it does nothing to you because there's no other forces working on you. Nothing putting you in the frame of the spinning tube.

Once you lose the Earth, it becomes a lot trickier to tie you to a frame of reference. Nothing we can make has the mass necessary.

The best we could likely do is accelerate a ship at 1G. But that has problems, because about halfway through your journey, you have to start decelerating. And there's also the issue of turning.

[vl]

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.

[skissane]

> 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.

[root_axis]

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.

[s5300]

Musk has touched on the fact that it's nearly guaranteed to not be possible within his lifetime.

This is one of the reasons (he's spoken of) that he's having a decent amount of kids and also doing things like Neuralink.

[skissane]

Colonisation of Mars is going to be a long process. There is going to be a gap of decades (maybe even more than a century) between the arrival of the first settlers and the attainment of self-sufficiency (autarky, the ability to survive without continual resupply ships from earth). From my reading of Musk's various comments, he doesn't think it is likely he'll live to see self-sufficiency (autarky), but he certainly hopes that the arrival of the first settlers can happen in his lifetime.

[vl]

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.

[skissane]

> people haven’t been on the Moon for 50 years

They are supposed to be going back in 4 years time. That's probably going to be delayed, but still people will probably be back on the Moon before the end of this decade. And this time they are saying they plan to stay.

> Both projects have been financed through relatively undemocratic, non-market means.

So are LHC, ITER, the International Space Station, Project Artemis. The US is unwilling to spend the massive amounts it spent during the Apollo project on space right now, but it still spends a lot of money (NASA's budget is about 22 billion USD a year, and the military space budget is about 14 billion USD – over 36 billion spent on space every year) and has been pretty continuously since Apollo was closed down. It would have achieved more by now if it had been spending that money more efficiently. The advent of SpaceX and other commercial providers is changing that.

[dyingkneepad]

> 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.

The Fermi Paradox discussion is fascinating.

[vl]

While personal ambition is commendable, realistically for inter-stellar colonization this has to be planet-wide project.

> suddenly we'll be in other planets.

Who is “we” in this case, how does it affect you and me? (The point being is that such long-term projects are beyond current society capabilities)

[staticman2]

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.

[AndyPa32]

> Our current gas emissions would disagree.

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.

[psychoslave]

This is not Earth that needs to be fixed, it's human behavior.

Teraformation and space conquest are fassinating topics, but "fixing our behavior to avoid to fuck up the only accessible viable environment we have" is far from deserving only a mere "might be more cost-effective".

[dyingkneepad]

But way less fun :)

Or we could, you know, just transfer our consciousness to machines that can easily survive Mars and other environments and start our colonization after declaring ourselves to be Homo-sapiens-machina.

[anonAndOn]

While interstellar travel would be impossible using conventional thrust in a straight line, could you overcome the distance by bending space time?[0]

[0]https://www.nasa.gov/centers/glenn/technology/warp/gravstat....

[ben_w]

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)

[skissane]

> 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?

[avhon1]

Atomic Rockets has some good info on this.

> 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.

http://www.projectrho.com/public_html/rocket/enginelist3.php...

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.

http://www.projectrho.com/public_html/rocket/enginelist3.php...

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.

http://www.projectrho.com/public_html/rocket/enginelist2.php...

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.

[ben_w]

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

[beamatronic]

That’s why the best thing any species can do for the other species is to leave signs that we were once here.

[buran77]

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.

[0] https://www.theoatmeal.com/comics/oracle

[njarboe]

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.

[beamatronic]

I like the comic.

It's almost like all intelligent life in the universe was put into escape-proof cages.

We need to rage against this! Do it for all the others who can't.

[dylan604]

> 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.

[sbelskie]

I don’t think civility has a lot to with civilization in the anthropological sense of the word.

[dylan604]

"...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]

[0]https://en.wikipedia.org/wiki/Civilization

[sbelskie]

“... 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.”