Cosmic Queries – Stoner Edition with Janna Levin

0:00Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk. Neil deGrasse Tyson here, your personal astrophysicist. We're going to do cosmic queries today. Everything black holes in space-time. I got with me my co-host Matt Kirshen. Matt, welcome back, dude. Thank you. Thank you. I'm joining you from my family's spare bedroom in London right now. Oh, you mean your parents' basement where you live. That's exactly it, yeah. I commute to LA every day from the basement where all my toys and games are. I knew you were full geek, but the whole story is still in your parents' basement.

0:50That's it. You can confess that. You are in safe grounds here to admit that to us. This is a no-judgment podcast? No judgments at all. Good to have you back, and you're the host of Sometimes Science? Probably Science, Neil. Probably Science. Right. Probably Science, on which I have been a guest. You have indeed. I have, and I enjoyed my time there. So, Matt, while I know a little bit about black holes and a little more about space-time, I don't count myself among the world's experts, but we have a friend of StarTalk who is, of course, that's Jana Levin. Jana, welcome back to StarTalk. Thanks, I'm glad to be here.

1:27Yeah, yeah. Jana, you're like a neighbor up the street from the American Museum of Natural History. You're a professor of physics and astronomy at Barnard College of Columbia. And it's just great to have you, just a friend of what we do and a supporter of all of this. Yeah, I love being here. And to lend your expertise. You're not lending it because we're not giving it back. You're giving us your expertise on black holes, cosmology, the space-time continuum, and all that goes with it. So just before we start off, I just want to alert people that in your spare time, you actually are one of the founders of a marvelously conceived project, Pioneer Works, over in Brooklyn across the river.

2:13You merge art and science in highly creative and imaginative ways. I just want to congratulate you on even going there. And you've been at it for like years now. Yeah, I really appreciate that. Yeah, we have a live programming where we feature scientists in conversation. You've been over. We've had parties with you, Neil. Yeah, but you haven't put me on the stage. No, I'm waiting for the right time. Oh, okay. I have also been there and not on the stage. They didn't want my expertise, but I went to a… Matt, you and I don't cut it. We're good enough for the audience, but not to actually do it. I mean, I think I'll get there eventually, but I'm not so sure about you, Neil.

2:55I've got some deep expertise to share. I know, Steph. I'm happy to put you both to work. Be careful what you wish for. So the big project there has been lately broadcast, Pioneer Works broadcast since the pandemic, which is our virtual manifestation. It's Pioneer Works Beyond the Walls where we cover art, science, music, tech, kind of multimedia extravaganza. Excellent. So now you can reach a far greater audience than who shows up in Brooklyn. All right. So Matt, you collected questions from our Patreon members. They have exclusive access to our Cosmic Queries format, and everyone else gets to hear their questions.

3:33And so what do you have lined up for us? I did. This is like a grab bag. There's a grab bag of black holes and stuff. Yeah, there's a really nice assortment of questions. I'm going to start off with this one from Matthew Power, my kind of superhero namesake.

3:49You're Matt Kirshen, and this is Matthew Power. It's Matt Power. This is Matt from New Jersey, who is also currently reading Black Hole Blues, which is one of Jana's books. I've read that. It's an excellent book, and Matt is also enjoying it. And Matt says, my question is, if there were two black holes orbiting one another and generating powerful gravitational waves, is there a possibility that a small object, says perhaps a ping pong ball, could actually be carried away by the waves, thus making gravity a repulsive force in this particular case? Wow, this is like a surfing ping pong ball. I love it.

4:22That's, what do you think, Neil? Oh, I love the idea. So because probably he's thinking deeply because if you're surfing on a wave in the ocean, the water isn't actually moving. It's just going up and down and you're somehow exploiting this fact. Moving with it. Yeah. Yeah. I think it's a subtle question. and I've wondered about this, but I haven't ever really worked it out. I'm sure somebody might off the cuff know the answer, but definitely what you're doing in space-time, if you're near those two black holes, is you're falling freely. We literally call it free fall. So you're falling freely on the natural curves in the space.

5:04So if those curves are changing, that's certainly going to change your fall. For instance, the Earth is falling around the sun on a curve, on a circle. And if the sun were to disappear tomorrow, The gravitational waves would radiate out, taking the time it takes until it reaches us. And then we'd go in a straight line as though the sun was gone. Right? So in some sense, we are definitely moving with those waves. But thinking of it as like surfing, it's cool. I don't know. Right. If we're not so heavy as the earth, let's say, or something as responsive as a ping pong ball, wouldn't the waves wouldn't the expanding gravitational wave from the disappeared sun or from the collapsed black hole will that have any effect on us at all to push us?

5:51How can a wave move out but we can't now move with it? The gravitational energy in the wave can be quite powerful the collision of the two black holes was the most powerful event human beings have detected since the detection of the Big Bang right and all of it came out in the gravitational waves but actually um i think their effect is really quite weak in the sense you would feel the squeezing and the stretching as you kind of bobbed around on the wave but i don't think it would have enough power to actually carry you along but we also do know i think the question was also about repulsive gravitational forces and actually we do know that gravity can be repulsive so for instance the dark energy in the universe creates a repulsive effect on the expansions.

6:43The universe is expanding. Things are getting farther apart because of the dark energy and that's happening at an accelerated rate. Yeah, but you're calling that gravity and are we allowed to do that yet? What do you mean? In what sense? You say, well, there's this dark energy and it's actually the opposite of gravity. So are you legitimately calling it negative gravity? No, I'm not calling it negative gravity. I'm saying that when we think about curved space-time, that coming together is not the only possibility. Although that is with Newton's laws, in general relativity, when I think of dark energy as a particular source for the way it deformed space-time, we see a very clear example where its effect on space-time is expansive.

7:30Oh, wait, wait, I got a good answer. I got another good answer. Can I raise my hand? on this? Janet, I'm raising my hand in the front row. You're the boss. You're the boss. Okay. Neil. Neil. Thank you. Thank you, Janet. So just thinking about this more holistically, the very expansion of the universe is carrying galaxies in the fabric of the expanding space-time. So in a way, we are moving, in a sense, not through space, but with space. and space is carrying. Oh, yeah. I know it's not a gravitational wave, but I'll take it as something, it's sort of surfing, even if it's not. Yeah, that's excellent.

8:15The dark energy is just a particular example of that causing the expansion in an accelerated way. But lots of things cause the universe to expand. Like the fact that it's full of light and energy in all directions causes the universe to expand. And I think you really hit it on the head, Neil. we are moving with the expansion of the space. We are not moving with respect to our local area, right? So that is like the surfer riding the wave. Yeah, yeah, cool. All right, Matt. Well, I'm going to jump from a question that is very theoretical to one that I know you have a good answer to because I know this is something you've both been asked before.

8:56Alexander Newhouse wants to know what is the universe expanding into? Yeah, Jana. Anybody wants to know that one? I know you've done this a bunch of times. No, no, I just make stuff up, what I think, what I've read. But you actually work on these problems. So let's hear it out of the horse's mouth. Well, if, let's take it as though the universe was expanding into something. Just pretend. Then we would be saying, oh, there's some distance the universe has traveled into this other space. But what we mean by the universe is the space. So there's really no logic to thinking of it expanding into something else.

9:37The universe is the whole space. There are some relational possibilities that you can think of where the expansion of the universe is like a map of the universe where we're only reading the legend between things as changing over time. But the map itself doesn't move into anything else. That's one kind of very strange relational way of thinking about it. But no, we do not need to nest the universe into another universe to have it expand. Okay, I get that. But who, what, okay, so let's up this game a notch. What conditions would, what dimensionality, what location, what state of existence must one have to observe the entire expansion of our universe?

10:29Well, you, okay, that's... From the outside. So there is no way to stand outside the universe. No, not really, but so. I think you're trying to disprove the existence of God with me right now. What kind of trouble are you getting into? I don't think I really know God in that. Nobody can see and know the entire universe at one time. There's no way of... Yeah, who are you to say that you can't, there is not some platform, some vista outside of everything we know and see that can just simply observe what's going on? Well, by observe, we mean collect particles and interact. And we do that through POWs in space-time.

11:14So, if you want to literally be in a position where you're gathering light so that you can see the universe and deduce what's happening to it, you're really talking about interacting with something. And that requires that we be in the same universe. Now, I mean, you could fundamentally say. You're no fun. You're no fun. We could say things that I think are actually quite. Matt, she could have said God is out there and he's watching us all. Right. Or Santa Claus. He knows when you are bad or good. And then roll credits.

11:50So it is interesting to push this idea and to say, look, these ideas about space being infinite or being finite or expanding, these are just ways of talking. We could also talk differently about the entire universe only as relations, only as interactions. And that's the only thing we understand, that interactions happen over a certain span of space and time. And there's no need to even think about geometry at all or to think about the universe as a space at all. It just appeals to our intuition. Wow. Okay. You're looking at me like I've had this woman on the show many times. Okay. Matt, she's crossed over.

12:37And I don't know that they're bringing her back at this point. Okay. I mean, and we know that we're often fooled by these interactions. So right now I have the illusion that you're a solid person, that Matt's a solid person, but really you're mostly empty space. These are illusions that we cling on to more easily comprehend the world, but we know that they're not true. Matt is mostly empty space. Yeah, a lot of people say that about me. I'm solid. Neil is solid. There's nothing going on in here. So, Janet, you're referring to the fact that atoms are mostly completely empty. Right. And then even if you look at fundamentally what the fundamental particles are with atoms, we only understand them in terms of the way in which they interact with things.

13:18That's the meaning of an electron, is the way it interacts with things. So in some sense, we're just these sort of lists of interactions. Damn, she got all philosophical. That's making me very much... Quickly, go to the next question before this gets worse. Because you got so philosophical, I'm going to jump onto Scott Allen's question. Because Scott from Arlington, who, by the way, gives the caveat that Scott is stoned right now, putting that right in there and if Scott is still stoned trying to listen to these answers I think we're going to put him in some real trouble we should do a stoner version of this show I'll host it and just get my I mean that basically is my podcast that is

13:58StarTalk for stoners oh my gosh we get all the topics best suited for when you're high oh my gosh you know Janet we'll bring you back that's going to be a show I promise our audience that's going to be a show. I just fall asleep. It'll be a very boring show. Yeah, while you're eating potato chips. Yeah, okay. So Scott says, is everything just a form of energy? Is time just a human invention? Combining the two ideas is what we call life and everything we can observe and understand with our limited senses and minds, simply a flow energy constantly changing form. There is no beginning. There is no end.

14:32There is no past. There is no future. There is just the present in whatever form of energy we can sense and understand with our mind. That is Scott's question. Make of that what you will, professional scientist. Yeah, okay. Wait, did you just give the answer and you said definitely? And now we move on to the next question. I think the answer is yes, and everything's fine right now. I just think he's definitely stoned. That is such a stoner question. But let's think about this. is how do what confidences do I want to restate the question what confidences do we have Janet can you and I offer as scientists that there is a physical reality and we're not all just perceiving ourselves in the moment and that yeah I mean what evidences do we have meaning and existence outside of our perceptions yeah i mean um we're all i mean which one of us is the one perceiving am i in your mind or solely or are you solely in my mind are we both in that's mind genius before scott started combining his his ideas there are two questions at the beginning that i don't uh that are more grounded in i think physical of theory and there is everything just a form of energy?

16:02And also, is time just a human invention? And I think those two are questions that are potentially more answerable. Well, to deal with the first one, yes, I think matter and everything is a form of energy that interacts in described ways. You just don't think that. You know that. Be careful how you use the word think. Okay? Like, you think it might rain tomorrow, But you know matter is energy, okay? Right. It's true. We know that matter is definable. Yeah. And that is interesting. I mean, I think that's also related to this kind of tangent we went on, which is that what does it mean to have atoms in your body?

16:46What does it mean to be made up of atoms? It means that you have a certain amount of energy and that those particles interact in very prescribed ways. That's what makes an electron different from the positron, is just the prescribed interactions, if not their energies. So, yeah, that's really all we are. It's beyond that to say what's real is, again, part of this illusion we have to cope with our perceptions of the world. We'll take a quick break. And when we come back, we'll pick up the second part of that question, whether time is just some kind of a human construct. with the help of Jan 11 giving us her insights into the universe on StarTalk Cosmic Aquarius.

17:32Hi, I'm Ernie Carducci from Columbus, Ohio. I'm here with my son Ernie because we listen to StarTalk every night and support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

17:53We're back. StarTalk Cosmic Queries. I got Matt Kirshen as my co-host. Matt, how do we find you on social media? I'm Matt Kirshen on Twitter. I think Matt underscore Kirshen on the Instagram I very rarely use. Twitter is the main place I am. Okay. And if you don't know the spelling, just kind of get vaguely close and Google will find me. Yeah, okay. And we'll find you on Twitter then without the underscore, because that's where you mostly are. That is. That's me. And Jana, tell me about your social media footprint. Yeah, I'm more on Twitter, at Jana Levin. Two N's, like Anna. And I'm on the Insta, same handle.

18:33I sort of treat them a little differently. On Instagram, I kind of post my personal stuff, my personal business. And on Twitter... Okay, we want to get all up in your situation, and we go there, okay? You know, yeah, exactly. You know, not exactly what I had for lunch, but yeah. So, but Twitter, I have pretty serious conversations with people. If they want to ask questions, I'm there. I love answering questions when I'm in the mood, at least, you know. Okay. Very good. Very good. All right. So, we left off. What's the name of that last questioner? So, Scott, we left off his part of the question was, is time just a human invention?

19:10Yeah. Yeah. So, Janet, the only thing I can say about time is a quote I remember from Einstein or from his student, John Archibald Wheeler. Was it, time is invented to make motion look simple. Have you heard that? I have heard it. I feel like it was Wheeler because he said lots of witty things. I also think it was Wheeler. He said time is what keeps everything from happening at once. Which is a good one. Okay. So. And just, I got to throw it in here. I first noticed the woman who would become my wife in a class taught by John Archibald. Oh, wow. No way. I didn't know that. Yeah, we took the class together.

19:56Wow. I was sitting in the back row. She was in the front row. So I don't, she probably didn't notice me, but I noticed her. Yeah. I can say I noticed her in the space-time continuum on the chalkboard. Right. Okay, so what do you have to say about his comment? Well, I think, I definitely don't think it's a human construct. Whether time exists in this kind of block time model of the universe where the past exists, the future exists, every bit as much as left and right exist, but we're confined on a particular path through this four-dimensional space where time is the fourth dimension. That wouldn't be just human beings, though.

20:36That would be everything would be confined to that space. I presume my cat's death comes before it's, you know, after its birth, rather. And, you know, I just presume flowers die after they bloom. And that those are things that are happening to everything in the universe. There are other models that time is sort of not an invention of the mind, but it's like it emerges from very subtle processes and that in some sense, it's not fundamental. But I think that, again, it's a very good thing to talk about. So if we want to meet, we don't just specify a point in space. We have to say a moment in time and it's very convenient that we all are able to find that moment in time and collect and get together at that moment in time.

21:26So that suggests it's not just a figment of our imagination or a human construct. So maybe I should save this for the stoner edition, but if you could find a region of the universe where nothing changes, then time cannot possibly have meaning. Absolutely. And in fact, that's kind of a, you know, a death of the universe model that the universe will, everything that can fall into black holes will possibly if the expansion doesn't dominate and those black holes will evaporate into random particles. and then the expansion will just make it so that there's only one particle in the entire observable horizon, and that's disconnected from all the other particles.

22:16And so there will be no meaning to time passing. I mean, even for me to experience time passing, there has to be change, which is my thoughts changed, my breath accumulated. There's actual measurable change that I experience as the passage of time. So that is true that we do have internal clocks, but they are very well aligned with our external clocks, making it seem as though there is something external and universal. Well, while we're talking about external and internal clocks, Jeff Johnson wants to know, why does gravity or high speed cause an entity to move faster through time? Oh, I see the question.

22:58Time dilation is the question. yeah why does time so um but first first he got it backwards so gravity slows down time and that speeds it up yeah so it doesn't actually slow my experience of time so my experience of time if I'm standing near a black hole is exactly like very ordinary my nicely made watch that I had once synced with my friend back at a safe space station is working perfectly well it's still matching, the number of breaths I take, time seems to be passing completely normally. Your heart rate, everything. My heart rate, everything is absolutely normal. I don't get any benefit out of this dilation.

23:38The dilation is only relative to somebody far away. And to somebody far away, I look like I'm moving slowly, like I'm breathing slowly, like I'm aging slowly, like my watch is ticking slowly. So it's only relative to them that it looks odd. But in my experience, it's quite normal. I think the deeper question is why does this happen? And we can think of both gravity and moving quickly as creating rotations between the space times of two observers. So if one observer thinks that this is left and another observer is facing them, they understand that they're going to disagree about which way is left.

24:18They're not surprised. but they know they can just rotate their systems and then they'll agree, right? So in some sense, as you go closer and closer to the black hole, it's as though you're rotating in space-time. So some of what you were calling space is folding into some of what your friend was calling time. And that leads to time almost as though you're rotating left into right, almost as though you've rotated time away entirely relative to your other observer. and um so Matt we should just rename this show I don't think it's fair that we got stoned it is it is happening in front of our eyes Matt there is a beautifully related question as well on this note from um wait Matt I just gotta wrap my head around what Jana just said so what you're saying is you use the left to right as an interesting analog to this.

25:16What you're saying is when you are moving faster in the vicinity of a black hole, your time coordinate is, let's use the term, rotates in such a way that it's giving of itself to a space coordinate. That's right. So one is losing time relative to the other. Exactly. And just like you can rotate left all the way into right, at the edge of a black hole in particular, you've basically rotated your time away entirely. And in fact, when you cross the event horizon, what your friend far away thought was a region in space, a center of the black hole, is for you a direction in time. So you've rotated it completely by the time you cross the event horizon to the point where you think that the dire singularity at the center isn't a point in space at all.

26:15It's in your future. And it is as inevitable that you will crush into that singularity as the passage of time is inevitable. Wow. And that was a Roger Penrose result. That was Roger Penrose. Yeah. Yeah. Yeah, actually, I wrote this little article after he won the Nobel Prize for that beautiful work in 1965 for Pioneer Works broadcast, actually, because we do this series called Picture This where you draw. We scientists write about technical articles, like technical drawings. And Roger Penrose has the most wonderful drawing that he drew in this 1965 paper where he shows basically time starting to move in a spatial direction.

26:57He shows that rotation. And he proves that at the event horizon, what's happened is basically time is starting to point inward towards the black hole. It's quite useful. And I love the left-right starter analogy there. You know what that reminds me? So, Matt, have you ever heard this joke? It's funny. So someone says, well, two wrongs don't make a right. But then you can say, but three rights make a left. You ever try that? Just try it. Make three left turns, you just turn right. If you do the geometry on that, it works out. All right, cool. Jana, thanks for that answer. I think we should rebrand this for stoners.

27:43AKA for stoners. The stoner edition of Cosmic Queries. Matt, keep them coming. Well, so Frederick Johansson asks, and this is related because you just talked about the difference of effects of both speed and gravity. Frederick wants to know, if I stand on the equator, my head would age less compared to my feet due to the speed difference. But wouldn't we have the opposite effect due to gravity? Would my feet or head age more in the end? So I believe he's asking that if he's standing on the globe, his head is moving faster than his feet because it's further out, but also his head is further away from the gravitational center of the Earth than his feet.

28:27So do these two things both have an effect on the time perception of your head and your feet? And if so, do they cancel each other? I would have to actually do the calculation because both are pretty tiny, right? But I can tell you that with like the GPS units, we see the effect of the time dilation when we send signals to satellites and back again. And they have two effects. One is you're deeper in the gravitational potential. So let's say we take the twins, like one astronaut that was in the ISS and the other twin astronaut who stayed on Earth, the Kelly twins, which one actually was younger?