Started notes for a new s-f universe. Still not sure what the stories in it will be like. Might end up being something I build that I can plug various stories into, even for that other site.
Basic premise is that aliens are more or less besieging Earth. They have banned space travel (they destroy anything that goes higher than 100,000m above sea level) and more or less enforce global peace by destroying military bases, military formations in the field, and such with brutal, powerful attacks from orbit when a war breaks out. If we give up things like nuclear weapons, then they will lift the "Alien Laws" as these restrictions are called.
This has a number of impacts, including things like losing the use of geostationary orbit and other high Earth orbits for things like GPS and communications satellites. Transoceanic cables come back into vogue for carrying communications between continents, high altitude atmospheric vehicles like balloons and planes are used for spying and collecting weather data, and so on. Still thinking through ramifications.
Rumours and conspiracy theories abound, of course, including the belief that the aliens actually have secretly landed on Earth and have somehow infiltrated governments, corporations, etc.
There's a couple core mysteries involved:
Who are they? Other than a few one-way communications in which they handed down the "Alien Laws", we have had no contact with them and have only seen their spacecraft.
What is their real agenda? Are they actually trying to force us to live more peaceably? Or some more sinister operation happening?
To be honest, even I haven't worked out those details yet.