Questions about Timelines and Stargate

[Davey]

We all know by now of the extremely interesting episodes in SG1 and SGA involving traveling in time by mistake through the stargates. Personally I think there are some very deep philosophical implications tied up with it. For instance, it should be assumed that if some Rodney McKay or Sam Carter changed a timeline, the rest of mankind would have no knowledge or memory of such an event at all. For that matter, someone could have changed a timeline yesterday somehow and today we'd know nothing of it.

What happens to the lives of all the billions of people whose world is changed by a new timeline? Do they simply go "poof" out of existence, out of all their years of life and existence, and find themselves in a new reality with a new history and background?

How did John Shepard know of the changed timeline when he returned back to the original Atlantis? Shouldn't he have now been the original Shepard, and not the Shepard who knew of the changed history from the McKay hologram?

What about Elizabeth Weir? Why didn't the young Weir remember anything of the Weir in stasis for thousands of years?
What about the SG1 team that went back into the year 1969? What happened to their lives and memories?
In the case of General Hammond, why didn't the older Hammond remember the encounter with the SG1 team from his youth? Or did he?
And if he did, wouldn't that process repeat itself infinitely?

[DigiFluid]

How did John Shepard know of the changed timeline when he returned back to the original Atlantis? Shouldn't he have now been the original Shepard, and not the Shepard who knew of the changed history from the McKay hologram?
Sheppard experienced the alternate timeline. He came back and changed the timeline, not himself.

What about Elizabeth Weir? Why didn't the young Weir remember anything of the Weir in stasis for thousands of years?
Why would one Weir remember the lifetime of a different Weir? The 'original' Weir went into stasis to alter the timeline, so that 'our' Weir never experienced the flooding and whatnot. They only share memories up till when they arrived in Atlantis.

What about the SG1 team that went back into the year 1969? What happened to their lives and memories?
What do you mean? They know they traveled in time, fullstop. This was referenced at other points in the series. I don't understand what the question is asking.

In the case of General Hammond, why didn't the older Hammond remember the encounter with the SG1 team from his youth? Or did he?
...did you fall asleep while watching the episode?

[Mnikolic]

Hammond did remember the encounter with SG-1 from his youth. He even asks Sam if her hand hurts at the beginning of the episode. He knew exactly when he was going to show his favorite team how to time travel trough the Stargate.

Old Wier is old Wier with her own experiences and life events. Our Elizabeth is the one who saw the city activating the failsafe that made the whole Atlantis show up on the ocean's surface and her experiencing a whole different scenario play out.

As for John - he did not change his own timeline and affected everyone else's life with doing so. He went to the future, talked to hologram McKay, stayed in the stasis pod for a while, traveled back in time and warned the others about Michael. Same version of the character preventing what would probably end up in a Galaxy-universal disaster.

People can't remember what they have not experienced. If you've got 2 versions of the same person in the same room, both will remember certain things differently. Both will have different experiences and both would have gone trough different things and also have different memories. Which is what happened to Wier. And probably to Mitchell in Stargate:Continuum as he now probably remembers a different history background for his family, while the rest of SG-1 members probably have no idea that Baal had been screwing with them using his time travel machine.

John was the same John that traveled to hologram MacKay into the future and the same one that warned the others about Michael. So that's a different thing.

[Davey]

Mnikolic and Digifluid, your points are well taken. Although Shepard went into the future, all subsequent history changed for some reason, which necessarily all change again once Shepard returned. However, it is not explained in The Last Man why all future history would change simply because Shepard disappeared. If he wasn't the reason for all the bad events, then they would still occur even if he were around.
I had had these thoughts which may not be relevant.
I saw the episode about Hammond years ago. But if he did remember meeting the team, then the process would have gone on constantly.
I guess the old Weir would have memories only of Atlantis before the flood, which young Weir would as well as the identical person.
But about the people who lived in the alternate timeline, if McKay changed it, they all go poof and then have awareness only of the current timeline. And those who had died are now alive and never knew about anything else.

[Xaeden]

Mnikolic and Digifluid, your points are well taken. Although Shepard went into the future, all subsequent history changed for some reason, which necessarily all change again once Shepard returned. However, it is not explained in The Last Man why all future history would change simply because Shepard disappeared. If he wasn't the reason for all the bad events, then they would still occur even if he were around.

Mckay very clearly explained that the reason things went bad in his future was because Michael and his hybrids took over the galaxy. His plan to undo that was to send Sheppard back in time with the knowledge of where they found Teyla's dead body as rescuing Teyla was key...

McKAY: And you will be – and knowing the address where we eventually found Teyla, you will be able to get there much quicker. You'll save Teyla, save the baby, change the fate of the galaxy.

SHEPPARD: What do you mean?

McKAY: Well, it was the turning point. It was the key to everything. Once Michael had that baby, he was able to complete his research and perfect the hybrids. After that, well, he really kicked things into gear.

When Sheppard returned to the present, he led a team to the planet Mckay told him about and found Michael's compound shortly before Michael was able to bring Teyla there. Things go hairy and the episode ends in a cliff hanger, so you have to watch the season 5 premiere to see the resolution.

I saw the episode about Hammond years ago. But if he did remember meeting the team, then the process would have gone on constantly.

Yes, it would have and it did. "1969" was Stargate's first time travel episode, and it used a concept known as the predestination paradox. What this means in a nutshell is that events predate the the time traveler's time traveling. As a result, it's impossible to make changes to the timeline because every one of a time traveler's actions has already happened.

After this they decided to retcon that form of time travel and instead made the past changeable. Every time travel episode post "1969" consistently followed the same changeable past formula.

I guess the old Weir would have memories only of Atlantis before the flood, which young Weir would as well as the identical person.

I think you may not be phrasing this as you intend. Your words here say that Old Weir and Young Weir would both only have memories of the first timeline even though Young Weir is from the second timeline in which Atlantis did not flood and instead rose to the surface.

In reality, they both have all the same memories up until shortly after they both arrived on Atlantis. After that, Old Weir found herself in a situation where she had to escape the flooded city in a jumper that allowed her to travel back to the past and live out the remainder of her life in a stasis pod, whereas Young Weir benefited from Old Weir's actions and instead found herself in a situation where the city was saved by Janus' failsafe program. I assume something along those lines is what you're trying to communicate.

But about the people who lived in the alternate timeline, if McKay changed it, they all go poof and then have awareness only of the current timeline. And those who had died are now alive and never knew about anything else.

Yes. Landry berated Sg-1 in the movie, "Continuum" for this exact reason...

LANDRY

(indignant)
But you don't have the right! If you were to succeed, events in the lives of thousands, if not millions of people, would never have happened!
(angry)
My goodness, people! The arrogance of what you're asking us to help you do is mind-boggling!

[Chaka-Z0]

I think I know what Davey means. What happens to those living the ''timeline change''? The answer is simple my friend, absolutely nothing. Life goes on for them, as usual.

Theoretical physics tells us that if someone was to go back in time and mess with causality, like our SG teams did, the resulting new timeline would become a brand new alternative universe. Therefore, the time travelers could never go back to their ''old universe'' unless a tech like the mirror as we've seen in SG1 exists.

Sheppard's actions in The Last Man

Xaeden just explained it quite well, they just need to stop Michael from gaining knowledge off Tayla's child to fix everything.

The knowledge Sheppard gained there, as Digi said, helped him change the present timeline by quickly dispatching a team to Michael's hideout. So in this case, the future that Sheppard witnessed in ''The last man'' is no more in the show portrayed on screen.The important distinction is that the red desert future we see in the episode still exists, but in a different parallel universe.

Weir ''twins'' in Before I sleep

Same thing for Weir, she changed the timeline and went back in time - then in stasis. Years go by, ''New Weir'' is born and becomes SGA's leader. The timeline where the SGA team drowned still exist, in another parallel universe. New Weir would have absolutely no knowledge of Old Weir, because they are two complete different persons. Old Weir traveled back in time, to our timeline, and put herself in stasis. What that means is that Old Weird disappeared from her own universe to go into ours.

Remember that episode in SG1 when Daniel goes to an alternate universe where the SG:C never discovered Atlantis and are about to get wiped out by the Goa'ulds? Well that could be a good example of what would happen in Old Weir's original timeline.

1969 and Hammond

This one is pretty straight forward. Hammond knows from the beginning what is about to happen, and is aware of the SG team visit in 1969, when they met him as young Hammond. He remembers everything, but, he kept to himself all these years because of causality, as explained by Carter. So this one is full-circle, Hammond had to let it happen. Not the best representation of TT but that's how it goes.

But about the people who lived in the alternate timeline, if McKay changed it, they all go poof and then have awareness only of the current timeline. And those who had died are now alive and never knew about anything else.

Nope, they don't go ''poof''. They still live in a parallel universe, which isn't the one we see on screen. If that timeline is doomed, so are they. Obviously a sci-fi show cannot follow the theoretical physic rules by the book, it wouldn't be enjoyable.

I've included a couple links below for your information, which might help you understand.

Ripple effect / Butterfly effect
Causality
Grandfather Paradox

[Mnikolic]

Stargate is a multi-verse storyline. Just count all the time-travel episodes with featured timelines in them in all 3 series and that's how many multi-verses the show has. Of course, with the one timeline we saw to pan out being the main one.

[NickEast]

With regards to the changes to a timeline, watch Back to the Future Part II. Doc explains it quite well (and it fits more or less with Stargate as well). The concept of an "alternate universe" doesn't really apply. Alternate universes are created based on all the different outcomes of every possible decision ever made. So if you have to choose whether you go left or right at a crossroad, then two universes will exist; one where you go left, and one where you go right. What happens here however is the creation of alternate timelines where every change to a timeline will create a new one. The explanations in the posts above are otherwise correct.

As for "1969", that was the first time travel episode and the "rules" weren't yet figured out yet (also why the Stargate and the gate room were there for a few seconds before vanishing). But basically, that episode uses a "causal loop", or "predestination paradox", rather than alternate timelines. Unlike normal time travel (as used in BttF and all later time travel episodes), a causal loop has no known beginning and will always happen. Or rather it has to happen, hence why Hammond let it happen rather than stop them from going. I don't remember any other examples, though.

EDIT: In case someone can't watch Back to the Future (shame on you), here's the specific clip: https://www.youtube.com/watch?v=W3LwlSlo5cw

[Chaka-Z0]

With regards to the changes to a timeline, watch Back to the Future Part II. Doc explains it quite well (and it fits more or less with Stargate as well). The concept of an "alternate universe" doesn't really apply.

I heard that before, but I wonder, what's the difference? An alternate timeline is a different outcome of a specific universe, isn't it? Isn't that by itself an alternate universe? Technically, this is a different, possible decision. I guess we could say that these universes already exist, since somewhere the SG team already took the ''correct route'' ? Unless you are suggesting that alternate timelines are part of the same universe, which wouldn't make sense to me.

EDIT: In case someone can't watch Back to the Future (shame on you), here's the specific clip: https://www.youtube.com/watch?v=W3LwlSlo5cw

Agreed, *Ding ding* Shame! *Ding ding* Shame!

[thekillman]

I heard that before, but I wonder, what's the difference? An alternate timeline is a different outcome of a specific universe, isn't it? Isn't that by itself an alternate universe?

You could technically make that distinction, but Stargate does not. In Stargate both behave identically with only a difference in how one comes about.

[NickEast]

I hate multi-quotes, so tedious, so this is for two above ^ ^ (unless someone ninja'd, in which case it's the two above that).

There is a distinction. An alternate universe is a natural universe, as part of the theoretical "multiverse". Every possible (natural) choice that could ever be made creates its own universe. In Stargate, these kinds of universes (realities) can be visited using the quantum mirror. Then there's the classic TV show Sliders which does the same thing.

An alternate timeline is one where a time traveller goes back in time and alters the past, thereby creating a new timeline that splits off from the same universe. These kinds of realities are unrelated to the natural choices that create alternative universes, rather they are created because someone meddled with time. They are "artificial". In some ways you can say they are the same as alternate universes, but since sci-fi can use either, and Stargate does, then there is a distinction. Basically, yes, an alternate timeline is part of the same universe, since you can't really travel between the different timelines. In all the time travel episodes, the characters could only "fix" the past by changing it again. When Shepard goes back to the present in "The Last Man", he goes back to his present, not another one. The future "history" is then changed because of the knowledge he possessed. The same with the Time Jumper. SG-1 travelled back in time to Ancient Egypt, then inadvertently altered the timeline where Ra took the Stargate. The "SG-1" of the new timeline then goes back to "fix" the past by warning the original team, creating yet another timeline which is almost what it was, except for the ZPM and (supposedly) the fish in Jack's pond. This is all in the same universe (the two tapes). And again, the same happened in Continuum where SG-1 remained in the same universe, but an alternate timeline (as they were in the wormhole at the time, thus being unaffected). Then Mitchell returned to the 1920s, waited until the Achilles was shipping the Stargate and killed the Ba'al of the original timeline before he had a chance to carry out his plan. The Ba'al who existed in the alternate timeline was the same Ba'al that initially travelled back in time. Again, implying it's the same universe, but an alternate timeline.

Both are types of alternate realities. There is no indication though whether or not the quantum mirror can travel to both alternate universes and timelines. The mirror allows travel between universes, the Time Jumper (and Stargates with solar flares) allow time travel.

[Chaka-Z0]

Thanks for the explanation, makes sense. I mean you guys are right saying SG wasn't the best at meddling with time travel, but at the same time I've yet to meet a time traveler to explain it to me.

So if I understand correctly, an alternate universe could be say, Sheppard doesn't join the SGC and stays in the regular Special OPS corps. An alternate timeline would be Sheppard doesn't go through the gate on a specific mission, diverging from the ''original universe'' path.

[NickEast]

Thanks for the explanation, makes sense. I mean you guys are right saying SG wasn't the best at meddling with time travel, but at the same time I've yet to meet a time traveler to explain it to me.

So if I understand correctly, an alternate universe could be say, Sheppard doesn't join the SGC and stays in the regular Special OPS corps. An alternate timeline would be Sheppard doesn't go through the gate on a specific mission, diverging from the ''original universe'' path.

I regularly travel through time... whoops

You're half right. Indeed, Sheppard not joining the Atlantis Expedition, and thus having O'Neill dismiss him (as he said he would if Sheppard declined) that would be an alternative universe. Since it's a binary decision (yes/no) it creates two universes, ours and another one.

But the alternate timeline part is incorrect (or rather incomplete). An alternate timeline is created when someone goes back in time and changes something--anything. Even their presence in the past would already create a new timeline (technically, since their presence is already a major alteration). Now, this one is difficult, because when it comes to time travel there is no 'past', 'present', or 'future'. That is all relative to the time traveller. Technically, if Sheppard goes back in time from his (or our) present and somehow prevents his past self from going on said mission, that would create an alternate timeline. If the 'present' Sheppard goes back to his time, he would have knowledge of the original timeline, but he never went on the mission.

It's best not to go further than this. The past/present/future dilemma and such can be headache-inducing. Basically, follow Doc's explanation and everyone should know as much as is required to understand 'general time travel theory'.

In case anyone's wondering: yes, I did spend time (pun intended) on figuring this kind of thing out (for any kind of time travel stories I wanted to write, unrelated to Stargate specifically). Yes, I am pretty crazy. And yes, I do once again have a headache, just like last time I was trying to figure this out...

[Xaeden]

Similar to Nivao, I think it's worth noting that the alternate universe form of time travel is not at all canon in Stargate. Viewers are free to come to that interpretation, but it has never been confirmed to be the case in the series and appeals to it being a higher regarded theoretical solution to time travel problems doesn't make it true as Stargate is ultimately willing to disregard science (see the 10% brain myth) for the sake of the story. Although, do keep in mind we're not even dealing with something scientifically provable here; the idea that each act of time travel would create a whole new reality is just a logical argument that people deliver with confidence and is no where near the definitive explanation.

The idea that a timeline can change without creating paradoxes or the need for the alternate universe to come into existence to avoid those paradoxes may not be overly popular among theorists, but it's a concept that gets a fair bit of use in fiction and for good reason: it's an idea that comes with consequences that are interesting to explore within a fictional setting.

Take for the example the "If you could go back in time to kill Hitler..." debate. It's a hypothetical scenario intended to challenge whether people would be willing to take one life in order to undo the millions of death that one life caused. People often view the challenge superficially, with some occasionally challenging the concept of the challenge itself by arguing that it's potentially impossible to change the past because of X paradox (e.g. if you have a gun it simply won't shoot).

What people too often fail to realize is that this hypothetical is asking you to imagine a version of time travel where changing the past is possible, so if we imagine a scenario free of paradoxes and free of alternate universes to bypass them, any time traveler who went back to kill Hitler would become a bigger mass murderer than he was. Why? Because he had such a huge influence on history that the majority of people alive today would not, according to the butterfly effect, be alive today had his horrific acts not occurred.

The most obvious example are all the troops who returned home after the end of the war in Germany and the baby boom it created. Some of those soldiers had children with people they were in relationships with already, others met people they wouldn't have otherwise because of the circumstances they found themselves in after the war. The former group may still have had children with those same people in a timeline in which the war in Europe did not take place (at all or in the way it did), but they would certainly have done so at different times leading to different sperm and eggs coming together to form different children. Then you have all the people who died and were removed from the gene pool when they died.

These are big, immediate ripples, but any death of any person, no matter how small will have tremendous consequences in the long term, so the further in time you get away from the murder (or slight change), the less likely you are to encounter people from the original timeline as their births will be replaced with the births of different children. This last part is not explored in Stargate, nor in most TV time travel stories as they prefer to rely on the trope of their main characters simply developing different personalities, often to comedic or dark effect. Sometimes someone won't be born or die who is close to a main character (e.g. Jack's son Charlie), but it doesn't explore how changes like this would greatly impact the gene pool, especially if those changes happened thousands of years ago, in Ancient Egypt.

That said, it is touched upon briefly in "Continuum." Landry's outburst is a condemnation of the idea that Sg-1 has a right both to end the lives of people as they know them and to undo all the lives that only exist in his timeline. Think about Mitchell's grandfather. He didn't have children with Mitchell's grandmother (same with the other people who died on the ship). Chances are this means that she has children with someone else and by meeting this other man before he had an opportunity to have children with his woman (or women) of choice in the original timeline that is the start of a massive ripple of people meeting different individuals and whole new children coming into existence. How these couples and their children interact with people in the world around them further impacts who people end up meeting and having children with and what time conception takes place.

"Continuum" asked us to imagine a world where it didn't have a big enough impact to prevent the births of any of the main characters, save Mitchell, but that doesn't mean it was asking us to imagine a world where there weren't plenty of people who owe their existence to the change Ba'al made to the timeline. So by thinking of what we were presented as simply an alternate reality, viewers would be missing a key moral consequence that the writers attempted to briefly touch upon.

Also, note that when Landry delivered that outburst, nobody corrected him and told him that they wanted to use to the Stargate to create a third universe, and his universe would continue to exist when they left. It was never even something that was suggested as a possibility, nor do they ever try to fix their time travel woes by finding a way to jump parallel realities in order to return to their original one, suggesting that they know (or at least, strongly believe) that there is, as Nivao notes, a clear difference between a timeline and alternate reality in their fictional universe, even if other hypotheticals blend the two as you did.

[DigiFluid]

People often view the challenge superficially, with some occasionally challenging the concept of the challenge itself by arguing that it's potentially impossible to change the past because of X paradox (e.g. if you have a gun it simply won't shoot).

For curiosity's sake: this is more accurately known as the Novikov self-consistency principle.