The scale theory is one of many unofficial names given to a theory that explains the inconsistencies between RuneScape's storyline and actual visible nature. As a theory it is open to debate: it is not prominently featured in the game and remains to be a developed thought backed up by evidence.
The theory has arisen due to the game's much more grandiose storyline, which would be impossible in the area actually seen in-game. For instance, it is possible to walk across the whole of the Gielinorian mainland in a matter of hours (if not minutes), whereas it is frequently described as a continent of massive size and scale. Also, cities such as Varrock, which are meant to be massive, sprawling settlements, possess limited inhabitants and often lack basic living facilities for all of the populace. These and countless other inconsistencies have led to the creation of the Scale Theory.
Scale Theory is the idea that RuneScape is a fictional world being viewed on a scale. The world is, in its fictional universe, logically designed, as the storyline suggests. The version presented in-game is much smaller than the actual fictional world of Gielinor and has been scaled down to make gameplay possible. Essentially, the world of Gielinor is being viewed through a filter that removes most of the details from the world that are not necessary for gameplay, and condenses all of the world's features into a reasonable size for playing.
Time is another part of Scale Theory. Time could actually go much faster in the "game" than in the real Gielinor. Every second could actually be an hour or even more. This is supported by the fact that during farming, plants grow up very fast, and sea voyages are displayed as brief cut-scenes. However, until the death of the young god Guthix, which advanced the Gielinorian perception of time to the Sixth Age it was officially stated to have been the year 169 of the 5th age since the release of the game despite the theoretical time that would pass and events that occur within the game, further increasing the disparity.
This opens up some very strange possibilities, such as that the player is controlling a "real" person in the "real" world of Gielinor, but having the avatar presented to them in the "game" world–essentially implying that the "real" world of Gielinor, the true real world, and the "game" world are three separate planes. The events happening in the "real" fictional world are occurring in the "game" world, but the "game" world is merely a sort of inter-plane device presenting the "real" fictional world to the player in the true real world. This makes the bartender's mention of a "magic box" discussed below very intriguing, and full of strange fourth-wall-breaking quest possibilities.
The Theory is briefly presented to the player by the bartender in the Blue Moon Inn. He explains that the RuneScape is a computer game which is in a "magic box", and this implies a difference between what players see whilst on the game and what the actual inhabitants see. Some obvious evidence of scaling exists even within the game itself; for instance, during Temple Trekking, players visit many parts of Mort Myre Swamp that do not exist when travelling through it normally, suggesting that huge swaths of it have been omitted from the standard map. Further evidence supporting it are various caves and quest areas, which are usually quite large in comparison to the outside world. For instance, in the quest Underground Pass, the player travels through a vast tunnel network, with the final cave area being larger than most cities, yet the World Map suggests nothing of the kind.
Scale theory is also supported by the illogical transition between terrain and climate. For example, the temperate woodland of Misthalin is right next to the desert of Al Kharid, separated only by a cliff.
Scale Theory is supported by several RuneScape Lores and stories. These are not ingame features, and as such the qualitative assumptions may not necessarily be extrapolated into the lore of the game. For instance, in the first RuneScape novel, Betrayal at Falador, it takes characters days to travel between settlements in the kingdom of Asgarnia. Falador is described as a vast city with more than 10,000 inhabitants and a large district of rundown houses (The Dens), a feature that does not appear within the game at all. The lore The Coat Thief makes the Dwarven city of Keldagrim sound far bigger, emphasizing the differences between East Keldagrim and West Keldagrim. Another lore, The Fall of Six, also supports this theory, proposing that a march from Misthalin to the Barrows site takes a full year, and can fit a massive army, yet the area from the Salve to Barrows is only big enough for maybe 200 people, and getting to the Barrows takes only a few minutes. The degree to which these observations are relevant for in-game play are questionable, and up to personal interpretation.
It should also be noted that in real world, what we see is what the land really is. In RuneScape, and in fiction generally, we can only see things that the developers have released. Some parts of the Northern Sea could, for example, be a placeholder for content to be released in the future, and cities such as Menaphos, while they currently appear blank, are in fact real cities in Gielinor, but have not been fully developed and released by Jagex.
The coordinate system used in Treasure Trail coordinate clues spans only about 50 degrees north-south and west-east, compared with 180 degrees north-south and 360 degrees west-east on Earth. However the northern regions already show arctic conditions, suggesting that either the coordinate system or the geographical circumstances differ significantly with Earth.