The Physics Of 'The Arrow Of Time'

Maureen Cavanaugh: Our top story on Midday Edition. We’ve all spent the last several days observing the change of the years. We say goodbye to 2014 and welcome 2015. But why can’t it go the other way around, why not end 2014 and welcome 2013 back, maybe do it better this time around. Of course we know the universe doesn’t work that way, but why not. That’s one of the questions my next guest studies and explains to audiences around the world. I’d like to welcome theoretical physicist, Sean Carroll. His most recent books are The Particle at the End of the Universe and From Eternity to Here. He is in San Diego to give a lecture tonight at the Reuben H. Fleet Science Center. And Sean Carroll, Dr. Carroll, welcome. Sean Carroll: Thanks for having me. Maureen Cavanaugh: Let’s start out with a simple question. What is time? Sean Carroll: You know, it sounds like a profound and puzzling question, but I want to say it is actually pretty simple. One of the things is people are stymied if you ask them to define time, but they have no trouble using it, right? It’s like show up at 8 o’clock, no one is, you know, cowering in fear that they don’t know what that means. Time is just a label. The universe happens and it happens over and over again and time is like the numbers on the pages in a book. The universe appears in a series of moments and time is which moment you are. The puzzling thing is what the relationship is between those different moments. Maureen Cavanaugh: What is the arrow of time? Sean Carroll: The arrow of time is that – you know, in some sense time is much like space. Einstein famously said the time and space are part of the same thing called space-time, but if you go out in space, there is no difference between up, down, left, right, forward, backward, but in time there’s a very profound difference between moving toward the future and moving toward the past. We think that we remember the past, but we don’t remember the future for example, the arrow of time is just that directedness, the fact that there is something pointing from the past to the future. Maureen Cavanaugh: And how do we know it can’t go the other way? Sean Carroll: Well, it’s what we see in the universe, we think that, you know, you can scramble an egg, but you can’t unscramble an egg. We don’t think that even if you ever met an alien civilization, even though they’d be very different than us, they would all be born younger then grow old and then become older. They would always be breaking their eggs and then scrambling them, never unscrambling them. They always remember the past. So, we think that we can explain that, also using the underlying laws of physics and what’s called entropy, the disorderliness of the universe. Maureen Cavanaugh: So, entropy as I understand it, very limited way that I understand it, it means that you go from something that’s organized to something more disorganized. Is that right? Sean Carroll: That’s exactly right. It’s like take a brand new a deck of cards and shuffle it, it will become more disorganized with time. It will never spontaneously reorder itself. Maureen Cavanaugh: So how is the universe becoming more disorganized? Sean Carroll: Well, the universe started out very small. We live in a universe that is expanding, and when it was so densely packed at early times, it turns out that there was a huge gravitational pull, one that would have just splintered the universe into black holes and wild fluctuations. But instead, it was very orderly. It was very, very smooth. And as universe has been growing and expanding structure, forms galaxies, stars, planets, and you and me, and that’s all a reflection of the fact that entropy is increasing, universe is becoming more disorderly. Maureen Cavanaugh: And the fact that scientists now say that the universe is seems to be continuing to expand, does that mean that this disorganization just continues and continues? Sean Carroll: That’s exactly right. We believe that the universe is about 13.8 billion years old since the Big Bang to today, but it will continue we think, we don’t for sure, forever, for infinity years into the future, and basically the entropy is going to keep going up and up until everything is just scattered to the four winds, and there’s nothing left, but empty space. Maureen Cavanaugh: I love that, it’s scattered to the four winds [laughter]. Sean Carroll: Four universal winds, yes. Maureen Cavanaugh: What about black holes though, isn’t time supposed to stop in a black hole? Sean Carroll: Well, what happens is if you get very close to a black hole, the time that you experience, the relative amount of time that you feel compared to people far away will change. Basically, if you go very close to a black hole, but don’t fall in, and then you come back out, you’ll have experienced a short amount of time, but the external universe will have experienced a long amount of time. So you will have basically been flung into the future by that black hole. Maureen Cavanaugh: So time can be relative so to speak depending how – like we see, we see the light of stars that were given off hundreds of millions of years ago, we see that light now in our present, but what you’re saying is that even though it’s relative, it only goes in one direction. Sean Carroll: That’s right. The rate at which your clock ticks depends according to Einstein on what you were doing in the universe, but the clock always ticks from the past to the future. Maureen Cavanaugh: This is all really fascinating stuff. I’m speaking with Dr. Sean Carroll, we’re apparently talking about time and space and the arrow of time, you know, and it’s all physics, you are a theoretical physicist. But many people remember that their high school physics classes were not exactly fascinating, they perhaps were a little boring, why is that? Sean Carroll: I think it’s a bunch of different reasons. You know lot of times – you don’t want to blame the poor teachers, but they’re not there to teach physics sometimes, you know, we shanghaied people in teaching subjects that they’re not ready for. We don’t value the profession of being a teacher enough to really prepare people, get the best students into that line of work, and then when we do tell people about physics, we kind of make it a bit boring about inclined plains and pendulums. We don’t go into the eighth grade or ninth grade classroom and tell them about black holes, and the arrow of time, and the Big Bang, and quarks and leptons. So, I think that physics should be taught in a much more procedural way in the sense that physics is not a collection of facts, physics is a way of looking at the world, science is a way of finding out how the world works, it should be like a game, it should be fun. And whether or not people become scientists, they should all share in the love of the scientific process. Maureen Cavanaugh: Another thing you hear from students and from others, is how am I going to use this in my life if I don’t become a physicist, why is this important, am I ever going to remember any of the stuff as I get on into my adult years, into my career? Sean Carroll: Well, I think there is sort of a two-sided answer to questions like that. One, is that science really matters, whether it’s physics, or biology, or ecology, we live in a world that is governed by science these days. Technology obviously is usually important. And just knowing the basic underlying principles helps us grasp the implications. The other is that science is the thing that has elevated human beings away from just sort of scrambling for food on the floor to living this wonderful lives that we do. It’s a way of thinking about the world. We should think of it in a similar way that we think of art or literature. It opens a window on to reality that we human beings have access to, it’s a terrible shame not to peer through that window. Maureen Cavanaugh: And it also could lead to a sort of educated audience when these great experiments are made and these great discoveries are made by scientists, so if you don’t have that background of physics or science education, you don’t know what the heck people are talking about. Sean Carroll: Yeah, I mean the vocabulary can be very intimidating and you hear about bosons and quasars and it all just sounds like Greek, right? Maureen Cavanaugh: Yeah. Sean Carroll: But, yeah, this is because the world is very surprising to us, because in our everyday lives, we don’t experience black holes or the Big Bang. It’s a least surprising thing in the world that these far-out scientific concepts come to us as kind of weird. Maureen Cavanaugh: Now, you are in San Diego, Sean Carroll, to give a lecture through Reuben H. Fleet Science Center, and to receive an award from the American Institute of Physics for – kind of for your ability to explain complex topics like this to the general public. Do you find people have a lot of interest in things like the Big Bang and the arrow of time, what kind of response do you get from audiences? Sean Carroll: Well, I think it’s a tremendous response. And actually I’m very grateful to the American Institute of Physics for this award, the Andrew Gemant Award, because its particularly for contributions to the humanistic dimensions of science and physics in particular. And I think that, you know, science can be very intimidating, physics especially, many people had bad experiences in junior high or high school, but when you give people the fun side of science in an accessible way, almost everyone loves it. There are very few people who are truly uninterested, they may have set up barriers to defend themselves against it, but when you capture their imaginations it’s very, very popular. Maureen Cavanaugh: And when you explain it in terms that don’t necessarily challenge people to the extent that they turn off, but also treat people like they are educated human beings, that they can grasp these concepts, do you find that hard to do? Sean Carroll: Well, it’s certainly something that is not natural, because explaining things is just as much a skill as discovering them in the first place, and it’s a different skill. There are some of my favorite scientists, there are people who I don’t want out there giving public lectures, they are better at doing the science, and many people who are fantastic communicators are not the people who are inventing the science themselves, but all that is important, you know, we – especially the kind of science that I do that does not directly lead to a better smartphone or a cure for malaria, the only reason we do it is because the human race wants to know the answers to these questions. And if we find the answers and then don’t tell anybody, it defeats the purpose. Maureen Cavanaugh: Now, your book The Particle at the End of the Universe is about the search for the Higgs Boson particle since the first round of experiments with the Hadron Collider, a lot of theoretical physicists have been in disarray, I mean it’s been a tough time for theoretical physicist, because the experiments seem to give way to the multiverse theory, what is a multiverse? Sean Carroll: I should say very quickly it’s a – I would qualify as an exaggeration to say the experiments give way to the multiverse theory. The multiverse theory is certainly on the table as a possibility that we’re taking seriously. It’s just the idea that, you know, we only see a finite amount of the universe around us, because it’s a certain number of year’s old and light travels at the speed of light. It could be that if we go past the universe we see, it still looks exactly like our universe more or less forever, but it could also be the far away, things look very, very different, conditions are just completely different, maybe even the laws of physics are very, very different. And those two possibilities, the universe continues the same way versus it’s very different give us a very different view on how we should be explaining the features within the universe we do see. Maureen Cavanaugh: Right, it didn’t support supersymmetry though, right, that a concept that they could give the – they could explain and add them with all the particles that they would find in this collider, super collider experiment, so that hasn’t happened yet, right? Sean Carroll: Supersymmetry is another good idea like the multiverse, which a lot of theoretical physicists love and for which we have no direct experimental evidence. However, we should point out that it is very plausible that the right theory beyond what we already know is something no one has thought of yet. So it’s a little bit hubristic to say, well, here are the theories we thought of yet, if one is not right, then the other one is got to be right. There is certainly the possibility that none of them is right and we’re going to have to do the experiments and take the data before we’re jogged into figuring out how nature actually works. Maureen Cavanaugh: If it is a multiverse, though some theoretical physicists say that, that means that the laws that we study in this universe are just basically random, they don’t necessarily have any overall meaning in the universe if there is just one universe here and one universe over there, so – but you’re okay with that. Sean Carroll: I’m okay with that. Maureen Cavanaugh: [laughter]. Sean Carroll: You have to be okay with whatever nature gives you. That’s part of your job as a scientist. You don’t get to choose ahead of time how the world works. And I’m open-minded. I’m not sure that the world does work that way, it could be that where we think of as the mass of an atom or something like that is universal constant, or it could it be that is very different from place to place. I think that we have a long way to go in developing our theories and connecting them to the data to figure out which one we should come down on. Maureen Cavanaugh: So do you think there is a limit to what we can know about the universe? Sean Carroll: You know it’s the kind of thing where no one neared that limit yet. So it’s kind of an academic question. We have a lot more that we can possibly learn. There might be a limit; I mean there might be that we reach the final understanding of the fundamental laws of physics. There will always be parts of the universe we don’t see. So there is always sort of some historical limit to our knowledge, but it completely figure out the basic laws of physics, that’s kind of why we’re here and trying to figure it out. Maureen Cavanaugh: There is a movie out now, a biography about Stephen Hawking, called The Theory of Everything. But the idea that we can ever actually get to a Theory of Everything has sort of not – seems not to be happening, is that fair to say? Sean Carroll: That’s right. It hasn’t happened yet, and there is a long history of scientists saying silly things along the lines of we don’t know everything yet, but next year we will. Maureen Cavanaugh: [laughter]. Sean Carroll: And it has never come true. So you should stop saying things like that. But we do know a lot, and I think that the most scientists operate under the assumption that there is some particular way that nature works, someday we might actually figure it out. Maureen Cavanaugh: All right. We’ll leave it there, and you have so much more to talk about at your lecture tonight. The lecture is on the Origin of the Universe and the Arrow of Time, Sean Carroll will be speaking at the Reuben H. Fleet Science Center at 7 o’clock tonight. Thank you very much. Sean Carroll: My pleasure. Thanks for having me. [Music…] Presenter: Coming Up: New York Times Columnist, Frank Bruni, addressed the San Diego Freshmen on the importance of opening up Their Customized Cocoons. It’s 12:19, and you’re listening to KPBS Midday Edition. [Music…].