 Think Tech Hawaii. Civil engagement lives here. And we're back live. We are young talents making way only here on Think Tech Hawaii. I'm Andrea Gabrielli. I'm your host. And this is the show where we talk about things in science that matter to Hawaii with our brilliant school students and their science projects. Today I'm particularly excited because we're going to talk about something interesting, something very interesting. And something that we often complain about, time. But what if time could actually be reversed? It is my pleasure to introduce you today to Aidan Chun from Roosevelt High School. Nice to have you here, Aidan. Nice to have you here. Nice to be here. Thank you for coming. Thank you. So we're going to talk about time reversal. But what actually is time reversal? How is it defined in physics? So for this project, what time reversal is, is you reverse the direction of the velocity of an object. So, for instance, if you got coffee and milk to make a latte and you mix them together, a time reversal for that would be that the swirling of the milk and the swirling of the coffee and they mix kind of go in reverse and they sort of are mixed. So within this project, you can think of time reversal like that. So it's like flipping it and we go, oh, for example, if we, if we, something fall, an object fall, it sort of bounces back. Yes. Yeah. Okay. And I know that you focused on a very particular object for time reversal. You didn't focus on cars or bowls falling from the ground, but you focused on galaxies. Yes. So what is a galaxy? A galaxy you could think of as just a giant glob or cloud of stars that you are, you know, attracted to each other gravitationally. And then what we did in the project is that we got two galaxies using programs that were created from Joshua Barnes back in the 80s. Works at the ECD for Astronomy. Yes. Yeah. And then because you already have the materials and I was already interested in time, there's only natural for us to get to this. And then pretty much your smash galaxies together, mix them together and then just un-mix them. Maybe let's see our first slide up. Let's have our first slide up so we can see. Okay. So these are two galaxies colliding. Yeah. Yes. Okay. So how many stars do we have as part of these simulations because it looks like a lot of dots. Yes. In total for both of the galaxies, it is a quarter of a million stars. It's impressive. Yes. So now what are we looking at here? The two galaxies are colliding. Yeah. Yes. And they're becoming one object. They're mixing together as you can think of it. So that's if you want, these are the two objects we're studying for time reversal, reversing the speed of these objects. So what did you do as part of your science project with these two galaxies then? So after smashing them together and then periodically recording, you know, the positions and the velocities of all the stars. Of all these half a million stars. Yes. Or a quarter of a million stars. Quarter of a million. You take the velocity of every single star because they're all tracing, you know, you're all going in their motion. Yeah. Going through a trajectory. So you flip the star's direction at the final frame of the forward run. So when everything's settled down and it's all mixed together, you wait for a certain time afterwards. Then you take that, you know, final state and you flip the velocities of every star in the galaxy. And what should happen, theoretically, you know, according to the Isaac Newton's equations and all that, is that the two galaxies should actually, it's like rewinding a video. Yeah. They should go around and then finally separate and just go off in their own way. I believe we have a video about this. Let's have a look at it. So this is the collision. And then you basically flip the velocity of every star. Yes. So this is what we're looking at here. Yes. Yeah. So and then they basically rewind back. And so yeah, we're looking at the two galaxies separating and going off in their own way. Yeah. But does this happen all the time that every time you flip the velocities, they go back or? Surprisingly, no, it doesn't. For, you know, using computers and all that, that doesn't happen, even though mathematically and theoretically, that's how it should be. Yeah. And that, you know, led to the problems. The way the physics laws are defined, basically. Yes. Yeah. The physical laws are perfectly time symmetric, but time symmetric. When you use them in computers or, you know, later on talk about this, but when you apply them in real life, it's not the case. And if you take a look at the problem, is there? Yeah, we have a look. Let's take a look at, okay. This is, I believe, our video where we're showing a failed time reversal. An unsuccessful reversal. That's an unsuccessful one. So the two galaxies stay mixed. Yes. Even if we flip the velocities. Yes. And the interesting thing is that it's like completely different. They don't stay mixed as they originally were. They just kind of separate and they just splat, you know, fall back into each other. So let's have our next slide up so we can see, we can understand more about the project, the problem, actually, you are trying to solve and you are to address as part of this project. So these are what galaxies look like. So you said individual clusters of stars. Okay, that's the problem. Yeah. Yes. So as a matter of fact, if you wait too long after the two galaxies emerge and you try to, you know, bring back time all the way to the point where they're separate, it would fall apart. You can't have them reverse the motion. So they stay mixed. Yes. They try to separate and then they just fall back and stay mixed. So why does this happen? So me and Barnes, as we're talking about this, we hypothesized that this was due to the lack of precision in computers. So if you take a look at the next slide, let's have a look, let's have a look. You can see, oh, okay, Google Calculator, it can't store an infinite number like pi or Euler's number. So it cuts off at a certain amount of digits. Oh, okay. Yeah. And that also applies to any other computer we have. And for these calculations, for something like a simulation that references back to its original state, every little cutoff at a digit adds up like a little figure right there. Like a snowball effect. Yes. The error gets bigger and bigger in the end. So as you wait longer, the more of those add up. The more the errors add up to, oh, I see. Yeah. And it comes to a point where the whole entire system of galaxies just can't be reversed at all. Right. And that's how you end up with an unsuccessful reversal. But in this slide, we're also looking at, we have in computers, we can store single precision numbers as well as doubles. Yes. Yeah. So did you consider this as well as part of the simulation? Yes. That's actually the whole kind of independent variable for it. So we ran all separate experiments on single precision, you know, the precise way, and then double precision, the more precise, you know, method of storing numbers. Right. Let's have a look at the next slide we have, so we can learn more about the experiment that you actually carried out. Yes. So can you tell us something about your methods, how you did this? All right. So with a simulation programs made by Dr. Barnes back in the 80s, it's pretty old. It was written in C, the, you know, the grand language at the time. Yeah. Yeah, that's right. And then we made references to the each of those files, as you can see there, like tree code underscore DP, that's a double precision calculations. Yeah, that's right. So these are the locations and velocities of all the stars in the galaxies. Yes. Yeah. Um, in fact, if you look at those, um, that, you know, those light blue, the different colors of this image, yeah. Yeah. Over at the terminal, the light blue text. So the lines of codes, basically. Yeah. So that, that, do they tell us any information? Yes. Um, they're actually directories or folders, housing dot that files. And these files are, you know, arrays or just giant lists containing information about the position of every particle and the velocity of every particle. And then, uh, you have math, you know, the Newen's equations and all that, that references these numbers and calculates them. How long did it take for you to complete? It seems like a hard-dose task. Yes. And that's why we have our computers do this. Even for a computer, back at the IFA, it took about a week to two weeks. But for you to, you know, take this code from back in the 80s and maybe model it and use it to actually do what you wanted to do to simulate all the stuff. How did it work? How did you actually, how are you able to work in the IFA and all that? Um, it was actually through High Star. That's where they gave me the opportunity to make these connections to great opportunities. Yes, it is. Um, it was made by JD Armstrong and Mike Nasser. You might know who those people are. And what it is that they have you work on a project for a week, just, you know, nonstop work for five hours. And then, um, they bring in guests like mathematicians and astrophysicists and they have their talks. And then it gives you another opportunity to just make conversation with these people and just really learn more about how, you know, the process of being an astronomer is. What a great opportunity to learn more from professionals. And it's great that you actually got to do this, to experience this. Yeah. It is a great opportunity. Yeah. And then that overall led me to Dr. Barnes for my science for projects. And then we first conversed over email and then that's when I was able to go to his office and perform these experiments. Me, team and everything. Yes. So, what do what do you see in as part of your future? Are you going to be an astronomer or? Um, I actually will set my focus on astrophysics or even computer science. I'm still kind of debating. Wow. Amongst those two. And then, uh, maybe perhaps after I get my undergraduates and all that, maybe I can go over to the IFA. Yeah. Yeah. Absolutely. And then, uh, do my graduate studies there. Right. Very nice. Yeah. Right. Right. So, let's continue to learn more about your science project, reversing time in galaxies. And let's take a look at the next slide here. Um, okay. So, you ran all these simulations and then you got, what did you get as part of the, what results did you get? What data did you get from these simulations? So, um, the raw data that I got is just, like I said before, the arrays. And I can use them to make text files. Yeah. Which you can load them into ipython to make those graphs over there. Also, these, um, the, the figure on the left is basically the two galaxies again. But the figure on the right is a graph time. And then we have expositions of the stars. Yeah. So, describe it for us. The expositions are the centers of the galaxies. So, the brightest points on the galaxies? Oh, the center. Yeah. Okay. Yeah. And then you could see how, um, you can actually see how they're, it just plots their trajectory and how they try to separate. Yeah. And they go on their way. And then for a successful one, you can see them go off in their merry ways. That's right. Yeah. So, this is, um, the two centers. Why did you consider the centers of the galaxies? Was it easier as a reference or? Yeah, it was. Because you could, yeah. Okay. And then you also considered all of the stars as well as part of that. Yeah. Yeah. So, all the stars are pretty much, you know, encased within that one point. So, you made plots, plots and plots and plots. Yes. Yes. How many simulations did you run? How many times the two galaxies collided? Um, it was, huh, you know, I've done so many of those. I kind of lost count. Yeah. I think if we take a look at the results. Yeah, let's have a look. Okay. So, here, so, we define the, the sets of experiments with single precision as well as double precision. Yes. So, here, we're looking at results from the single precision. What did you find about this? So, um, for a single precision, you could see that, uh, by the time you wait, 20 time units, which are just arbitrary. Yeah. You can think of them almost as the amount of time for the sun to orbit around the core of the Milky Way. Yeah, that's right. Because, um, the question I was going to ask you is, simulations are run basically, uh, on a computer, so they go fast, I suppose. Yes. But in, in the real universe, a galaxy, two galaxies to collide, it takes a, a long time. How long does it take? Millions of years. Hey, millions of years. Yes. Millions of years. And, and our galaxy, the Milky Way is actually going, is, is set on a collision route with the Andromeda Galaxy, isn't it? Yes. And, uh, if you don't want it to be that way, if you figure out how to reverse every star, every atom, within the galactic group, maybe you could pull it off. That's fascinating, but how could you, do you have any ideas how you could actually do this, or? I have no answers. I guess it might deal more with quantum mechanics and atoms as well. Yeah. There are some studies from physicists in the world who are trying to work with quantum and other tiny particles. I think, um, there's even like research with, uh, like protons for X-rays. Yeah. And then you know how they have their spin. Yeah, yeah. They actually like reverse it. I guess to a certain degree, that's like reversing their motion. Wow. Here we're talking about really advanced physics. Yes. Yeah. So what about your, um, so you carried out the simulations with single and double precision as part of this, uh, computer work. What about the double? Maybe let's see our next slide so we can see. Yeah. Okay. So what's the difference between the single and double precision in these experiments? With the double precision, you can actually wait way longer than, uh, the single precision. As you can see with, you know, more rows of data, you know? Yeah. We saw 20 was basically the single precision. The single precision where the galaxies couldn't go back. Yes. Basically, yeah. But here, okay, so you can wait longer, I guess. Yes. Okay. Okay. And then, um, just want to find a note, you know, that amount swap might be, uh, confusing at first. Yeah. What is it? Yeah. It's a good metric of measuring how close you are to, uh, the unsuccessful reversal or that point of no return. And what that is, is that, um, when the two galaxies collide and they do their thing and you try to reverse them, some interesting thing happens when, when they finally reverse, there's some stars that are supposed to be in the red galaxy. Yeah. They're in the, like, core of the blue galaxy. Wow. And some stars in the blue galaxy, they're supposed, you know, they're supposed to be in the blue galaxy in the core of the red galaxy. Yeah. Wow. This is, this is a reversal. And we'll be back soon for, uh, we're going to take a break now. We're going to be back soon. Hi, I'm Pete McGinnis-Mark, and every Monday at one o'clock, I'm the host of Think Tech Hawaii's Research in Monart. And at that program, we bring to you a whole range of new scientific results from the university, ranging from everything from exploring the solar system to looking at the earth from space, going underwater, talking about earthquakes and volcanoes, and other things which have a direct relevance, not only to Hawaii, but also to our economy. So, please try and join me one o'clock on a Monday afternoon for Think Tech Hawaii's Research in Monart, and see you then. And we're back with life. We are young talents making way here on Think Tech Hawaii. Today, we're talking about the time reversal and galaxies collision. And we have here Aidan Chun, who is enlightening us with this very interesting topic, really advanced physics. Thank you for being here with us. Thank you for having me. So, before the break, we were talking more, we were talking about this galaxies colliding, and we mentioned what happens with single and double precision, when we carry out these experiments, single and double precision on computers. And while we were having a break, you were talking, you were telling me more about the physical laws that you consider to run this experiment. And you focused on gravity. Yes, that was the only thing we focused on was purely that Newtonian gravity. Nothing to do with relativity or any other forces or anything like that. So, this experiment could potentially be more complicated. It could get more. Yes, it could be so much more complicated. But, you know, for the sake of not having the computer burning out and the resources that we have. That's important. We kept it strictly to the, you know, classical mechanics and just gravity. Right, right. What are the implications in real life for this time reversal studies and physics as well? So, it does two things. One that it ties the realm of computer simulations where effects are isolated with the real world. And on top of that, it also actually kind of tells us in reality why we have a direction in time. Why we only go forward in time. And it actually has to do with thermodynamics. It has to do with the concept of entropy. What is it? Entropy is the principle that everything is bound to go from a state of order to disorder. Kind of like if you had a perfume bottle, it's ordered when everything is within that glass bottle. Once you open that cap, you can see that everything just kind of mixes in and just... With the air, and stay mixed. So, there is a direction in which these things happen. Yes. And that's what entropy tells us. Yes. From basically order to disorder in this sort of sense. And the, you know, the lack of precision, the little errors that add up, you can actually think of them as a direct analogy in the computers to entropy in real life. This is, so it's useful basically to, for computer sciences and understanding the direction of time. And what have you learned while doing these experiments? Even in terms of your future career, you know, because carrying out this, I mean, it's fascinating. Yeah, it is. It's really fascinating. I've learned so much more than I thought. You know, not only just, you know, typing up a well description of this abstract concept, but also all kinds of programming and even how repetitive the job can be. Programming as well is very useful because it can be applied to a variety of other fields as well. Yes. You could be applied to almost anything, you know, you know, even business and... Absolutely, absolutely. That's the great thing. And maybe we could reverse some of the bad businesses that we... Yeah, we could reverse what happened at Wall Street and then everything would be good. Action, everything. Yeah. And you mentioned that you also went to the state of Hawaii science and engineering field. Yes, I did. Yeah. What did you learn presenting this advanced physics research there? It was mainly me refining how it was presented because this is a pretty hard thing to grasp. That's fine, I guess. So it was that, but also I had the time to actually talk with my peers and learn more about their product of projects. Their projects as well. Did you have any judge who was... made some particularly good comments or feedback, give you some ideas for this project? Oh yeah, absolutely. I got comments talking about... I think it was mainly from like a mathematics point of view where they talked about how it had a great connection to chaos theory. Oh, that's right, yeah. So they said that this project has a great implication in that and just... you could be applied all kinds of things too. As well as the concept of entropy that you mentioned earlier. And then even, I believe, don't quote me on this, but there was some research on it where they used that to test out code. They bring it back to test out how well or the performance of their code, yeah. So here we're talking about the implications of your work. Yes. Yeah, yeah, yeah. But next, what do you see next as part of this project itself? Are you going to consider... you mentioned you focused only on gravity, but are you going to consider... are you going to make the experiment more complicated to test more hypothesis or... Oh yeah, absolutely. Another thing I did too was me and Barnes actually dabbled with satellite galaxies. So we have a satellite galaxy that is not reversed, unlike the two main galaxies colliding. So a satellite galaxy for our audience, what is it? Yeah. So it's just a galaxy that's separate from the two main ones, it just orbits them. It's a small cluster of stars that orbits a main big galaxy. Yes. So how does it... does it perturb the system? Absolutely. It... what we did here is that we got three different sizes, right? One big, medium and small. For the small one, yes. And there are all different ratios for the masses of one galaxy. And then as proposed by Newton and all that, that's an external force, right? Proterving a system that's being reversed and that can actually just... it just goes downhill. The Milky Way, our own galaxy, that's the galaxy where the star is part of. Yes. Has two dwarf galaxies as well. They can be seen in the southern hemisphere here in Hawaii as well. This is the sorts of things that you try to simulate. The presence of dwarf galaxies orbiting the main galaxy. Yeah. I do would like to say for you know to destroy any confusion is that none of these galaxies are based off of real-life galaxies. They're made based off of an equation made by Walter Jaffe. It's called the Jaffe density profile and that's kind of just like a vanilla elliptical galaxy. So that's how you... So the stars are more... there are more stars around the center rather than... that's how you define the galaxy. It gets more sparse the farther you get from the center. But one thing I didn't ask you, galaxies have all sorts of different shapes, spirals or elliptical galaxies or spherical. These are... you consider spherical galaxies? What kind of shape... They are spherical elliptical galaxies. This is for the sake of simplicity. Yeah. As you can tell, spiral galaxies are a lot more harder to model. Yeah. And with elliptical galaxies it's just as simple as applying a model like the Jaffe density profile. Potentially you could use these equations to simulate really hard shapes and you know spirals as well. Oh yeah. You might even be able to apply it to the Milky Way and Andromeda. Wow. Let's see how things go. Wow. That'd be awesome. Yeah. Are you planning on doing that or... Sure. No. I was kind of thinking about taking it to that way or even just pursuing other projects. You know through High Star this year too. I can make more connections and... Yeah. Because you mentioned earlier that you're going to Maui as part of this training. Yeah. You want to tell us more about this wonderful opportunity I think. So you... For my case I'll be staying a week at Maui and then... It's kind of like a nine to five job for a astronomer where you go in and then... It's not a vacation. It's not a vacation. It's... You do a lot of work with you know people of your age. So also I was going to ask you if there were astronomers or people who are already in the field. Yes. Okay. They'll be mentoring you for like a week-long project. So they're going to be mentors. They're going to be your peers. Is it a teamwork or... Yes it is. We usually get into like groups of three based off of the categories that we like. That's a wonderful opportunity. It's going to be intense. Yeah. It is. I remember in this previous High Star the thing that... The only thing I survive on is loads and loads of coffee. You know. Because you just had your computer right there and then you do a lot spreadsheet calculations and just that's what every astronomer have to do yeah. Yes. They're just drinking a bunch of coffee and then just typing on a computer. That's amazing. Yeah. Do you have any idea the projects you're going to work with at this time? I would like to work more with these big-scale projects that have to deal with... Simulating. Yeah. Simulating galaxies and all that. So that's definitely a you know category I'll be pursuing. We have about one minute left today in our show. So what do you want to tell our audience to sort of summarize this physics work that you carried out? Overall if you like to do time travel figure out how to reverse the motion of every atom in the universe and no exceptions even if you have a small fraction things just falls apart and even then time travel has limits. So you can't be like Dr. Miro. That would be your job for the future. You're going to come back here on Fink Tech, Hawaii. I'll tell us more about it. Yes. I'll be coming back with a time machine. And perfect. We're going to be waiting for you. All right. Sounds great. Thank you Aiden. Thank you. Thank you. Thank you. Thank you for being here. And you've been watching Fink Tech, Hawaii here. Young talents making way. We're going to be back for more. Stay tuned.