Web of Time

The Web of Time or Spiral Politic was the orderly structure of history, built and maintained by the Time Lords. It was Gallifrey's noosphere.

Structure
Rather than being a necessary fundamental aspect of the universe, the Web of Time was a meta-structure created and imposed on the universe from the Matrix by the Time Lords during the anchoring of the thread, when Rassilon used the Eye of Harmony as "the hitching post of chronology". (AUDIO: Neverland, PROSE: The Book of the War) Before this, the universe had no history or defined set of physical laws. (PROSE: Christmas on a Rational Planet)

It could be visualised as a map of history, with the Homeworld at its center. The Homeworld was immediately surrounded by a core set of worlds over which it had the most influence, locked into place as protections against the uncertainty outside. Like any noosphere, the Spiral Politic had an edge, the frontier in time, beyond which the Great Houses had great difficulty penetrating or even observing. Worlds made up the majority of historical systems on the map of the Spiral Politic, but there were some significant exceptions: these included regions outside normal time, like the Eleven-Day Empire and the City of the Saved, as well as a rare few individuals of blinding historical importance.

Homeworlders were directly linked to their noosphere. (PROSE: The Book of the War) The Ninth Doctor told Rose Tyler that he could see all that was and all that could ever be, and it was maddening. (TV: The Parting of the Ways) The Web was in constant flux, like an ocean of shifting possibilities; it could only be frozen into certainty by a Time Lord's direct touch or intervention, through the observer effect. It was for this reason that the Time Lords established their non-interference policy. (PROSE: The Gallifrey Chronicles)

Amaranths could also be used to rebuild unstable or discontinuous elements of the universe (PROSE: Christmas on a Rational Planet) along the lines of the established laws of the Spiral Politic. (PROSE: Against Nature)

Flexibility and fixed points
The Eighth Doctor explained that the Web of Time was resilient. In some cases, events could be reshaped; for instance, some people could safely have been made to die early if they led quiet, unobtrusive lives without any children. (AUDIO: The Zygon Who Fell to Earth) An example of this was Andrew Edwardson, who lived a quiet life on his own, so his death could not disrupt causality. (AUDIO: My Dinner with Andrew) In legal terms, such people whose deaths would have little to no impact on the causal nexus were deemed "future-proof". (AUDIO: Moving Target)

In other cases, when specific events were removed from the Web, analogous events would take their place. (PROSE: The Left-Handed Hummingbird) For instance, if Adolf Hitler was prevented from rising to power, a different man would have taken control of the Nazi party and begun World War II, though the War would've ended differently. (PROSE: Timewyrm: Exodus)

However, some events called fixed points in time had effects so significant that they would cause significant disruption to the Web if changed. This could cause disastrous repercussions in every corner of the universe, killing billions, instantly disappearing major civilisations, and threatening the fabric of the universe itself. (PROSE: Attack of the Cybermen) An early death for the Doctor would cause the stars to go out, (TV: Turn Left, The Name of the Doctor, AUDIO: The Furies) and when the fixed point of the Eleventh Doctor's apparent death was altered, time itself began to fall apart. (TV: The Wedding of River Song) The Tenth Doctor explained to Donna Noble that only Time Lords could tell the difference between fixed points in time and events that were in flux. (TV: The Fires of Pompeii)

The Sixth Doctor once explained that the Web of Time would be disrupted if Earth were destroyed before its time, (TV: Attack of the Cybermen) as Earth was a nexus world linked to the destinies of many major intergalactic powers. (PROSE: Alien Bodies) The saving of the Titanic would have similarly perturbed the Web by condemning all the later ships that were saved by round-the-clock radio surveillance, lifeboat capacities, or the International Ice Patrol, all of which were developed due to the Titanic's sinking. (PROSE: The Left-Handed Hummingbird)

Early in the War in Heaven, the enemy would often drastically alter certain worlds' relationships with history. On the map of the Spiral Politic, these previously-static worlds would appear to suddenly shoot across the chart. If one of these "shooting star" worlds collided with the Homeworld, it could take the Homeworld's place and retroactively replace it as the centre of history, wiping the Great Houses and their influence from the timeline. (PROSE: The Book of the War)

Even concerning events that were not fixed points, time could be crystallized along a particular web-way, (PROSE: The Sands of Time) making that event a fixed part of the Web of Time so that it had always happened and would always happen. (PROSE: Attack of the Cybermen) This could occur when a person learned about their personal future, (PROSE: The Sands of Time, TV: The Angels Take Manhattan) an effect first predicted by Blinovitch. (PROSE: The Sands of Time)

Events in the Web of Time
Events the Doctor stated as being part of the Web included the destruction of Mondas, (TV: Attack of the Cybermen) the sinking of the Titanic, (PROSE: The Left-Handed Hummingbird) the destruction of the Halcyon race through the Ice Warriors creating an atmosphere on Halcyon more suited to them, (AUDIO: The Resurrection of Mars) Deimos becoming an artificial sun that heated Mars, (AUDIO: The Resurrection of Mars) Gallifrey's Racnoss Wars, (AUDIO: Empire of the Racnoss) the burning of Joan of Arc, the assassination of Francis Ferdinand, (AUDIO: Cobwebs) the Manussan Empire overthrown in Manussan year 2326, (AUDIO: The Cradle of the Snake) Magnus Greel dying in the 1800s, (AUDIO: The Butcher of Brisbane) and humanity's 50-year war with the Eminence. (AUDIO: The Death of Hope)

Events in the Web that were explicitly recorded in the Matrix included the R101 crashing and all passengers dying, Adolf Hitler becoming Chancellor of Germany (and being alive to continue World War II), Edward VIII abdicating the British throne, German forces invading Poland, the evacuation of Dunkirk, Peladon entering the Galactic Federation, Zephon overthrowing the Embodiment of Gris, Mavic Chen being elected Guardian of the Solar System, Dalek forces assembling on Kembel and being engaged with the Movellans in 4-X-Alpha-4 in 4949, the Cult of Morbius being established, plans for the Doomsday Weapon being stolen by the Master, Chancellor Goth visiting Tersurus, President Romana and Etra Prime being taken by the Daleks and the subsequent Dalek invasion of Gallifrey being repelled by Romana, and a Dalek time fleet being captured in the Time Vortex. (AUDIO: Neverland) Charley Pollard was added to the Web when she saved it, not having died in the crash of the R101 as had been recorded. (AUDIO: Storm Warning, Neverland)