Maybe a Who fan can help me out,

Rose Tyler would be 26 in 2012, if she had returned to Earth before 2012 would she be able to bump into her 26 year old self in tonights episode if they had gone back to London 2012?

Hope that makes sense.

No she wouldn't. In 2005 Rose left Earth in the Tardis and would not be on Earth in 2012. But of she went back in time to, say, 1992, she could see herself.

How do we know that she didn't go back to Earth a minute or so after her mother walked off last week, after having been journeying around with the Doctor for a bit? The only way she won't exist in 2012 is if a) she never returns, b) she returns after 2012. or c) she returns before 2012 but dies at some point before it.

Ok so another thing , in theory then if the Dalek had killed Rose, the Doctor could of get in the TARDIS and gone back to the 'start' of that episode and killed the Dalek.

But is that what happened with Tegan, the Doctor dropped her back to earth at the exactly the same point in time he met her so she hadnt in theory been gone at all.

That would create a very annoying paradox.

The Dalek kills Rose, so the Doctor goes back to kill the Dalek.
Rose isn't killed, so everything is fine. But it's not
If Rose wasn't killed, the Doctor doesn't have a need to go back in time, so he doesn't kill the Dalek, so it kills Rose, so he goes back and so forth.

Why would they be stuck in that loop? The Doctor would be the only one with the true memory of what happened so would know killing the Dalek early on would prevent the death of Rose. So he could go back in time, kill the Dalek. The future changes.

It depends how you look at time travel. Actually, in dundee_mark's case, the Doctor that would go back in time to kill the dalek couldn't exist.

So the Doctor cant alter the future by going back in time?

Not when it involves himself.

But has the Doctor actually altered the past or the future deliberately?

Mmmm ok. So in the film the Daleks invade Earth in 2150 AD, yet in 2012 the last Dalek is supposedly killed.

So if that were the case would that mean that 2150 doesnt happen?

The film has nothing to do with the TV series. The Daleks have been killed finally on several occasions but time travel is a funny old thing. The never-ending loop described above is tied up with the Blinovitch Limitation Effect and Time Lords cannot do this (unless they're Paul McGann! )

The Peter Cushing films are not considered to be part of Doctor Who "canon".

But didn't the Dalek that was captured in last nights episode slip through time and end up on Earth as part of the Time War ?
So in effect 2150 did happen ??

(Totally confused )

No - the events in the film were a replay of the TV story The Dalek Invasion of Earth (which took place in 2164). Although this happens in our future, it takes place in the Daleks' past. Simple!

So are none of the Daleks on Earth episode set on Earth beyond 2012?

Why couldn't the Doctor exist?

*****brain explodes*****

Until the Dalek itself decides not to kill Rose - which is what happened in the episode. That would break the loop and resolve the paradox.

Ha - for all we know The Doctor and Rose met the Dalek thousands of times trying out different tactics until it decided not to kill Rose.

Causality Paradoxes suck (A-B-C-A). Star Trek uses them all the time, and they never really make sense.

Thankfully, Dr Who is usually far cleverer than that.

Is it not just a rule that The Doctor is not supposed to cross his own timeline, i think he can, its just forbidden by the Timelords. Seen on screen in The Three Doctors etc.

I'm really getting a headache, while reading all these! .

I think some of you are confusing Doctor Who with Groundhog Day!

guy's guy's please!

time traval goe's both back and forwards as well as (sideway's)
havent you seen passed dr who episodes come to that back to the future part 2?
changing the past doe's not mean changing the future but mainly creating an alternate one/ time lines??

well i hope that helps

Erm Tv Watcher, thats not right.

The actions in BTTF2 do change the timeline, thats the whole point - they are trying to correct problems that they themselves created by changing the past.

come to think of ot sliders is also a good example that used to be on sky one/ bbc2 a good few years back

Time travel: Don't even try to understand it.