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Lots of assumptions.
(quot freely:)
Take a second intelligent species on earth, the dolphins. We humans think we're the smartest on earth, because we have digital watches, and they just play and bounce around in the water. They think they're the smartest, for exactly the same reason.

Beta Magellan

Although I’m always tempted to go full Lem on debates about alien intelligence, Jarrett set his two axioms at the beginning, nice and clearly, which not only has the advatange of stifling our flights of fancy but also, rhetorically, reinforces the point about transit’s geometric restraints. Analogously to mathematics, if you start with a few assumption’s, you can build a system which follows certain rules. So, I’d say the basic approach—having “transit axioms” and building on them—serves your argument nicely, but I’m glad to see particular example was dropped—the borts seem a bit like a distraction, and even after stating your starting conditions I found myself wondering what a *truly* alien transit system would look like. :)

Incidentally, my background’s in the earth sciences, so I try to keep up with what’s going on around the solar system as well; over the past month or so the planetary exploration blogosphere’s been discussing the possibility of sending affordable missions to the outer solar system, so imagine my surprise to see a picture of Uranus in Google Reader and then discover I’m reading Human Transit! Strange how I’m attracted to subjects with multi-decade timelines and are easily derailed by budget issues…


Sticking to your first two assumptions:
- If Borts could move freely in three dimensions, I'm not convinced congestion from private vehicles would be such an issue, with the additional degrees of freedom for vehicles to move past each other.
- Private vehicles driven by a cooperative system with faster-than-human reactions would also have far fewer congestion conflicts, and could join together to share a route rather than getting in each other's way.
- Borts with perfect "virtual reality"/online communication, or teleportation devices might still live together in cities in order to keep latency times as low as possible. This sort of desire leads human finance companies to build their servers relatively close together (to get the absolute most up-to-date market info), but space taken by the fiber optic cables connecting these servers is small and has almost never been a limiting factor.
- Borts might be much less individualistic. It can take a long time for an ant to walk from one side of a large ant colony to another, but it rarely matters because another ant is already there.
- Your dismissal of "flexible routes" seems especially weak. With a sufficient understanding of supply/demand or ant-like perception of common good, Bortmovers could be dispatched to run directly between whatever pair of points would happen to serve the most Borts at the current time. There would be no fixed schedule or route; either Borts would be able to predict where and when to catch Bortmovers by their own perception of demand, or they might be happy to wait/'walk' while the greater number of Borts is served.
- If for example Borts or Bortmovers propagated through electromagnetic waves rather than physical matter, they'd still have issues with congestion of the electromagnetic spectrum, requiring something like dedicated rights of way (just as we dedicate sections of spectrum to different uses). But ideas like "stop spacing" and "branching divides frequency" would seem meaningless in such a model.
Really it seems to me that frequent transit only makes sense in a pretty narrow part of the space of all possible worlds. If moving in vehicles were a bit easier, the benefits of private vehicles would outweigh the cost, like packets on the internet or even (sometimes) bicycles. If moving in vehicles were a bit more difficult, a frequent transit network would become too congested and cities would be limited in size or heavily dependent on telecommunication. It's hard to quantify the size/"likelihood" of the middle area of transit feasibility compared to these two extremes, but it's definitely not universal. The above are just a few ideas of how a civilisation might satisfy your assumptions and still look very different from what you've imagined; I have no doubt that a real alien civilisation would seem stranger still.

Peter Laws

Bortsh*t. :-)

We know nothing of the Bort's feelings about things like time and personal space.

Maybe time is not important to your average, working-class Bort so being able to predict when the next Bortmover is due isn't a big issue and if it's a circuitous route they don't care because they all enjoy the ride.

Or maybe it is and Borts are all tied to some subliminal rhythm so that they naturally prefer things to happen on a regular beat, say every Bortspan or deciBortspan.

Likewise, we don't know how interpersonal relations are between Borts. Maybe they like being packed into Bortmovers to get where they are going.

Or maybe they don't, and while they enjoy the company of their fellow Borts, they don't actually like to be within scent range of them.

IOW, what you've described sounds a lot like Terra and how Terrans react to their environment.


"...odd shiny things in the discard pile..."

While the use of mythical aliens might not be appropriate to the book, the analysis is.

And this is a good example of what makes for a good practical book, the way that Jane Jacobs analyzed how the city really works in "Death and Life..."

Stripping away the glitzy posters and politicians' speeches and master theories, just dealing with how things actually work, is important. Sadly, there are way too many books stating how things "should" be according to the author, and not enough that further the depth of knowledge of actually existing sitatuations.

So definitely keep that focus in the book.


I don't know how universal transit is at all. Remember that in the ancient world (before railroads) cities could grow up to one million denizens or more and none of them had mass transit outside of large boats.

London, Peking, Angkor, Paris, and Tenochititlan grew into giant metropolises utterly dependent on walking as a form of transportation. We might want to compare the just-so story in this post with the reality of horses and boats in cities before transit.

Tenochititlan had half a million citizens in 1500, probably the largest city in the world, and didn't even have horses, though water transit on gondolas was common. After the smallpox epidemic of 1521 it took four centuries for that city to once again be the most populous on the planet but by that time it had a world class metro.

Anyway, it's easy to imagine a 3-D city that has millions and millions without needing transit, so long as all the residents can float or fly. Everything could just be very close together.

Alternatively, routes and stop spacing and the like could be irrelevent in a city with demand-based transit called to wherever a resident is waiting which delivers him wherever he is going like a fleet of taxicabs with computerized prediction and universal smart-phones to ensure availability and efficiency. With the right technology we could build that system now and everyone would get to destinations faster in medium sized cities.

So in both the ancient world and the future, maybe we can imagine things less constrained than in this essay.


Perhaps there are two colors of Borts, red and blue; with a high percentage of Red borts holding the Blue variety in contempt, and are generally unwilling to share a confined public space with them.

Sucks how culture always manages to mess up geometry...

Morgan Wick

I don't think a third dimension would change the analysis much. Borts would probably still have to move in dedicated spaces between the places where they live and work. Perhaps their cities are a "series of tubes". :)

"Private vehicles driven by a cooperative system with faster-than-human reactions would also have far fewer congestion conflicts": Only if by "faster-than-human" you mean "instantaneous". Any reaction time delay will have some impact on congestion.


Since someone brought up packets on the internet, I'd like to point out that congestion is a potentially huge problem there, and that the internet actually only works at all because everyone connected to it, down at the individual level, has agreed to restrain themselves to avoid congestion. Back in the 1980s, once computers and local networks got reasonably fast, it became possible to send lots of data quickly, and the internet of the time suffered from "congestion collapse", where connections became so congested that their effective capacity to deliver the data that was needed (what the networking people call "goodput") fell by three orders of magnitude. The solution was the TCP congestion control algorithm, which relies on client machines to detect congestion and slow down their rate of transmission in response. It basically relies on everyone cooperating for the greater good, because if you don't cooperate, everyone loses.


Brian. The pre-modern "metropolises" that you cite wouldn't seem huge to us now. Paris within the old city walls was under a 30-minute walk from one side to the other, which is on the outer edge of acceptable travel time if you'll be making lots of trips per day. These metropolises were also hierarchical societies where a fairly small number of important people had access to the powers of others for their travel around the city.

I should have added a third assumption, namely that bort society is relatively egalitarian, such that a large share of borts need mobility around the city. That may be necessary to arrive at the likelihood that they have significant congestion -- although of course the compact medieval city was so dense that it had pedestrian congestion.

Alon Levy

Jarrett, even if the borts are relatively humanoid, there are lots of less obvious questions influencing urban development in their society:

1. Which resources are available?

2. What is the state of path-dependent technologies? (Surprisingly many things today depend on crazy WW2- and Cold War-era arms races). At a minimum, is metallurgy good enough for steam engines and their derivatives?

3. How easy is it to grow and transport food for the borts?

4. How sensitive are the borts to various forms of pollution and to various diseases?

5. Does the bort social organization favor what we humans think are organic cities, or does it favor the clannish cul-de-sacs common in modern American suburbia and in some medieval Arab cities?

6. How much is bort psychology affected by enclosed spaces, elevated structures, etc.? Do they have the same reactions to elevated freeways as humans?

7. How does bort psychology construe safety? Does it have the same cultural theory of risk as humans, the same reaction to fatality rates of cars vs. planes, the same reaction to crime, etc.?

8. Does bort society have the same urban-rural social issues as most industrial human societies?

Matt T

I've met these Borts. They actually have a very efficient postal system, and their ability to fold themselves up from their amorphous blobs into something akin to an aerogramme is legendary. It costs only two Jarretts to post themselves airmail from anywhere to anywhere on their home planet, and riding in the postal tubes is fun, so life is grand and they wouldn't have it any other way. They however are like most humans, in that they refuse to ride in buses.


Or maybe the borts prefer a natural environment, with horses, coaches, keeping main cities walkable, with some electric trolleys and trains.
The borts use the relationship of agriculture and the city to shape their transit. So like early St. Louis, (19th century)and in many traditionally designed cities they established market gardens ringing the city
The borts made a conscious decision to avoid confinement operations for animals and emphasized local foods, which in turn influenced their physical planning as well as transportation planning,(distances, frequency, connections and so on)
The borts had a big advantage in that they read the "The History of Earth" before they started building.


Clever! And instructive. Maybe it should be in the book if only in the appendix so readers can use it to explain the realities of geometry to those less familiar with transit issues.


"If the borts had either perfect telepathy or perfect virtual reality, then they would never need to move for any of the purposes of interaction. But in this case, why would they have cities?"

One reason: Reproduction.

I can't think of its title at the moment, but there is an older piece of science fiction regarding the Far Far Future that addresses just this issue. In the story, most human beings live their entire lives in small, automated cells that provide for all their physical needs. They communicate through view screens. The one time they leave their pods is to travel - by dirigible, mind you! - when assigned by The Computer That Makes All Such Decisions to meet a scientifically selected partner for reproduction. Everything else is done by automation (until, of course, the automation breaks down...but that is a different topic). Now, I suppose you could also automate the transfer of reproductive material, but in any case the major question in such a society is not one of mass transportation of beings, but rather mass transportation of materials.

Jarrett at HumanTransit.org

Scott.  Well, yes, but your scenario is close to saying that the borts are basically intelligent plants.  Even our world's dumb plants have, in the vastness of time, devised numerous clever ways to reproduce without moving.  But plants don't form cities! 


So maybe they can slither onto a series of conveyor belts, where the outer belts move slowly for slitherers entering and existing, and the inner belts move faster for those going longer distances. Or maybe they can flow through fluid, or electricity, or they have pink tubes attached to vacuum cleaners that suck them from place to place. Or maybe they have a network of guideways that allow a personal pod vehicle to get from point to point directly (requiring some network intelligence).

Or (and I know this is hard to imaging) maybe they have a system of exchange that allows them to set prices to balance supply and demand for space and other precious resources, and they use it to ration access of personal mobility devices to rights of way to avoid congestion.

Probably not teleporting though. Imagine the security bureaucracy that would be needed to keep people from teleporting into your bedroom, or from teleporting your alien Tivo into their living room?


@Rob: The fact that a technology would be difficult to regulate has never prevented one from being invented. (Though most scientifically conceivable teleportation technologies would require a physical device on both the sending and receiving ends.)

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