Blinovitch Limitation Effect

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Two temporal versions of Brigadier Lethbridge-Stewart about to experience the consequences of the Blinovitch Limitation Effect (from Mawdryn Undead).

The Blinovitch Limitation Effect is a fictional principle of time travel physics in the universe of the long-running British science fiction television series Doctor Who.

It is usually understood as having two aspects: firstly, that a time traveller cannot "redo" an act that they have previously committed, and secondly, that a dangerous energy discharge will result if two temporal versions of the same person come into contact. The first aspect is similar to a real-world physics conjecture, the Novikov self-consistency principle.

[edit] The classic series

The Effect was first mentioned in Day of the Daleks (1972), when Jo Grant asks the Third Doctor why a group of time-travelling guerillas on a mission to assassinate a diplomat cannot simply go back into the past and try again if they fail. In reply, the Doctor cites the principle and begins to explain, but is interrupted before he can explain further. The Effect was invented by script editor Terrance Dicks and producer Barry Letts to gloss over the plot problems inherent in the time travel premise of the serial, but was never laid out in detail.^[1]

The Effect is next mentioned in Invasion of the Dinosaurs (1974), where the Third Doctor states that it "tends to limit research into time travel" but once again he does not go into detail as to why. The novelisation of the story reveals that Blinovitch was a "great bear of a man from Russia" who had reversed his own timestream, reverting to infancy.

The next time the Effect is mentioned on-screen is in Mawdryn Undead (1983), but here it is not simply a scientific principle that prevents people from redoing their actions (for whatever reason), but as a physical effect that occurs when two versions of the same person from different time periods make physical contact. This results in an energy discharge, shorting out the "time differential" between them. It is possible, however, as Lawrence Miles and Tat Wood theorise in their reference book About Time 5, that the energy discharge is simply a side effect of the principle's operation.^[2] It also appears, given the number of times that the Doctor has met his other incarnations, that the Effect does not apply to Time Lords, or at the very least can be mitigated. The Doctor appears to show sensitivity and resistance to temporal distortions, particularly in The Time Monster (1973) and Invasion of the Dinosaurs.

The Virgin New Adventures novel Timewyrm: Revelation by Paul Cornell gave Blinovitch the first name of Aaron (and the title of his book as Temporal Mechanics). The Virgin Missing Adventures novel The Ghosts of N-Space by Barry Letts claimed that Blinovitch formulated his principle in the British Museum's reading room in 1928, and although he was not the first to discuss it, he was the first to formulate it properly. Like all tie-in media, the canonicity of all such books is unclear.

[edit] Theories

Miles and Wood suggest that the key word is "Limitation"; that is, the effect limits the amount of interference in the past as opposed to completely prohibiting it. This interpretation is supported by the Barry Letts-written Doctor Who radio play The Paradise of Death (1993), where the Third Doctor explains to Brigadier Lethbridge-Stewart that it is possible to leave a location in the TARDIS and arrive at a time before they actually left, since the Effect only stops someone from interfering with their own past. Although the First Doctor claimed that it was impossible to alter history in The Aztecs (1964), other stories such as The Time Meddler (1965), Day of the Daleks, Genesis of the Daleks, Pyramids of Mars (both 1975) and Remembrance of the Daleks (1988) imply that changing history is still possible.

[edit] The new series

In the 2005 series episode Father's Day, Rose Tyler manages to cross her own timestream and redo her actions, managing to save her father from dying in 1987, although this paradox results in serious repercussions dealt with in the story. Speaking at the Gallifrey convention in February 2006, episode writer Paul Cornell said that although his script does not mention the Blinovitch Limitation Effect by name, it was in the forefront of his mind while writing the episode. The warnings that the Ninth Doctor gives to Rose about not attempting to cross their timestreams a second time and not to touch her infant self are consistent with this.

However, if the Effect were to behave as described in earlier stories, it should have prevented Rose's "redo" as well as her interference in her personal history, but it does not, although a paradox is created that summons the Reapers which proceed to "sterilise" the resulting wound in Time by devouring everything in sight. Also, when Rose briefly carries her younger self in her arms, there is no visible energy discharge (although a Reaper appears immediately, possibly as a result of the contact).

In this case, layers of clothing separated Rose and her earlier self, so it is possible actual physical contact was needed and not achieved. It is also possible that a "redo" could only be done because of the loss of the Time Lords and their stabilising influence on time (hinted at in The Unquiet Dead). This fits in with Miles and Woods's suggestions of a cosmic observer effect imposed on the universe by the Time Lords, resulting in the creation of the Blinovitch Limitation Effect as a safeguard against tampering with causality. It is also consistent with the Doctor's observation that if the Time Lords were still around, they could have repaired the paradox.

In The Parting of the Ways (2005) and The Girl in the Fireplace (2006) the Ninth and Tenth Doctors respectively make reference to becoming "part of events". In the former episode, Rose asks the Ninth Doctor why he cannot go back in time and warn Earth of the Dalek attack that is happening and he replies that once he "lands in that second, [he becomes] part of events. Stuck in the timeline." Once again, the Effect is not mentioned by name, but the consequences stated appear to be similar to those in Day of the Daleks, where the guerillas become caught in a predestination paradox, doomed to create the very future they are trying to avert.

Ultimately, how the Blinovitch Limitation Effect works is still not clear, nor has it ever been made clear by any of the television programme's production teams. It remains more a convenient plot device than an attempt to rationalise time travel in the Doctor Who universe.

[edit] Popular culture

Blinovitch is mentioned a number of times (presumably as an in-joke for Doctor Who viewers) in the romantic comedy Happy Accidents (2000), which has a plot involving time travel. In the film, Blinovitch is said to have been from "Yugoserbia" and discovered how to bend spacetime. Two of his laws are invoked: "Blinovitch's Second Law of Temporal Inertia" and "Blinovitch's Fifth Law of Causal Determination".

Blinovitch's Second Law apparently states that is impossible to time travel in your own lifetime. One can only time travel to the distant past, and only small changes in history are possible, which will "dampen out" by the time they reach the relative present. Blinovitch's Fifth Law resolves (in an unspecified manner) all paradoxes involved with time travel.

[edit] Footnotes