Time Travel paradox

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If Weir went back in time and never came back she would not exist
after she left. She would have had to return at the same time as leaving.
To me no way I could leave. stay in the past and then meet myself,
after I never went back in time.
It would have made more sense to have a crew member (like the one in
Rising ll who found the space ships) to have gone back in time, then be found
in the stasis field and told the story of how the city almost sank, if not for
him going back. I can see someone leaving (going back in time) and being
listed as missing , then found, explaining way he has been missing, than to
have two exact people existing at the same time. How could the old Weir
exist if the Young Weir never goes back ? Somehow she has to go back
in time to be able to live in the past.
What are your thoughts
George Jr.

[N8ball88]

Welcome to Gateworld!

In Stargate, they use the alternate reality theory to explain time travel. If you go back in time, you are jumping to an alternate reality. Which is why there can be two Weir's in the same time.

[Admiral Mappalazarou]

Yeah well....Big Sally down at the pub had the exact same thoery and I'll tell you what I told her.

'Sally, get me a drink then maybe we'll talk about time travel.'

[Catsitter]

They do discuss this question in the actual episode (which was "Before I Sleep" in season ONE by the way!) and Rodney explains it with that alternative reality theory. They don't seem to subscribe to the same theory in a certain double episode near the end of SG1 season 8, though.

[Burning-Liquid]

When Dr.Weir went back into the past, you would assume that if she where to die there there would never be two Weir's in the same point in time.

However she alters her own future (past) so she doesn't have to go back in time. But if she doesnt have to go back in time... who gave the acients the idea to build the fail-save or the city?

That's why there had to be two Weir's, sort of two reality's getting merged.

[Scyld]

They do discuss this question in the actual episode (which was "Before I Sleep" in season ONE by the way!) and Rodney explains it with that alternative reality theory. They don't seem to subscribe to the same theory in a certain double episode near the end of SG1 season 8, though.

Actually, the SG1 double episode can be explained via alternate reality.

- SG-1 goes back in time to find the ZPM. In so doing, SG-1 creates an alternate future in which Ra took the Stargate with him when he left Earth, and everyone except Daniel Jackson is killed when they try to start the rebellion years too early. The original SG-1 timeline continues, but now SG-1 and General O'Neill are dead in the far distant past. Life goes on.

- An alternate Colonel O'Neill, Carter, and Teal'c (with the alternate Daniel Jackson getting killed on Chulak) go back in time to prevent Apophis from attacking Earth. Unfortunately for them, all they do is create yet another alternate reality - in their world, Apophis attacks, and the Earth is destroyed. The alternate reality that they create turns out to be almost identical to the original reality except for three key differences:
1 - There is fish in O'Neill's pond
2 - The ZPM is found buried where they left it in the past
3 - The battle at the end of 'Lost City, part 2' happens in a slightly different manner (Colonel Mitchell is included in it)

[The Signal]

3 - The battle at the end of 'Lost City, part 2' happens in a slightly different manner (Colonel Mitchell is included in it)

How do you know that there is any relationship with the events of Moebius and those of Lost City, for all any of us know Mitchell was always involved with that battle.

[Scyld]

How do you know that there is any relationship with the events of Moebius and those of Lost City, for all any of us know Mitchell was always involved with that battle.

Don't make me explain the joke. If I do, it will immediately cease to be funny.

[Catsitter]

Actually, the SG1 double episode can be explained via alternate reality.

- SG-1 goes back in time to find the ZPM. In so doing, SG-1 creates an alternate future in which Ra took the Stargate with him when he left Earth, and everyone except Daniel Jackson is killed when they try to start the rebellion years too early. The original SG-1 timeline continues, but now SG-1 and General O'Neill are dead in the far distant past. Life goes on.

- An alternate Colonel O'Neill, Carter, and Teal'c (with the alternate Daniel Jackson getting killed on Chulak) go back in time to prevent Apophis from attacking Earth. Unfortunately for them, all they do is create yet another alternate reality - in their world, Apophis attacks, and the Earth is destroyed. The alternate reality that they create turns out to be almost identical to the original reality except for three key differences:
1 - There is fish in O'Neill's pond
2 - The ZPM is found buried where they left it in the past
3 - The battle at the end of 'Lost City, part 2' happens in a slightly different manner (Colonel Mitchell is included in it)

Yes, I agree, Moebius can be EXPLAINED by the alternate reality theory, but what I really meant was that the characters don't seem to believe in it. Otherwise why would Sam be so bothered about changing the timeline?

[Daryl Froggy]

Yes, I agree, Moebius can be EXPLAINED by the alternate reality theory, but what I really meant was that the characters don't seem to believe in it. Otherwise why would Sam be so bothered about changing the timeline?

Because, while they had a time machine they didn't have a dimension hopping machine. Therefore when they changed something in the past then went foreward in time things could be drastically different for them due to the fact that they arrivied in a different reallity than the one from whence they came.

At least that is what I think.

[Daniel Jackson]

"Before I Sleep" is easy to explain. The only way for the episode to work is to say that in Stargate, the past is alterable. There is evidence of this in "2010" and "Moebius, Parts 1 & 2." In Stargate, we've encountered two kinds of alternate realities. One is a parallel reality that always existed and can be traveled to via the Quantum Mirror for example. The other is an alternate timeline, the result of tampering with the past.

In "Before I Sleep" we see two timelines. The first timeline is the Atlantis Expedition arriving at Atlantis, the shield failing, Weir and Sheppard leaving in a Puddle Jumper, and then Sheppard unkowingly sent the Puddle Jumper back in time. When Weir awoke in the past, the future she came from had been nullified. The new timeline began with the arrival of the Weir's time traveling Puddle Jumper appearing over Atlantis in the distant past. Fast forward to the present where the Atlantis Expedition discovers Old Weir. Weir explains the original timeline and that the Atlantis Expedition is the result of an alternate timeline that she and an Alteran scientist created to ensure their survival and the preservation of Atlantis. How do we end up with two Dr. Weirs? Old Weir is from the original timeline that ceased to exist when she went back in time. She was protected by changes to the future by being a component of the past.

While the original timeline ceased to exist, that doesn't mean it never happened, because Old Weir is evidence that it did happen, it was simply "written over" by the new timeline. Weir being in the past effectively protects her from changes to the future.

Any questions?

[FallenAngelII]

There's a name for the way timetravel works in Stargate. Every time you go back in time, you create an alternate timeline. When you return to your own time, you will return to your present in that timeline.

You see this in "Moebius", among other things.

[Daniel Jackson]

I disagree. Going back in time alters the timeline, it doesn't send you to a parallel reallity. If it did, you would be traveling through parallel reallities, not through time.

[FallenAngelII]

I disagree. Going back in time alters the timeline, it doesn't send you to a parallel reallity. If it did, you would be traveling through parallel reallities, not through time.

There are two ways to deal with time-travel:
- One where there's only one timeline and when you mess with it, like time paradoxes.
- One where an alternate timeline is created.

The one used in Stargate (SG-1 and Atlantis) is the 2nd one, with the alternate timelines. This is why our SG-1 acquired a ZPM through the actions original!SG-1 and alt!SG-1 minus alt!Daniel without lifting a finger.

According to the first theory, this wouldn't be possible. They've have to go back in time, steal the ZPM, hide it and then travel back or there wouldn't either be a ZPM or any they to use it.

[Daniel Jackson]

I agree with the multiple timeline take on time travel. Whut I am saying is that an alternate timeline is not a parallel reallity, it is a reshaping of one, single reallity.

When Dr. Weir went back in time, the timeline she came from ceased to exist. She remains, because she was in the past and thus protected from changes to the future. You can only have one timeline at a time.

Alternate timelines and parallel reallities are two entirely different things.