Speaker 1: Brought to you by Toyota. Let's go places. Welcome to
Speaker 1: Forward Thinking. Hey everyone, and welcome to Forward Thinking, the
Speaker 1: podcast that looks the future and says, tell me, dr
Speaker 1: where are we going this time? I'm Jonathan Strickland, I'm
Speaker 1: Lauren Vocabon, and I'm Joe McCormick. Joe, I I've got
Speaker 1: a question for you. Okay, I've really been thinking about
Speaker 1: this for a while. What if I had if I
Speaker 1: had to nail you down and say, what movie that
Speaker 1: involves time travel do you feel really gets it right?
Speaker 1: What's the best depiction of time travel in the movies?
Speaker 1: What would you say? Well, I don't know if it's
Speaker 1: possible to get time travel right in the movies, because
Speaker 1: I'm not sure if it's possible to actually do it period.
Speaker 1: The movie that that convinces me the most is a little,
Speaker 1: uh indie sci fi movie called Primer. Have you all
Speaker 1: seen this now? So? Yeah, so in your version, time
Speaker 1: travel and evolves getting a storage unit. Yeah, so you
Speaker 1: run a U haul and you put a little box
Speaker 1: in it and you go sleep in the box, and um,
Speaker 1: and then everything gets really confusing. But there there there
Speaker 1: are a couple of things I really like about the
Speaker 1: way it depicted time travel. Number one is that it
Speaker 1: depicts it the technology, the technology aspect of machine they
Speaker 1: build feels like a real project. You know, you see
Speaker 1: the scenes where they're designing it, and it doesn't sound
Speaker 1: like a bunch of sci fi magic talk. You feel
Speaker 1: like these are these guys are they're real engineers who
Speaker 1: were talking about the kinds of problems engineers encounter when
Speaker 1: they're building a machine. Number two, The thing I like
Speaker 1: about it is that it's the thing I said before,
Speaker 1: It gets really confusing when once they keep using the machine,
Speaker 1: it's hard to keep track of what's going on. It's
Speaker 1: a movie that challenges you too, because if you if
Speaker 1: you aren't willing to really pay attention and listen and
Speaker 1: try and be engaged, you could be lost before there's
Speaker 1: any time travel at all. In fact, you can be
Speaker 1: lost before you realize what the heck they're trying to build. Yeah, definitely, Yeah,
Speaker 1: all right, Lauren, what about you do you have? Do
Speaker 1: you have a time travel like a favorite kind of
Speaker 1: depiction of time travel? Well, I think that probably the
Speaker 1: closest to what will eventually be reality is is what
Speaker 1: the Simpsons portrayed in the Treehouse of Horrors episode Time
Speaker 1: and Punishments, which of course was was kind of based
Speaker 1: on the old Bradberry story. A sound of Thunder is
Speaker 1: that the one where Homer goes back in time accidentally
Speaker 1: steps on a on a butterfly and changes everything all right, right,
Speaker 1: comes back to the to the present and uh and
Speaker 1: and winds up in what seems to be this amazing
Speaker 1: perfect dimension, right and well, but but but he goes
Speaker 1: he goes like they're all like rich and fabulous, and
Speaker 1: he's like, Marge, give me a donut, and she's like,
Speaker 1: what's a donut? And then and then he leaves and
Speaker 1: then starts again. My favorite part of that one is
Speaker 1: where he goes back in time and just starts killing
Speaker 1: things randomly. But that also does try to sort of
Speaker 1: address a real issue that's possible with time travel. We're
Speaker 1: time travel a reality, and you were to go way
Speaker 1: back and change some small thing you have no idea
Speaker 1: how much of an effect that might have in the future. True, Now,
Speaker 1: before we get off too far down that road, because
Speaker 1: we are going to address that, it's my turn, Yeah,
Speaker 1: what's your job? Spill and Ted's excellent adventure because Sand
Speaker 1: Demons High School football rules. Yeah. I actually was just
Speaker 1: reading about how scientists at M I. T Are working
Speaker 1: on a time traveling telephone booth. Yeah, yeah, yeah, it's uh,
Speaker 1: it's it's phenomenal, powered by George Carlin magic. I was
Speaker 1: about to say, I mean, this has to involve George
Speaker 1: Carlin very short supply Now, well, I mean just because
Speaker 1: he's passed away in this current time. If it's a
Speaker 1: time machine, then that should that should be no problem, right, Okay, okay,
Speaker 1: so time travel is really fun for the movies, especially
Speaker 1: because it creates all these weird questions. We have no
Speaker 1: experience with which to compare it to, so you can
Speaker 1: you can almost try anything. Yes, And we of course
Speaker 1: have talked about time in a previous episode. We were
Speaker 1: really talking about time and general relativity and special relativity,
Speaker 1: and so we're not going to go too far into that,
Speaker 1: but we will give a little bit of a refresher
Speaker 1: so that we can have at least a kind of
Speaker 1: an agreed upon foundation upon which we will build our
Speaker 1: contraption of time machine that will fall a part of
Speaker 1: the moment's notice. Yeah, okay, so let's talk about time
Speaker 1: travel today. Is it possible? Uh? If it is possible.
Speaker 1: How might it work? And if it does actually work,
Speaker 1: what would it mean. Well, it depends on how you
Speaker 1: define it, because if you just define it as traveling
Speaker 1: through time, technically we're all doing that, not where Yeah
Speaker 1: that's a great term. Yeah, well it's true. You just
Speaker 1: you know, you just have to be and you and
Speaker 1: you and you would go through time. All right. So,
Speaker 1: first of all, defining time we've mentioned in our previous episode,
Speaker 1: it's really hard to do that without it becoming this
Speaker 1: kind of crazy recursive, uh you know, tautological definition. So
Speaker 1: Einstein said time is what you read on a clock. Yeah.
Speaker 1: One one definition you could apply is say it's the
Speaker 1: rate of change in the universe. And this is not
Speaker 1: something that is as globally consistent or universally consistent. In
Speaker 1: other words, it can you can actually have very localized
Speaker 1: rates of change that are much different than on the
Speaker 1: universal scale. As it turns out, time is in fact relative.
Speaker 1: It is different depending upon your perspective. And that doesn't
Speaker 1: just mean it seems relative to different people. You know,
Speaker 1: based on how long it feels like this horrible movie
Speaker 1: has been going on, or this lecture or something. It's
Speaker 1: measurably relative like it actually changes depending on how close
Speaker 1: you are to say, massive objects, or how fast you're going. Right,
Speaker 1: that's a gravitational time dilation, yeah, exactly. Yeah. And and
Speaker 1: both of these, you know, gravitational time dilation and the
Speaker 1: speed at which you're traveling. Uh, those those two effects
Speaker 1: are what make it um necessary for us to have
Speaker 1: satellites that correct their time gradually, because, as it turns out,
Speaker 1: the time on their clocks passes at a different rate
Speaker 1: than the time of our clocks down here on the
Speaker 1: ground level. Right. So, even if you were to take
Speaker 1: a fast airplane trip and you had a very precise
Speaker 1: clock on board the airplane when you landed, and you
Speaker 1: compared that against another clock they have been started the
Speaker 1: exact same time, has that same level of precision, you
Speaker 1: would see that time had passed at slightly different rates,
Speaker 1: not a lot. I mean, it's not like you land
Speaker 1: and you you land an hour earlier than what you
Speaker 1: you would have landed, uh if the hadn't gone well,
Speaker 1: not just speed, but the fact that time is actually
Speaker 1: passing in a a different rate for you. But it's it
Speaker 1: is a tiny amount, it's it's measurable with satellites. It's
Speaker 1: a little bit more important because one, the effect is
Speaker 1: larger and tow we're depending upon satellites for things like GPS,
Speaker 1: and if your time isn't exact, if you haven't corrected
Speaker 1: for this time dilation, you're not going to get an
Speaker 1: accurate reading of where you are on Earth based upon
Speaker 1: those GPS readings. So we already see dilation and effect
Speaker 1: on today. It's not like it's just hypothetical. Yeah, it's
Speaker 1: definitely just an accepted fact of science. But despite the
Speaker 1: fact that time is relative and influenced by things like
Speaker 1: nearby massive objects and the speed at which an object
Speaker 1: is traveling, one thing that we do seem to know
Speaker 1: about it is that it only seems to move in
Speaker 1: one direction, right, right. We don't seem to cause and
Speaker 1: effect goes in one way. Right. You don't have a
Speaker 1: a an effect and then later a cause happens. You
Speaker 1: have a cause and then the effect happens. Sort of
Speaker 1: the arrow of time. Yeah, and in points and only
Speaker 1: one direction as far as we can determine, at least
Speaker 1: intuitively mathematically, it's a different, different matter, I suppose. But
Speaker 1: first I would also mention that time travel inherently has
Speaker 1: a paradox attached to it, which is that you get
Speaker 1: two different, completely different experiences of time, at least based
Speaker 1: on the type of time travel where there's some time
Speaker 1: passing for the traveler as well as for the rest
Speaker 1: of the universe. So in other words, Joe, if you
Speaker 1: decide to go back into the past and you're taking
Speaker 1: some sort of trip where like let's say it's the
Speaker 1: Tardest from Doctor Who, there's actually time that passes for
Speaker 1: you as you take this journey. So you're leaving today
Speaker 1: and you're going back two years into the past, and
Speaker 1: it doesn't take that long. I mean, there's basically just
Speaker 1: a series of whoo, whoop whoops, and then any land.
Speaker 1: But it's not instantaneous, so you experience time moving forward
Speaker 1: to an independent observer who I guess has been around
Speaker 1: for a few centuries. Uh, they will remember the fact
Speaker 1: that you arrived before you departed. So that's two different
Speaker 1: experiences of time. My question would be, if there really
Speaker 1: is this kind of movie style traveling backward through time
Speaker 1: uh motion, where are you physically well? I mean, space
Speaker 1: and time are very much connected. We have this whole
Speaker 1: idea of the space time continuum. But where is not
Speaker 1: so much of an issue as when Uh, as it
Speaker 1: turns out, because at least with the Doctor's tartists, it
Speaker 1: travels both through space and time. Uh. If you're in
Speaker 1: a DeLorean going eighty eight miles per hours, somehow you're
Speaker 1: magically in the right place, uh, the right region as
Speaker 1: you as you would have been had somehow you've managed
Speaker 1: to track the Earth. Yeah. That thing is what always
Speaker 1: mixes me up about a lot of this time travels.
Speaker 1: I mean, in addition to many other things like the
Speaker 1: Dolorean doesn't just appear in the cold reaches of space
Speaker 1: and parting I fly immediately perishes like Doc Brown. That's
Speaker 1: a really smart guy. Um, but no, I mean, I mean,
Speaker 1: with that kind of essential paradox, even the very small
Speaker 1: differences and in time that happened between us and our satellites,
Speaker 1: for example, are actually really hard to wrap your mind around.
Speaker 1: So anything as large as time travel is is necessarily problematic.
Speaker 1: Whack I think is the accepted scientific term. Yeah, quite
Speaker 1: quite whack. Yes, it's wackness is uh is sufficient, It's
Speaker 1: it's a it's enough of a wackness to actually detect
Speaker 1: with the naked eye. Okay, so I've got a question,
Speaker 1: does time travel is there any way, we could just
Speaker 1: rule it out at the beginning to say no, we
Speaker 1: just know it's not possible because it violates some law
Speaker 1: that we are almost positive cannot be violated. All right,
Speaker 1: To answer that question, first of all, spoiler alert, According
Speaker 1: to at least some mathematical models, time travel is at
Speaker 1: least hypothetically possible. But there's still some things that we
Speaker 1: have to talk about. For example, the law of conservation.
Speaker 1: Now we've heard this, right, the idea that you cannot
Speaker 1: create nor destroy matter or energy. You can convert one
Speaker 1: into the other, but you cannot actually destroy it or
Speaker 1: create it, right, can't make energy disappear or matter. You
Speaker 1: can convert energy into less useful states. Sure it's never
Speaker 1: going away, right, right. So in other words, when we
Speaker 1: are you know, we talk about how systems lose energy,
Speaker 1: they don't really lose energy so much as they produce
Speaker 1: other forms of energy that is useful. They're they're pooping
Speaker 1: out heat. Essentially, heat which is hard to harness, is
Speaker 1: just diffused. Right. So that law of conservation suggests that
Speaker 1: there's a problem with time travel. And that problem is this,
Speaker 1: if I send something into the past, whether it's a
Speaker 1: person or an object or time, shame, whatever it is,
Speaker 1: then that thing will suddenly be in a time where
Speaker 1: it wasn't before. That seems to suggest that I am
Speaker 1: actually creating more matter at that moment in time, and
Speaker 1: that spacetime region then was there before. Does that violate
Speaker 1: the law of conservation more so than even just creating
Speaker 1: a really weird time sonic boom? Yeah. The fact that
Speaker 1: the fact that something is there that wasn't there before.
Speaker 1: You had a uh, let's say, a certain amount of
Speaker 1: matter in that region, and now there's more matter, and
Speaker 1: it wasn't that you converted energy, it's that you've produced it.
Speaker 1: Mm hmm. I can tell you what the general answer
Speaker 1: to this is about how they get around it, which
Speaker 1: is the idea that in an infinite and unbounded universe,
Speaker 1: you have regions where conservation takes place. But it's not
Speaker 1: a global thing. It's not it's not applied across the
Speaker 1: entirety of the universe. It's so it's it's kind of complicated,
Speaker 1: but it's it's assuming that there is an infinite universe,
Speaker 1: and therefore you're not really creating more matter because the
Speaker 1: concept of infinite alone means infinite like like there's no
Speaker 1: more to infinite. You've got that that that alone is
Speaker 1: you know, it's meaningless. You're not creating a lack or
Speaker 1: additional but localized it would be a problem. But if
Speaker 1: you look at the universe as a whole, as a
Speaker 1: system and considered infinitely and bounded, you don't apply that
Speaker 1: that law in that instant. So that's the way of
Speaker 1: getting around it. Yeah, it's kind of a lot of
Speaker 1: the stuff we're gonna talk about today with these time
Speaker 1: travel rules and the ways to get around it. It
Speaker 1: reminds me a lot of if you've ever played a
Speaker 1: a pencil and paper role playing game and you've got
Speaker 1: one of those players who's trying to find a way
Speaker 1: around every rule in the game, and that's the way
Speaker 1: they play the game. I you guys have friends who
Speaker 1: don't play the game that way. I thought, I thought
Speaker 1: that was the entire point of the game. I've I've
Speaker 1: had games where people didn't do that and they were magical.
Speaker 1: But at any rate, So another thing we can talk about,
Speaker 1: does it um? Is it? Is? It? Is it violating
Speaker 1: space itself? Um? And according to some models of general relativity,
Speaker 1: time travel is possible through something called a closed timelike
Speaker 1: curve or c t C which are quote worldlines that
Speaker 1: end at the same point in space and time as
Speaker 1: they begin. And we'll talk more about what c t
Speaker 1: C s are and how you might be able to
Speaker 1: travel through time backwards through time in fact, because a
Speaker 1: lot of people say, oh, time travel would be possible
Speaker 1: if you're talking about traveling into the future, But traveling
Speaker 1: into the past is problematic. I mean, especially if you
Speaker 1: think about using special relativity. So you're just talking about
Speaker 1: moving really really fast. So to you, time passes a
Speaker 1: different rate than it does to someone on some other
Speaker 1: you know, moving body, right, if they were to look
Speaker 1: at you, you would appear to be moving in slow motion, right,
Speaker 1: and you would see every things sped up back home. So,
Speaker 1: for instance, if we're talking about here on Earth and
Speaker 1: Joe leaves to go on an interstellar super fast joy ride,
Speaker 1: he might go for a year and be traveling at
Speaker 1: almost the speed of light and return to Earth and
Speaker 1: it will be like two centuries have passed, but to
Speaker 1: him a year has passed. Now to that that you
Speaker 1: could argue is just like basically traveling into the future. Yeah,
Speaker 1: it's like it's like traveling into the future for you Joe.
Speaker 1: For for the rest of us, it's just like boy Joe,
Speaker 1: you remember him? Whatever happened to that guy? And then
Speaker 1: maybe someday or descendants would be like, oh, you're this
Speaker 1: Joe guy who never shows up the things. But at
Speaker 1: any rate, the CTCs would allow you to travel back
Speaker 1: in time, assuming that they are actually in play in
Speaker 1: this particular model general relativity, and we'll get into that
Speaker 1: in a little bit. Okay, I've got one. Okay, what
Speaker 1: about basic causality? I mean, can you you've heard of
Speaker 1: the grandfather paradix? Obviously you have, Yeah, I wrote the
Speaker 1: notes right. Well, okay, so the grandfather paradox is a
Speaker 1: fun one. Uh. This this is a very common one.
Speaker 1: That's that's mentioned. There are a lot of different variations
Speaker 1: as well. But the the easy way of saying it
Speaker 1: is imagine that time travel is in fact possible where
Speaker 1: you can go back into time and then you go
Speaker 1: back in time. You're an assassin and you have a
Speaker 1: specific target that you have to hit in the past.
Speaker 1: You travel back in time and your target is eighteen
Speaker 1: years old, and you assassinate your target. But it turns
Speaker 1: out your target was actually your grandfather, Your grandfather didn't
Speaker 1: have kids until he was, you know, in his twenties.
Speaker 1: So you have killed your grandfather before your your mother
Speaker 1: or dad were born, which means that you wouldn't have
Speaker 1: been born, which means you couldn't have gone into the past,
Speaker 1: which means you couldn't have killed your grandfather. Thus the paradox.
Speaker 1: Now we're not saying there's any reason this would need
Speaker 1: to arise, but if traveling into the past really were possible,
Speaker 1: why shouldn't you be able to do something like this? Well, again,
Speaker 1: if through your action you end up negating the ability
Speaker 1: to even go back in the first place, that's the paradox. Right,
Speaker 1: You've created an incoherent loop, is what it's called. It's
Speaker 1: it's something that could not continue. Uh once it happens
Speaker 1: like once it once you were successful in doing whatever
Speaker 1: the task is, and it doesn't have to be kill
Speaker 1: your grandfather. That's the paradox. But there are a lot
Speaker 1: of different variations. Generally speaking, what they're saying is, even
Speaker 1: if time travel were possible, you probably couldn't go back
Speaker 1: and change anything, because if you did, then it could
Speaker 1: negate the possibility of you traveling back in time in
Speaker 1: the first place. So There's an argument that extends from that,
Speaker 1: saying that maybe there's no way to affect the past
Speaker 1: at all. But that also seems like a problem to me,
Speaker 1: because by appearing in a place, I mean, even if
Speaker 1: you don't really do much of anything, you're still affecting it,
Speaker 1: I mean, just by your state of existence there. Sure
Speaker 1: it's accidentally stepping on a butterfly thing and creating a
Speaker 1: universe where it rainstonuts. Yeah, it seems like it wouldn't
Speaker 1: be possible to go to a place without having any effect. Well,
Speaker 1: there's some interesting ways around this one too. One is
Speaker 1: suggesting that you would be able to do whatever you wanted.
Speaker 1: It's just whatever you did happens to be whatever has
Speaker 1: happened anyway, That makes more sense to me. So in
Speaker 1: other words, it's not that you are prevented from doing things,
Speaker 1: it's that whatever you choose to do is what has
Speaker 1: happened already and what led to the state of the
Speaker 1: universe that allowed you to travel back in time in
Speaker 1: the first place. And this becomes a coherent causal loop
Speaker 1: where you end up having You can have variations on
Speaker 1: this where the only way it could have happened is
Speaker 1: if you had traveled into the past, which I love.
Speaker 1: These two the very popular in science fiction. Well, yeah,
Speaker 1: I mean one of the one of the big ones
Speaker 1: that seems to emphasize the strangeness of this kind of
Speaker 1: loop would be, what if you only know how to
Speaker 1: invent a time machine because a time traveler from the
Speaker 1: future came back and showed you how to invent a
Speaker 1: time machine. Yeah, and there's another great example. In fact,
Speaker 1: I'll go ahead and say it. Let's just say that, uh, Lauren,
Speaker 1: you have created a way of uh, you've gone into
Speaker 1: the future. You've got a time machine where you can
Speaker 1: actually move into the future, and you you steal from
Speaker 1: the future an amazing device, and this steal things all
Speaker 1: the time, mostly from the future. Yeah. So it's a
Speaker 1: really cute nutcracker that looks like a sure from an
Speaker 1: antique store. I have a have a specific example. Lauren,
Speaker 1: Lauren the chronographer kleptomaniac, steals a device it turns great
Speaker 1: jelly into strawberry jam, and she travels back in time
Speaker 1: to present day and starts to thus turn all the
Speaker 1: grape jelly into strawberry jam. And she loves that. She's
Speaker 1: fantastic guests And then as she's you know, she's traveled
Speaker 1: far into the future to get this amazing device uh
Speaker 1: on on her her deathbed, many many many years into
Speaker 1: the future. She then gives this this device to a
Speaker 1: little vagabond, and and the vagabond, it turns out, ends
Speaker 1: up being the quote unquote inventor of this device. In
Speaker 1: other words, this device was never actually invented. It only
Speaker 1: exists in this loop of time. It turns out that
Speaker 1: the adult version of this vagabond is the person from
Speaker 1: whom Lawrence stole the device in the first place, and
Speaker 1: this device only exists within this closed time loop. From
Speaker 1: that perspective, yeah, that doesn't seem to make any sense,
Speaker 1: because in that case, the device was never actually built.
Speaker 1: It always just exactly Yeah. See, it's another one of
Speaker 1: those kind of and if you've ever read any hind Line,
Speaker 1: hind Line has got a billion stories that involved this
Speaker 1: kind of of closed loop where nothing in the story
Speaker 1: could have happened unless this other thing that hasn't happened
Speaker 1: had already happened. It just gets more and more confusing
Speaker 1: as it goes along. I think it's much more likely
Speaker 1: that um that grape to strawberry jam converters are a
Speaker 1: universal constant, and it therefore um that they have to exist.
Speaker 1: There must exist, unmust they must at some point exist, right. UM.
Speaker 1: I also am very fond of the theory that um
Speaker 1: that the universe kind of kind of equalizes anything that
Speaker 1: you would do and or try to do in the past,
Speaker 1: Like if you went back and tried to shoot your grandfather,
Speaker 1: um that the gun would misfire, or that that's suddenly
Speaker 1: a strong breeze with the bullet off course, right, or
Speaker 1: that that a weird reflection gun in your eyes and
Speaker 1: messed up your aim. And but the the idea being
Speaker 1: that the universe itself counteracts anything you try to do
Speaker 1: and thus prevents it from happening. Uh. I can see
Speaker 1: that if you're just saying like this is another way
Speaker 1: of saying that whatever you go back and change is
Speaker 1: what already happened. If you're talking about the universe having
Speaker 1: like an active deterrent mechanism, that that seems only possible
Speaker 1: if you're positing like time travel, police ghosts. I think
Speaker 1: that Final Destination has proven beyond a doubt to us
Speaker 1: that this kind of thing happens at the Great documentary series.
Speaker 1: But also it doesn't necessarily have to be conscious. It
Speaker 1: just has to Again, it's very similar to this is
Speaker 1: what has happened, therefore, this is what will happen if
Speaker 1: you were to go into the past. But another interesting
Speaker 1: idea that tries, you know, one way you can try
Speaker 1: and get around this. It's sort of similar to what
Speaker 1: you were talking about with the Simpsons, Lauren, this idea
Speaker 1: of parallel timelines. This is what it's like in Back
Speaker 1: to the Future and a lot of stories. Yes, you
Speaker 1: go back and you change something. It doesn't have to
Speaker 1: be incorporated into the future you've already experienced. You create
Speaker 1: a new future. Its branch to split off. So in
Speaker 1: this sense, some people say, well, technically you're not altering
Speaker 1: the past so much as avoiding the present. In other words,
Speaker 1: in other words, the president present every day, the present
Speaker 1: that you are from. Let's say, uh, you you have
Speaker 1: left the present, You've gone into the past. You've made
Speaker 1: a change in the past that would affect your present,
Speaker 1: the one that you came from. It splits off the
Speaker 1: timeline and now you are in a parallel timeline where
Speaker 1: the the change that you made is fact. It's a
Speaker 1: historical fact. And so therefore whatever your present, uh, will
Speaker 1: be now it will be different from what it was
Speaker 1: in the timeline you left. But the timeline you left
Speaker 1: could theorectly still be going on. It's just now it
Speaker 1: doesn't have you in it because you left UM, and
Speaker 1: I guess you probably wouldn't be able to get back,
Speaker 1: would Yeah, I mean that's not hypothetically. I mean I
Speaker 1: think that if you can get over there in the
Speaker 1: first place, then there is surely a clause and she
Speaker 1: can get back if you were to go back even
Speaker 1: further into your timeline so that you could stop yourself
Speaker 1: when you appear the first time in order to change
Speaker 1: the timeline and thus prevent yourself changing the timeline by
Speaker 1: going back and changing it again. Maybe I don't know,
Speaker 1: I need to have like some trees, you know, to
Speaker 1: illustrate all this on UM. But yeah, again, some people
Speaker 1: say that this this ends up being some sort of
Speaker 1: universe hopping as opposed to time travel in the purest
Speaker 1: sense of being able to go into the past and
Speaker 1: change things around. O. Well, let's just say maybe one
Speaker 1: of these things really can happen. Now we've accepted that
Speaker 1: based on relativistic physics, you probably could travel into the future.
Speaker 1: That's not really the problem. We're talking about traveling back
Speaker 1: in time. How would you actually do it if one
Speaker 1: of these models, any of them, at least one of
Speaker 1: them works, what's the way you get there? Because this
Speaker 1: is a thing that that legit physicists have legit thought about.
Speaker 1: I mean there's some there's some not just physicists but
Speaker 1: also philosophers who have really talked about, you know what,
Speaker 1: what is the likelihood of this and if if it's possible,
Speaker 1: how would it be possible? And some of the models
Speaker 1: are uh, you know, hypothetically possible but not practical, right,
Speaker 1: And actually I'd say all of them aren't because if
Speaker 1: they were practical, we would have totally been doing them
Speaker 1: already or at least tested them. But one of them
Speaker 1: would be using what are called Care black holes k
Speaker 1: e r R or care ring not caring care rings. Uh.
Speaker 1: So this is after a physicist named Roy care who
Speaker 1: proposed this back in nine and talked about the concept
Speaker 1: of a rotating black hole. That would be a care
Speaker 1: black hole. And if you're looking for size, it would
Speaker 1: be about the size of Manhattan, but it would have
Speaker 1: the mass of our sun, so would be incredibly dense.
Speaker 1: You know, sun is obviously much larger than the Earth,
Speaker 1: so for it to be reduced in size to the
Speaker 1: size of Manhattan, but retain its mass incredibly dense. So
Speaker 1: the idea of a caring is a ring of collapse
Speaker 1: neutron stars that are spinning with enough rotational force that,
Speaker 1: at least in theory, they would never create a singularity. Now,
Speaker 1: the singularity is that that point of infinite density, that
Speaker 1: point that has zero length, infinite mass, so you would
Speaker 1: never be able to escape from it. Light itself cannot
Speaker 1: escape from it. Uh. That's not the same as Event Horizon,
Speaker 1: which is a great movie that we watched for tech stuff,
Speaker 1: but it's also event horizon is also the zone around
Speaker 1: a I call that's the point of no return. Yeah,
Speaker 1: which is why it's a terrible idea to name your
Speaker 1: spaceship after don't name don't name your don't name your
Speaker 1: your cruise ship Iceberg, and don't name your your spaceship
Speaker 1: event Horizon. But yeah, So the idea with the care
Speaker 1: ring is that perhaps there would not be a singularity
Speaker 1: at all. This rotational force would end up preventing that
Speaker 1: from happening, and the ideas that you might and I
Speaker 1: stress might be able to pass through such a thing
Speaker 1: in a spacecraft. Uh, and not be spaghettified and crushed
Speaker 1: and killed as a result. Uh. And the idea would
Speaker 1: be that you would be spit out of the other end,
Speaker 1: which essentially would be a what is what is in
Speaker 1: theory called a white hole? I say in theory because
Speaker 1: we haven't observed one, why these might not actually exist?
Speaker 1: And yeah, yeah, one of the ideas of that a
Speaker 1: white hole is essentially I mean, that's like the opposite
Speaker 1: of black holes, where stuff is being spouted out, like
Speaker 1: matter and energy is coming out of this. Uh, you
Speaker 1: know it would be black hole be one end of it,
Speaker 1: and white hole would be the other end of it.
Speaker 1: But while we've observed the black holes, the white holes
Speaker 1: are still something we don't really see. I'm trying to
Speaker 1: wrap my brain around that. What would be the opposite
Speaker 1: of a black hole. It seems like it could be
Speaker 1: something like a little big bang kind of wouldn't it,
Speaker 1: like like a continual big bang? Yeah, singularity expanding outward,
Speaker 1: putting energy and mass. I would just think of it
Speaker 1: was the other end of a pipe. Oh way, so
Speaker 1: wormhole is kind of similar in a way. But um, again,
Speaker 1: we haven't observed white holes, And one of the other
Speaker 1: theories is that black holes are are kind of a
Speaker 1: window into another universe, right, the idea being that there's
Speaker 1: some sort of hole through our spacetime that connects to
Speaker 1: some other perhaps space time. Perhaps it's something we can't
Speaker 1: even fathom because it's so different from our universe. But
Speaker 1: why The counter arguments against that is that, well, does
Speaker 1: that mean our universe is exit only because we can't
Speaker 1: find any entrances, We don't see any of the the
Speaker 1: what we you would imagine would be the opposite of that,
Speaker 1: where stuff is coming from somewhere else, although you could
Speaker 1: argue maybe dark matter and dark energy or somewhere in there,
Speaker 1: because we can't directly observe those at any rate. There's
Speaker 1: the possibility that you could fly through one of these
Speaker 1: black holes and thus travel through time, either in the
Speaker 1: future or in the past, but you wouldn't necessarily be
Speaker 1: able to control that at all, So it just be
Speaker 1: kind of where every wherever and whenever you end up,
Speaker 1: that's where and when you are. It's it's like when
Speaker 1: the kid goes to make a suicide at the fountain
Speaker 1: drink machine, except you're doing that with time and space. Yeah,
Speaker 1: you just you gotta you gotta blindfold on. You don't
Speaker 1: know how much lemonade versus Dr Pepper you're putting in
Speaker 1: that mix. It could be delicious or it could be noxious. Yeah. Similarly,
Speaker 1: there's the wormhole approach that I just mentioned. So wormhole
Speaker 1: essentially is curvature of the space time into a tunnel,
Speaker 1: where going in through one side and popping out the
Speaker 1: other side, you would end up in a totally different
Speaker 1: area of space time. Okay, so give us the real scoop. Wormholes.
Speaker 1: They're in all these movies and they just they're just
Speaker 1: magic tunnels basically, well in the movies their magic tunnels. Yeah, yeah,
Speaker 1: what's the real deal with the wormhole? They exist? Uh?
Speaker 1: In fact, wormholes, well we think they exist. Again we
Speaker 1: we we haven't observed them, but mathematically, Einstein and Rosen,
Speaker 1: who were two pretty smart dudes, uh said, said that
Speaker 1: it's logical that they exist. Yeah, if you look at
Speaker 1: it as like a teeny tiny lasting for a split
Speaker 1: second basis in large particle accelerators, they technically exist. If
Speaker 1: you didn't hear me rolling my eyes, I I just
Speaker 1: rolled them really hard, Okay, Okay, and not that that
Speaker 1: isn't true that is extremely true and and wonderful and beautiful,
Speaker 1: and not particularly useful to the conversation that we're having
Speaker 1: right now, because first of all, none of us are
Speaker 1: Adam sized, and and second of all, we exist in
Speaker 1: periods longer than um nanosection. So well, I'm just being pedantic.
Speaker 1: So but yes, your point stands, Lauren, there is we
Speaker 1: have never observed any kind of wormhole. In fact, there
Speaker 1: may not be a style of wormhole where you could
Speaker 1: create something that has stability that would allow you to
Speaker 1: actually pass through it, that would have the size and
Speaker 1: duration necessary for that to happen. Nor do we really
Speaker 1: know what would happen if we were to pass through it. One,
Speaker 1: don't you end up? Yes, you end up. You end
Speaker 1: up being in the the arguably the least popular of
Speaker 1: the Star Trek series on I guess Enterprise probably cases
Speaker 1: a run for its money or or on a living
Speaker 1: ship using the word frell a whole lot. But at
Speaker 1: any rate, Uh, the the issue is, we don't know, one,
Speaker 1: if it's even possible to create a wormhole or to
Speaker 1: find a wormhole in nature that would allow us to
Speaker 1: pass through it, we don't know what would happened to us.
Speaker 1: If we did pass through it, and again you wouldn't
Speaker 1: have the control, right unless you were able to fold
Speaker 1: space time itself specifically to your desires, you would not
Speaker 1: be able to determine where and when you would come
Speaker 1: out the other side. Yet again, kind of like the
Speaker 1: black hole. So it might be a way of traveling
Speaker 1: through time, but again it may not be practical. Um.
Speaker 1: And you know, in order to imagine this, this is
Speaker 1: the always the hardest thing for me to imagine because
Speaker 1: you have to think of space time. It's it's a
Speaker 1: afford menstional construct as we understand it, right, Yeah, and
Speaker 1: I've seen some pretty interesting like like gifts of this
Speaker 1: on the internet. But but I understand that, um, that
Speaker 1: that is not really inaccurate to pick I mean, I mean,
Speaker 1: I have a hard enough time perceiving three dimensions and
Speaker 1: when you add the fourth in there, and like yeah, yeah,
Speaker 1: because it's easy enough if we reduced it to two. Right,
Speaker 1: if we think of the standard example is you have
Speaker 1: two people holding a sheet taught between them, and then
Speaker 1: on top of the sheet you lay some sort of
Speaker 1: object that has mass that that pulls the sheet down, right,
Speaker 1: it curves, the sheet curves around the object, so even
Speaker 1: when you're holding it tightly, you see it where it's
Speaker 1: dipping down depending upon the mass or the weight of
Speaker 1: the object. Uh, that determines how how much curve you get. Well,
Speaker 1: the same thing happens in four dimensional space time, So
Speaker 1: space itself curves around massive objects, and time does too. Uh.
Speaker 1: It's just really hard to imagine that for one thing,
Speaker 1: you know, even if you're able to imagine it in
Speaker 1: some kind of abstract three dimensional way, adding a fourth dimension,
Speaker 1: like you said, Lauren, really hard, I mean not, I
Speaker 1: certainly it baffles me, sure, and especially once you get
Speaker 1: past the concept of just a sheet curved by by
Speaker 1: like a bowling ball for example. Um. Further, in order
Speaker 1: to make a wormhole, you have to punch through the
Speaker 1: sheet with the bowling ball to perhaps another parallel sheet
Speaker 1: beneath it, or maybe a little bit of the sheet
Speaker 1: that's on the floor underneath it, and then there's like
Speaker 1: stars involved. And I don't and I don't follow. Technically
Speaker 1: you could wrap the sheet around the bowling ball and
Speaker 1: thus create a tunnel that way, although I don't know
Speaker 1: that that makes it any more useful. Another way, maybe
Speaker 1: thinking about it now, tell me if this is totally off.
Speaker 1: Is Uh, you drill a hole in an apple, and
Speaker 1: so if you imagine the two dimensional surface of this
Speaker 1: apple is actually the three dimensional space world, and that
Speaker 1: that third dimension of the apple is the fourth dimension
Speaker 1: of time, you can sort of go through from one
Speaker 1: side of the apple to the other. Yeah, you're I
Speaker 1: can't wait for your time travel movie and you're you're
Speaker 1: gonna call it the core and the discappointed to find
Speaker 1: out there's already a movie called that, and there's already
Speaker 1: a worm in there. That's true. So uh, anyway, wormholes
Speaker 1: again very much hypothetical when it comes to time travel.
Speaker 1: There's also the closed time like curves that we mentioned earlier.
Speaker 1: So this is um an interesting concept. Comes back to
Speaker 1: another another big thinker, right, it's it's not a it's
Speaker 1: not a new concept. Some of the ways of explaining
Speaker 1: how to make it work are very new, but it
Speaker 1: might date back as far as like the nineteen forties
Speaker 1: with um Kurt Girdle, who was a buddy of Albert Einstein,
Speaker 1: pretty pretty smart and a little bit nutty mathematician who
Speaker 1: was was talking about the geometry and movement of the
Speaker 1: universe and and put forth the idea that these loops
Speaker 1: might exist, like like if you had a long enough
Speaker 1: journey um due to the way that that the universe
Speaker 1: he thought might spin, that you could loop back on time,
Speaker 1: right and Uh, then we have the entrance of string
Speaker 1: theory into the idea of these closed timelike curves. So
Speaker 1: string theory, it's we're not gonna go too far into it.
Speaker 1: We could do a whole episode on string theory too.
Speaker 1: But a string theory, you can imagine that all matter
Speaker 1: in the universe and talking about all the way down
Speaker 1: to sub atomic particles, is made up of these these
Speaker 1: strings that are either either open ended or they're closed
Speaker 1: in loops. Uh, and they vibrate in different ways, and
Speaker 1: you know, superstring theory. Supersymmetrical string theory suggests that the
Speaker 1: vibrations of the strings are what determine what kind of
Speaker 1: subotomic particle gets represented. For instance, protons vibrate, the strings
Speaker 1: vibrate one way, electrons they vibrate another way. Anyway. One
Speaker 1: of the concepts here is that by using cosmic strings,
Speaker 1: either two of them very close together or one sort
Speaker 1: of attached to a black hole, you could put them
Speaker 1: under such pressure that you create this closed time like curve.
Speaker 1: In the universe, which if you were to travel using
Speaker 1: this close time like curve, you could move back to
Speaker 1: the point of origin in both space and time when
Speaker 1: that curve was created. So you could travel back in
Speaker 1: time up to the point when that curve was created.
Speaker 1: You could not travel further back because the curve wasn't
Speaker 1: around before then, right, unless a dinosaur did this for you,
Speaker 1: you couldn't go back to the time of dinosaurs exactly.
Speaker 1: So in other words, if I built one today the
Speaker 1: furthest back I could travel would be today. I wouldn't
Speaker 1: be able to go back to yesterday, but any time
Speaker 1: from here forward, assuming I have a way of harnessing
Speaker 1: that I could travel backward. Uh, this could become really
Speaker 1: useful if you have a short term plan of making
Speaker 1: a lot of mistakes, and you want to be able
Speaker 1: to go back and try a lot of different options
Speaker 1: before you settle on whichever one is going to be
Speaker 1: the least harmful of all the mistakes you're gonna make.
Speaker 1: Sort of like creating a safe point. Yes exactly, Yes,
Speaker 1: you've got three doors ahead of you, and you know
Speaker 1: two of them lead to certain death. But wait a second.
Speaker 1: Every time you go back a few minutes. Is there
Speaker 1: another one of you there that you have to kill
Speaker 1: before you can make the decision? An excellent question. I
Speaker 1: don't know the answer to that. Uh you know, again,
Speaker 1: this ends up being very much hypothetical. Obviously, no one
Speaker 1: has actually created one of these closed time like curves
Speaker 1: that they could travel around it and go back into time.
Speaker 1: And uh so it's again very much kind of a
Speaker 1: philosophical and scholarly discussion, not a practical discussion. Okay, So
Speaker 1: I wanna raise an issue, which is that all of
Speaker 1: these things that seem even remotely close to plausible do
Speaker 1: not happen to be the kind of machines you can
Speaker 1: build in your garage, like in the very Victorian kind
Speaker 1: of looking or or or primer like I brought up earlier.
Speaker 1: You know, some people in their garage want to build
Speaker 1: a time machine. It doesn't seem like that's the kind
Speaker 1: of thing that lets you travel through time. This is
Speaker 1: the closed time like her of where you wouldn't be
Speaker 1: building one of those in your garage. But maybe you're
Speaker 1: building a spaceship in your garage. Well, I guess you
Speaker 1: could build a spaceship in your garage to go to
Speaker 1: occur ring you know, yeah, something like that, but it's
Speaker 1: not a time machine in the sense of, like you
Speaker 1: set a dial to nineteen fifty seven. I wonder if
Speaker 1: this is because time itself exists in a relativistic framework,
Speaker 1: and you might need relativistic forces which means really really
Speaker 1: huge or really really energetic, in order to manipulate it. Yeah,
Speaker 1: there's some studies that have suggested that if you wanted
Speaker 1: a time machine, you would have to harness the equivalent
Speaker 1: amount of power that you would find in a galaxy
Speaker 1: in order to make it work, which is not necessarily practical.
Speaker 1: We think we have energy problems now, but when it
Speaker 1: comes to you know, I want to go back to
Speaker 1: last Thursday, but I need to harness the power of
Speaker 1: an entire inner galaxy to do it. It's certainly not
Speaker 1: convenient from your girl. Okay, So, folks, if you want
Speaker 1: to know how what we have to do in order
Speaker 1: to create time travel, go listen to our episode on
Speaker 1: the Cards Show scale. We need to get to CARDASSHEV
Speaker 1: level three and then we'll have time travel. Well, assuming
Speaker 1: that no one else wants to do anything. Right. Hey, guys, guys,
Speaker 1: I know you're really crazy about your iPhones. And your
Speaker 1: kindles and your internets. But we're going to turn all
Speaker 1: that off so I can go back to last off
Speaker 1: the galact of irrigation systems and all the life support. Now,
Speaker 1: what what if we what if all this this talk
Speaker 1: is truly moot? What if? What if there is no
Speaker 1: such thing as the future or the past, only the now? Well,
Speaker 1: that was Girdle's idea, actually, he he suggested that the
Speaker 1: end result of his model of the universe UM, which
Speaker 1: which branched, by the way from from Einstein's theory of
Speaker 1: general relativity UM, is that since time travel is hypothetically
Speaker 1: possible within the realms of physics as we understand them,
Speaker 1: therefore time it's as we understand it cannot exist. Yeah,
Speaker 1: I mean, that's that's the The idea is that nothing
Speaker 1: is ever really in the past or in the future
Speaker 1: because time travel can exist, uh and and and therefore
Speaker 1: the past and future don't exist. So, in other words,
Speaker 1: it would be that you again a time time travel device,
Speaker 1: but you'd have no destination to go to. There be
Speaker 1: There'll be no place to go to because there is
Speaker 1: no past in the sense of a a point in
Speaker 1: space time that still is relevant. I'd argue there is
Speaker 1: no present, that there is no now. Well, you know what,
Speaker 1: Einstein would agree with you, in the sense that simultaneity
Speaker 1: is as a concept that doesn't work in Einstein's model
Speaker 1: with general relativity because it all depends upon your point
Speaker 1: of reference subjective. Right, yeah, h well, andy, I mean
Speaker 1: if you try to, I mean, if you actually just
Speaker 1: sit down and try to think, Okay, what is happening now?
Speaker 1: There there is no now and more sitting here. The
Speaker 1: more you try to examine the idea of an instant
Speaker 1: of now, it just slips through your It's another one
Speaker 1: of those things where you know, in order you sit
Speaker 1: there and think of it on the scale of all right,
Speaker 1: let's take let's take a unit of time. Let's say
Speaker 1: it's a minute. All right, well, let's let's break that down.
Speaker 1: What's happening this very second? And then you think, wait,
Speaker 1: you know, you can actually break a second down into
Speaker 1: smaller and smaller slivers, and you just keep thinking that, well,
Speaker 1: technically you can just keep reducing be half over and
Speaker 1: over and over. Paradox Yeah. Yeah, you get to a
Speaker 1: point where it's not perceptible by humans by any stretch
Speaker 1: of the imagination, but it's still happening, and it's still
Speaker 1: significant in a mathematical sense. Yeah. So then you think, well,
Speaker 1: wait a minute, how did I ever get from? Especially
Speaker 1: when you start getting really far away from units of
Speaker 1: time that we can perceive, you think, how is anything
Speaker 1: ever happening? Ever? Yeah, I mean when the past nanosecond
Speaker 1: transitions to the next nanosecond, what's that? What's now in
Speaker 1: between them? See, that's where a lot of other science
Speaker 1: fiction comes in, where you have entire worlds that are
Speaker 1: existing and and and growing and falling apart in the
Speaker 1: time between the seconds. So it's a it's there existing
Speaker 1: in a in a way that is imperceptible to the
Speaker 1: rest of us because we we only see the seconds.
Speaker 1: We can't see what's in between them. That's great stuff.
Speaker 1: But anyway, that the point being that when it comes
Speaker 1: down to is time travel possible? Will we ever see
Speaker 1: time travel? There's still a lot of disagreement on it.
Speaker 1: You know, mathematically, according to the laws of physics as
Speaker 1: we understand them, including Einstein's theories of relativity, there's nothing
Speaker 1: that expressly forbids it from being possible. Well, again, I
Speaker 1: want to stick with what I said earlier, is that
Speaker 1: I feel pretty good about time travel into the future.
Speaker 1: I'm very skeptical about time travel into the past, well,
Speaker 1: especially since you know, as far as we can say,
Speaker 1: there's no there's no evidence that we can point to
Speaker 1: that it's ever happened before. And you would imagine that
Speaker 1: if it's in fact possible, someone from the future would
Speaker 1: have traveled back in time. Their counter arguments against that too,
Speaker 1: but you can find them posting on the internet. Let's
Speaker 1: not go into that. I've done a whole podcast about that.
Speaker 1: But uh yeah, so, but you know, the classic argument
Speaker 1: is that if time travel ever is possible to go,
Speaker 1: you know, if it's ever possible to travel back into
Speaker 1: the past, then sometime travel traveler from the future needs
Speaker 1: to come back to this time when we're recording this
Speaker 1: right now and knock on our door right now. Oh,
Speaker 1: son of up, Now that was me. I'm just kidding. No,
Speaker 1: one was actually at the door. No, but that's the art.
Speaker 1: If some horrible reptilian did bust in and say, I'm well,
Speaker 1: that would be you two, I'd be like, hey, look
Speaker 1: for the record, I did not make fun of retilience. Yeah,
Speaker 1: I know that would be Yeah, so really, you're just
Speaker 1: telling me I gotta get new co hosts. Uh all right,
Speaker 1: So anyway, this, do you guys have anything else you
Speaker 1: want to say about time travel? I mean, this is
Speaker 1: this is one of those fun things to talk about, because, like,
Speaker 1: you start feeling pretty confident, right, the stuff that you
Speaker 1: can intuitively grasp, You're you're, you're, you're zooming along. You're like, okay,
Speaker 1: this makes sense. Then you start getting into some of
Speaker 1: the math and you think, okay, wait, intuitively that makes
Speaker 1: no sense, even though the math itself works out. And
Speaker 1: then the further you go, the more you're like, Okay,
Speaker 1: now I don't even know what I'm thinking anymore. Our
Speaker 1: intuitions are great when we need to get the groceries.
Speaker 1: They are not very good when we need to solve
Speaker 1: questions about time and space. Yeah, it's very true. Things
Speaker 1: on the cosmological scale and on the quantum scale often
Speaker 1: are they defy our intuition because our our experience is
Speaker 1: not on that those scales. Yeah, there's no reason our
Speaker 1: ancestors on this planet ever had to think about time travel.
Speaker 1: The monolith just appeared and then let's you just go
Speaker 1: from there. Well, anyway, that wraps up our discussion on
Speaker 1: time travel. So the jury is still out. Technically, again, mathematically,
Speaker 1: there's nothing that specifically says this is completely off limits. Practically,
Speaker 1: could very well be that there's no practical way to
Speaker 1: do it, and certainly we don't have any evidence of
Speaker 1: it that we can point to. And even if there
Speaker 1: is a practical way to do it, that that practical
Speaker 1: is in extreme scare quotes, because because practical like blowing
Speaker 1: up the galaxy is not necessarily right. That's that's not
Speaker 1: not in my book. That doesn't fall under the category
Speaker 1: of practical. But anyway, if you guys have any suggestions
Speaker 1: for future episodes, you've got some sort of futuristic topic
Speaker 1: you think we should tackle, let us know. Send us
Speaker 1: an email or addresses f W Thinking at Discovery dot com,
Speaker 1: or drop us a line on the social networks we
Speaker 1: frequent Those include Facebook, Twitter, and Google Plus. We have
Speaker 1: the handle f W thinking at all three of those,
Speaker 1: and we will talk to you again in the future
Speaker 1: May the Beast. For more on this topic and the
Speaker 1: future of technology, visit Forward Thinking dot Com Problems brought
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