The human race is spread through the inner Solar System.

Technological and scientific progression is thriving, but we still haven't developed FTL travel, research has its focus on developing a device similar to a dyson sphere.

So, travelling from planet to planet is a safe journey, but it's still a long one.

Artificial intelligence is very developed, and robots almost have unique personalities, but humans still have a work life and most work related machines are relatively archaic.

The Moon is colonized, and so is Mars, and Venus has a number of floating colonies in its atmosphere. Mining colonies exist in the moons of Mars, and many more in several asteroids.

Colonizing the outer Solar System is still a challenge; resources and distance are the two important factors to overcome.

I'm interested in hearing what you think: what is a "realistic" year for this to take place?

  • $\begingroup$ Your second paragraph looks like joke in comparison with rest. There's no sense in Dyson stuff if you have nicely developed fusion power, which should be much easier imo. Also what FTL if you don't have sublight... $\endgroup$
    – Mithoron
    Dec 28, 2015 at 0:05
  • $\begingroup$ A dyson sphere would solve all humanities problems, including the ceassing of work, except for the maintence of the sphere and related systems. To evolve in the Kardashev scale a dyson sphere is probably one of the few things we can do when we think about the evolution of the technology we have today. For example, FTL travel is something that might never happen, because it does not depend on technology it depends on a scientific discover that might or might not happen. Colonization, interplanetary travel and sustenance on other planets and solar energy storage are realistic extrapolations. $\endgroup$
    – SOL
    Dec 28, 2015 at 4:21
  • $\begingroup$ worldbuilding.stackexchange.com/questions/8993/… $\endgroup$
    – Mithoron
    Dec 28, 2015 at 18:09

5 Answers 5


A pessimistic answer? I would argue that it's never.

The Drake Equation describes the number of extraterrestrial civilisations that we expect to detect by radio communications.

$$ N = R_{\ast} \cdot f_p \cdot n_e \cdot f_{\ell} \cdot f_i \cdot f_c \cdot L $$

N is equal to the mathematical product of

(i) the average rate of star formation, $R_*$, in our galaxy,

(ii) the fraction of formed stars, $f_p$, that have planets,

(iii) the average number of planets per star that has planets, $n_e$, that can potentially support life,

(iv) the fraction of those planets, $f_l$, that actually develop life,

(v) the fraction of planets bearing life on which intelligent, civilized life, $f_i$, has developed,

(vi) the fraction of these civilizations that have developed communications, $f_c$, i.e., technologies that release detectable signs into space, and

(vii) the length of time, $L$, over which such civilizations release detectable signals.

The fact that we have never observed any other civilisation transmitting into space implies that the expected value of $N$ is under one. Assuming spacefaring capabilities exist and it is possible for civilisations to spread across planets, we should have been visited by aliens already. This is known as the Fermi paradox.

Considering that a civilisation that manages to get off a planet and manages to not destroy itself before should manage to transmit significant amounts of information into space (and therefore be detected) as well as physically visiting most of the planets within known space, one explanation for the reason nobody has ever received an alien transmission is that all civilisations destroy themselves before managing to spread to new planets.

This is a pessimistic but plausible way to resolve the paradox.

  • 3
    $\begingroup$ I know a lot abou the Fermi Paradox, it's a theme that really interests me. But it has absolutely nothing to do with colonization, it has to do with the possibility of extraterrestial lifeforms. Colonization of the Moon, for example is something that it's possible right now if all resources and money were wasted on it. $\endgroup$
    – SOL
    Dec 27, 2015 at 10:09
  • 3
    $\begingroup$ The fact that we have never observed any other civilisation transmitting into space implies that the expected value of N is under one. - Really, this only implies that we have crappy observational capabilities. We only know of a relatively small number of exoplanets, while there must be many, many more. $\endgroup$
    – HDE 226868
    Dec 27, 2015 at 14:40
  • $\begingroup$ Agreed. Space is a vast expanse, and we can only monitor a fraction of the night sky for radio communication at any given time. And even if we're listening in the right spot at the right time, we have to be listening for the right thing. $\endgroup$ Dec 27, 2015 at 20:25
  • 1
    $\begingroup$ I think the Fermi Paradox is very important. I find it hard to imagine a long-lived interplanetary civilization that doesn't colonize the stars. Someday some misfits are going to decide to leave. Orion can boost a slowboat. If there are ETs out there we should see them. $\endgroup$ Dec 27, 2015 at 22:45
  • 1
    $\begingroup$ @TheAnathema Sure, you'll go for the closest suitable planet. Those at the edge of the civilization will sometimes find the closest suitable planet being outward. It doesn't matter--you can model it with slowboats and millenia between colonization and sending out a colony ship and you still colonize the galaxy in a very short timespan in comparison to the age of the universe. A starfaring ET that evolved 1% earlier than we did should already be here no matter where in the Milky Way they started. $\endgroup$ Dec 29, 2015 at 23:41

From a technical perspective, this could have been done a long time ago. "Das Marsprojekt" was a fictional vision of a Martian voyage written in the early 1950's based on the technical and astrophysical knowledge of the time, written by Wernher von Braun. The visuals in the movie "2001: A Space Odyssey" were based on a relatively straightforward extrapolation of the 1960 era space program. Even today the ISS could be considered a long duration spacecraft that is missing an engine.

What is actually missing is the economic justification for colonizing space. While there are compelling non economic reasons to go (escaping from persecution and settling new worlds to carry out your social, cultural or religious ideals are well known motivators), even the Mayflower pilgrims were sailing on a commercial vessel (and the design was refined over centuries to allow for long distance commerce). Without commercial motivation, building the vessels and refining the designs to create cost effective transports isn't going to happen.

Unfortunately, while there are resources in space, there is a sort of chicken and egg effect. It is cheaper to gather water from an asteroid to refuel your ship, but unless you are planing to travel to an asteroid, there is no justification to develop asteroid mining to gather water to refuel your ship. And if your ship is the only one (like an Apollo mission), then the costs associated with mining and water extraction make no sense at all. Other Mcguffinite solutions like 3He (Helium 3) for fusion reactors only works if you have working aneutronic fusion reactors to fuel, and extracting hydrocarbons from Titan for export to Earth makes no sense at all from any economic or energetic point of view.

So unless there is some sort of economic justification to going to space on a regular basis to develop reliable spacecraft and drive costs down to the point where it becomes practical and economical to send people to colonize places (and to allow other people to piggyback on them to experiment with religious, social or economic systems, or to found business to do the service and support of the colony business, then the founding date will be a long way off. Since there is no way to determine what the McGuffinite will be or when it will be discovered, you could set an arbitrary date. On the other hand, since there are multiple reasons to go once it becomes practical to do so, and we do have a reservoir of technology to build from, settlement will be fairly rapid once it can get started.

  • 3
    $\begingroup$ The ISS is just 400 km away from us, there are regular crew exchanges and supply flights, it is protected by our magnetic field, and it is controlled from Earth. There is more missing than just an engine to turn it into a long duration spacecraft that can travel distances. $\endgroup$
    – his
    Dec 27, 2015 at 11:33

Pessimism was never my strong suit.
I think we will be colonizing Earth orbit with permanent stations and multiple daily shuttles running within the next century. From there, I think the many tentacles of human ambition will reach out into our solar system simultaneously. Settlement/bases on our moon and Mars will come first, but asteroid mining and planet-free colonies will happen in about the same time-span.

Greed is a powerful motivator. So let's see humans spreading out across everything this side of Jupiter within three hundred years.

It will be rough out there, and will make all previous human exploits seem tame by comparison. We will forget about the Wild West of our past and teach our children about the present Wild Expanse instead. Life above the atmosphere will be where the action is, and fortunes born in that darkness will dwarf the sum of all earth-bound enterprises.

Permanent colonies on the planets you've listed will take a little time, but deep colonization will follow the money. Venus will probably turn out to be a fuel producer, mining the ammonia rich atmosphere for volatile compounds and energizing batteries from abundant solar power. Mars might be a food producer, farming the surface in domed structures and easily boosting the produce into orbit for sale across the expanse. The environmental-freedom and resulting low cost to orbit will also make Mars a manufacturing and population center, where products can been produced and space-faring workers can get a little ground-time. The asteroids will of course provide water and metals, providing the most direct path to personal-wealth that humanity has ever known. As with historic pioneer efforts, the planets and other solar system locations will be colonized in the order that serve the economic interests of the colonists, and each new colony will take advantage of some attribute of its chosen location.

Somewhere between five hundred and a thousand fifteen hundred years from now, the solar system should look something like what you are describing.

That is not very pessimistic, as I don't foresee all the horses tripping during this single race. Certainly some countries will falter as we leap to space, but the beauty of living in a multi-national and multi-corporate world is that other powers will take up the slack whenever a front-runner stumbles. There is too much treasure waiting at the finish line to think that we will ever, collectively, give up the race.

Edited after reading several of the newer answers.

Boy, you guys are better at pessimism than I am!

@Thucydides has made a strong argument to the effect that the economic prosperity that I see in space, is going to be economically unfeasible due to the high start up costs and the idea that we don't really need the wealth of the solar system until we go out into the solar system. I'm not sure that that is true, but I will add a little incentive to get us over that hurdle...

Let's imagine that the global warming supporters are right and we see dramatic climatic change over the next century. Is it unreasonable to believe that humanity, finally respecting the fragile planet which sustains it, might choose to move all of polluting power-production and manufacturing into space? In order to restore our planet to proper function, we either need to give up all our planet-harming practices, or find another place to practice them. Space and the nearby planets are that place.

Many thanks to @MikeScott for helping me fix some errors in my original answer.

  • 2
    $\begingroup$ One thing Neptune definitely does not have is "abundant solar power". $\endgroup$
    – Mike Scott
    Dec 27, 2015 at 8:08
  • $\begingroup$ Why not? It is closer to the source than we are. You just have to put your solar panels above that murky atmosphere. $\endgroup$ Dec 27, 2015 at 8:21
  • 2
    $\begingroup$ I think you've got your local geography a bit confused. Neptune is thirty times as far from the Sun as the Earth is, and thus gets about 1/900th as much solar power. Only Venus and Mercury are closer to the Sun than we are. $\endgroup$
    – Mike Scott
    Dec 27, 2015 at 11:32
  • $\begingroup$ Good Grief! I was writing Neptune while thinking Venus the whole time! I will edit my answer immediately. Thanks! $\endgroup$ Dec 27, 2015 at 14:06
  • $\begingroup$ I edited my answer to repair mis-arranged solar system. Thanks @MikeScott! for politely pointing out my gaff. My avatar will be wearing the Copernicus hat today, for well-intention-ed but totally inaccurate solar system arrangement. $\endgroup$ Dec 27, 2015 at 14:28

We've got 3 major hurdles to clear, technology-wise.

Radiation Shielding

This is currently the big issue being talked about for future manned space missions. A lot of ideas are being thrown around, but no one has a totally great option yet. With slow travel of months to years in space, that's a lot of rads you could be soaking up. Maybe if we're lucky with all the push in material sciences, we might find some kind of nano material or something that works really well at radiation shielding without being too heavy.

Self-sustaining life support

Those months and years of travel without resupply means food, water, and oxygen are problems to deal with. Our attempts to create enclosed ecosystems have rarely lasted more than a few months before failing. I'm distantly optimistic we'll have a better shot at this with genetically modifying plants. (Since, we're probably going to have to do a lot of that for Earth anyway, in the next 100 years between topsoil depletion, desertification, rising water levels, and carbon reduction...)

Cheap Lift

The biggest hurdle is escaping gravity. We need to be able to get enough stuff up in space that can allow us to get to anything else, in order to farm those resources. The problem is that it's expensive in terms of money, manpower, and material resources.

We either need to find a way to synthetically make rocket fuel, cheaply, or find some physics-changing way to get to space. It needs to be cheap enough, and we need to have the whole launching process down, to where we can just do multiple launches one right after another, to get enough tonnage of gear, ships, people, resources, etc. up into space to start going other places.

Best guess?

So... assuming we manage to maintain our tech levels and not fall back under ecological collapse (which...is honestly optimistic given both scientists and military projections...), let's say 100 years to GET the science and the infrastructure to start getting up into space consistently with enough gear. We could get a moon base much sooner, but it will probably hold the same position that the ISS does now - good for research, but still needing a lot of regular re-supplies and not anywhere near self sufficient.

Maybe another 200-300 years to really colonize multiple other planets? Part of the problem is that collectively we're more likely to focus on working on one planet / space resource at a time. Each environment has such different problems to tackle, and it's easier to keep building on the lessons learned than to try to go take on completely new problems.

Colonizing space is absolutely NOT like colonizing other parts of Earth - instead of moving to a new land, or a continent, it's like digging a mine shaft and trying to live in it. You don't have food, running out of air is an issue, and the only things which you can get are valuable but don't necessarily keep you alive. (yes, we could mine ice, which gives us water, and we can crack it for oxygen and hydrogen, but how far are we gonna go for that? It also doesn't give you arable soil...)

Realistically, though, I'm guessing the next 200 years of human life are going to get really rough as our food and water ecosystems fall out of kilter and non-sustainable resources that push much of our technology run out. Ecologists predict this. The scientists working for big oil predict this. The scientists working for the US military predict this. That's going to put a massive crimp in us doing pretty much anything else when basic needs start to fail.


Pessimistic answer: never. We crash our civilisation and Earth's ecology with global warming triggering a permafrost melt and methane driven positive feedback loop. Optimist says some humans will survive. Pessimist says they never regain C20 technology because of resource depletion the first time around.

Greater optimism involves a technological singularity. Canned primates in space won't work. Robots containing intelligences derived from uploaded human beings might. They don't need to breathe and solar panels work better away from a wet oxidising atmosphere. Alternatively humans migrate into virtual realities in computer substrates in solar orbits.

Put any timescale you like on that. As Della Lu says, the only way to understand a singularity is to create one and live through it.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .