"I am always reluctant to talk about the Low Age as a whole as if it had been some kind of unified period in time. It lasted for five hundred years. That's half the duration of the Middle Ages. Some civilizations have lived for less long than that. The industrial one, for instance." -- quote attributed to historian Sybil Masani.

All civilisations are mortal. This idea, however widespread, wasn't always accepted. For about three centuries the thermal-industrial civilisation assumed it would go on forever: that the future would only be like the present, but more. And then it all collapsed.

Historians still debate upon what exactly caused the industrial civilisation of the mid-21st century to collapse the way it did. Climate change and resource depletion played an obvious role, but they weren't the be-all and end-all of this collapse. The systemic failure of complex technological networks, widespread resource wars and political uprisings did play an equally important role. In reality, the very idea of collapse is not accurate: the apocalypse was more of a slow transition rather than the brutal end of the world. Despite being framed as "the second middle ages" in many history books, the Low Age didn't see the end of modern civilization nor the erasure of a thousand years of technical and social progress. Its first immediate effect was what historians call the "energy drop": with the depletion of many a fossil fuel resource and the need to brutally transition towards nuclear energy and renewables, the overall energy capacity of the human civilisation decreased immensely during the 2050-2100 period, destroying economic and technical systems that weren't meant to go through such restrictions. If the Low Age lasted about three centuries, most of the destruction and loss of knowledge happened during the initial stages of this time period. Computer science, aircraft manufacturing, space technology were the most affected, as well as most things that had to do with fossil fuels. Even in places where knowledge remained, the know-how was lost.

The world, however, didn't fracture into warlord kingdoms and post-apocalyptic raider dominions. With the temporary loss of almost all instantaneous worldwide communications the human civilisation went back to a technological state comparable to the late 17th century, but with modern scientific knowledge and still available renewable and, to a very small extent, nuclear power sources. In that framework, modern states couldn't work anymore, but the disappearance of worldwide markets and the drastic reduction in travel and transport capability led to the rise of local communes and syndicates as the main framework of governance. As time moved on, loose continent-wide communes (the ancestors of present-day USRE or Pacifica) emerged as a way to unite these local initiatives together. Sciences were geared towards immediate concerns of survival in a more hostile world, which led to a relative decline in fundamental sciences, with domains such as agronomy, biology, geography, urban planning and engineering being favoured. In the 2050-2100 time period, conservation of knowledge was deemed paramount and was often handed over to secular or semi-religious groups essentially functioning like monks of the European middle ages when it came to copying and archiving knowledge. Warfare had in many ways gone back to a quasi-medieval logic, with very few groups capable of mounting organized, professional armies. The few still operational nuclear weapons acted as counter-power, cementing the rise of regional and later continental organisations.

"The Low Age - why low? Because it was less technologically advanced than the pre-existing era? Because we temporarily ceased to go to space? Because some of us likened it to the new Middle Ages? The truth is, I have no idea why this name came to be. Perhaps because we all needed to slow down. To go lower, but better." -- quote attributed to Oak-class AI Thot.

By the 2150s, this new world order had achieved a mostly stable state, with the biggest communes and syndicates re-creating continental markets. A mix of technological innovations and re-discovery had enabled worldwide information networks and transportation to reach a degree of capability similar to the mid-19th century. As many a city, especially in developed countries, had been abandoned or severely damaged by infrastructure failures, new cities started emerging from the ruins. By the 2200s, it was clear that Africa, China-India and Europe were the most well-preserved and developed areas: they would form the basis for the USRE and Laniakea in the coming century. By 2257 the Earth had returned to a mid-20th century technological level, albeit mostly devoid of fossil fuel vehicles, and had launched satellites in space again. Most of this technology was operating on centuries-old theories but modern engineering developments.

The 2300s saw the beginning of the end of the Low Age. The first successful experiments on nuclear fusion, based on leftover from research more than two centuries old, opened a path out of the energy conundrum the civilisations of the Low Age were operating on. In 2320 humankind started expanding to the solar system again. 

Then, a while later, the Geometry Drive was found. 

The Low Age had come to an end.