Can Someone Explain to me how time travel works?

[auroraclass1]

Ok so my friend always use to make fun of me for watching Stargate so I made him watch the first episode of SGU and now he is hooked. But the Idiot will not let me explain the Episode "Time" to him. He claims that the episode makes no sense and i have tried to explain it, even having Mckay explain it in an old Atlantis but the idiot doesn't understand. Can Somebody pleas help me out with this problem?

[Quadhelix]

I think that the first step would be to avoid calling him an idiot.

I have to admit that I'm not sure what he is asking. In order to address the problem, we first need an explanation of why he feels that the episode "makes no sense." Without knowing what his specific complaint his, I'll try to start generally.

One interpretation of time travel is derived from the "Many Worlds" interpretation of Quantum Mechanics; according to the "Many Worlds" interpretation, every possible outcome of a quantum event occurs, but each is in a "separate universe" from the others (it's actually far more elegant than that, but I don't want to add needless detail). Under that interpretation, a time traveler arriving in the past is a quantum event that creates a "new universe," separate from the "universe" that the time traveler came from.

Applying this to the episode "Time," there are three "universes" involved; all three are effectively identical up to about the beginning of the episode. In the "first universe," evens occur as recorded on the Kino: the team arrives, gets sick, and is killed by the aliens. The "second universe" is the one we see in the episode, where they find the Kino, release that the disease is on the ship, and fail to recover the creatures in time to make a cure. The "third universe" is where the remainder of the series takes place, where they recovered Scott's message and were able to create a cure.

I hope this helps.

[Snowman37]

Ok so my friend always use to make fun of me for watching Stargate so I made him watch the first episode of SGU and now he is hooked. But the Idiot will not let me explain the Episode "Time" to him. He claims that the episode makes no sense and i have tried to explain it, even having Mckay explain it in an old Atlantis but the idiot doesn't understand. Can Somebody pleas help me out with this problem?

I didn't see the episode, but I am familiar with the premise. Basically, a team gates from Destiny to a planet, and they find a KINO that has filmed their deaths. They go back for reasons unknown to me, they all die, and the KINO is thrown through the stargate into the past. The story loops, each time there is more information than last time. Eventually, the timeline would loop enough times for a solution to be found. I don't subscribe to the multiverse, because traveling back in time to an identical parallel world isn't time travel at all, it's traveling to an entirely different universe. From the perspective of the present you left, you simply vanished, never to return. I subscribe to the rewritable timeline theory. You can go back in time and change the past. Don't like how the present turned out? Go back in time, change it again. You can do this over and over. If you accidentally erase yourself from existence (never born, for example), you're adult time-traveling self still exists as a left over remnant protected from the changing timeline due to being the catalyst.

I hope that helps clear time up.

[Quadhelix]

I don't subscribe to the multiverse, because traveling back in time to an identical parallel world isn't time travel at all, it's traveling to an entirely different universe.

Well, as I said, calling it "another universe" is a gross oversimplification. Additionally, it isn't that you "travel" to another universe, it's that you cause your own universe to "branch" in two at the point were you arrive in the past: one branch (the one you come from) where you don't arrive and one branch (the one that you are traveling to) where you do arrive.

Moreover, all that your objection really means is that "time travel" episodes are actually just "alternate universe" episodes.

From the perspective of the present you left, you simply vanished, never to return.

Interestingly enough, that is exactly what happens in "Time": Rush travels into the past at one point, but the present is completely unaffected.

I subscribe to the rewritable timeline theory. You can go back in time and change the past. Don't like how the present turned out? Go back in time, change it again. You can do this over and over. If you accidentally erase yourself from existence (never born, for example), you're adult time-traveling self still exists as a left over remnant protected from the changing timeline due to being the catalyst.

Except that your argument implicitly assumes a multiverse interpretation of time travel: if you never existed to go back in time, how can you be the catalyst that kept you from being born?

[Jedi_Master_Bra'tac]

Timeline A - The team all gets killed and send a kino back in time
Timeline B (where the episode takes place)- The team finds said kino, but are all killed before they figure out what's wrong. Scott records another kino with a direct warning to stay away
Timeline C (not seen) - We assume they find both kinos and simply stay away from the planet

[Quadhelix]

Scott records another kino with a direct warning to stay away
Timeline C (not seen) - We assume they find both kinos and simply stay away from the planet

That's incorrect: in Timeline B, they were killed by a disease that they had already contracted. They needed the venom from the animals on the planet to cure said disease, a fact that Scott explicitly mentions in his Kino warning.

In fact, they make use of the venom of the animals from that planet fairly consistently over the remainder of the series as a general purpose antibiotic/anesthetic.


EDIT: From "Time":

SCOTT: If you found this, it's because a solar flare interfered with Gate travel and I managed to send this Kino back in time. All right, listen very carefully. There is a disease in the water we brought back from the ice planet. It is fatal and we have all been drinking it. But there is hope. There's a creature that-that lives on this planet - lots of them, actually - that could hold the key to saving you. In small doses their venom actually cures the disease, but be very careful. They're deadly, but they're also nocturnal. They only come out at night. You get them during the day while they're asleep in their nests, and they're not far from the Gate. Please believe me. You don't have much time. Act now, or you are all going to die.

[Jedi_Master_Bra'tac]

That's incorrect: in Timeline B, they were killed by a disease that they had already contracted. They needed the venom from the animals on the planet to cure said disease, a fact that Scott explicitly mentions in his Kino warning.

In fact, they make use of the venom of the animals from that planet fairly consistently over the remainder of the series as a general purpose antibiotic/anesthetic.


EDIT: From "Time":

I haven't seen it in ages, I'd forgot the specifics

[Quadhelix]

I haven't seen it in ages, I'd forgot the specifics

Yeah, I should have been more polite about the way I corrected you, especially since, as far as I can tell, you were right in just about every other respect.



Anyway, back on topic; elaborating slightly on the "Many Worlds" interpretation: one description of it that I found particularly compelling was the idea that, when a observer makes a measurement of a quantum event, that observer (rather than the entire universe) splits.

Borrowing the Schrodinger's Cat thought experiment: when the box is closed, the cat is split into two states (an "alive" state and a "dead" state). When an observer opens the box, instead of the cat collapsing into one of the two states (the Copenhagen interpretation of quantum physics), the observer splits into two states: "sees the cat as dead" and "sees the cat as alive"; the observer, of course, is completely unaware of this. Moreover, the "sees the cat as dead" "part" of any observer can interact only with the "sees the cat as dead" "part" of any other observers, not the "sees the cat as alive" "part."

[Jacdru]

Yeah, I should have been more polite about the way I corrected you, especially since, as far as I can tell, you were right in just about every other respect.



Anyway, back on topic; elaborating slightly on the "Many Worlds" interpretation: one description of it that I found particularly compelling was the idea that, when a observer makes a measurement of a quantum event, that observer (rather than the entire universe) splits.

Borrowing the Schrodinger's Cat thought experiment: when the box is closed, the cat is split into two states (an "alive" state and a "dead" state). When an observer opens the box, instead of the cat collapsing into one of the two states (the Copenhagen interpretation of quantum physics), the observer splits into two states: "sees the cat as dead" and "sees the cat as alive"; the observer, of course, is completely unaware of this. Moreover, the "sees the cat as dead" "part" of any observer can interact only with the "sees the cat as dead" "part" of any other observers, not the "sees the cat as alive" "part."

Hmm, i have to admit that your use of Schrodinger's Cat is a bad way to explain the multi-vers theory.

The reason some people have come up with the muliti-vers is to get around some of the fall groups there is surrounding time travel, one being the Grandfather-problem. Which by assuming that you will not go back in time in your own timeline, but go back to one of the many other worlds.

[Snowman37]

Well, as I said, calling it "another universe" is a gross oversimplification. Additionally, it isn't that you "travel" to another universe, it's that you cause your own universe to "branch" in two at the point were you arrive in the past: one branch (the one you come from) where you don't arrive and one branch (the one that you are traveling to) where you do arrive.

If your universe branches in two, then why should there ever be any concern over changing the past? If something is going to happen in the future, you can't stop it, because you'll just be changing the future of some other reality. This all makes time travel utterly pointless. Whenever you go back in time, you change the past. Whenever you visit the future, your return to the present nullifies that future due to your knowledge of it.

One timeline, one reality. If you screw up the past and destroy your future, it simply never existed except for a few left over elements in the past at the point of diversion or before. The only way to restore your future is to go back and stop yourself from doing whatever it is you did that changed history to begin with. This is basically what played out in SG-1 "Moebius" and why I love those episodes.

Moreover, all that your objection really means is that "time travel" episodes are actually just "alternate universe" episodes.

Time travel, alternate universe, you can't have both. Well, maybe in Enterprise "In a Mirror, Darkly."

Interestingly enough, that is exactly what happens in "Time": Rush travels into the past at one point, but the present is completely unaffected.

No comment as I have not seen the episode.

Except that your argument implicitly assumes a multiverse interpretation of time travel: if you never existed to go back in time, how can you be the catalyst that kept you from being born?

It doesn't implicate the multiverse, it implicate multidimensional existence. When you go back and prevent yourself from being born, the changes in the timeline move forward. You and your time machine are intact, because you are the catalyst to the changing timeline. Your future is rewritten, but you are left intact for you are no longer in that future as it is rewritten.

[morrismike]

It's all about really big magnets.

[thekillman]

the moment you travel back in time you create an alternate Timeline.


it slightly differs from an AU, as an AT is an alternate universe formed by time being changed.

because history has already happened, you can't change it as you'd change the "present day " and thus you could prevent the changing of history.

the Quantum Physical Multiverse is one where every possible outcome is true. it exists in "superposition" as you could say. we have one state, another universe has another state.

because you would be changing history, the Universe essentially is forced to change state, because you alter things. you add, simply put, more options. more options equals more universes.


so you generate another universe in which you are present in the past (i always intend my puns).

from an energy perspective, it HAS to happen this way too. after all, you alter the sum of all energy in the universe per unit of time. since that has to remain the same, you could not travel into the past.


for Stargate, the sum of all energy stays the same because the energy you remove fro m 1 universe is transferred to another. so while the energy per universe is allowed to change (Mckay-miller device and Road Not Taken device come to mind, and so does the Reality Drive), the sum of all energy of all universes is not.


this is why you can't REALLY use SGU's Time to exploit an infinite loop of supplies.
the problem would be, if you used a time loop to multiply stuff, that stuff would be taken from the universe the person multiplied it in, and dropped in the resulting universe.

so if Person A sends Box A into the past, he already created a new universe. so if Person A' from Universe A' finds the box A, and sends Box A and Box A' into the past, he creates a new universe A'' where box A, Box A' and Box A'' exist.


this leaves Universe A and A' without the box, and gives A'' two boxes.



you get it?

[Snowman37]

because history has already happened, you can't change it as you'd change the "present day " and thus you could prevent the changing of history.

Then what is the point of time travel to the past? Further, how do you just poof into existence and complete and total copy of the entire universe? I suspect that would require a lot more matter and energy than a time machine could produce. In fact, it would require you to create everything from nothing. You're basically giving a time traveler the power of creation.

[thekillman]

Then what is the point of time travel to the past?

you can alter another you's future.

Further, how do you just poof into existence and complete and total copy of the entire universe

well there's no way to say that's what happens. if anything, it's possible that the universe already exists, all synchronous, but every time there is a possibility, every possible outcome is represented by a universe.

In fact, it would require you to create everything from nothing. You're basically giving a time traveler the power of creation.

actually no.

how do i put this?

i think One-minute-science can do this better than me


How the universe appeared from Nothing

[Tanith0709]

Could always just travel back in time and not change anything. Witnessing historical events has an appeal

But if you did change something you would need something like other universes to solve the Grandfather Paradox.