Duskflow Theory is a (debatably) scientific set of principles and hypotheses that attempt to describe why and how individuals known as "espers" are able to interact with their environment and the people and things in it in ways that ordinary non-espers are unable to. The basic idea is that a substance, called duskflow, that is similar in nature to aether flows from the moons; rather than interacting with air and voltaicity, however, it interacts with the minds of espers, giving them their supernormal abilities.
Duskflow Theory is less a modern scientific theory than it is a collection of folk wisdom and extrapolation, tenuously supported by some empirical testing and the fact that no other theories explain esper abilities, or in fact have even been seriously put forward. Much of what is currently called Duskflow Theory was developed very recently, following the discovery of a large lexograph cache in the farthest corner of the Sinderlands; while most scholars were interested in the find because it was largely written in Middle Miro (thus proving that Artic influence was strong and widespread even in the Sinderlands as early as nearly a millennium ago), a certain group were more interested to discover that many of the texts dealt with stories of great (probably fictional) espers and the culture's elders' wisdom regarding the nature of espers' abilities.
In fact, current Duskflow Theory resembles near-exactly that "wisdom of the elders", with all the mysticism and storytelling pared away to make it more palatable to the scientific ear. The scholars who are the biggest proponents of Duskflow Theory have been widely criticized, but their rebuttal usually boils down to "Experiments have supported our theories." and "Nobody else can explain it better, so we must be right!"
The moons, through some unexplained quirk of their makeup or nature, produce duskflow, which then filters down through the aetherosphere and settles on the world. Espers unknowingly collect this duskflow and then manipulate it to create such effects as moving things, communicating mentally, and turning things into other things; we all know what espers can do, and this article isn't here to discuss that. Duskflow Theory proposes that espers' brains are uniquely designed such that they channel the duskflow if the esper thinks in the right manner, but it's just as likely and provable that they have an invisible duskflow gland that gathers the stuff, or that it all gets stored in their bones.
It has long been known that even non-espers can access some esper abilities with the correct rituals and even infuse these abilities into an Apparatus; it is similarly true that these rituals gain power and efficacy as more moons are present and the fuller those moons are. Duskflow proponents point to these facts as further evidence of their theory, but without proof, it's as likely that there is no duskflow, but rather the sun produces an inhibitatory substance and the moons block that, rather than the converse. Who knows.
The experiments that Dusfklow Theory scholars most frequently reference are known as the Solarite Studies; contained in the lexographs that these scholars based their theories on was a recipe for a material known as solarite. Solarite is essentially an alloy of several metals that is then treated with a very specific heating and cooling cycle; the texts claim that this material blocks duskflow, thus preventing ritual use and gradually draining even espers' ability to manipulate duskflow as it cuts off their supply.
Essentially, a large number of people, espers and otherwise, were housed in small chambers made of solarite and told to perform rituals and/or use their esper abilities repeatedly over the course of two weeks. The scholars monitored the subjects' esper capacity over this time, and reported a steep decline in functionality, with rituals ceasing to function in as little as two days and even powerful espers unable to do the simplest parlor tricks after a week.
Of course, with no reliable (or even unreliable) way to actually measure duskflow or the power of an esper, these results are speculative at best. On top of that, the Studies were run entirely by Duskflow Theorists, with no impartial or uninformed parties present; this makes it entirely possible that the results were entirely fabricated to support the theory. There is little hope of a better-conducted repeat of the Studies at any point in the near future; solarite is prohibitively expensive, and in any case most scholars are too uninterested in the question "what makes espers and rituals possible" to devote time, money, or energy into studying the theory.
Of course, espers are not the only things capable of producing near-supernatural effects: several animal and and a few plant species are capable of esperlike abilities; most such species make their homes in the Shadowlands, but several have been identified even above. The most notable and relevant example of this is the Indikos Bloom, whose glowing flowers and preternaturally-tough stalks have been used since time immemorial for a tremendous variety of purposes; chief among these is, of course, the plant's ability to store memories or speech, making them an excellent archive before even the development of lexographs.