In Philip Pullman'sHis Dark Materials and The Book of Dust trilogies, Dust or Rusakov particles are elementary particles associated with consciousness that are integral to the plot. Dust features in the multiverse written about in these trilogies and companion books. In these universes, Dust is attracted to consciousness, especially after puberty; the Church within the series associates it with original sin and seeks its end. Pullman described Dust in a 2017 interview as "an analogy of consciousness, and consciousness is this extraordinary property we have as human beings".
Naming
In Northern Lights, Lord Asriel reveals the origins of the term "Dust" to be from a passage from the slightly alternative version of the Bible in Lyra's world: "In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return" . Dust was previously known as "Rusakov particles" named after their discoverer, Boris Mikhailovitch Rusakov. Rusakov discovers a field permeating the universe enabling consciousness; before the discovery of Dust, its existence is predicted, as "the existence of a Rusakov field implies the existence of a related particle". Mary Malone researches dark matter in an alternative universe, referring to it as "Shadows". The name "Shadows" was given to the particle by her colleague, Oliver Payne, in references to the Allegory of the Cave, involving "Shadows on the wall". When she is able to communicate with Shadows by interfacing with her detector, it confirms that they are the same as Dust and dark matter. The Mulefa, who are able to see Dust directly, use the word "sraf" accompanied by a leftward flick of the trunk to describe it.
Functions
Dust is attracted to objects that have been formed by consciousness, and can be viewed by special photographic emulsions. It is particularly attracted to consciousnesses that have matured; in the case of humans in Lyra's world, this happens when their Dæmon is fixed in shape. For the mulefa, this happens when adolescents start using wheels. Dust is also what connects humans to their dæmons. If the bond between a child and their dæmon is severed, both the child and the dæmon will eventually die. If the separation occurs after Dust has settled on the person, the person becomes a lifeless shell. In Pullman's trilogy, Angels are formed when Dust condenses. It's noted that they only appear as winged humans because that's what is expected; in reality, they are much more complex shapes, more similar to "architecture". Dust is able to communicate with humans via several methods shown throughout His Dark Materials and The Book of Dust, including by use of alethiometers. Mary Malone is able to construct a computer program that, when paired with a detector, can communicate with Dust by typed questions. Later, Mary uses I Ching divination, which Lyra confirms to be a method of communicating with Dust.
Alethiometers
In Lyra's world, six alethiometers were constructed. Also known as symbol readers, alethiometers have a ring of 36 standard symbols, but differ in level of decoration. Over the course of the books, several alethiometers are shown being read, including by Lyra Belacqua, Hannah Relf, and Fra Pavel. Each symbol on the rim of an alethiometer has indefinite levels of meaning; for example, the anchor can mean steadfastness, hope, or the sea. To phrase a question, three adjustable arms are pointed towards symbols, and the reader has to hold the level of meaning for each symbol in their head. A fourth arm, made of an alloy sensitive to Dust, swings around, stopping on different symbols to give an answer, with the number of times it stops at a given symbol indicating the level of meaning intended. In La Belle Sauvage, it is said that no more alethiometers can be built as their construction depends on a rare metal being subjected to special treatment, knowledge of which has been lost. Oxford has an alethiometer in its library, which is read by Hannah Relf, various other universities have one, and one is missing. After the Magisterium attempts to steal one, a secret society opposed to their actions is able to obtain it and give it to Relf to use for them. The missing alethiometer is found by Malcolm Polstead in the pack of Gerard Bonneville and given to the Master of Jordan College at the same time as Lyra is given, for safekeeping. In Northern Lights, this alethiometer is given by the Master to Lyra, who learns to read it by intuition, and it is said that there are only two others in existence at that time.
History within the books
Dust came into existence when consciousness did, as it is created by consciousness as well as being itself conscious. Dust condenses into Angels; the first of these was called The Authority, and told all future angels that he was the creator of the multiverse. About 33,000 years ago, Dust induced changes in sapient species, including humans and mulefa, to allow them to interact better, conferring more consciousness. For the mulefa, this was the start of their oral history and memory as a species. When asked directly, Dust states that this was done by rebel angels for "vengeance" over the war in heaven. 300 years before the start of His Dark Materials, scientists in Cittagazze created the Subtle Knife, which allowed them to travel between worlds. However, Dust was lost in the cracks of these windows into the void between universes, and the mulefa noticed that their trees, which depend on Dust for fertilisation, started producing fewer seeds.
