I've loved science fiction for almost as long as I can remember, at first just watching old black and white movies like The Blob, Earth Versus the Flying Saucers and The Day the Earth Stood Still on Nightmare Theater, then eventually discovering books and never looking back. It's from that position of love that I'd like to challenge your thinking on one of our most powerful and enduring visions: humans colonizing and adventuring on worlds already filled with exotic alien lifeforms. I do think we will find them, I just don't think we will live on those planets.

I'd read plenty of science fiction before stumbling across Dune when I was a freshman in high school, but it was the first book that truly transported me to new and wondrous worlds. I was stunned by the vast and unforgiving desert world with its titanic sandworms, mysterious sand trout and the human Freman who had learned to live there. As I continued to gobble up science fiction, I grew to realize that my favorite fictional worlds are those that don't exist simply as an exciting backdrop for human adventures, but seemed to have a life and history of their own. So quickly added to that list were worlds like Harry Harrison's Pyrrus from Deathworld, where the entire planetary ecosystem acts as a rapidly evolving immune system to expel the human virus, the intelligent world Solaris and even the thread ravaged world of Pern. And like all fans of this greatest of genres, I was charmed, transported and awed.

But like the humanity portrayed in Childhood's End, we have to grow up. As our tools get better and we explore real alien worlds, we expand our understanding and sometimes learn that our exciting imaginary worlds don't often match up to reality. I remember watching for hours as space-suited astronauts constructed the International Space Station. This was science fiction made real. Humanity was building our first real home in space! Yet most of my friends, many of whom were huge space and science fiction fans, found the process mind numbingly boring. For the population at large, shuttle launches became no more exciting than airliners taking off, and even robotic probes reaching Ceres and Pluto were only momentary exciting news blurbs. Thanks to our amazing rovers and orbiting spacecraft, we found that with no canals, no Barsoom or ancient sandship-riding civilizations, even Mars has become boring to the average Joe.

Even taking all of that into account, some of us humans have to know what is out there. We want to see it. We are born to wander and hardwired to not rest until we see what is beyond the next hill. So if our civilization survives long enough, we will go. It's only a matter of when and where.

Statistically, considering the number of planets estimated in just our own galactic arm, Earth analog worlds should be out there, but as our human species matures and spreads through the galaxy, I suspect that reality or our needs will force us to bypass them for something more mundane and practical. Space is vast, so the chances of any of those worlds being closer than a hundred light years away are also statistically slim. That means first we will need to develop equipment capable of confirming all of the critical factors like atmospheric composition, liquid water availability, correct temperature range, mass and gravity range of planets that far away. This will probably require something equivalent to a huge optical interferometer array spread across the dark side of the moon.

Once we do find a candidate world, we have to get there. Baring the development of FTL drive technology, we'll have to rely on sub-lightspeed solutions like sleeper ships, generation ships or robotic seed ships that carry only the DNA needed to construct human colonists upon arrival. These methods are well explored in science fiction and are plausible means to accomplish the task, but they all carry the same inherent weakness: a need to build ships that can function reliably and independently in the cold, radiation-heavy vacuum of interstellar space for hundreds of years. This is glossed over in most fiction and might not sound like a serious problem, but my non-writing job is to help design mechanical systems for the military and I can assure you that it will be a big issue. Probably the best fiction I've read that addresses this problem is a novel called Exit Earth by Martin Caidin, published by Baen in 1987. The ark built in this story starts breaking almost immediately and becomes the potential colonists’ primary survival issue.

These are some huge obstacles to overcome, but I believe in human ingenuity and determination, so let's say we build ships with FTL drives or AI babysitters, controlling nano-scale robots that continuously refresh and rebuild the systems on a long haul ship, and stipulate that humans eventually arrive at a new extra-solar world teeming with strange and wonderful life. This is where I suspect we will deviate wildly from science fiction. We will study it of course, probably for centuries, but we won't colonize this world for several reasons. Primarily we won't need it for a place to live.

Long before humanity is capable of spreading through the Milky Way we will colonize our own solar system, but living on Sol's other planets isn't really a good option. Thanks to the earlier mentioned robotic probes, Mars, Venus and our moon have transformed from exotic worlds inhabited by mysterious and sometimes scantily clad aliens to the more familiar and uninhabitable dead or toxic hells. One of the most tired and overused tropes in modern science fiction is that we will need to find another world to colonize because an eco-disaster is rendering Earth uninhabitable. Let's say that the worst actually happens; our atmosphere becomes unbreathable, the ice caps melt causing sea levels to rise and swamp all the coastal cities and ozone depletion increases the radiation reaching us here on the ground. Even then, Earth will still be a paradise for human life compared to every other planet in our solar system. We would still have our protective magnetic field, the gravity will still be perfect, the temperature—even if we get an ice age or greenhouse effect—will still be better than any other planet in our system. Terraform Mars? Sure, we could do that, but it would probably take centuries to get a shirtsleeve environment on Mars, and even then radiation would always be an issue. But if we have the technology and resources to terraform Mars, then I suspect terraforming a sick Earth by shoving her environment back on track would still be far easier.

Of course humans are a stubborn and determined lot, so we will no doubt eventually build cities on Mars and Luna, probably other bodies in the solar system too, but they will not be easy or hospitable places for us to live. As a matter of fact, I suspect that these colonizing efforts will be hard lessons for us. Our best options for living away from Earth will be to build our own small worlds.

This will not be an easy or quick transition either, but it has the best long term potential. We're a race of engineers and are very good at modifying our environment to suit our needs. We've been doing it since we first overlapped pine boughs or animal skins to form a shelter to keep the rain out and heat in. Of course we don't always get everything perfect the first try, but we learn from our mistakes and make changes in the next version. Look at the design of automobiles as an example. A Tesla sedan is an entirely different animal than the Model T Ford, but they are still both cars. They still both carry people down the road to visit the grandparents or get a daughter to soccer practice. The differences between the two are just a matter of degree and have been introduced over a hundred years of fine tuning. With lessons learned from our experience with the ISS, we will eventually build larger space stations, then the first small habitat, then larger ones, and we'll do it by constantly adding layers to our knowledge base. This is what we do. This is how we design and build.

Every time I discuss this, especially with people who have never considered the possibilities or encountered the topic before, I get the same response; "I don't want to live in a tin can floating in space, I need to live on a planet, with wide open spaces with wind on my face and clouds above!" Even the first of these huge habitats like those described by Gerrard K. O'Neil will have lengths and diameters measured in miles or even dozens of miles and as we get better at building them they will only get larger. They'll be so large that standing on the inside surface of this can and looking up will be reminiscent of looking out the window of an airliner and seeing wispy clouds and beyond them lakes reflecting sunlight, squares of cultivated fields, long snaking rivers and roads, all made dim and indistinct by distance. You'd live like those in the tropics, with open air houses, comfortable shirt sleeve weather, sidewalk cafes, parks and lakes for sailing and swimming. Gravity would be Earth normal, supplied by the cylinder rotating so slowly, even the most sensitive inner ear couldn't detect the movement. The outer shell of these habitats would be twenty to thirty meters thick, filled with soil and water so would provide good radiation shielding. By the time we're capable of building such huge structures we'll probably also have the power systems able to generate artificial magnetic fields around the colony, giving us at least as much protection as we have on Earth. Doing that on planetary scales to protect Mars and moons would be much harder.

We are only biased toward planets because that is what we know and most of us would have a hard time imagining that there is a better alternative. But children who grow up in huge space habitats will not be saddled with the planetary bias that we have. It will be their natural environment. They might not think a planet is the best home for a space faring race. Gravity wells are a huge problem. We may eventually develop things like space elevators or even gravity manipulation that would make it less so, but mining minerals and growing food to ship into space seems counterproductive. These future tin can children will see the sense in being able to move their home out of harm's way or into orbit around Saturn where they can easily harvest ices and gases or eventually even move to another star system.

Future potential colonists will also need to consider some critical ethical issues. If we find a planet that already has a thriving ecosystem—life that has evolved there and is perfectly adapted to that world—would it be ethically acceptable to introduce ourselves and other Earth evolved biota into that system? Even if none of the life is intelligent? Chances are, we would not be able to use the flora and fauna on the new world for food. Our only options would be to bring our own food crops and animals with us and probably adjust their biology enabling them to live on the new world, or bioengineer ourselves—including the millions of necessary microorganisms that live inside us—so the local biology will be compatible. Or of course we could modify the new planet's biology to fit us instead. In all of those cases, either introducing new organisms or modifying the existing ecosystem would interrupt or destroy the local biology.

I'm a big believer in technological solutions, so that far into the future we might become wizards of biology and be able to tweak things so that two separate ecosystems can live side by side in harmony, but I suspect by that point if we even still desire to live on a planetary surface, we will be more likely to find what I think of as "blank slate" worlds that have the requisite size, location, water etc., then terraform them. This sounds like the optimal solution for humans moving to extra-solar worlds, since we could tailor make them to our exact requirements without destroying other biospheres. While we do that, the human populations will of course live in huge orbital habitats as the dead world is slowly brought to life. We humans are stubborn and contrary, so there might always be those throwbacks among us who prefer to live on a planet, but the largest percentage of humanity will live in space, in giant houses of our own design, and when those terraforming projects are finished, they might leave a few hardy and adventurous people behind, but the rest will move on.

So regardless of where we go in our distant future, we will be building our homes to order, either as vast colonies free to drift among the stars or terraformed marvels that will indeed be new Earths, but like so many of our cool-yet-wrong visions of the future given us by science fiction, we will most likely not be taming worlds filled with alien monsters.

Copyright © 2017 William Ledbetter

William Ledbetter is the winner of the Nebula Award for best novelette for his story “The Long Fall Up.” He is the long-time administrator of the Jim Baen Memorial Short Story Award contest for Baen Books and the National Space Society. Ledbetter has more than fifty speculative fiction stories and nonfiction articles published in markets such as Fantasy & Science Fiction, Jim Baen's Universe, Writers of the Future, Escape Pod, the SFWA blog, Analog, and Ad Astra. He's been a space and technology geek since childhood and spent most of his nonwriting career in the aerospace and defense industry. He lives near Dallas with his family and too many animals.