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Doctor's Dilemma

By Jon Preddle

The column in which you send in questions about Doctor Who, and former Mastermind contestant Jon Preddle attempts to answer them. This issue, we address a tricky problem involving Dalek invasions and time travel...

Jeff Stone sent in the following question regarding the Day of the Daleks story: "The guerrillas travel back in time from the 22nd Century (say, 2172), to prevent the outbreak of nuclear war in 1972. The nuclear war that began in 1972 was (directly responsible for the Dalek invasion a few years later. At the end of the story, the wounded guerrilla blows himself and the Dalek invasion force sky high. As Styles and the other world leaders were not killed, World War 3 never happened. Ergo, neither did the Dalek invasion. So, why are the Daleks in control of Earth in 2172 when the invasion never happened? Paradox!

"However, if WW3 never happened and the Daleks never invaded, there would be no point in the guerrillas travelling back in time because 1) their present (our future), never took place - they would never have been born - and 2) there would be no point in stopping an invasion (and a war) that never happened!!

"But - if this is true, the guerrillas would not have travelled back to 1972 - all of the Day of the Daleks would not have happened, and the Daleks would not have invaded. Double paradox!"

I am a fan of time travel paradoxes in both literature and media, and as such, Jeff's question struck a chord - but it has taken me several attempts to come up with a workable solution!

Before I begin, I would like to point out that the Dalek invasion seen in Day of the Daleks is not the same invasion as seen recently on our screens in The Dalek Invasion of Earth. The Day of the Daleks Daleks clearly state that they have invaded Earth "again", so these Daleks are from a future time than those seen in The Dalek Invasion of Earth.

The answer to Jeff's question comes from Pyramids of Mars. In that story, the Doctor shows Sarah an alternative time stream; a possible future for Earth should Sutekh win. Basically, that works on the concept that since the Doctor has left 1911, he is no longer there to stop Sutekh, and so the Osirian destroys Earth. It is this time stream that the TARDIS travels along because it is real. But when they return to 1911, and kill Sutekh, a new time stream is created. Think of it as a torch, pointed at a wall and turned on. The light beam can be likened to a timeline. Turning off the torch ends that light stream, but pointing the torch at another wall and turning it back on creates another.


To apply this to the time paradox problem, I have used a diagram. We start in 1972. The guerrillas have travelled back from 2172 on time line Y in order to kill Styles and prevent the war that allowed the Daleks to take over. The Doctor accidentally returns to 2172 with them (Q-Q). He is no longer in 1972 and so is not able to warn the delegates, leading to the war recorded in the guerrillas' history. The guerrillas are responsible for causing the war by removing the Doctor from 1972! But the Doctor does return to 1972, warning the delegates and saving the conference, thus preventing the outbreak of war. By doing this, he has effectively shut off one 'light beam' (Y), and turned on another (X).

The events of A, the common elements of both time lines, are crucial to the next set of events. Junction Z is the explosion which destroys Styles' house, as this is the only common factor in both histories - one in which the delegates are killed, and one in which they are saved from death. Both time lines exist at the same time, although line X is the one that the Doctor stays in.

We now jump ahead 200 years to 2157. Earth has now developed space travel, and come to the attention of the Daleks on Skaro. The Daleks invade Earth, and the consequences of this are seen in The Dalek Invasion of Earth, when ten years later, the Doctor arrives and assists in the defeat of the Daleks. Now, 700 years later, the Daleks have discovered the secret of time travel (possibly stolen from the Time Lords because the dematerialisation circuits in the portable time travel devices are miniature TARDIS dematerialisation circuits!), and they plan to travel back in time to Earth, but arrive about 100 years before their previous invasion. They want Earth's valuable minerals - they know of these from mining out the planet during their previous invasion. This is the plan, but it goes wrong. Their time machines are unstable, and they are shifted sideways in time (like the Doctor in Inferno), and they arrive on Earth in the Y time line (H-H).

They find the planet in a state of war - but this contradicts their records because according to the Daleks who invaded in 2157, Earth wasn't at war. Nevertheless, the Daleks are able to take over as there is no power capable of stopping them.

They rule the planet for another 100 years - until guerrillas steal the plans for the time travel devices and travel back to 1972 to prevent the war, and the rest, as they say, is history...

I hope that was as easy to follow as it was for me to write! If anyone has any other ideas, then drop me a line.

I think the Doctor sums it up beautifully when talking to Jo in episode one of Day of the Daleks. He says, "It's a complex thing, time, Jo. Once you start tampering with it, the oddest things happen..."

This item appeared in TSV 22 (April 1991).

[See also How the Day of the Daleks makes sense]
Index nodes: Doctor's Dilemma, Day of the Daleks
Reprinted in: TSV: The Best of Issues 21-26