Talk:Causality

Preserving initial attempt
When I encountered it, the article contained this text, which contains multiple violations of our basic rules. It's preserved here int he hopes of finding something with which to rebuild the article. 04:16: Mon 18 Mar 2013

Causality is the relationship between cause and effect, and that concept that a cause must precede an effect in relative linear time. Classically, a causal nexus is a generic term for that set of factors (or causes) that influenced an end effect.

When the Tenth Doctor says that time is "more like a big ball of wibbley-wobbly, timey-wimey stuff," he specifies that this is from a "non-linear, non-subjective viewpoint." (TV: Blink)

Although our genius Time Lord appreciates that time is not necessarily bound in a linear flow, we know from example that his experience of time is linear (and therefore causal), if strictly relative to his own subjective viewpoint. The strongest evidence for this is when the Doctor's TARDIS, in the body of Idris, who earlier stated that she exists across all time and space, states that she has archived 30 different versions of the TARDIS control room, the Eleventh Doctor protests that he's only changed it twelve times and "you can't archive things that hasn't happened yet!" The TARDIS replies that he can't, confirming that the Doctor must experience linear time even if she doesn't. (TV: The Doctor's Wife)

The Eighth Doctor referenced causality while describing anti-time, effectively equating causality with time itself. "Anti-time: as intractable and destructive a force to causality as antimatter is to space."

The Tenth Doctor frets about staying relative in the causal nexus in TV: The End of Time.

When asked to help save her younger self, Older Amy says, "You’re asking me to defy destiny, causality, the nexus of time itself?” (TV: The Girl Who Waited)

The Eleventh Doctor says that they "have to stick to the established chain of events, one mistake and the whole timeline could collapse". When he resolves the issue, he says that "the localised time field is no longer about to implode and rip a hole in all causality." (TV: Time) He also chastises Amy Pond for reading ahead in "Melody Malone", as reading ahead forces them to ensure that what they learned comes to pass. (TV: The Angels Take Manhattan) On several occasions he ensures that he and his companions complete the actions to which their past selves have already reacted. (TV: The Lodger, The Big Bang, Space / Time)

Behind the scenes
In physics in the real world, causality is the generic relationship between causes and effects, and is considered a fundamental concept of all natural sciences. In relativity theory, for every given event there is a set of things that influence the event and a set of things that are influenced by the event. In the real world, a signal is said to violate causality if, to any possible observer, it appears to be travelling faster than light, or in other words, backwards in time.

The real world concept of the closed timelike curve describes certain sets of solutions to the equations of General Relativity where causality would break down, allowing event to be simultaneous with cause.