LuLu: Hello again and welcome back to Geek Time. Hello, Brad.

Brad: Hello, Lulu. So thinking about all the technologies out there, out of all the technologies and movies and TV and everything, what is the one that you want the most？

LuLu: You mean like technology that's not reality yet?

Brad: Right, yeah.

LuLu: Definitely time travel.

Brad: Interesting.

LuLu: Now hugely into Doctor Who, so I would love my own TARDIS.

Brad: Yeah, Doctor Who is really great, I love it.

LuLu: But time travel that is like recurring theme in so many sci-fi films, books, TV, right？

Brad: I mean, like you can go back almost nearly a hundred years ago and read the story about the time traveler, but then like in more recent fiction, in the eighties there was Back to the Future about a a boy who goes back in time and accidentally stops his parents from their first meeting, and has to find a way to bring them back together so he's born in the future.

LuLu: That's actually a comedy. I've heard that reference I haven't really watched Back To the Future, not in its entirety, but they mention it so much on a Big Bang Theory, they were trying to argue the theory behind it.

Brad: That's actually really funny because there's lots of theories that are coming out in relationship to the movie and thinking how is this movie actually possible and thinking about actual time travel in relationship to the movie because they were trying to be very accurate to how time travel might work back then.

LuLu: So what I'm getting is a lot of nerves and geeks out there.

Brad: Yeah.

LuLu: Alright. Apart from Back to the Future, which is one of the big ones, what else?

Brad: There's like Primer and Predestination, both of these films have to do with the people going back in time and like basically finding out that everything that they've done has already been pre-determined.

Brad: They're actually going back in time, but it ends up being that it's everything is like one timeline and they can't change anything that they wanted like a predestination is actually I don't want to give it away, but there's actually a really interesting hook at the end where the main characters actually seeing themselves throughout the entire film. They just don't know it.

LuLu: You can't change anything.

Brad: Right. Or if you can like, this actually you do the time travel, it just. . . it's already been pre-determined that you will do the time travel within the timeline.

LuLu: That just sounds like a never ending cycle.

Brad: Yes, there is a time loop. And then we can also think about like something more. . . it's a kind of like a more modern take on it. It would be like the arrival or arrival which is time travel not with any type of device, but seeing the 4th dimension within your own mind, learning the language of time and then being able to travel through time, just within your own mind and actually see future events or see past events, kind of maybe feeling like it's a dream or something, but actually being there and actually traveling through time because you're not in stuck within your three dimensional body anymore.

LuLu: That sounds really cool. So basically it's the idea that you can do time travel without time machine.

Brad: Right.

LuLu: But a lot of the arguments, let's say, for example, on the Big Bang Theory among the guys when they were talking about time travel, and the theories is they don't really agree with one another because there are a lot of paradoxes in this that basically saying time travel doesn't make a lot of sense. Could you give us a few of these paradoxes?

Brad: There is that like the grandfather paradox, for example, which is kind of like this idea that you go back in time, and when you go back in time, you actually are your own grandfather, or like you actually go back in time when you kill your grandfather and then you're no longer born so that you're no longer born to go back in time to do this. So it's like the timeline basically just goes back to its original shape.

LuLu: That's a paradox. And any other paradoxes?

Brad: There's like the self consistency paradox where like if you go back in time and try to change something, it then creates a new universe and that universe that you were in before no longer exists for you, you are now in the new universe because you've created a timeline split. And there's kind of like an idea in quantum physics where every time there's a possibility of two things occurring that both things actually occur and we just split off into separate universes.

LuLu: Let me sort of make this easier to understand. Let me simplify it. So let's say now I'm a teacher. But if I travel back in time and for example, I wanted to be a doctor and then I traveled back in time and chose to be a doctor, went to medical school, but even though that could happen. But that means I would no longer me as a teacher would no longer exist in this universe. Lulu as a doctor will exist in another universe.

Brad: Right.

LuLu: That's really freaky. That's really freaky and all these talks about time travel in fictional works, I bet there are people who are actually trying, who have tried at least to do time travels.

Brad: There's lots of people who have tried, there are lots of physicist are trying to find ways, there's actually lots of urban legends out there where people have said they come from the future. There is actually if you watch one of Charlie Chaplin's videos, one of his movies, you can see someone in the background who looks like they might be a time traveler because they have a device that they put up to their ear, and it looks like it might be a phone. Some people have said it's just like an early version of like a hearing aid and someone was just trying to use it to hear something. But from like the untrained or naked eye, it looks like they might have like a phone or something in their hand, you can't really quite tell what it is. It just looks like a square basically. So people are like, is that a time traveler? And similar things have happened throughout the years where they have a picture of someone who is in a historical context which could just be with photoshop and everything out there these days, but there are lots of people have said this is an actual photo without any modifications whatsoever. Some people have vetted it, but it's really hard to tell, they might be if I vet it say then people will think there's time travelers, so. . .

LuLu: I mean, maybe it's a good idea for us to go through some of the old films and see if there are things or people or devices that really shouldn't have been there. Maybe that is a little bit of evidence for possible time travelers. I've also heard of The Montauk Project and Philadelphia Experiment that is related somewhat to time travel as well.

Brad: So basically they were connected to early like nuclear experiments. And one of the things that happened to us when they were testing devices, someone said that they actually went back in time like 11 seconds or 11 or something was really short amount of time. But it was actually like recorded on their devices that certain amount of time had passed, but everywhere else the time had passed at a different rate. So could just be that all of the devices on the ship like had a power malfunction since they were all connected, but there could be another reason who knows what actually happened, but yeah.

LuLu: That's very, very well known urban legends in the United States, right？Do people generally believe them to be real？

Brad: I think a lot of people just kind of ignore it and kind of just say it probably isn't actually something that happened. It probably just that was something different about the sensors or something happened on the ship that caused them to have that malfunction.

LuLu: By the way, Brad, if someone appears in front of you and say and claim to be a time traveler, what would be your reaction？

Brad: I'm probably going to be quite skeptical. As there's actually been several reports of people who have gone out to the news and said they've come from the future and that something is going to happen. And if you have actually been quite interesting, there was a, I can't remember the man's name, but there was a a few years back, there was a guy who said he came from the future and that something was going to happen and his prediction came true. And so a lot of people were kind of like, wait, what？And they thought this might actually be a real thing. It turns out the man has fallen from it into kind of obscurity. No one knows where he is right now and no one has heard from him. And so maybe like he returns back to his time or but or maybe he just kind of of like isn't really true or maybe he created a like a false identity for this.

LuLu: And now comes to the question that I've asked in our alien episode. If time traveling seems to be quite possible in a way, then why don't we see more time travelers？I mean legit ones. Are there any theories about this？

Brad: There are actually quite a few theories. I wouldn't say mythology but like the science behind it. There are some very bad things that can happen as a result of time travel, and so that these consequences could be very bad for the universe. And so there might be like a group of police who actually go back and forth in time that actually prevent people from stopping or from creating a timeline drift.

LuLu: It's like a time travel border control.

Brad: Exactly.

LuLu: You are not allowed to do it.

Brad: I think a lot of TV shows, I think even Doctor Who had an episode where they had something similar where maybe someone was going to kill Hitler or something like that, and they had time traveling police. But that's actually a kind of recurring theme. There are some different theories where people might only be able to travel within their own time. Another theory is that the device that you make to travel in time can only transport you from one point to another. So we have to wait until we actually create the device. And once we create the device, we can then bridge the future to the device that we have now. So we may not be able to travel in the past once we create the device, but we can travel to the time once we do create that device. That's a major theory right now.

LuLu: So only travel forward. You can go to the past, you can try to go to the future.

Brad: We can that. . . the theory states that we can travel to the past, but we have to have the device first. And so for example, say this year we create a device for time travel.

Brad: Then in like 2040, we could travel back to now.

LuLu: I see. So after you create a time travel machine, then any point onwards, you can travel back to this point. I see, well, that basically means we can't travel to past, our past.

Brad: Yeah, our past. And so those are kind of the theories that are out there now as far as why we haven't found time travelers.

LuLu: Interesting. And let's wrap up here for this episode. We've introduced some of the basics about time travel and in the advanced episode, we're going to get a bit more into the theories about time travel movies. Thank you, Brad, for coming to the studio.

Brad: No problem. Thank you, Lulu.

LuLu: I'll see you next time.

Brad: See you next time.

LuLu: Bye~

Brad: Bye.

更多英语资讯，获取节目完整文本，请关注微信公众号：璐璐的英文小酒馆。每天大量英语干货更新！