Fans of the hit TV series Lost are awaiting the big event next week: the premiere of Season Six on Tuesday night. The show is famous for its mysteries and plot twists, so this year has a special status: it’s the final season, where everything that’s going to be revealed will be revealed. That might not be absolutely everything, but it should be a lot.
Lost has always played with time and narrative — characters’ backstories were told through elaborate flashbacks, lending a richness of nuance to their behavior in the main story. But time travel as a plot device was established as a central theme during Season Five. One happy consequence was the invention of Lost University, through which fans could learn a little about physics and other real-world subjects underlying events in the show.
Naturally, scientifically-minded folks want to know: how respectable is the treatment of time travel, anyway? We are, as always, here to help. My short take: Lost is a TV fantasy, not a documentary, and it doesn’t try all that hard to conform to general relativity or the other known laws of physics. But happily, the most important of the Rules for Time Travelers is very much obeyed: there are no paradoxes. And more interestingly, the spirit of the rules is obeyed, and indeed put to good narrative effect. The potential for time-travel paradoxes helps illuminate issues of free will vs. predestination, a central theme of the show. And what more can you ask for in a time-travel story than that?
Details below the fold, full of spoilers. (Not for the upcoming season, of course.) See also discussions from io9, Popular Mechanics, and Sheril.
The way that time travel works in Lost can be analyzed on three separate levels: physics, logic, and metaphor. (Or by ignoring all these high-falutin’ ideas and just enjoying the show, but where’s the fun in that?)
Physics
Make no mistake: the point of Lost is not to present a realistic depiction of time travel according to the laws of physics as we know them (or ever expect to know them). As explained in Chapter Six of From Eternity to Here, a remarkable feature of Einstein’s general relativity is that it provides a context in which we can sensibly talk about the idea of traveling in time. Space and time are curved together, and the amount of time elapsed between two events is affected by motion and gravity. Traveling near the speed of light, or lingering in a powerful gravitational field, you will “move into the future faster” than someone floating freely in empty space.
It’s easy to imagine — likely impossible to construct, but easy to imagine — curvature so intense that you can hop in a space ship and come back before you left. One particularly evocative mechanism for dramatic spacetime curvature is a wormhole, a shortcut through spacetime through which one could easily reach tremendous distances or wildly separated times via a relatively short journey. But it would still be a journey, involving relatively conventional means of transport; no flashing lights, no dematerializing and popping into existence elsewhere or elsewhen.
The tremendous amounts of energy and spacetime curvature necessary to maintain a realistic wormhole don’t fit easily into the island milieu of Lost. So the show simply doesn’t bother with such details. Characters, not to mention the island itself, do indeed pop randomly from one time to another. Even more divorced from realism, Desmond and other characters have their consciousness travel through time (“temporal displacements”), appearing in their physical bodies with all the memories and feelings of their future selves. Neither Einstein nor anyone else suggests any way that could happen in the real world.
Which is fine; it’s a TV show, not a science documentary. It’s an invented world, not the real one. But the writers do nevertheless hint at a scientific basis for time travel within this invented world, one that borrows from real physics. I probably was not the only viewer to laugh during Season Three when one of the hated Others was shown deeply engrossed in A Brief History of Time. More directly, in one of the Dharma Initiative orientation videos “Edgar Halliwax” (Dr. Chang) explains that the island contains a pocket of exotic matter, perhaps sustained by the Casimir effect, which lets them conduct unique experiments in space and time. That’s all on the right track. Even though general relativity lets us talk about wormholes, under ordinary circumstances we wouldn’t expect them to be useful for purposes of time travel — even if a wormhole were created, it would collapse to a singularity before anyone could cross it. A hypothetical way out is to invoke exotic matter, which would have a negative energy density and prevent the wormhole from collapsing. And how can we get negative energies? Perhaps from the Casimir effect, which arises when materials alter the energy contained in quantum vacuum fluctuations. Again, it’s not a full-blown respectable and realistic theory of time travel; but I’m happy that the show nods in the direction of real ideas, which will hopefully inspire the occasional viewer to dig more deeply into them.
Logic
It’s much more important that time travel in Lost makes logical sense — it’s consistent and obeys rules, even if the rules are not those of the real world. Most fundamentally, you can’t go into the past and alter the future; there are no alternate histories or any such cheap ploys. Daniel Faraday says at one point, “What happened, happened”; Sawyer just says “What’s done is done.” Dr. Chang, confronted in the video above with a worker who jokes about going back and killing Hitler, reacts in anger: “Don’t be absurd. There are rules!”
And the main rule is that things happen in a unique way at every place in space and time. If we have good reason, based on memories or some other form of records, to think that events played out in a certain way, then that’s what they did. There’s no changing things, and more than we can imagine changing the past under ordinary circumstances; the past already happened. As far as I can tell, the events we’ve been shown conform very well to this principle. Of course, there are certainly mysteries, and we’ll have to see how those are resolved in the season to come.
There is one seeming exception to this rule: Desmond’s visions of future events. He can see something happen in the future, and then take some action to prevent it (at least for a while). But as long as we’re being sticklers, we have to admit that a vision of the future isn’t the same as having that future actually happen. There is no paradox; only one thing ever happens in the real world, it’s just not necessarily the thing Desmond sees in his vision. When Desmond shuttles information back and forth between the past and present, it doesn’t conform to our ordinary notions of causality, but there’s nothing inconsistent about the complete history through time. I’m inclined to grant this bit of poetic license in the cause of interesting storytelling, as it still respects the no-paradox rule.
Despite the importance of this rule, fictional invocations of time travel tend to violate it all the time. Most such stories are all about changing the past, acting as if there is some narrative “meta-time” with respect to which events unfold, independently of the good old time we measure with physical clocks. (Think of Back to the Future, where Michael J. Fox does something in the 50’s and conditions “immediately” change back in the present day — erggh.) Personally I find the restrictions of logic to ultimately provide a more satisfying story structure.
By the end of Season Five, Faraday has become convinced that you can alter time, and hatches a plan to donate a nuclear bomb in 1977 to ultimately prevent everything we’ve later seen happen on the island. Faraday is killed by his mother, Eloise Hawking, but Jack and the other survivors try to carry out the plan. The finale of Season Five ends with a bright flash of light. We don’t know exactly what this means — that’s what cliffhangers are all about — but presumably this is the “Incident” referred to in later Dharma Initiative videos. I hope so, anyway; after all this wonderfully consistent if complicated narrative, it would be a shame to throw out a universe and start all over again.
Metaphor
Why does time travel fascinate us, anyway? Why do we find it so interesting? Part of it is the interest in changing the past — all of us have things we’d like to do over. But part of it is the fear of predestination. We like to think that, while the past is set in stone, we can make choices about our future — we have free will. But if we are able to travel into the past, then our future is part of the time that already happened — so in fact we don’t have complete freedom of action. Whatever it is we do when we get to the past, it must ultimately be consistent with how we know that past ultimately evolved into the present. That seems a bit irksome, even if it does respect the laws of physics.
This is where I think Lost really shines. One of the major themes of the show is destiny vs. free will, as embodied in the characters of Locke and Jack. Are there places where we are “meant” to be, or can we choose our paths for ourselves?
Well, there’s a balance. I can choose to turn right or left at a fork in the road, but I can’t choose to simply float into the air — there are the laws of physics to be obeyed. Lost uses the device of time travel to play with this tension — we think certain things are destined to happen, but we don’t know how. The logical restrictions of time travel are used as metaphors for the competition between predestination and choice.
A great example is the idea of “course corrections,” explained to Desmond by Eloise Hawking. Even if you see the future and try to prevent it, ultimately the designated fate is going to come to pass, perhaps in a different way (as with Charlie’s death). As a physicist this originally annoyed me, as that’s not how the laws of nature work — things happen or they don’t, but they’re not teleological, working through multiple channels to fulfill some crudely-specified goal.
But taking off my physicist’s cap and thinking more as a storyteller, I came to really appreciate this conceit as an interesting metaphor for how we try to think about fate. Determinism and the laws of physics are not the point; it’s simply that certain kinds of conditions pretty much inevitably result in certain kinds of outcomes. (Ever had two friends get together, and you knew from the start that it wasn’t going to last?) In our human lives, the rigid inevitability of the underlying physical laws isn’t very relevant to figuring out what’s going to happen next, but there is still some degree of predictability. The battle of destiny vs. free will isn’t one that has a winner and a loser; we are both constrained by circumstances, and free to make choices within that framework. That’s what makes life interesting.
Ultimately the idea of free will is tied to the arrow of time. Given perfect information about the present, in principle we could predict both the past and the future, without any wriggle room. But we don’t have perfect information. Because of the low entropy boundary condition in the past, we can nevertheless reconstruct what already happened with a certain amount of reliability; that’s why we think the past is unchangeable. But the future has no such boundary condition, and many possibilities are open. Otherwise I would tell you what’s going to happen over the next eighteen episodes of Lost.
Isn’t there a big assumption in your claim that there are no paradoxes in Lost — namely, that the actions taken by the main characters at the end of Season 5 won’t have actually worked to change things? I mean, I’m expecting (and hoping) that what Jack and Juliette do at the end of Season 5 doesn’t prevent the plane from ever crashing on the island, but Lost has surprised me before. Or do you just mean to say that there have been no paradoxes in Lost so far?
Just so far. As I said, there are still mysteries, but I hope everything works out consistently in the end.
There is one paradox in LOST: The compass.
Locke gives it to Richard in 1954. Richard gives it to Locke in 2004, and Locke then flashes back to 1954 and gives the compass to Richard again.
Where did it originally come from?
The compass might be a mystery, but not (necessarily) a paradox. As long as it behaves consistently at every moment in time, there’s nothing paradoxical.
I believe we discussed this over the summer but a reminder (and for the benefit of the readers here): how does this total determinism* jive with quantum mechanics? Is a many-worlds interpretation the only feasible way out?
*Referring to “Given perfect information about the present, in principle we could predict both the past and the future, without any wriggle room.”
As for storytelling, I have a feeling they’re going to leave behind this strict whatever-happened-happened, unfortunately; I can’t conceive of how to do such a thing without making the dramatic stakes a lot lower. But I have faith the writers will make it work out in the end 🙂
The most important rule for time travel in fiction is you cannot go back to anytime before the mechanism for time travel first existed. The first scene in the season 5 finale — the one involving Jacob and the man in black — leads me to believe that there’ve been some kind of large scale cosmic games being played for a long, long time, from that point onward.
The three most important things we see in that episode are 1) the two actors, light & dark, 2) the tapestry Jacob is weaving, and 3) the book Jacob is reading when John Locke falls 5 stories – Everything That Rises Must Converge.
If the time machine / island / time travel mechanism has been used over and over and over again, from the instant it was either created or first used by a conscious being, to at least the year 2007 (the year of Ajira flight 316), then my guess is there’s been a sort of temporal feedback loop going on, while these two actors have been battling it out — and a new kind of element to the concept of time travel has emerged: umm, emergence itself.
Within the structure of “the rules” – Novikov’s Self Consistency, mostly – it’s probably like you said: what happens, happens (death) but the circumstances can probably change (type of death). There’re probably “windows” that the “variables” are afforded the opportunity to exist in, where they have free will, but when it comes down major events, and when it comes down to preventing paradoxes and for there to be this Fate / destiny, what is “supposed” to happen will always happen. The universe will always course correct, and attempts at changing the past or future will always fail.
Still, within that time the time machine has been going, and within that structure of rules / laws, there must be some sort of strange cause and effect going on in the time loop, over and over, something I can only define as emergence.
The compass Richard gave to Locke, and Locke gave to Richard — it has no origin. It was never created. Causality violation. So I believe this to be the metaphor for that type of emergence. This is where Jacob’s tapestry and the book he was reading come in. All those threads, weaving toward something greater emerging – the “progress” Jacob referred to, before it “only ending once” (the loop). The quote the book’s title was taken from:
“Remain true to yourself, but move ever upward toward greater consciousness and greater love! At the summit you will find yourselves united with all those who, from every direction, have made the same ascent. For everything that rises must converge.”
I should think about this more. But I think Jacob is planting the seeds for certain outcomes to happen, and he’s doing it in a new, big picture, strategic way, where new things emerge: Walt’s, Hurley’s, Miles’, and Desmond’s special abilities. Progress.
Adam– Quantum mechanics does complicate things. The Schrodinger equation is perfectly deterministic, just as much as Newtonian mechanics. But we appear to see wave functions collapse. Either that collapse is merely “apparent,” as in the many-worlds interpretation (which I tend to believe), or it’s a real physical process that is not deterministic. None of which matters for the present argument, really.
“The compass Richard gave to Locke, and Locke gave to Richard — it has no origin. It was never created. Causality violation.”
It seems to me that the compass originated before the loop, entered it, and then continues on in the normal flow of time after it. Within the loop, the compass would age continuously and infinitely, which makes for a paradox, but I don’t understand why this would be a causality violation. Or do you mean it’s a causality violation *within* the loop?
Sean, I read the rules for time travelers, and maybe I’m just misunderstanding the rules, but I can’t quite understand how there can be no paradoxes — that what happened has irreversibly happened.
Say I’m on a tiny island, and I have a pile of 100 bricks, and there are no other bricks for 1000 miles. I stack all the bricks up to make a 100-brick tower. Sometime later, I use my time travel device to go back in [space]time to the island 5 minutes before the erection of the tower and I destroy one of the bricks, pulverize it into dust, and throw it in the ocean. How can the 100-brick tower possibly get built? If it doesn’t get built, isn’t history changed?
In fact, seems to me that the act of going back in time is in itself necessarily changing what happened. If I go back in time and I’m in a different place than I was at that time previously, isn’t that a pretty objective difference?
I suppose I’m just looking at this wrong. Please to edumacate.
The answer would be, you can’t go back and destroy the brick. You know you can’t, because the tower did get built. That’s why the restrictions of time travel are the same as the restrictions of (true) predestination, in apparent conflict with free will.
That doesn’t mean you can’t go backwards in time — just that, if you do, you can’t cause anything to happen that the future knows didn’t happen.
“Ultimately the idea of free will is tied to the arrow of time. Given perfect information about the present, in principle we could predict both the past and the future, without any wriggle room. But we don’t have perfect information.”
Seems like your notion of free will here is simply lack of knowledge and therefore unpredictability: the future only *seems* open and changeable because we don’t have perfect information. As philosophers sometimes put it, since we’re not omniscient the future is “epistemically open,” but according to what you say it might be metaphysically closed and fixed, not exactly compatible with what I suspect most folks think of as free will.
I thought that Lost was about a bunch of people whose plane crashed on a tropical island…
Tom– That’s the notion of free will I’m using, which is why I try to say “the idea of free will” or “the appearance of free will,” although I’m not always careful. I know that there are stronger notions of free will, but that’s not an argument I’m entering right now. (Although I could.)
Chris– That’s where it all starts…
Here is Sean’s Rule 6.
“If something happened, it happened.
What people want to do with time machines is to go into the past and change it. You can’t. The past already happened, and it can’t un-happen. You might wonder what’s to stop you from jumping in your time machine, finding your high-school self, and convincing them that they really shouldn’t go to the senior prom after all, thereby saving yourself all sorts of humiliation. But if you really did go to the prom, then that can’t happen. The simple way out, of course, is to suppose that travel into the past is simply impossible. But even if it’s not, you can’t change what already happened; every event in spacetime is characterized by certain things occurring, and those things are fixed once and for all once they happen. If you did manage to go back in time to your years in high school, something would prevent you from dissuading your younger self from doing anything other than what they actually did. Even if you tried really hard.”
Sorry, I have trouble understanding this restriction given the possibility of time travel into the past. Please bear with me.
First, I assume that you can’t get more bricks to build your house by traveling back by yourself. That is, say you had 100 bricks and you wanted 200 to build your house. If you traveled back by yourself one hour in time, you could not expect to take 100 bricks from yourself back then and climb back in to your time machine and have 200 bricks when you arrived in the “present”.
However, say you took back your 100 bricks with you. Now you could gift your former self with them so that s/he could have 200 bricks to build a house. Or more to the point, what if you simply sent the bricks themselves, and your former self then sent 200 to a former former self who then sent 300 back to a former former former self, and so on. If the bricks were tiny quark sized ones, and the ‘you’ of this story were space-time, is not this scenario the same sort of inflation as the cosmic inflation of the early universe?
“I know that there are stronger notions of free will, but that’s not an argument I’m entering right now. (Although I could.)”
Just hypothetically, were you to enter, I’m guessing you’d agree with fellow eternalist Brian Greene in The Fabric of the Cosmos that we don’t have contra-causal (libertarian) free will, in which human choices somehow transcend or intervene in or are exceptions to the cause and effect relations (probabilistic or deterministic) that physical law describes as evolving over time, or that appear as static patterns from a block universe perspective. My take on free will, control and the block universe is here, written in the context of the ABC primetime series FlashForward, starting up its second season in March.
“Donate” should be “Detonate”
@babyBones The problem is when you reach the point where you took your bricks back, they would simply vanish, as you would have taken them back. If you, at said point did not take them back, then the ones from the past would simply not exist, as you did not take them in the first place.
Oddly enough the most accurate depiction of time travel I’ve seen on TV was the episode of Futurama where Fry goes back in time and becomes his own grandfather. It was only possible because it had already happened.
@MickeyG: In the first case I mentioned, I think that the time traveler (let’s say it is me) would retain a total of 100 blocks, but those would be the ones I brought back via the time machine. That way, bricks don’t dematerialize in an unphysical way. The nature of the machine is the issue though. That is, imagine that the time machine is a certain police box and I go back in time with it to fetch 100 blocks from myself and return to the ‘present’ just moments before I left. I could tell myself not to go and I would contradictorily have 200 blocks. To avoid that sort of paradox, you have to suppose time travel by another means, i.e., one not like a TARDIS.
And I think this is what Sean is getting at with rule number 6. Basically moving forward in time at relativistic speeds would be moving forward within one’s light cone. By such a rocket ship time machine, I could get back to my starting time but I’d still have only 100 bricks, the one’s I took with me in the machine. My former self might have left a message calling me a dummy for wasting my time. I’d be coming back to a different present than the one I left but I don’t see that it is contradictory within the Many Worlds Interpretation.
Instead, however, simply sending bricks back in time does seem to allow for multiplication of bricks (and me), provided that the time machine or facsimiles of it existed in the past, and the scenario seems to be identical to cosmic inflation. Cosmic Inflation shut down long ago after overwriting some previous less inflated versions of the universe, so I could never use it to multiply bricks or myself arbitrarily.
If I got this wrong, I’ll admit my bad. I took some general relativity in university but I was always looking for an origin in dual space.
Oh WOW who cares?
Tom– Yes, all that’s right.
Baby Bones– The primary restriction is simply that there is only one thing that happens at every event in spacetime. If you had 100 bricks when you started building your house, and you ask why you couldn’t just go back and bring 100 more bricks to that time and place, the answer is — you just can’t, because you didn’t. I can’t tell you why you didn’t, as there isn’t any one specific mechanism in place. All I can tell you is that it didn’t/won’t happen, just like you can’t decide to have been in California yesterday if you were actually in Florida yesterday in the real (non-time-traveling) world.
1) You have 100 bricks in 2009
2) You build a time machine in 2010 and go back to 2009
3) You choose (via your free will) to destroy a brick, so there are 99 left
4) But the past is what it is, so there are 100 bricks
Since this chain of logic leads to a contradiction, we have to toss something out. Sean, you want to toss (3 = free will), but I don’t see that as any more plausible than tossing (2 = time travel is possible) or tossing (4 = the past is immutable).
Personally I like the idea of tossing (4) and imagining “alternate timelines”, but I think we both have to admit there is no real way to know.
Sean:
Almost off topic, but about those wormholes… Most discussions have concerned transporting a body with mass through a wormhole. I’ve wondered (leaving a FEW practical details aside), if there was any theoretical bar to sending a packet of photons (having energy but no mass) through at the speed of light. So information could be transmitted but not objects. Seems like it also might violate all sorts of cosmic speed limits some people have tried to legislate. Of course in this example, the wormhole might also be sort of a telescope, and if gravitons exist (or some such exchange particle) there might even be other gravitational anomalies.
Which could, I suppose, really tie space/time up in knots, if one is writing logically consistent speculative fiction.
To everyone else also, much as the show sometimes abrades (character development could be better, people of color hardly escape stereotyping, etc.), I’ll be there, is it 2/2?, my 62 y.o. bones propped up right in front of the TV.
Take them bones to FlashForward, you likely won’t regret it!
The compass is what’s known as an ontological paradox, an object which seems to have no genesis and to exist in a closed loop of time. It’s a very interesting concept; a common example is to travel back and time and give Shakespeare a complete collection of his works, which would then exist without ever having been authored.
Also, I disagree that time spent watching Flashforward would be anything but regretted.