Which isn’t much compared to the amount of space-time that gets manipulated during the series. Literal time travel, giving items more space inside, than that take up externally etc.
Most of the spacetime manipulation are still within the realms of physics, or at least can be reasonably described as long as you change a few assumptions e.g. the existence of negative mass, an infinite energy source etc. Only the time turning and fidelius have actual philosophical implications and former has been thoroughly studied and debated in both normal philosophy and natural philosophy.
"The Fidelius Charm (incantation unknown) is an extremely difficult, multifaceted and potent charm that can be used to conceal a secret inside an individual's soul; the witch or wizard who houses the secret is known as the Secret Keeper.[1] A dwelling whose location has been protected by this spell is then invisible, intangible, unplottable and soundproof. This is an extremely old spell, one of the most ancient of all."[0]
it's sort of like an in-world deus ex machina device, much like many of the spells and artifacts in the HP franchise.
The most important crux of the matter is that it can hide both a posteriori and a priori knowledge. An existing piece of information in the world can literally be rendered unavailable except to a select group of people.
In the book:
> As long as the Secret-Keeper refused to speak, You-Know-Who could search the village where Lily and James were staying for years and never find them, not even if he had his nose pressed against their sitting room window!
This raises a lot of uncomfortable metaphysical and epistemological questions. Is this a purely psychological effect? Or does this operate on the information itself? If it operates on information itself, how big can you scale the effect?
Ignoring magic, if such an effect truly exists, what are its implications for information theory? (Especially since the information is clearly not destroyed as the spell can be undone.) Information itself could become weaponized. Can a RAM bit flip be triggered though the application of such an effect? Or is this effect purely mental?
What about second and third order effects? Does the effect propagate? Assume a machine learning system with the following knowledge/word vectors: Food + Italy = Pasta. If Italy is placed under the fidelius, are the vectors and weights going to magically re-arrange themselves? How will people talk about the dish pasta?
Of all the spells in J.K. Rowling's world this is probably the most creative/disturbing. The whole gimmick with the seven horcruxes is merely distributed systems theory applied to a lich's phylactery, a concept that can be traced back millennia to various ancient civilizations. Splitting and and anchoring soul has nothing on arbitrarily erasing, manipulating, and restoring information itself on an infinitely large scale.
