as reported in Thud!, the red- and blue-shifting of light becomes noticeable when travelling at speeds of merely a . The power of belief Reality is spread thinly on the Disc, so events may be affected by expectations, especially those of 'intelligent' species such as humans, dwarves, etc. As such, the Discworld is not governed by real-world physics or logic but by belief and narrative resolution. Essentially, if something is believed strongly enough, or by enough people, it may become true. Jokes such as treacle mines and drop bears are real on the Disc; in reality lemmings do not actually rush en masse off cliffs; on the Disc, they do, because that is what people believe. These concepts of Discworld physics are also exploited in both wizard and witch magic. For example, when a character wishes to turn a cat into a human, the easiest way is to convince the cat, on a deep level, that he is a human. In fact, the main reason the Auditors of Reality dislike sentient beings in the Discworld universe is that the Auditors are the personifications of the real-world laws of physics, but the Discworld physics' power of belief and the humans' ignorance constantly remake the world, making their work fruitless. More significantly, it is also belief that gives Discworld's gods their powers. Discworld gods start off as tiny spirits, and gain power as they gain believers; this is explored most thoroughly in Small Gods. A similar effect has led to the personalisation and "reification" in the Discworld universe of mythological beings symbolising abstract concepts, such as Death, the Hogfather and other anthropomorphic personifications. In Hogfather, the assassin Mr. Teatime tries to kill the patron of Hogswatch by using an old magic that involves controlling a person with a part of their body (in this case, the teeth collected by the Tooth Fairies), in order to stop children from believing in him, and almost succeeds. It is also possible for humans to gain godly powers through the power of belief, such as the Kings of Djelibeybi as seen in Pyramids, and the Duchess Annagovia of Borogravia in Monstrous Regiment. Such is the nature of belief on the Disc that temporary new gods come into being on a regular basis, and often for such mundane things as stuck drawers; Anoia, Goddess of Things That Get Stuck in Drawers, came into her powers in such