A Future History
Some worldbuilding for... something.
The year was 2050.
Space exploration had moved to the first, precarious steps of colonization. China, India and the United States had operational bases on Luna (aka the moon) while Mars was home to smaller US, European, Arab and Russian colonies. While the US efforts are chiefly driven by private industrial concerns, most nations of any size see a footprint in space as necessary for national prestige. The first asteroid platforms were in initial development, as a bootstrap to possible colonies in the Jovian moon belt.
Although climate change and its extreme weather effects and consequent dislocation of millions of people drive the search for new places to live, it was clear that space is not the answer; although the bases were for the most part after 20 years self-sufficient in most areas, they are still spartan and dangerous affairs, best described as "being trapped inside an airplane, for the rest of your life".
Then, suddenly, it didn't matter any more.
No one, to this day, is sure how the Three Day War began - whether from a North Korean missile test going awry and impacting Japan, a Pakistani dirty bomb going off in New Delhi, an Iranian missile wiping out Tel Aviv, or some hellish combination of all the above, but very quickly every nuclear-armed nation, set on an automatic pilot of doom, unleashed their entire arsenal on every possible opponent that could threaten them, ever.
They would never threaten anyone again. Because, Earth died.
Not from the bombs. Oh, they did their share - it's estimated over three hundred cities in North America were destroyed, and over five hundred in Russia - but humanity could have survived that.
The winter that followed the Three Day War, no one could. The winter that lasted fifteen years, that destroyed all life. No survivalists emerged from their bunkers, no governments came with help, no one was saved. The survivors of the bombs, mad with hunger and thirst, those that did not die of the radioactive poison, ate what insects were left, what shards of plant life lay dying in the earth, and finally each other. And then there was no one.
Except for the people spending their entire life "trapped in an airplane" - which now contained all of humanity.
The next ten years were grim, for those spacemen. There were no more spare parts save what they could build. No more food save what they could grow. Most of the belter outposts died, unable to support themselves. On Mars and Luna, a few clung to life.
Then, when humanity seemed doomed to perish with a whimper after the bang, the first wormhole was found by a long-forgotten Jupiter probe. And beyond, a minor star, Tau Ceti, with an unassuming planet. That had water. And air.
The Exodus had begun. Humanity would survive.
The year is 2250.
Humanity has spread, through the wormholes that connect countless stars, to hundreds of star systems.
Some even returned to Old Earth; a group of settlers carved out a new city in what was once New Zealand. There, where every party had to enter from an orbit of a world the governments that once represented them destroyed, on August 15, 2124, the Andreyev Accords were signed.
No nation would go to war with another nation. There was enough room for everyone in the stars. If a nation had laid stake to a new world, colonists would move on, to reduce the possibility the old ways of war would return. And nuclear weapons would never again threaten anyone.
Of course, every nation signed.
Of course, every nation then proceeded to cheat.
But it kept things stable, after a fashion...
A Galactic Geography: Humanity amongst the stars
First, there was Sol, humanity's origin, and object lesson in what could happen if man's greed spirals out of control.
Then, spiraling outword from Sol's wormhole network, the seventy or so worlds of the Six Powers: The United Free States, the European Union, the Russian Imperium, Bharat Ganarajya, the Heavenly People's Republics, and the Dar al-Islam.
And spiraling beyond that, the hundreds of worlds of the Free Colonies, settled by those who wanted to make their own way outside the Core Worlds. Life in the Outer Reach can be... interesting. Especially for those who have the ambition of going their own way.
The United Free States, populated by survivors of the American colonies, are run in a fashion very familiar to those who lived in 1890s America. Government is vestigal at best, and corporations jockey for dominance in the Interworld Congress. Generally, UFS colonists enjoy wide open spaces, lots of guns, and the freedom to do whatever they want, as long as they can afford it. If you can't afford it, you may want to hop on the next shuttle Reachward...
The Heavenly People's Republics, descended from the Chinese colonies, are almost an exact opposite of the UFS anarchy - a heavily planned, hierarchal society constructed, if you believe their brochures, for the betterment of all who live there. Those who dissent from the People's Line may beg to disagree, but they tend to be deported to the Outer Reach fairly quickly...
The Russian Imperium is definitely the most militaristic of the Six Powers; tracing a direct line from the Russian military commanders that managed to survive the Three Day War and make it offworld. The Czar sits on his throne in Novy Rossiya and enjoys all the pomp and circumstance due his station, but the generals are in charge of the actual decision making. After all, there will always be a threat to the Russian Worlds - if you disagree, just visit Old Earth sometime...
The European Union is still the same EU that ran Europe on Old Earth; even the flag remains. Now, though, instead of squabbling nation states, there are squabbling planets keeping Parliament busy. "Europe" was always more of a state of mind than an actual place, and the descendants of the EU colonies prefer it that way. Within the loose confederation, the member worlds, whether the traditionalists of New London, the madcap inventors of Outer Berlin, or even the monks of the Vatican Planetary State are free to live life as they will. After all, the EU is, without a doubt, the most free and most prosperous of the Six Powers. Just ask them, you'll get a position paper to that effect thrust in your hands immediately...
The Bharat Ganarajya, the descendants of the Indian colonists, are known for their extremely strict laws in almost every sphere of life. According to them, it is the only way that the ecological paradise (and, to be fair, every world of Bharat is a thing of beauty) can be in any way sustained. The fact that it also imposes total social control of the population is, of course, an unfortunate side effect. Most free traders tend to avoid Bharat worlds; too many ships have been confiscated for breaking some arcane law of "the Raj"...
The Dar al-Islam, ("House of Islam" in Anglic), unique among the Human colonies, is a theocracy ruled by the precepts of the Muslim faith that drove its founders. Much of life in the Dar is unchanged from how its forefathers lived on Old Earth, and yet much has also changed, given the realities of interplanetary life. Many explorers of the Outer Reach hail from the Dar – whether to better understand the galaxy humanity lives in, or simply to get away from the Dar's many restrictions is best asked when the morality enforcers aren't listening...