Worlds full of high technology are nearly ubiquitous in science fiction - but in a few cases, authors choose to focus on worlds and people where technology is in decline. I find the question of decline in technology fascinating, and in fact my Varin world is in a state of technological decline. So I thought I'd share a few of my thoughts on the subject.
How do declines and losses occur? There are, I suppose, lots of possible ways for this to happen.
The one that leaps immediately to mind is some kind of large-scale natural disaster - but for this to affect an entire technologically rich society, it has to be on an extremely large scale. The book Life as We Knew It by Susan Beth Pfeffer is an example: a meteor hits the moon and changes its orbit, and civilization basically comes to an end.
Another immediate thought is that of the Luddite rebellion - somehow a group of people comes to power and tries systematically to eliminate advanced technology. It strikes me that they have to have sophisticated enough technology to enforce their aims, but it doesn't take many guns to make a lot of people change their behavior. They might end up scuttling their society more than they'd hoped by cutting off the means of production for modern luxuries.
Both of those are sudden and extreme. What about just plain decadence? Could that alone lead to a decline in technology?
Well, sure. Particularly in a society where resources are controlled by a relatively small group of people, any change that moved those resources away from the maintenance of technology could seriously slow things down. Over a prolonged period, that lack of resources could mean fewer people properly educated to maintain advanced technologies, and the techniques for developing materials or designing technological marvels would slowly die off along with the population that had the required specialized knowledge. Lack of money, or excessive control over, critical substances for research, design and manufacturing could also have a depressive effect.
There are other losses of technology that we don't usually think of as "losses." Take for example the decline of the vinyl record, or the fact that modern firearms have replaced the blunderbuss. While "progress" continues, the older technologies fade and sometimes die. Most people I know have moved away from the expensive but extremely reliable land-line phone services. Many people don't have home telephones at all, but use their cell phones exclusively. The rotary phone has been supplanted, but it won't be the last to go.
In a place where the technology has been continuously developed, generally speaking signs of the old infrastructure will remain. But some countries might come late to technological developments, and so leap straight to the use of cell phones, for example. Why should they then go to the trouble of laying all the land lines in the first place? They shouldn't, of course, because it would be economically impractical.
This leads me to speculate about a different kind of technological decline, which I call technology losing its roots. What if a highly advanced technology - for example in communications, transportation, or medicine - had already supplanted an earlier technology used for the same purpose, to the extent that the old infrastructure had largely broken down, or the old supplies thrown out or recycled. What would then happen if something (information virus, fuel exhaustion, contamination) made the new technology fail? Suddenly the society would find itself having to fall back on a failing system, and wind up doubling its decline, or finding itself helpless, because neither the advanced system nor its immediate predecessor would work properly.
I've talked before about technology sets, i.e. technologies that seem to go together. Both advances and declines can affect a society unevenly depending on its technological needs, thus defeating the typical Earth sets. In my Varin world I use a combination of decadence and loss of roots as the basis of a society in which building intercoms function, but messages between buildings are typically sent by human messenger, and messages between cities are transmitted by radiography.
It's something to think about.