Doesn't the Doctor Who episode Blink have a paradox?

Question

I have a problem with the Doctor Who timeline in several episodes. For example, in the 10th Doctor episode, "Blink", the Doctor and Martha Jones were trapped in 1969 and are able to leave a message for Sally in 2007 to assist them getting back the TARDIS, which was stuck in 2007. After the problem was solved,

Sally encountered the Doctor in 2008, but at that time the Doctor didn't even know Sally, and Sally passed the Doctor the clues to escape from 1969 - in particular, the DVD Easter Egg script that Larry wrote in 2007.

In my point of view, Sally wouldn't be able to solve the problem if the Doctor didn't know about Sally before the Weeping Angel sent them back to 1969, and the Doctor can't leave a message to Sally in 1969, because the Doctor couldn't know the exact events that would happen in 2007.

Sally needed to know about all this before the Doctor was trapped, and her source of information is the Doctor, and at that time the Doctor don't know about the trouble he was going to encounter.

This complex timeline of Doctor Who is a "chicken and egg" paradox, isn't it? There are other examples of this in Doctor Who, such as:

• The 11th Doctor episode "The Big Bang" - how did the Doctor get out of the Pandorica?
• The 10th and 11th Doctor "River Song" story arc.

Answer 1

That's more or less what's explained in the episode.

Remember the video of The Doctor explaining what time is?

Time is like a big ball of wibbly wobbly timey wimey... stuff.

There's a "Children in Need" mini-episode on that theme, too. The Doctor (10th) find himself stuck with The Doctor (5th) on the TARDIS. The only way to save himself is to press a series of buttons on the TARDIS console.

Which he knows because he (the 5th) saw himself do it (the 10th). And the 10th knows, because 5th knows and they have the same memory.

It's a paradox, but it's not, because it's Doctor Who.

Answer 2

Believe it or not, these sort of "closed timelike loops" aren't a paradox at all. They've been debated by better brains than yours or mine, and the mathematics holds out.

Quoting from Wikipedia's article on the "Novikov self-consistency principle":

Joseph Polchinski ... argued that one could avoid questions of free will by considering a potentially paradoxical situation involving a billiard ball sent through a wormhole which sends it back in time. In this scenario, the ball is fired into a wormhole at an angle such that, if it continues along that path, it will exit the wormhole in the past at just the right angle to collide with its earlier self, thereby knocking it off course and preventing it from entering the wormhole in the first place. Thorne deemed this problem "Polchinski's paradox".

After considering the problem, two students ... were able to find a solution beginning with the original billiard ball trajectory proposed by Polchinski which managed to avoid any inconsistencies. In this situation, the billiard ball emerges from the future at a different angle than the one used to generate the paradox, and delivers its younger self a glancing blow instead of knocking it completely away from the wormhole, a blow which changes its trajectory in just the right way so that it will travel back in time with the angle required to deliver its younger self this glancing blow.

This is the model that current "Doctor Who" writers follow whenever "wibbly wobbly timey wimey" is invoked.

In summary: time travel (whether using closed timelike loops or TARDISes) cannot be used to create a contradiction, which is a paradox -- but it can be used to create self-consistent loops.

Answer 3

Basically, the point of that episode and others like it (Such as Big Bang 2 when the only reason the Dr got out of the box is that after he got out he went back and told Rory to get him out.) is that time isn't "linear" in respect to itself - a person always moves forward along his own timeline, but the universe's timeline may have "loops". In the Doctor Who universe, time may be circular (and as noted by others, Paradoxical).

Look at it this way in Blink - once the Doctor was able to help Sally save the Tardis from the Angels, it was inevitable that Sally would, in her future, share the story with the doctor. Once the doctor received the information from Sally, it was inevitable that he would help her, in his future. It's a perfect, unbreakable circle - once entered at any point it cannot be left.

Answer 4

i believe that the doctor may have sent out a different message "earlier" (in a previous continuity of time) to sally sparrow after meeting billy in 1969, either through a video or through billy (a simple message such as "send the TARDIS back" may have enough) later in 2008 she meets the doctor outside the dvd store and gives him some sort of account of what happened, so that when the doctor "later" (for the doctor this happens later on) gets stuck in 1969, he checks that information, and this may happen many times until it stabilizes into a healthy loop. the truth is, that once she tells the doctor even a little, "before" (from the doctors perspective) he travels to 1969, a time loop is created that will loop over until the same exact events happen in 1969 twice (think about it) so without a time loop there would be a problem.

Answer 5

Yes, it has a paradox. No, the billiard ball comment is not relevant.

There are different types of paradoxes. The type all these comments seem to discuss is a paradox where one changes his/her own past through time travel, causing a circular loop that cancels itself out. For example, if you travel back in time and kill your past self, you create a paradox. Since past-you died, future-you never existed, thus future-you never killed past-you, meaning future-you does exist, so future-you kills past-you, and so on.

The paradox in this episode is essentially the same, with one major difference. The problem here is not that future-you can't kill past-you, but rather that future you can't save past-you. The difference between the paradoxes is that the "kill" paradox can theoretically occur, while the "save" one can't.

Let me explain. Theoretically, and particularly in Doctor Who, time is a dimension, yet each person has a personal timeline, or progress. In DW we follow the Doctor's timeline.

-If you are at a certain point in your timeline, then jump to another point in the "past" and kill the "past" version of yourself, you are stuck in a continuous loop, but you had some way of getting there. The paradox started at a certain point. It is logical.

-If a future version of yourself saved you, there is no connection or progress. You could never reach that "future" point in time because you died. Meaning, you could only survive because you saved yourself, and you only saved yourself because you survived. The events are not a part of any timeline, and are dependent on each other.

The "kill" paradox could occur in nature, although it may result in a black hole, or some "Back to the Future" type of situation. The "save" paradox can NEVER happen.

Sally survived because the Doctor warned her and guided her, but the Doctor was only able to help her because she survived. Every single aspect of the episode was impossible, from the transcript to Sally's eventual meeting with the Doctor. Steven Moffat tried to wave if off as Wibbly Wobbly, but DW is a science fiction show, and he can't just disregard science (that hasn't stopped him, though).

To be honest, this episode might be impossible, but it's still fantastic and pretty clever. One of my favorites.

Answer 6

How about a multi-universes answer to this question:

All of the universes where the 'send the information to the future' method did not work - don't exist because the story ends there.

We are just watching one of the examples of the 'information successfully arrived in the future' outcomes and that makes the story work!

This means that while there are possible cases where Sally does not solve the problem (or even get the message) are automatically outside of the world case we are observing.

This is the same for the case where the Doctor remembers pushing the right buttons in the Tartis -> In all of the cases where they push the wrong sequence of buttons the 10th doctor does not exist.

In another way of saying it: Time travel could be naturally iterative (and wibbly wobby) thus every event that takes place is one iteration (or the last iteration) case where everything that didn't work.... has now worked itself out.

How happy ending....

Answer 7

Well remember. He didn't know her because he had never seen her face. He only read the transcript. But also remember just because he was in 2008 doesn't mean he had been to 1969 yet.

Answer 8

I think time uses all possibilities. The possibility Doctor does all to free past doctor, to be still alive, if not there again, and again stays created new possibility Doctor to use new possibility. Time Ping-Pong Paradox.

Answer 9

Blink was a paradox/bad science or badly explained, but I am banking on the former since RTD is not as good as Steven Moffat. Yes, time-streams do not run linearly, but what happened in Blink could not conceivably have happened unless Sally, figured out on her own the first time, which I doubt that she did.

Regarding the Pandorica, easy explanation is that it was not an impenetrable prison after all, and that the Doctor escaped somehow and acquired a vortex manipulator since he no longer had access to the TARDIS.

The River Song arc is not paradoxical at all.

Let's say that Doctor A (which is the very first instance of the Doctor) reached the Field of Trenzalore and River A (First instance of River was not stolen from The Doctor's timeline). The Silence then go back to steal River B (Younger instance of River) in order to prevent The Doctor from reaching that point. River B grows up to attempt to kill Doctor B and uses up all her regeneration energy to save him, and the Doctor does not find out about his death since it has not happened yet. Eventually, River B ages some more, and is caught by Kovarian and sent to kill Doctor B (An instance of the Doctor after Doctor A), who is the first Doctor and ONLY instance of the Doctor dying at Lake Silencio. River B goes back in time to the Donna era with Doctor C and dies (First time that the Doctor is called to the Library since River is the one who beckons for him to come). The second instance of The Silence intervening results in a River C that uses up all of her regeneration energy to save Doctor C (older instance of the doctor), who finds out that he dies at Lake Silencio. The Teselecta dies in Doctor C's place for all of future instances of this scenario when River C kills it after finding out that the Doctor has no intention of dying, and River D and Doctor D (delayed invite for The Doctor) are invited to this event. River C does not suggest to Amy that she already knew that it would happen, just that she knew that the Doctor did not die. Eventually River C calls Doctor E to the library and is saved this time because Doctor D gave her his screwdriver in anticipation of her death. After it happens once again with River E and Doctor E being invited to the event, River D tells Amy that she already knew that the Doctor D wouldn't die as she had been invited to the event when she had been younger. I believe that the Pandorica occurred as a result of The Silence eventually finding out about Doctor D (and future instances) surviving to reach Trenzalore, resulting in the second Big Bang first occurring in Doctor E's timeline. Yes, I do believe that many extra points in time were created for future instances of The Doctor as they could not have feasibly occurred in previous scenarios where the timeline was being fixed so that The Doctor could reach Trenzalore.