Microsoft Flight Simulator began as a simple physics model for the Apple II. The instrument panel gauges are basic shapes; the terrain, a wireframe grid of white. If you crash, a cartoonish message tells you so. There are no trees, buildings, rivers, terminals, windsocks. If you want to see the plane’s outside, tough luck. But advance a few generations, and you’ll see this sketch of world start to fill out. Colors appear, then bodies of water, then day and night. Regions of the country take shape in a chunky three dimensions, different models of aircraft become available, and for the first time—allowing for the limitations in the hardware of the time—you begin to hear the propeller’s roar.

It is difficult to explain, to those who do not enjoy them, the appeal of computer simulations. They are games only in the broadest sense: you cannot win them, and there is no direction given. Some people prefer to call them “software toys.” But a good simulation is more a world unto itself, a perpetuum mobile through which something organic evolves. When done right, a simulation has all the inexorable momentum of reality. Things proceed by themselves and can hardly be predicted, but when they do, they seem entirely correct—as though they could not have happened any other way.

As a kid, I went nowhere without Air Nikko: a garish, radio-controlled, sticker-covered plastic toy with illuminated wingtips, a modest selection of audio effects, and—of course—a face. When I came to the age of caring about the realistic, I graduated to real models, sprawled out around an improvised terminal laid out on my car carpet city. I had a methodical imagination: my friends did not like playing with my planes, because I demanded strict imaginative submission to what I then considered the harmonious laws of aerodynamics and air traffic control. I should have either outgrown this fascination or else started begging for kiddie lessons at flight school, but neither of these things happened—the simulator did.

When my sweaty grade-school hands first pulled apart the packaging of Microsoft Flight Simulator 2002, the series was in its eighth incarnation, and I was nine years old. By this time it was a full-scale model of the Earth as experienced from tarmac to sky, complete with every known airport and square mile of ground. The major cities and airports of the world are modeled as they really are, with accurate buildings and ground texture. You can fly everything from a glider to a jumbo jet on every continent, in every season, and at every time of day. The weather can be downloaded in real time. Every minute complaint of my nine-year-old nerd’s pedantry had been preemptively done away with. The game was perfect.

Upon first running the game, I expected that the world as represented would be exact, that if I flew over northern New Jersey, navigating by dead reckoning along a series of water towers, I would arrive within view of my house. To my extreme disappointment, it did not work like that: outside of a few major areas, the scenery was automatically generated. A blocky, blurry ranch house, one wall sliced through by a misplaced palm, was there where my childhood house should have been.

What I had expected from Flight Simulator, in my naïve exuberance, was something like what Daneri, the mediocre poet in Jorge Luis Borges’ short story “The Aleph,” discovers in his basement—an Aleph, a point in space which contains all other points. Upon finding the Aleph, Daneri devotes his life to the composition of an epic poem describing everything he sees through it. With the same ambition (and the same mediocrity), I decided, at eleven years old, to complete this inadequate Aleph of my own. I started to make scenery files for the simulator, making trips to local airports with a camera and stumbling through the basics of three-dimensional modeling software. I uploaded my little projects to sites I had discovered, all dedicated to hosting add-ons filling in the mosaic of Flight Simulator’s world. I built, and accumulated from others—file by file, year after year—a world that looked and behaved more and more like the one I saw from passenger windows of planes.

Then my hard-drive crashed. And after years of work, I didn’t have the heart to reassemble the world. Because even without me, it’s still going on. The entire world is grist for the simulation’s mill, and once the airports, the satellite topography and the real-world air traffic have all been modeled, there will remain for the designer the question of individuals, animals, and trees.

—Columnist Julian C. Lucas can be reached at julianlucas@college.harvard.edu.