San Antonio resembles Los Angeles resembles Dallas resembled NY -- same chain stories selling the same chinese-made goods.

I will concede the language issue. Ultimately, one language will most likely obtain global dominance given enough time (with second languages spoken within smaller cultural and religious circles). However, my biggest gripe is with these stories seeing one city and environment as representative of the entire planet.

It would be incomprehensible, in my mind, for Earth to ever be represented by one city, nevertheless one country. I know all the movies focus on the US, especially NYC and LA, but ultimately space will be an international affair. I do not forsee the nations of Earth ever coming under the sole sovereignty of one government. Is it possible? - yes, but not very probable.

Reasoning from history: The United States is a less linguistically diverse area than England, even though England colonized the United States and some elements of their linguistic diversion imprinted it on the country. (For the sake of a simplistic argument, this excludes the Indians and the non-English immigrants, but you get the general idea.)

I'm a little dubious of the notion...I figure humans being humans, they'll evolve into contentious groups, any number of 'em, and colonize different areas. I try to work in a little variety myself whenever possible.

When I travel to a location I hadn't been before, I don't tell my friends on my return about what didn't matter to me. ("When I was in Kansas City--where some people speak Spanish, I'm guessing--I tried Korean food for the first time.")

Obviously, if the main point of the story is the exploration of a planet covered in an alien people, then the author better come up with enough diversity to satisfy modern readers. Otherwise, the story wouldn't be worth publishing (IMO).

Second Thought (and I know this has been mentioned): If a people existed long on one planet, through war, politics, or even biological necessity, one language or one culture might take over all others. The people might connect all cities until they are one. (OSC is one author who's addressed this; remember Capital?) Going into the history of the planet or exposing the environments the POV character(s) don't see (because those environments are hidden by the borders of a single city) or don't care about might distract from the story, depending on the premise.

Third Thought (and possibly the least believable): If a planet had only one location for space launches and landings, people of other worlds may learn only of the culture surrounding that planet's space operations base. The government(s) of the planet might refuse to build multiple space bases as a means of containment, to give power to one city (maybe the capital), or because only that city can afford the base.

I've never liked the (usually fantasy rather than SF) timelines where a single empire lasts seemingly indeinitely without technological or cultural advanacement (or even change), but it probably is plausible that a genuinely universal culture might become static rather than dynamic.

How about internal corruption? The way I see it, the outside forces didn't destroy empires but only picked its carcass. The real death came when individual leaders believed they could do a better job and each ripped his own part away. Think of the Diadochi, the roman Tetrarchs. Decay came from within. Why? Because they were unified? I don't think so.

A collective society is like an insect colony where there seems to be very little, if any, free will. Decisions are based more on genetics and chemical messages.

For example, despite the fact that it was common parlance for a while, they wouldn't let people call a computer "le computer;" they needed something more native to French, and so it became "l'ordinateur."

Even if a lot of people end up speaking English on Earth, I doubt if I can ever see anything close to 100% coverage -- 50% would be a miracle. I do see languages dying out, and only a handful remaining other than in tribal areas.

Until fairly recently, America was a place where one HAD to learn English just to do business, as everybody before them spoke English. Parents did not even want their children to speak their native language so they would have a chance to survive, to thrive where they suffered. People arrived and melted in and became American, a melting pot.

Now, when we are able to warp space and send people off to other solar systems with a fair amount of ease, who will go? Will they all be scientists? At first, yes.

Let's assume we get into terrafarming (that way we don't have to deal with indigenous plants, animals, and bacteria!!!). After the scientists get the planet ready, who will then go?

I would propose that it will be people as diverse as the groups who settled the americas 500 years ago. Unless someone invents some kind of mind control, there will develop factions and differences and quarrels and separation, etc.

If it did, we would still fight with swords over issues instead of debating. In the Western world democracy is only a few hundred years old and the British parliament symbolises how democracy ended armed conflict within our Nation with lines between the two debating sides that are two swords-lengths apart. Women got votes only a few decades ago and America finds itself surprised it has elected a black President, something that until very recently was predicted by many as impossible.

The mission of the United Nations, founded after the second world war, is to avoid world wars. While it's not very successful at stopping armed conflict between and within nations, it's surely better to have a global talking forum than not, because ultimately conflicts are resolved through dialogue. If we continue to develop the UN in accordance with its mission and without the corruption and insincerity, is there no chance that, as democracy has transformed many nations over the last couple of hundred years, Earth will be more united in a century or two?

One lesson from the United States is that individually ruled territories--States--are more powerful when they work together towards common goals. That was one of the inspirations for the formation of the European Union in an increasingly competitive global economy.

The internet increases mutual understanding amongst nations and individuals. As it becomes stronger, with satellite and wireless links and ever cheaper access, repressive regimes will find it harder and harder to rule by restricting information.

Climate change, scarce oil, hunger and bird flu will bring nations together into larger and larger blocs which will either fight or, I hope, unite to fight common global enemies.

I see no reason to believe Roddenberry's harmonious future Earth is impossible to achieve, and we've always achieved betterment by striving for dreams.

So I think stereoplanets are a plausible idea--and they avoid the difficulties of familiarizing readers with several worlds each comprising several nations which each comprise many factions which speak their own languages that have to be learned or translated ...

Contact with an alien civilization could possibly unite humanity if they became our enemies. But if they were friendly, I bet it would divide us (more Alien Nation than First Contact). I see the conflicts with various ideological religions alone as being a great problem. I'm not saying any of these religions are necessarily bad or have bad people, but alien contact could severely threaten the core tenants of many religions and put people at odds with aliens and each other. I believe this represents about 2/3 of the Earth minus Buddhists, Hindus, atheists, and a small assortment of others.
I foresee governments, and military organizations in particular, as being extremely hesitant to trust in an alien encounter. I don't believe this is simply the fodder of sci-fi movies; I believe it is truly a concern and in many ways justified.

I know, I know - who brought up aliens? I bring this up partially as an example of how diverse we really are, and how divided. I do not believe 2/3 of Earthlings would fear or dislike the aliens; but I do believe it would become a highly dividing issue.

Let's move on to terraforming (this is where I believe our distant future lies - preexisting bacteria will most likely be deadly to us, making meeting aliens face-to-face very challenging, at least at first).

We will need to create a pseudo-military organization that manages colonies in space, like the UFP. My reasoning for thinking that factions will develop is based on matters of representation. It took 200 years for North Americans to fully resent the British government. There was not a lack of communication, the British were already there. The subjects were, in essence, British. However, they had become self-sufficient and felt they weren't getting anything out of the deal. It was give, give, give, and get nothing in return that they couldn't do for themselves. Once a civilization is established they will want to govern themselves and become autonomous. This creates tension.

Say that the UHP is very liberal and allows self-governing from the very beginning. I would tend to believe that people will at first become very planet-centered and differences would evolve from that point. Both scenarios end with planeteers becoming mostly autonomous and differentiated.