The Joe Walker Podcast - The Meaning Of Human Existence, And The Search For Alien Life - Avi Loeb

Episode Date: September 23, 2020

Avi Loeb is Chair of Harvard's Astronomy Department.Show notesSelected links •Follow Avi: Website •The Myth Of Sisyphus, by Albert Camus •The Structure of Scientific Revolutions, by Thomas Kuhn •'The End of Spacetime', public lecture by Nima Arkani-Hamed •Rendezvouz With Rama, by Arthur C. Clarke •'Glowing Auras and "Black Money": The Pentagon's Mysterious U.F.O. Program', NYT article (16/12/17) •'2 Navy Airmen and an Object That "Accelerated Like Nothing I've Ever Seen", NYT article (16/12/17)Topics discussed •Avi's childhood growing up on a farm in Israel, and journey into academia. 5:16 •Avi's romance with philosophy, Satre, and Camus. 10:11 •When in their careers should scientists court risk? 15:24 •Albert Camus and The Myth Of Sisyphus. 21:10 •How does alien intelligence change the meaning of human existence? 24:50 •If there was no other intelligent life in the universe, would that make a god more likely? 34:51 •How far off is technology for 3D printing of...humans? 40:49 •What are the a priori odds of other intelligent life in the universe -- and how do we calculate them? 42:49 •Why is it so quiet out there? 47:25 •Space archaeology. 52:33 •Is space-time a doomed concept? 1:04:14 •How do we verify what happens beyond the event horizon of a black hole? 1:12:08 •The multiverse: bullshit or not? 1:17:25 •What could spacefaring aliens teach us about physics? 1:30:00 •'Oumuamua -- a possible interstellar spacecraft lurking in our solar system. 1:31:45 •The Pentagon UFO releases. 1:43:47 •Hostile aliens. 1:46:00 •The advantages of generalism. 1:54:43 •The meaning of life (42). 2:01:21See omnystudio.com/listener for privacy information.

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select the mixed red case, and enter the discount code SWAGMAN. You're listening to the Jolly Swagman podcast. Here's your host, Joe Walker. Ladies and gentlemen, boys and girls, swagmen and swagettes, welcome back to the show. It's great to have you here. If you're a new listener to the show, it is doubly great to have you on board., so look out for that. This episode is a fantastic conversation with a brilliant physicist. Avi Loeb is chair of Harvard's astronomy department. His research includes everything from the study of black holes to designing spacecraft. In 2018, Avi attracted attention when he suggested that Oumuamua, a mysterious object which had entered our solar system, might actually be an

alien spacecraft. In this conversation, we discuss Oumuamua. We discuss various topics that Avi has researched about physics, about space travel. But what perhaps I enjoyed most about this conversation was our philosophical discussions. Because whilst Avi is an impeccably credentialed physicist, many of the questions he studies touch on deeply profound questions about human nature and existence. So, without much further ado, I really hope you enjoy this fascinating conversation with the brilliant Avi Loeb. Avi Loeb, thank you so much for joining me. My pleasure.

It is an honour to speak with you. I've been looking forward to this conversation for some time and I know we have a lot to get through, covering issues ranging from the actual physics you do to more meta questions about the sociology of the physics profession. So I'm very much looking forward to speaking about all that with you. But first, I'd just like to establish your bio for our listeners and for myself. You were born in Israel in 1962 on a farm about 20 kilometers outside of Tel Aviv. Tell me a little bit about that and your earliest memories growing up in Israel. Yeah, so I grew up on a farm. I used to collect eggs every afternoon. And on weekends, I used to go to the hills of my village on a tractor and read philosophy books.

I was very interested in philosophy, the big questions. As a young kid, I didn't realize that it makes more sense since we live such a short amount of time. It makes more sense to focus on questions that we can solve. I was more interested in the biggest questions that we have, irrespective of whether we can solve them. And then I was drafted to military service as any other teenager at the age of 18 in Israel. Now, I had two options, either to run in the fields with a rifle or to pursue intellectual work and take advantage of my experience in physics and so forth.

And I was selected to a special program that allowed us to finish degrees in university, the Hebrew University in Jerusalem, while being trained in the military and using the education that we received for the benefit of the security of Israel. And I was sufficiently lucky to be able to finish my PhD. So I was the first one in this program called Tal Piot. And at the age of 24, I had a PhD. And I was able to do scientific research,

which was closer to my interest in philosophy. That's why I moved into physics. And then we were funded by the Strategic Defense Initiative of Ronald Reagan. Back then, we proposed the project and the United States funded it. And it had to do with launching payloads to very high speeds in space. And as a result of this funding, I used to visit Washington quite frequently during my military service. And in one of the visits, I decided to visit Princeton, New Jersey, the Institute for Advanced Study. And I asked whether I can visit and the administrator there said, well, we don't allow just anyone to come and visit us.

Send me your list of publications. I sent her, I had about 11 publications back then. And she allowed me to get there. And then she said that, you know, there is only one person that really has enough time to meet with visitors. All the others are very busy in research. His name is Freeman Dyson. Would you like to see him? And I said, of course, I mean, I know his name from textbooks. And he introduced me to John Bacall, a prominent astrophysicist, who later on offered me a five-year fellowship there under one condition, that I'll switch to astrophysics. And given the prestige of that place, that's where Einstein was a faculty several decades earlier than that, I decided to accept that offer. And so I moved into astrophysics.

And then I always had in the back of my mind my true love to philosophy and sort of like falling in love when you're a teenager and then remembering your first love. But I was never able to fulfill it. And then an opportunity arose to come as a junior faculty to Harvard in astrophysics. And I accepted that. And eventually I got tenured at Harvard three years later. For a couple of decades, they didn't tenure anyone from inside. And I was lucky, fortunate to be tenured. That's why the position that I received was not really desired by anyone because people thought the chance of being promoted at Harvard are really small.

So at that point, when I was tenured, it looked as if it's too late for me to change direction and go back to philosophy. But then I also realized that astrophysics addresses very fundamental questions that used to be in the realm of philosophy, and that it's sort of like going through an arranged marriage and realizing that the person you are married to is your true love. And so, a circle was sort of closed for me. That's interesting because a lot of physicists are very dismissive of philosophy. Now, I read that when you were on the farm reading those early books of philosophy, two of your favorite philosophers were Jean-Paul Sartre and Albert Camus. Do you remember any of their works in particular

that influenced you? Oh, yes, definitely. I mean, I read many of their books and articles. And what I liked about their approach is the sincerity, the fact that they do not pretend, you know, they are not formal philosophers of the type that existed in previous centuries. They basically describe the human conditions from the perspective of our existentialist life, the life that we live through. You know, they didn't put any makeup. They just described our experience and our dilemmas and so forth. For example, Albert Camus talked about the feeling that we often have that is similar to Sisyphus, the Greek mythology story where you try to bring a boulder up the hill and then it falls back and you do it again and again.

And the question is, why do we do that? And the most fundamental question is, why do we live our life? And what is the meaning of life given this experience that we have? So they basically did not consider philosophy as an academic occupation, more as a description of the human condition. And I like that because and actually that's what we do in science. We do not pretend to know the truth. One of the biggest privileges of being a scientist is that you can say, I do not know, if people ask you a difficult question. Such an answer is not acceptable in the business world or in politics or in religion.

If you're a clergy, if someone asks you a question about God, you're not allowed to say, I don't know. You have to say something. And otherwise you don't get paid, you know. And this privilege that you can say, I don't know, is really fundamental to science because you're not supposed to put any makeup. You're not supposed to pretend more than what you actually know. And so it's a very sincere kind of exchange with other people.

And what I liked about it is in a way that, you know, when we are kids, we don't pretend. We learn about the world. It's a learning experience. And we make a lot of mistakes as kids, we don't pretend. We learn about the world. It's a learning experience. And we make a lot of mistakes as kids as we learn. And we try a lot of things, you know, and we do foolish things. But by doing that, we learn something new. And somehow something happens to us when we become adults. We don't want to look foolish.

We don't want to show that we can make mistakes. And so, you know, we put all this makeup and then we don't dare going in directions that are risky. And the problem with that is that we never, if you just restrict yourself to what you expect to find, you never discover new things. So what's beautiful about science is that it's a learning experience. You're not supposed to have a prejudice. You're not supposed to know in advance what you will find. It's sort of like a detective story. You have some clues and you're trying to figure out what's behind them.

And that's what I like about it. In a way, it's a continuation of our childhood curiosity. And that's the sincere way of doing science. Unfortunately, many of my colleagues in academia, once they become tenured, you know, a tenured professor has a job security. The purpose of that job security is to allow you to think freely, not to be guided by what your colleagues think or what other people say about you. You have the freedom, you have job security, you don't need to worry or what other people say about you. You have the freedom. You have job security.

You don't need to worry about what other people say. You can basically follow the truth, your internal compass. And that's a great privilege. Unfortunately, many people, when they get tenured in academia, they start thinking more about how to get awards or honors. And they are basically giving up on this privilege because they are tailoring what they are saying to the likings of other people. And it's sort of like being, you know, in social media and trying to get as many likes as you can.

And the problem is that, you know, the scientific truth is not dictated by how many likes you have on Twitter. It's problem is that, you know, the scientific truth is not dictated by how many likes you have on Twitter. It's whatever the evidence tells you. And so, you know, if you want to pursue science in a way that is sincere, you don't need to care about what other people say. You just need to follow the evidence and use the scientific methodology and figure out the truth. Allow me to play devil's advocate for a moment, Avi. Is it not a good strategy to view these two opposites sequentially rather than as opposites? In other words, shouldn't scientists first amass some career achievements, get tenure, get job security, and then start to do whatever they want once they

have that safety net? Yeah, that's what would be logical. However, what you find in reality is that, you know, at least in my time, the younger people would dare to explore new territories, you know. It's sort of like like you can think about it. You can ask, why is the military recruiting young people? You know, one good reason is, well, aside from the fact that they are physically very capable, because they are willing to go into the battlefield and risk their life, you know, and and older people, they have a baggage. They have good reasons why they wouldn't sacrifice their life, you know, and older people, they have a baggage, they have good reasons why they wouldn't sacrifice their life. And so you can think about the same thing in science, you know, young people without prejudice, without a baggage, could potentially explore new territories, new directions of research that the older people, you know, are not willing to risk.

So in my time, in my career, I noticed that young people are more willing to dare. But nowadays, the situation is a bit different. Nowadays, people are worried, even at a young stage, as you say, they're worried about their prospects of getting a permanent position. So even when they're young, they don't dare say anything different from the mainstream. And so that means that this early phase is blocked, you know, because people are worried about their job security and so forth. And then in the second phase, once the same people get tenure, they start worrying about their image and about, you know, getting awards and honors more than about, you know, using this tenure appointment to explore, you know, the truth wherever it leads you.

And not necessarily in the direction of the mainstream, you know, because let me give you an example. Most of the stuff that the universe is made of, we don't know what it is. It's called dark matter. It's a component that fills up the universe, and we don't know what its nature is. And, you know, in the business world, if you were to say that you are working on something whose nature you don't know, you will get fired. You know, it makes no sense. You can't just... But in cosmology, studying the universe, it's completely legitimate. So we talk about the dark matter. We don't know what it is.

And for many decades, people had ideas about what the dark matter may be. You know, it may be this type of particles, other types of particles, you know, and they, scientists invested large sums of money, hundreds of millions of dollars in various experiments that were aimed to detect dark matter without success. So it was considered part of the mainstream, and people explored that and didn't find anything. And yet you ask yourself, why was it, why were these possibilities singled out and not other possibilities? For example, maybe the law of gravity, the way we conceive of it, is modified.

And so there were some people suggesting that, but they were pushed aside. Or people that were talking about other types of dark matter were not very popular. And, you know, there are other areas of science, for example, that we will talk about the search for extraterrestrial life, you know, intelligent life, that's considered outside the mainstream. And you ask yourself, why is that more speculative than the search for particular types of dark matter? That makes no sense. We know life exists here on Earth. We know that about a quarter of all the stars have planets like the Earth at the right distance from the star to have roughly the same temperature on the surface and to have potentially liquid water

there and the chemistry of life as we know it. So there are billions of stars in the Milky Way galaxy alone. And then you have trillions of galaxies like the Milky Way in the observable volume of the universe. And so altogether, you have 10 to the power 21 zeta. That's a number, 10 to the power 21 planets with conditions similar to the Earth. And so if you have similar conditions, you know, it's quite possible that you'll get the same outcome. That's not speculative at all. So why is searching for intelligent life the way we find here on Earth more speculative than searching for particular types of dark matter? To me, it that's sociological.

But that has nothing to do with evidence. And my point is we should be open-minded and use tenure as a vehicle to explore many possibilities and not just what the mainstream says or the majority of people say. Yeah, and I think we should come to the search for extraterrestrial life now. But first, I just wanted to dwell on philosophy for a moment. You mentioned Albert Camus' essay, The Myth of Sisyphus, which is actually my favorite of all of his books. And as you say, it opens with what Camus calls the most important question in philosophy, which is given the absence of gods and the absurdity of existence,

why doesn't any of us just commit suicide? And then he proceeds to try to answer this question and in the last section he returns to the image of sisyphus pushing his boulder up uh the mountain uh only for it to roll back down again and sisyphus becomes a representative for the everyman who kind of struggles against his fate and gives the middle finger to the universe and the best way to to respond to the absurdity of existence is actually to rebel against it, in Camus' opinion. And I think that that might also be a good metaphor for what physicists and scientists should do. You know, many of these questions are incredibly difficult, perhaps even intractable, but we should still try anyway. We should still ask questions.

Right. I mean, personally, I have a different answer to this meaning of life. And I was always driven by the desire to understand something new about the universe that would change our perspective and stimulate aspirations for space. And the meaning I assign to my life is using the perspective of a spectator of the universe, observing the universe as an astronomer to motivate new challenges for our civilization on the cosmic stage. And, you know, given all the accomplishments that we have through engineering here on Earth, this broader perspective could lead us to develop new technologies and modify the larger

habitat around us through space engineering. And we are just starting to do that now. I mean, with SpaceX, Elon Musk's ambitions, and Jeff Bezos' ambitions, and Blue Origins, and so forth. People are starting to talk about going to space. I should say that, you know, in principle, we could discover a meaning to life just by exploring space. Because, for example, there is this fundamental question, how did life start on Earth? What's the origin of life? Suppose we find that life was planted on Earth, and we are part of an experiment of a more advanced civilization. We are not the smartest kid on the block. There is someone else out there, much more advanced than we are, that planted life on Earth

and is watching. So if we were to understand that, it will obviously give us a completely new perspective, right? And we will figure out the meaning of our life is actually as part of that experiment. And also doing astronomy allows us to explore questions of how the universe started, you know, how we came to exist, you know, how did the earth form around the sun? How did the sun form in the Milky Way galaxy? How did the Milky Way galaxy form out of the cosmic soup of material that existed early on? And where did the universe come from? You know, these are really fundamental questions. Whenever you ask what's the meaning of life, you have to go all the way back because these are our roots, you know, overall.

Yeah, let's dig into that a little further, Avi. Arthur C. Clarke famously said, quote, either we are alone in the universe or we are not. Both are equally terrifying. End quote. What do you think the implications of each of those results are? Say we discover there is other intelligent life in the universe. What does that tell us about the meaning of existence, if anything? Alternatively, if somehow we could prove that there was no other intelligent life in the universe,

what would that tell us about the meaning of our existence? Oh, I think the meaning, I mean, it will have tremendous implications. So, first of all, let me say, if we find intelligent life out there, that it's most likely to have existed far longer than we did, because we are just at the beginning in cosmic terms, you know, we were around for only a percent of a percent of the age of the universe as an intelligent species. And just talk me through the mathematics of that. Well, so the universe existed for almost 14 billion years. And, you know, humans, just to give you a perspective, left Africa about 100,000 years ago. So that's, you know, 10 to the minus five, 10 parts per million of the age of the universe. And humans may have existed in Africa a little

before that. But we're talking about, you know about less than a percent of a percent of the age of the universe that we exist in the suspicious. Not to speak about a more advanced lifestyle that we encountered over the past hundred years with the modern technology. That's really a tiny period of time. Right now, our technology is evolving exponentially on a few years' timescale. You know, the car that we are driving now is very different from cars that were driven a decade ago. It's mostly software. It's not so much the hardware as it used to be. And, you know, you just think about what will happen in a hundred years if you take this exponential growth in technology

every few years. It would be unrecognizable. Now, think about a technological civilization that existed for a thousand years instead of a hundred years, or a million years, or a billion years, you know, if they can get their act together and not destroy themselves, you know, they would be an approximation to God, as far as we are concerned. When we meet those technologies, they would perform magic,

you know, things that we cannot really understand. And as far as we are concerned, they would be a good approximation to God. I mean, they would be capable of doing things that we cannot imagine. And by the way, biological life, the way we are, you know, that may be superseded by technologies that are much more durable, much, you know, can achieve much more. I'm not a particular fan of what the earth produced in terms of the life that we see, because it's not necessarily optimized. If you make a cake, you start with some ingredients, and you can put these ingredients in different order and, you know, heat up the ingredients at different times and so forth, and you get very different cakes, right? And the cake that the earth baked

in the form of life as we know it is not necessarily the optimal cake. You know, I can imagine other circumstances that would produce much better cake, much more intelligent cakes, you know. And one way to figure this out is to produce life, synthetic life in the laboratory. And, you know, there are several groups trying to produce synthetic life in the laboratory. Then we can try and see, you know, whether the life that emerged on Earth is really the best form of life, or maybe we can do better when we design life. You know, it's sort of like comparing a cave that you find in a mountain, you know, that was produced by nature, you know, as a result of water dripping and making a hole in the

mountain. You can live in that cave, and that's the way we lived for many centuries early on. But you can also design your home and have an architect optimize it and then you get a much better lifestyle, much more convenient. And so in the same way, you can imagine designing life forms that are far better than what nature produced out of random processes on Earth. And you know it's possible that advanced civilizations reach that point where they design forms of life that are far better than the ones that nature produced. And you know they don't necessarily live on the surface of a planet like we do.

They don't need, they're not so delicate. You can send equipment to space and it will survive, you know, and that may be the most common evidence, you know, that these civilizations exist, that it's all technological equipment flying through space. It's not really biological life on the surface of a planet. That may be the most common thing. And, you know, if we do find evidence for that, it will obviously change our perception, because it will give us sort of a jump to a state that we never imagined, you know, it will be a shortcut. Instead of us evolving to that state, suddenly we will be shocked to see something so different than what we are used to. And it will give us this image of ourself in the distant future. And, you know, that will be obviously a wake up call. Now, the other thing I

should say is, you know, it's possible that civilizations like ours are not smart, you know. And, you know, when you open the newspaper in the morning, you see a lot of things that are not necessarily very smart that humans do. And what do I mean by being intelligent? What I mean by being intelligent is promoting your well-being, trying to promote your better future. And clearly humans are engaged sometimes and very often. You know, you just look through the newspaper. You find a lot of actions that we do that do not promote our well-being, that damage us one way or another. We do not cooperate.

We fight with each other. We do all kinds of terrible things. And, you know, that shows that we are really not, that you can imagine something more intelligent than we are. And, you know, one way that we can learn a lesson from looking at space is if we find a lot of planets with burnt out surfaces that went through a nuclear war, for example, or that had an atmospheres that were polluted and destroyed life eventually on those planets, then, you know, if we find evidence for a lot of dead civilizations, for the graveyards of other civilizations, maybe it will be a wake-up call to get our act together and not share the same fate in the future. So that's another important lesson that we can learn by looking at an image of

us in the future that is not very flattering, and that will change the way we behave. We will feel as if we, you know, have to act as one team here on planet Earth, rather than fight each other on territories and so forth. Now, I should say there is another very important lesson that we can learn, and that is a bigger perspective, you know, being more modest. Kings and emperors throughout human history boasted whenever they conquered a small piece of land, you know. And when you think about these 10 to the 21 planets that are similar to ours in the observable universe, you know, being very proud of yourself after conquering a piece of land on the surface of the earth is just like, you know, an ant that is hugging a single grain of sand on the landscape of a huge beach, you know, because there are more planets like ours in the observable volume

of the universe than there are grains of sand on all beaches on earth. And if you just think about it, it means that we are not so significant, that you can't be arrogant, that the universe is teaching us modesty. And this is a fundamental lesson that you learn as a scientist, that not only that you are a small piece in the big picture, but also every now and then you make mistakes. So you should always be humble. You should always be modest because we are learning about the universe.

You know, the knowledge that we have is just a small island in a vast ocean of ignorance. And we should be modest. Now, I should say, even scientists, you know, very often are quite arrogant. And I just find it inappropriate, given the big picture.

The only way you can be arrogant is if you narrow your view to a very small part of the universe. For example, you focus on whatever you do, and there you are the best in the world, and then you think very highly of yourself. But if you were just to expand your field of view, you would realize that you're not so significant. Alternatively, imagine that we could and did prove that there's no other intelligent life forms in the universe. Now, you and I are both atheists, but if we did discover that, what would that force us to do in terms of changing our beliefs? How much more likely would the claim that there's a God or the claim that we exist in a simulation be? No. So, I mean, first of all, it's a very difficult task to prove that there is nothing out there because you can always suggest, you know,

you could always have life forms that are difficult to detect that do not produce signals. For example, they might be hiding because they are so intelligent that why would they make any signal that is easily detectable? They realize that there might be predators out there and so they remain quiet. But suppose we, just hypothetically, suppose we were to find out. Take it as given. I think it puts a big responsibility on our shoulders because the one thing that we tend to believe is that we can change things. That here on Earth, for example, we have the ability to change the Earth, to change the conditions around us universe and ask, what can we do to

the bigger habitat, not just the earth, but going beyond that? So one thing we would like to do is, of course, preserve our culture, everything that we care about, our DNA. And right now, we have all the eggs in one basket. We have the Earth. And pretty much, you know, if something bad happens to Earth, if a big asteroid collides with the Earth, we would lose everything. So it reminds us of, you know, the early copies of the Bible. You know, there were very few copies of the Bible,

and if something bad would happen to one of them, you would lose it. And then Gutenberg came along and invented the printing press, you know, the ability to reproduce copies. You don't need to just, you know, in the old days, you would have to copy the Bible, you know, handwritten. And there

were people that tried to do that, but you could only produce very few copies. And each of them was extremely precious. So Gutenberg produced masses of copies. And the importance of that is not only that it was accessible to many more people, but if something bad happens to one of them, it was not a tragedy. You could produce new copies. So you can expand on this and say, if we produced copies of what we care about here on Earth, like copies of our DNA, and printed those copies elsewhere. So if we were to send 3D printers equipped with artificial intelligence so that you can use the raw materials on other planets to produce the same type of life as we find here on Earth, on other planets, then if something bad, you know, if an asteroid impacts the Earth, it wouldn't destroy all evidence that we existed. You know, there would be some copies elsewhere that will continue.

So that's one thing that we can do if we want to survive much longer than each of us individually. But beyond that, we can potentially harness resources that exist beyond the Earth. There are things that we don't find on Earth. Just to give you an example, the gold that I have on my wedding band, this gold was produced, by now we know, it was produced when two neutron stars collided. A neutron star is the core of a massive star that collapses. And it has roughly the mass of the sun.

And it collapses to a size of a city like Sydney, roughly 12 kilometers in size, in radius, and it has a density of an atomic nucleus. So that's the end product of the evolution of a massive star, more than eight times the mass of the sun. And when two such neutron stars form a pair and collide, as they collide eventually, a little bit of material gets ejected and it decays into elements like gold, for example. These are rare elements because the collisions of neutron stars are rare events in the universe. We happen to be at some distance from the nearest collision of two neutron stars, so we have a certain amount of gold on Earth.

And it's very valuable because it's rare. But if Earth was positioned, located closer to the nearest neutron star merger event, we would have much more gold. So, you know, even practical issues to do with the world economy, you know, would be heavily influenced by how close we are to a site of a neutron star merger. By the way, a neutron star merger also produces uranium. So, gold and uranium, the sources of evil on Earth, you know, uranium is used for nuclear weapons. So if we ever meet another civilization that happened to be born close to such a site, they might have much more uranium and much more gold than we have. So we should be careful. So 3D printing of humans, is that sort of technology decades away, centuries away, millennia away?

What's your estimate? I would say centuries away, but eventually we could get there because right now, I would say producing synthetic life in the laboratory is maybe decades away. Because we have one group at Harvard led by Jack Shostak. And, you know, he started his work about a decade ago, he's a Nobel laureate. And when he started, he thought, you know, it would be really difficult to make life perhaps, you know, it was not done by random processes on earth, because he thought that it's really challenging. But then he realized after working on it for a decade that, in fact, he's getting close to doing it synthetically in the lab. And he's now convinced that, you know, if you start with a soup of chemicals on the

early Earth, you could have gotten the life that we see right now started. And so I would say, you know, maybe decades from now, we will have synthetic life. And it's really important because it could have implications to medicine, not to speak about, you know, in the search for life, it would be very important because it will expand our imagination. We will be able to realize a wider range of conditions that could lead to life. Right now, we are just thinking about copies of what we found here on Earth. But if we produce other forms of life in the laboratory, we could look for those as well. So we would have a wider spectrum of possibilities that we are searching for in the sky.

Okay, Avi, so there are 10 to the power of 21 planets similar to Earth in the observable universe. What are the odds a priori that there are other intelligent life forms in the universe? And how do you go about calculating that probability? Okay, so I have to answer this since there are many uncertainties in answering this question. I will give you my gut feeling. My gut feeling is guided by modesty. Okay, so humility. As I said, the universe teaches us modesty. We are a small part of the big picture. And whenever people arrogantly thought that they are at the center of the action, they were proven wrong. Early on, the Greeks had an image of the universe centered around us.

And that was wrong. And very clever people thought that we are at the center of the universe, including Aristotle. But eventually we realized that the Earth is moving around the sun, and the sun is moving around the center of the Milky Way galaxy, and the Milky Way is So we're really not at the center of the action. And physically speaking, we are not at any special place, you know, in the universe. And I think the same holds for biological, the biological, the living universe. Out of modesty, I would say, we are probably not special. It would be arrogant to think otherwise. I mean, when I look at my daughters, I have two daughters, they are now teenagers, but when they were young, they tended to think that the world centers on them. When they were born, they thought everything centers on them.

And then once they went out to the street, they met other people, and they realized that they are not that special. You know, there are lots of people out there that have similar qualities and they became more modest as a result. And, you know, that's part of part of becoming mature. You mature once you realize that, you know, not everything centers around you. And our civilization needs to go through that process. And we went through that process in the context of the physical universe.

We now know that we are not at the center of the physical universe in terms of where we are located, but we haven't gone through that process in the context of life. And I think we will eventually because I think it's, I don't see any reason,

I don't see us as the most intelligent possible. I don't see life on earth as optimized. I don't see the conditions on earth as being very unique. So all of these considerations lead me to the conclusion that we are not special and that there are lots of things similar to what we have here on earth out there and not only that that there must be a lot of

dead civilizations out there so we should do space archaeology we should dig just as we dig uh you know through the surface of of the earth and look for ancient civilizations, relic from that. We can dig through space and potentially find evidence for dead civilizations. So I think space archaeology is a subject that should be pursued in the future. It's not being done right now. I mean, there is some level of searching done, but not full-fledged. I wrote a number of papers on what one can look for. One can look for industrial pollution of atmospheres of planets.

One can look for photovoltaic cells that reflect light differently from the surface of a planet or redistribute the heat or light on the surface of a planet so the night side is partly illuminated. You know, you can look for that. You can look for megastructures that surround stars. You can look for technological debris that is passing nearby and we might find evidence for it. So anyway, you can do space archaeology. And, of course, that is very important because it will give us

the bigger perspective that, as we discussed before, that we are not unique, we are not special, that there are things, not only that we are not alone, but we are not the smartest kid on the block. I'd like to probe some ideas in space archaeology further with you, but I just want to come back to the chances that we're alone in the universe. So you would say it's likely that we're not alone, maybe a 50% chance or greater? I strongly believe, I mean, as I said, out of modesty, my underlying premise is that my conjecture is that, you know, we are not alone. And not only that, that we are not the most sophisticated, and we're sort of common and not really at the top of the food chain, so to speak.

And, you know, we're sort of in the middle. And now, of course, I'm talking about throughout cosmic history. So right now, there might not be a lot of civilizations that are alive. You know, they may have a short lifetime because look at how we behave. If we go through a future world war and annihilate each other and life on Earth, then we will have a finite lifetime. And it's possible that a lot of civilizations go extinct after a while. So this is the notion of a great filter, that civilizations inevitably trend towards their own self-destruction. It's possible. We don't know.

So I regard this subject as a scientific topic that is worth investigating and collecting evidence on. So we should not have a prejudice, definitely not have a prejudice that we are alone. As some people say, some people say, well, there is no point in checking. There is no point in looking. It's speculative. You know, this is for science fiction movies. It's not, it shouldn't be part of science.

And I don't think so. I think we have good telescopes now and much better instruments than we used to have. Let's use them to search. Let's not have a prejudice. And let's make it part of the mainstream of astronomy because I don't see a difference between that and the search for dark matter. And I think we should search for that as much as we search for the nature of dark matter. Despite those odds, we're still yet to find alien intelligences.

And the Fermi paradox famously asks, where is everybody? How do you reconcile that tension? Right. So I have two ways of thinking about it. One is that indeed the great filter civilizations have a short lifetime. And at any given time, you have a relatively small fraction of them that you can get signals from. Okay, so that's one. But then another possibility is that after they evolve technologically, you know, they develop into a phase that is mostly technological, and they send the small equipment.

Like our von Neumann probes. Yeah, but those are very difficult to detect, even with our best telescopes. An object that is 100 meters in size will be visible to our survey telescopes only when it gets within the orbit of the Earth around the sun. only then it will reflect enough sunlight for us to see it. And I'm talking about 100 meters, you know, the size of a soccer field or, you know, that's a big object. If you imagine smaller objects like Voyager 1, Voyager 2, you know, unless they transmit exactly in the bands that we are looking, we would never be able to see them, even if they pass relatively close.

So, you know, it's very difficult to see. Only now we're starting to get to the point where we might detect some debris from interstellar space, and the first two objects were reported over the past few years. But, you know, it's quite possible that there is lots of stuff flying around and we don't see it. Now, it's also possible that civilizations prefer not to show their existence, you know, to reveal themselves after a while because of the fear from predators. You know, if they are intelligent, there is no reason for them to speak out loudly. They can collect all the information they want, but they remain relatively silent. It's sort of like, you know, these airplanes that are used for espionage that are not easily visible to radars.

And for a good reason, they just want to collect information, not to reveal their existence. So the aliens might be sort of too cool for school at the moment. Well, the advanced ones, those that are not advanced, that were revealing their existence, are not around anymore. So you can think of it as a darwinian selection those that are loud disappear and those that are smart enough to be quiet stay around yeah currently we have technology that can detect a tokyo-sized city at the edge of the solar system what are we technologically able to do in terms of space archaeology that could help us begin to gather or search for evidence about intelligent life

forms? Funding and resources notwithstanding, what things could we do at the moment to search for that evidence? Right. So, I actually wrote a paper about eight years ago about this subject of the fact that indeed our telescopes, like the Hubble Space Telescope, are able to detect a city like Tokyo at the edge of the solar system about 100 times farther than the Earth is from the sun. And of course, you know, we don't expect any of the objects there to produce its

own light. But you can tell if there is an object passing by like a spacecraft that is producing its own light and is not just reflecting sunlight. And the way you tell that is, as the object changes its distance from us, if it reflects sunlight, it will dim much faster as the distance increases. Because it dims as it goes away because there is less light from the sun impinging on its surface. And then there is dimming because its distance from us gets larger. However, if it produces its own light, you just get the latter effect. It produces the same amount of light,

just like a light bulb, and you only get its fading away because it increases its distance. So the way it fades away is different in the two cases. And you can tell if it reflects sunlight or produces its own light. And I asked the astronomer that discovered most of the objects in the outer solar system one time, I asked him, did you ever check how these objects fade away as they change their distance from the sun?

And he said, why should they check? It's obvious they're reflecting sunlight. You know, why would it be anything else? So this is just an illustration that you can collect data, but if you have a prejudice, if you think that you know in advance something, you think that all the objects reflect sunlight, you would never check if they produce their own light and you would never find something that is unusual. And that's extremely important.

And I can give you another example. So just collecting data is not enough. You have to be open-minded. So for example, we visited with my family, we visited Mexico a few years ago, and we went to see the ancient Mayan city of Chichen Itza. And the tour guide was, you know, very proud of the fact that the Mayans collected a lot of astronomical data. And in fact, astronomers were at the highest level in society.

They were regarded very highly and treated very nicely. They were called the astronomer priests. And that puzzled me. How come astronomers are, you know, at the highest level in society? Because nowadays, you know, astronomers are treated nicely, but they're definitely not receiving the most lucrative salaries, you know. And back then in the Mayan society, they did benefit the most. And the reason is that the Mayans thought that you can forecast the future based on celestial objects. So depending on where Venus is or other objects in the sky are, you can forecast whether you would win a war.

And that is astrology. And so they believed in that and they assigned these observers to look at the sky and make forecasts so that they will decide when to go to war, when is the best time for them to win a war. And they base it on historical records, that they won some wars when Venus was at a particular position.

So they collected a lot of data, and they used it for that purpose. Now, you know, at the same time, the same data could have been used to discover, you know, Newton's laws of, you know, at the same time, the same data could have been used to discover, you know, Newton's laws of, you know, and, but because they had this prejudice, you know, they didn't use the data in a way that is completely open minded. And that shows you that collecting data alone is not sufficient. You have to allow yourself to discover things that you haven't expected. We might, for shorthand, call this theory-induced blindness. Right. Prejudice. Which is a term I steal from Daniel Kahneman. Right. Yes. And unfortunately, many scientists nowadays have not learned the lesson from history because they keep forecasting what they will find. They don't want to be wrong. So they want to preserve their image. And the best way to preserve your image is by forecasting what you will find and finding it. And then you can get funding from, you know, federal agencies, and you can get

awards because you predicted what you will find, and you confirmed it, and you didn't violate anything that the mainstream believes in. So there is this natural tendency to always not be wrong, not make a mistake. But if you think about the progress in science, it was usually through anomalies. Most of the discoveries in science came about as a result of anomalies, when we found things that we haven't expected. And as a result of that, we revised our notions about reality. And a good example is Galileo Galilei. Before him, people thought that heavy things fall faster than light things under the influence of gravity. So he said, let's test it. And he dropped objects of different composition from the tower in Pisa and saw that they fall exactly at the

same rate. And he said, no, this preconception is wrong. And actually, my experiments show that all objects fall the same way under the influence of gravity. Once you take out the friction with the air, of course. And Einstein, centuries later, said, well, that's really interesting. You know, what Galileo found is really fundamental because all objects follow the same path under the influence of gravity. So what does it tell us? It tells us that perhaps gravity is a property of space and time because objects follow the same shared space and time, right? So that led Einstein to conclude that perhaps gravity is not a force. It's actually space and time being curved by objects, by matter.

And for example, the sun is curving space and time around it. And as a result, the earth is moving in a circle around the sun. So it's just like putting a very heavy object on a trampoline, and that bends the surface of the trampoline. And then when you let the marble go in the trampoline, it doesn't go, you know, if the trampoline was flat, the marble will go in a straight line. But because it's being curved, the marble would go in a circle around the center. And it's the same effect. So that's the insight that Einstein had as a result of Galileo saying, let's not have a prejudice, let's test something. So, you know, and there is another example of Cecilia Payne Kaposkin. She did the first PhD at Harvard in astronomy. And she looked at the sun and analyzed the spectrum of the sun and realized that, you know, we know the composition of the earth and the earth was made from the debris of the sun.

Therefore, the sun should be made from the same ingredients as the earth, mostly iron and heavy elements. And she said, no, I actually think, you know, what I see is that the sun is made of hydrogen. Now, when she defended on her PhD thesis, the director of the Princeton Observatory, Henry Norris Russell, who was the most respected astronomer at the time, he told her, you know, that makes no sense. You should take this statement out of your PhD thesis because we know that, you know,

the sun has the same composition as the earth." And she, being a woman and also being a student at the time, took it out from her thesis. And he, Henry Norris Russell, wanted to demonstrate that she was clearly wrong and in the subsequent years collected data and analyzed it and realized that she was right. So eventually, you know, and she became chair of the astronomy department at Harvard decades later, the same role that I have right now. And she lived in the same town that I live in, Lexington. That's why I feel a connection to the experience that she went through. But, you know, it's a very fundamental ingredient in doing research that you shouldn't be trapped by prejudice.

You should allow yourself to be wrong. There is nothing bad about being wrong. The only way for you to be right all the time is by not daring, by not exploring the unknown. Einstein made three mistakes towards the end of his career, between 1935 and 1940. He argued that there are no black holes. He argued that there are no gravitational waves. And he argued in a third paper that quantum mechanics cannot have spooky action at a distance. All three of these statements were proven experimentally to be wrong. I mean, we discovered

gravitational waves five years ago. The Nobel Prize was given to that, you know, two years ago. We discovered black holes in the same instance because the gravitational waves, which are ripples in space-time, were produced when two black holes collided at the edge of the universe. And then quantum mechanics was shown to have spooky action at a distance. Einstein was wrong on all three counts. And we admire his intellect. And what does it tell us? It tells us that you cannot be right always.

Nature is more imaginative than we are. We better let the evidence guide us rather than our egos. Einstein and Cecilia's efforts are, of course, examples of an underlying pattern that Thomas Kuhn called the structure of scientific revolutions, whereby at any moment in history there's a prevailing paradigm, and once you accumulate enough quote-unquote anomalies, the paradigm is finally overturned. But this is a process that can take, sadly, many decades, maybe even centuries. Let me ask you a somewhat cheeky question, Avi. I know Nima Arkani-Hamed, the physicist at the Institute for Advanced Studies at Princeton, has said that space-time might actually be doomed as a concept. Do you think Einstein's space-time is likely to be another one of these paradigms that's

eventually overturned? Well, we know one thing. We know that Einstein's theory is incomplete. And that's because it doesn't incorporate another facet of modern physics, which is quantum mechanics. And Einstein knew about it. And of course, tried to remedy that by coming up with a theory that unifies gravity and quantum mechanics. He was not successful. He worked on that until his death, basically, on his deathbed. He still tried to do something about it. He wasn't successful. And then, you know, generations of scientists tried to fulfill his legacy and try to find a unification of quantum mechanics and gravity. The latest popular mainstream incarnation of that is called string theory.

And, you know, Nima Arkani-Hamid is working on that. But there is by no means evidence that we are on the right path right now. No experimental evidence that shows that, you know, string theory is the right path forward, even though, you know, it existed for four decades, and people worked on it, it doesn't provide, it doesn't, it was not tested experimentally. And it's clear that the theory of Einstein needs to be modified, but we don't really know, for sure how to do it. And there is another piece of evidence that tells us that it must be modified. And that's the fact that the theory itself admits what we call singularities. These are places where the theory breaks down. So, for example, if you let a star consume its nuclear fuel, it eventually collapses and it makes a black hole.

A very massive star collapses to a black hole. And we have seen evidence for that. So basically a black hole is a region in space and time that is sort of the ultimate prison. If you fall into it, you can never check out. And that's what happens when matter, you know, drains down to a point, basically. And there is a so-called event horizon around the black hole, inside of which whatever happens cannot be seen by the outside world. It's sort of like what happens in Vegas stays there. But we know that, you know, if we follow matter, it must, you know, it gets to a singularity according to Einstein's theory. And that's where the theory breaks down. A year ago, I had a flood in the basement of my home because it turns out that the sewer was clogged by roots, tree roots.

And I invited a plumber to help me resolve that problem and we solved it. And during the hours when we worked to open up the sewer, the tree roots, I started thinking, you know, this issue resembles what happens inside the black hole. You know, an interesting question is, you know, at home, when we let the water run down the pipe, we don't think about the fact that it has to leave our home and go somewhere to a reservoir where it collects, you know, that's a town reservoir or somewhere. And the same happens in a black hole, the matter that falls into a black hole must go somewhere, it could potentially collect near the center in some object, or it may go to another place, you know, and there aren't many, there aren't papers in the literature, scientific papers, explaining where the matter goes. And I think that's one of the most exciting unsolved problems of figuring out what happens near a singularity of a black hole. And to figure this out reliably, we need a quantum theory of gravity.

There is another place where Einstein's theory breaks down, and that's at the Big Bang. You know, if we look at the universe today, it's expanding. But we can extrapolate it back in time, sort of reversing the movie, and it would be contracting, and its density, the density of matter, would increase as we go back in time until it becomes infinite at some point. And this is called the Big Bang. And it becomes infinite everywhere. It's not as if there is a center to the universe. But it happens everywhere that the density blows up. The way to think of it is, you know, imagine a cake that is rising, and it has raisins

in it. The raisins are separated from each other everywhere in the cake. It's not, you know, just at the center of the cake. So as the cake is rising, the raisins are separated. But if you go back in time, the raisins get closer to each other everywhere in the cake. And so that's true of the universe, that it had an infinite density at some point in time everywhere. And this is called the Big Bang. And the question is, you know, what really happened? Because Einstein's theory breaks down. How did the universe start? You know, what happened before the Big Bang?

I should note that, you know, the fact that when we look at the universe and realize scientifically that there was a beginning of time, that fact is consistent with the story of Genesis in the Old Testament, which I think is a remarkable insight that whoever was responsible for putting this story together, you know, had an insight because actually Einstein favored having a universe that existed in the same state forever. It's much more philosophically appealing not to have an initial point in time when things started. So Einstein wanted a solution like that, but his equations did not admit it. His equations that he wrote down for the general theory of relativity back in November 1915 admitted an expanding solution or a contracting solution. And a steady solution turned out to be unstable. And Einstein realized that.

And so, you know, there was a beginning in time that we call the Big Bang. But the real question is, what happened before the Big Bang? And how did that Big Bang, how was it created? And this is, again, an unsolved problem because we don't have a quantum theory of gravity. So the two instantiations of singularities in the universe are the Big Bang and black holes, these points where quantum mechanics and general relativity come into conflict. The Big Bang happened at one point in time. Black holes are places that we could potentially explore today. If black holes are like Hotel California, where you can never

check out, how do we experimentally verify what happens inside of them? Well, we cannot. The only way to do that is to go inside of them. And I suggested to some of my friends who work on string theory to enter the horizon of the nearest black hole, board a spacecraft, go to the nearest black hole and test their theory there. But I was blamed actually by Nimar Kani Hamid. When I suggested it at the conference, Nimar Kani Hamid stood up and said that I have ulterior motives for sending them into a black hole. But, you know, indeed, as you say, I mean, you may find the answer, but you will never be able to report it back. I should say that, you know, in my class for freshman students at Harvard, I asked at the last class of the freshman seminar that I gave last year, I asked the students a hypothetical question. I said, suppose you were invited to join on a spacecraft tour to a black hole, and you were offered the free ticket to go into a black

hole, would you do it? And the second question is, suppose instead of going into a black hole, you were offered a ride with an extraterrestrial civilization. Again, you wouldn't be able to come back, but you would just take that one-way trip. Would you do it? So the answer that all of them gave to the first question is no. They would never board on a trip that is one way into a black hole because they want to live for as long as they can. And also because they cannot really communicate once they get into it.

And to the other question of whether they would go into a spacecraft that is being hosted by extraterrestrials, they said that they would be happy to do that as long as they have internet connection and can share their experience on social media. So that was the most important thing to them, the ability to send out on Instagram photos of their experience, which to me was a surprise. Because, you know, if I would do it, I would do it for my own experience. You know, it's just like climbing the Himalayas or the Everest or doing something that is unusual, you know, doing something. I don't care if other people know about it, but for them, you know, these freshmen, the ability to transmit their experience to their friends was the most important thing, to share it with their friends on social media. That was an interesting insight for me as to the way they think. It's not so much

the experience, but the actual ability to share it with their friends. If you could cut your life short by 10 years, but you got to experience that death by going past the event horizon of a black hole would you take that option um no i wouldn't do that because um uh you know i enjoy uh looking at the universe learning about it and then this way you know i will um be limited uh but there are lots of fun things you can do just outside the black hole. You can, for example, you can see your own back by looking forward because light can execute a full circle around the black hole. So you can look at your back by looking forward if you are at the right distance from the black hole. You can, for example, surf a sail close to the speed of light near a black hole on these jets that are produced very often near it.

You can produce clean energy easily. If we were living close to a black hole rather than the sun, we could throw our trash into the black hole and get clean energy in return with a very high efficiency. You can convert up to 42% of the rest mass of material that you throw into a black hole into pure radiation. And that's much more efficient than, you know, nuclear energy by at least a factor of over 100. And more efficient than, obviously, chemical energy batteries that we use by a factor of 100 million or so. So, you know, and you get clean energy

instead of the trash that you throw in. You can use a black hole also as a prison. You know, you can send people on a death row into it. There are lots of things you can do with a black hole. Yeah. Avi, I want to ask you about the multiverse especially because there seems to be a word and a theory that has entered the public consciousness in recent years and i wonder whether people have jumped the gun in accepting or swallowing the theory whole i understand in physics the appeal of a multiverse

is that it makes the anthropic principle more plausible, or some form of multiverse theory arises as a consequence of cosmic inflation. But I was hoping you could tell me what the problems with the theory are and how we should think about it properly. Yeah, the main problem that I see is that it's not, at least at this point in time, it's not possible to disprove this idea experimentally. So if someone would propose an experimental test of the multiverse by which we can do an experiment and figure out if it exists or not, I would regard it as part of the multiverse by which we can do an experiment and figure out if it exists or not,

I would regard it as part of the scientific inquiry. Even in principle, you know, I don't care about the practicality of such an experiment. It may require advanced technologies, but I just want something in principle that would prove the multiverse exists, then I would know it's part of the scientific inquiry. But if you cannot prove it wrong, then, you know, it's not part of our learning experience. You know, it could be a philosophical debate. It could be part of philosophy. I don't see any difference between that and some of the statements made, you know, by religious cults. If you can't disprove something, then it's not, in my view, in my book, it's not part of science because to me, science is a learning experience by which you can prove yourself wrong.

So the aspect of being able to prove yourself wrong is fundamental to science because if you can't prove yourself wrong, then you don't learn anything. You basically make assumptions or have ideas. And it's just like in a dream, you know, you just float through these ideas. It's just like being on drugs. You can be on drugs and you can feel very good about it. And, you know, you might feel elevated and you might feel, you know, very proud of your intellectual accomplishments and your ability to imagine things. That's fine. You can be very happy under these circumstances. A lot of people are happy, you know, but it's not part of science.

To me, an integral element of being a scientist is the ability to look at evidence and figure out if your assumptions are correct or wrong. And if you can't have that privilege, if you can't disprove yourself, if you can't show that, if you can't put skin in the game, then you are not doing science. And, you know, I'm talking about empirical science, not mathematics. In mathematics, it's completely legitimate to have conjectures that have nothing to do with reality. But as a physicist, I think all physicists should make what I call a Galilean oath. Just like medical doctors swear by the Hippocratic oath, there should be a Galilean oath whereby the ideas that you propose are at least in principle testable and can be proven wrong.

And, you know, that is part of the, it's not a nuance, it's a fundamental way of learning, you know, and Galileo was really the pioneer in that sense because he basically said, let's not have prejudice. Let's test our ideas against evidence. Now, when he said that and argued that the earth may be moving around the sun and not vice versa, he was put under house arrest by the church because it had some political ramifications for the church. The fact that they put him in house arrest didn't change anything about the motion of the earth around the sun. You know, so what you do to an individual, what popular view is, what is being said on Twitter, that is irrelevant.

You know, there is the physical reality and it is whatever it is. If we refuse to pay attention to evidence, if we have prejudice and fixed opinions, if we never take risks to check whether our ideas are correct, if we never dare to show that we were wrong, we will not learn the truth about the physical reality. That will not change the physical reality. It will be whatever it is. The earth moved around the sun before Galileo and it moved around the sun after Galileo. The fact that the church put him in house arrest

only affected the politics of the day. And of course that you can change. You can suppress people's views. You can do whatever you want. But it doesn't matter. In the big scheme of things, reality is whatever it is. It doesn't matter what is being said on Twitter and what is socially popular. It's really irrelevant.

So if you are a real scientist and you are guided by evidence and you want to find out the truth, you want to put a skin in the game. You want to test your ideas against evidence. And only then you will feel that you learn something about reality. So if you talk about the multiverse and you say, okay, that's a beautiful idea, that comes out, that's a derivative of some other ideas that I had, but sorry, I cannot give you a test and let's change the definition of science and include things that we cannot test. I say that you are betraying your duty as a physicist. You know, it's just like the argument that we might be living in a simulation, which to me sounds like,

you know, in a way being on drugs, you know, like, hallucinating. So, you know, once you get to those levels of models or conjectures, now, I can think of actually testing this model, you know, of being in a simulation, because, you know, when you do a simulation on a computer, there is a finite resolution, you know, there is always some pixels that you cannot resolve. And so far, all the experiments that we have done as physicists did not recover any pixels in space or time or images. So there is no evidence that we are in simulation. Also, you know, in a simulation, very often you get the simulation to crash, you know, that something gets wrong,

there is a bug in the program. I haven't seen any bug in reality. You know, I've never seen reality crash and gets rebooted, you know, something like that. Not even the presidential election in 2016? Well, so I would say, you know, until I find such evidence, this model is inconsistent with the data that I have. It's unusual to think that the scientific profession

doesn't agree precisely on the definition of its own method. Well, it's not because if you are driven, you know, by intellectual gymnastics, what I call intellectual gymnastics, which is basically showing that you are smart. If that's what your goal is, then, you know, it doesn't really matter whether there is a test or there is evidence for it. And over the years, you know, when I actually, when I started doing science, when I was a postdoc, a student and then a postdoc, I noticed a lot of senior people being motivated by the drive to demonstrate that they are smarter than other people. You know, that was their fundamental driving force for them. And if that's what drives you, you don't care about whether reality is reflecting your ideas. You just want to show through mathematical sophistication or through ingenuity of ideas, that you are smart.

And you can demonstrate that and get awards and prizes and establish your own mainstream this way, you know, a group of students and colleagues that would do the same mathematical gymnastics. But, you know, it wouldn't say anything about nature. And it's sort of like putting Galileo in house arrest didn't change the motion of the Earth around the sun. Having a group of people impress each other, give each other awards, does not change what the unification of quantum mechanics and gravity is in nature. So the fact that people will propose all kinds of ideas and never test them and be very proud of themselves means nothing you know it a reality may be very different reality might be much simpler you know

all these gymnastics might be wrong-headed in in the wrong direction so talking about the multiverse as an idea that is intellectually stimulating is you know it's fine for a dinner conversation, but you really need the evidence in order to make it a scientific endeavor. So what you call intellectual gymnastics is like a nicer, more positive version of putting Galileo under house arrest. They're essentially the same thing. I would say they're both driven by social drivers, driving forces. Basically, it's the difference between being focused on nature and evidence, data, and so forth, rather than doing that, being focused on people's attention and people's reaction. By the way, that's what social media is all about. You're trying to maximize the number of likes. Okay. So if that's what you're doing, you want to maximize the number of likes,

then you will try to sound smart, to go, you know, together with the herd and just show that you are smarter than other people. If on the other hand, you want to be guided by evidence, you know, evidence does not necessarily point in the direction that is most intellectually stimulating. You know, sometimes nature is complex. Sometimes it's completely counterintuitive. For example, with quantum mechanics. Quantum mechanics was completely counterintuitive to Einstein. He resisted the notion of spooky action in this. But it turns out that

quantum mechanics, as unusual as it is, is a good description of nature. Nobody would have thought about quantum mechanics just based on, you know, mathematical brainstorming. It came about because of experiments. And that teaches us a lesson, you know, nature is whatever it is. It's not, it could be more imaginative than we are. And as physicists, we better follow the evidence. We should, I can give you another example. There was this idea of supersymmetry that was extremely popular in recent decades. And, you know, people got awards for it

and gave each other awards and people were so proud of the idea that they assumed it must be correct and therefore built whole castles of theoretical physics on top of that. They said, okay, let's assume it's correct and use supersymmetry to construct theories of super string theory. So string theory based on supersymmetry, That was the mainstream. And so it was all accepted to be valid. And then the Large Hadron Collider looked for it and didn't find it at the energy scale that would make it most natural. So what's the reaction? The reaction is, okay, well, maybe it's just around the corner. Maybe the next collider will find it. But the truth is that this idea that appeared so natural to the mainstream of particle physics

was not recovered by the Large Hadron Collider, the most natural place for it. And, you know, it again demonstrates that science is the learning experience. We are wrong often in doing science at the frontier because nature is whatever it is and we could be wrong you know so that there is nothing to be ashamed about but it also teaches us not to build castles on top of a base that was not proven by evidence avi i want to come back to aliens. Would interstellar civilizations, by virtue of the fact that they can space travel, would they have answers to some of these questions about singularities and the multiverse? about as to suppose you met an advanced, a much more scientifically sophisticated civilization than we are, and you could ask it questions. It would feel like copying in an exam because you're trying to find answers, trying to find

a shortcut, an answer to a question that you don't know the answer to from a smarter student next to you, you know. But nevertheless, it's very tempting because it would provide a shortcut. Instead of us working on the problem for, you know, thousands or millions of years, they may have figured it out. So what are the questions that we would like to ask them? So we could ask them, what is the nature of dark matter? You know, what is the nature of dark energy that is driving the accelerated expansion of the universe?

You know, we can ask them, what was before the Big Bang? What is the meaning of life? You know, we can ask a lot of questions. I'm just worried that, you know, for example, if we ask what is the meaning of life, there might be dead silence on the other end because they may have not figured it out. But some of the other questions they might have answers to.

They might have discovered the particle that makes up most of the matter in the universe. you are known publicly now for your relation to an object known as amuamua which was the first detected interstellar object to reach our solar system but it had some unusual properties which suggested that its providence might be consistent with you know an artificial origin but before we started recording we were talking about Arthur C Clarke's book Rendezvous with Rama where an interstellar object enters our solar system and humans in the year 2100, whenever it is, realize that the orbit of this object means that it's probably not a comet or anything of natural origin and they go to investigate and find that it's an object from an alien civilization. Tell me, what about Oumuamua suggests that it may have an artificial origin?

Say as much as you feel comfortable saying. And secondly, should we have a rendezvous with Oumuamua? Well, so I should say that I approach this subject in the same way that I approach the search for dark matter. And most of my career, I worked on the universe, cosmology, and on black holes. And only recently, I became interested in much more nearby objects, like Oumuamua, for example, and the search for life. But I approach these subjects in the same way as I approach anything else. And just to give you an example, a couple of years ago, some astronomers reported that hydrogen in the early universe was much colder than we expected. And the only constituent in the universe that is colder than hydrogen is the dark matter. So we wrote a paper where we suggested that maybe the

dark matter has a little bit of charge so that it couples to the hydrogen and cools it. And, you know, that was a speculation. And there wasn't much of a reaction to it. But the paper was published in the most prestigious journal in physics. And so when Oumuamua was discovered, and it started to show some unusual anomalies. It didn't have a cometary tail. It had a very extreme geometry, and also it deviated from an orbit shaped just by the

sun's gravity. And because of these anomalies, we just suggested in a paper that it might be a solar sail, some kind of a sail that is pushed by the sunlight because there is an extra force acting on it. That was a short paper that was accepted for publication in the Astrophysical Journal Letters. The amazing thing is that immediately after that, there was a huge response to that paper, unlike the paper on dark matter. And I was surprised, I was really surprised by the level of reaction. For example, I was interviewed on CNN, and Smirconish, the interviewer, basically took excerpts from the scientific paper in the Astrophysical Journal

Letters and asked me specifically about these quotes and asked me to address them and explain them. I don't think there was ever a paper published in the Astrophysical Journal that was quoted on a news broadcast like on CNN, as if it was a statement that requires a lot of attention. And obviously, you know, the public is very interested in the possibility that life may exist out there. And I think it should be part of the mainstream. And so I try to explain the scientific process that, you know, there are all these anomalies, we don't know what it is. And, you know, we need more evidence. And it's just like

anything else in science, you it's not as if we are saying it's one way or another, we're just saying it's a possibility that should be put on the table, that's all. And I don't see anything wrong about it, just like the possibility that dark matter is charged, you know, was put on the table and, you know, with more evidence we could test it. So we could test this hypothesis by collecting more data on Oumuamua in principle or by waiting for the next object that would look unusual you know and there could be a lot of typical like the second

interstellar object that was discovered was Borisov and it was a typical cometary object so we saw a cometary tail it looked very similar to... But, you know, when I met my wife, she looked very special to me.

And the fact that I met a lot of other women afterwards did not take away my impression that she's special. So the fact that we see other objects that look like comets after Oumuamua does not take away the fact that that first object was quite unusual. But it illustrated to me how much prejudice and how much social trends you find in present day science in the way that scientists are willing to be to entertain possibilities this is the main reason I wanted to have you on the show

and why I have so much respect for you is that while many scientists are preoccupied with advancing their careers not exposing themselves to ridicule. You were prepared to do just that, that is to expose yourself to ridicule by following the argument where it leads according to first principles and suggesting this extraterrestrial hypothesis for Oumuamua.

And I was very impressed by that. It really stood out to me. I wanted to explore with you, though, what do you think accounts for this resistance by the community of cosmologists? Why is claiming that Oumuamua could be of extraterrestrial origin somehow counter-narrative? Well, there is this tendency of scientists to shy away from controversial subjects or subjects that are of great interest to the public, sort of like isolating themselves in the ivory tower and maintaining a professional level that

is difficult for the public to understand because of the technical details. And the problem with this subject of the search for extraterrestrial intelligence is that there are lots of science fiction literature and films and also reports about unidentified flying objects that are not up to the scientific scrutiny of evidence. So many scientists prefer not to be controversial, not to make statements that are of great interest to the public. I see that as actually inappropriate, given that science is being funded by the public, you know, by taxpayers' money. If the public is interested in the subject, we should not shy away from it.

We should use the scientific methodology to address it in the same way that we address the dark matter problem, you know. And we should just be straightforward about things we know and things we don't know, admit what we don't know and lay out the evidence the way it is, and not just hide it behind sort of the walls of an ivory tower and say, you know, let us first figure out for ourselves what it is before we speak to the public. I think that the scientific inquiry should be transparent to the public. I enjoy speaking with people that are not professionals.

They often come up with excellent ideas, excellent insights, and they are very often authentic and straightforward. And that's the way science should be done. Because only when the public sees that we are not confident of a conclusion when the evidence is not robust, only then the public would really believe us when we are confident that the evidence was robust. We cannot just

figure it out for ourselves and come out with statements to the public as if the public was a bunch of students in a classroom, you know, just telling the students what the truth is and without, you know, getting into the details. Because it's really important that the public would understand that when the evidence is not conclusive, then we don't have a consensus in the scientific community. And we have some ideas, some conjectures, but we need more data. We need more evidence to figure out the truth. And we should show that most of the time, we are not certain. Most of the time, we don't have enough evidence. And that's the whole process of the scientific inquiry is to collect enough evidence so that we will be convinced. And then when we come out with a flat statement that there is a lot of evidence in support of something, then the public would believe us because they would see that on many

other occasions, we were not sure when the evidence was not sufficient. It's exactly the opposite of what many of my colleagues argue that they say we should never come out exposing the scientific process when it's uncertain. I think we should, in my view, we should be transparent, we should be clear about it, and show that most of the time we are uncertain, most of the time there is not enough evidence. And it's a learning experience, it's work in progress. So where is Oumuamua right now? well it's too far for us to see so it's sort of like having a guest that came for dinner and then by the time you realize that the guest is very strange it already left through the front door

and you can't really speak with that guest anymore and the problem is not so much that it's in the dark street that we can't see it it also went in a direction that it's in the dark street that we can't see it. It also went in a direction where, you know, it's such a small object. We can't really know exactly where it will be in the future. So it's almost impossible to find it. You know, you need to send a spacecraft that is equipped with a telescope, very powerful telescope that will be able to track it

and there is no spacecraft no rocket that would be able to move faster than it does right now so it's sort of a lost cause we have to wait for the next one, it would have been much better if we had collected more data

about this one but nobody suspected. You know, people thought, oh, it must be a piece of rock. And so there is a lesson to be learned to study future objects more carefully. And, you know, I would be the first to accept evidence that it shows a rock, you know, and that's the way science is done, by evidence, not by prejudice. You mentioned UFOs beforehand. Did you see the 2017 New York Times report on the United States Navy's encounters with the Tic Tac UFO in 2004 and the so-called G UFO in 2015? Well, I should say the following about UFOs,

that our technology in terms of recording evidence through imaging devices improved dramatically over the past several decades. So the cameras that we had several decades ago were much lower quality than the cameras we have today, much less sensitive. And the UFO reports were always on the borderline of being believable. You know, they were always marginal. And that's not what you expect. You expect that if these things are real, then as you improve your equipment, you will be able to

see them more clearly. So to me, that indicates one of two possibilities, either that these UFOs are just artifacts. There are things that happen by chance that you think are unusual, but actually are, you know, just mirages, you know, things that are not real, that you see the reflection of light from some cloud and you think that it's something unusual. The other possibility is that they are related to equipment, military equipment, you know, the things that we don't know about that we see. And obviously, that will always track the latest technology. So it will always be difficult for us to identify the nature of. And, you know, these are the two natural interpretations that I can think of.

But, you know, so far I haven't seen something that, you know, stands up to the evidence of alien intelligences is that as we discussed earlier they might give us these shortcuts or allow us to cheat on the exam of answering some of the most important questions in physics but do you also worry that we might be inviting our own destruction if we come across hostile civilizations? Well, I do think that it would be prudent on our side to listen and not transmit signals. So, you know, we haven't been careful because since radio technology was developed here on Earth about 100 years ago since then we have been transmitting quite a bit and these signals went out to about 100 light years by now and they indicate that we exist we weren't careful about it it would be i think prudent and of course the present day technologies are not transmitting as much as the old technologies. We are not using very powerful radars as we did in order to detect ballistic missiles after the Second World War.

We are not using radio for communication as much as we did because nowadays you have fiber optics and other means of transferring information. So I think overall we should reduce our radio footprint and anything we transmit and try to detect first if there is anything out there. That would be the smartest thing to do and perhaps what the advanced civilizations are all doing. What strikes me is that you seem like a guy who's interested in the welfare

and the longevity of the species. You think very big picture. And the reason that's interesting to me is, you know, you spent some time in the Israeli army for a guy who was probably nationalistic when he was younger. You've kind of moved beyond that to a wider circle. How did that journey play out for you? Well, I should say I was always naive and simple-minded. I haven't changed much, as far as I can tell, from the time that I was a kid, growing on a farm and thinking about big questions.

And you can ask people that know me, and you will get the same sense that I refused, I basically refused to change the way I deliberate. I prefer to stay honest. You know, so when I became, was asked to become department chair, the chair of the astronomy department at Harvard, you know, my wife thought that I may not last very long as chair because I'm relatively straightforward and I say what I think and I'm not trying to manipulate people. It turned out that I... Terrible qualities. By now, I'm the longest serving chair in the history of the astronomy department at Harvard. I've been in this role for nine years. Three terms.

Each term is three years. And you may ask, how come? It's a complete opposite to this forecast. And I think people recognize that I'm not trying to manipulate them. And so they cooperate. A lot of energy is being wasted in relationships with people because they don't trust each other. So when you don't trust the person that you deal with, you waste a and I'm always honest in the way I describe situations.

And it works very well. And everyone in the department collaborates and cooperates with me. We have constructive colleagues and so forth. So I found that perhaps under other circumstances, this approach may not work in the political world, in the business world. It worked very well for me, both in terms of the way I do science. I have tenure at Harvard. I'm able to pursue whatever I'm interested in. I have a lot of students in'm concerned. I had 72 publications, 50 of which were scientific papers. So a lot of work, and most of my work is with one other colleague. It's not big teams, big groups. I prefer to think creatively with a single student or a single postdoc. And I just write papers that have two authors on them most of the

time. So in a way, you know, it proved very effective, this approach of maintaining my childhood curiosity, maintaining my approach of being straightforward, honest about the way I deliberate. But it also worked on the leadership side. I'm chair of the astronomy department and director of two centers at Harvard. One is the Institute for Theory and Computation. And the second, which is a center that focuses on theoretical astrophysics and brings in the best minds among postdocs in the world to Harvard. And then the second center is called the Black Hole Initiative, which is a center focused on the study of black holes. And that is interesting because it brings

together astronomers, mathematicians, physicists, and philosophers together, all of which are interested in black holes. And it's interesting because it combines philosophy with science in a way that I haven't seen in any other center. And it works extremely well. Now we are into our fourth year, and we have been funded for three years and have an extension for another cycle of three years. And this center is extremely interesting.

There are very bright young people that come through the center. And for example, the image of the black hole that was on the front pages of all the major newspapers, the image of M87 with a shadow, was actually produced in the meeting room, in the conference room of the Black Hole Initiative. And so, you know, it is a very interesting center.

So I have these leadership positions, and I feel that, you know, I'm pretty much fulfilled. I enjoy my work, and it somehow worked out. You know, I can imagine many scenarios by which, you know, I would not get tenure at Harvard because of some circumstances, or I would not be allowed to be as straightforward as I am. And there must be a lot of Avis out there that were not as fortunate as I was. They didn't have exactly the same circumstances that allowed them to operate this way. And that's why I'm trying to create around me an environment that tolerates mistakes, an environment that encourages young people to take risky directions of research,

and an environment that also encourages diversity. So most of my students over the past decade were women, like vast majority, about 80% of them. And many of the postdocs that we bring and the students that we bring are underrepresented minorities and women. And we try to promote diversity because my lesson from my life experience is that if you originate from an unusual background, you often think about the problem differently.

And it's good to have multiple ways of approaching a puzzle, because then you have a better chance at cracking it. And so that's why I try to foster an environment that encourages diversity. You've written about 750 papers, but at the same time, you come across as a generalist. Do you think generalists have an intellectual advantage? Yeah, I think generalists are a rare species these days. They also go by the name of Renaissance people, you know, people that have broad interests that used to be very admirable during the Renaissance age, you know, when

it was possible to master many different disciplines at the same time. Nowadays, you know, science has become so detailed that it's very difficult to know things beyond your specialty and know the state of the art in many other fields. And so very, very few people have a broad knowledge. Most scientists focus on a very narrow niche, and they are guided to do that also by their mentors, because that's the only way where you can establish yourself as an authority, as the world expert in something. So you dig very deep our knowledge in that niche. And it's sort of like digging deep and getting eventually to a hard edge where you can't dig any farther. And so the problem with that is if you develop a very narrow set of skills, you can't dig any further. And so the problem with that is

if you develop a very narrow set of skills, you can't really adapt to this new reality and you cannot move sideways and work on other things. So being a generalist allows you to adapt to changing trends. So for example, today in astronomy, there is a completely new frontier that did not exist before, and that is by detecting gravitational waves, ripples in space-time that propagate without any light necessarily associated with them.

You can see objects that are completely dark, for example, black holes colliding, not producing any light. And the traditional way of finding sources in the universe was using light, using telescopes to collect light and looking at sources like stars, galaxies, and so forth. So now we have a new way of looking at the universe using gravitational waves, another messenger that we can use to detect messages from the universe. And people that were stuck in using just telescopes, traditional telescopes, cannot easily adapt to this new reality.

And in fact, I should mention an anecdote that in 2013, I gave a lecture at a winter school to students in which I described gravitational wave astrophysics. I was interested in it before gravitational waves were detected by LIGO. And 10 minutes into my lecture, another lecturer, a faculty, junior faculty, came to me and said, or raised his hand and said, why are you wasting the time of these students on a subject that will never be relevant in their careers? Gravitation wave astrophysics,

who knows if gravitational waves will be detected. And just two years later, LIGO reported that they found the first signal. And the same students that were in the audience, most of them were still doing their PhDs, clearly falsifying this assertion that the lecturer had made. Just to show you how conservative astronomers or scientists are very often and how wrong they can be in terms of forecasting future trends. Now, if you are not a generalist, you will have a difficulty adapting to a new reality. You will be stuck in your own niche, and it may not be as

productive in the future as it was in the past. And there is an advantage, sort of a Darwinian selection of people that are able to adapt to changing circumstances. And being a generalist is an advantage, obviously, in that sense. Yeah. I mean, by the same logic, Homo sapiens has been an incredibly successful species. Whereas other species, which are more ecologically specialist, for example, panda bears, which just feast on bamboo, or koala bears, which can only eat eucalyptus, live more precarious existences.

I agree. Unfortunately. I agree. Now, since you are located in Sydney, Australia, I should say that, you know, it's quite possible that space exploration will select people that are willing to adapt to changing circumstances. And obviously, England sent out some people that they thought should be sent far away, and they arrived at Australia. But look how Australia is blossoming right now. And these people that were sent out of England ended up producing an amazing society that is innovative and successful. And so I would say that perhaps, you know,

sending communities of people to space may select for those that are able to adapt to new circumstances, just as the experience in Australia was. As I said to you before we began recording, if there was any evidence that criminality is not genetic, it is Australia. Yes, and in fact, there is even stronger evidence if you look at Tasmania, that's what the place

where the second time offenders were sent. Yeah, that's right. The worst of the worst. Avi, this has been so much fun speaking with you. Before we finish, tell me, what are the big remaining questions that you hope to see answered in your lifetime? And just for good measure,

what do you think happens when we die? Okay, so let me answer the second question because I have a straightforward answer. I think the experience is very similar to pulling a plug out of the wall for a computer. It shuts down and there is nothing, basically. So the same thing, the human body, you can think of it as a piece of hardware. And of course, you know, we have thoughts and we have all kinds of emotions and all kinds of things that are all linked to this body that we have. And when we die, it's just the same experience as when a computer shuts off, stops operating. That's it. There is nothing. And of course, you know, people tend to believe otherwise.

They tend to believe that there is afterlife. The only problem with that idea, just like the multiverse, you know, nobody can come back and report, or going into a black hole, nobody can come back and report to us about the experience after death. And it's all a conjecture. So if we had evidence for something else, I would consider that as a real possibility. But all the evidence shows that people that go through that phase of not staying alive never come back, and there is nothing really that we can see as evidence that indicates that there is something after that.

So that's my answer to the question of afterlife. Now in the context of that, I should say there is potentially a possibility that science will figure out what is causing death. Just like in the case of a computer, you can figure out what are the bugs that cause it to crash. So we may be able to repair the damage that is caused to our human body over the years and increase the longevity of humans. You know, in principle, you know, there could be a transformative discovery that will allow

us to live for a million years or, you know, a very long time, except, of course, accidents. So if you walk down the street and someone runs over us, there is nothing that will prevent that. But in terms of our biological life, if nothing catastrophic happens, it's possible that human life will be extended significantly. There is a problem with that because, for example, in universities, you will have to abolish tenure beyond a certain age because otherwise you would never replace the professors

if they live for a million years. All the students that come along will never have a faculty position. But anyway, in terms of life, we might in the future extend our life much longer than 100 years, let's put it this way. And also we might discover that replacing biological organs by technology would enhance the life expectancy. You know, we would replace organs. For example, you can imagine replacing the heart by some piece of technology that would operate just like a heart. So if there is a heart failure, you just put something there and that's it, that will replace. So altogether, I say, you know, when you die, there is nothing after that, but maybe we will develop the ability not

to die so quickly, you know, that could be quite nice. Then, with respect to your other question, in the future, I really hope that we can figure out whether we are alone. That is, to me, the most fundamental question, because we can realize a lot of things about our future by finding the answer to this question. And I'm also interested in in the meaning of life you know then what is the i mean we are born into this life uh without any narrative without any script it's sort of like being put on a stage without any um director that tells you what to do.

And you have to figure it out yourself. And when you go around the stage, you realize that everyone else is an actor. You know, that there is nobody you can complain to. You cannot find the person or the authority to whom you can complain or ask for an explanation. And we are put into this reality, into this situation without an explanation of what's the meaning of life. Why are we doing what we are doing?

And that is not so satisfying to me. And so I hope that maybe by exploring the universe we'll figure out some deeper meaning to our life. We can only try. Avi Loeb, thank you so much for joining me. My pleasure. Thank you. Thank you so much for listening. I hope you enjoyed that conversation as much as I did.

For show notes, transcripts, and links to everything discussed, you'll find those on my website, josephnoelwalker.com. That's my full name, J-O-S-E-P-H-N-O-E-L-W-A website, josephnoelwalker.com. That's my full name, J-O-S-E-P-H-N-O-E-L-W-A-L-K-E-R.com. If you like what we're doing, the biggest thing you can do to help us out is to leave a rating

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The audio engineer for the Jolly Swagman podcast is Lawrence Moorfield. Our very thirsty video editor is Alf Eddy. I'm Joe Walker. Thanks for listening. Until next week, ciao.