Instant Genius - Prof Avi Loeb on what 'Oumuamua tells us about the problem with modern physics

Episode Date: March 22, 2021

In 2017, the Pan-STARRS telescope in Hawaii spotted an interstellar object passing by Earth for the first time. Shortly after, Harvard’s Prof Avi Loeb was met with a backlash from the scientific community for suggesting it could be of alien origin. Now, several years on, he has written a book, Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, outlining why we still can’t out rule the possibility, and why scientists should always keep an open mind. We speak to Avi on this week's episode of the Science Focus Podcast. He tells us why he believes the object, 'Oumuamua, was of alien origin, and what problems this reveals about the way modern physics is conducted. Read an edited excerpt of this interview Let us know what you think of the episode with a review or a comment wherever you listen to your podcasts. Subscribe to the Science Focus Podcast on these services: Acast, iTunes, Stitcher, RSS, Overcast Read the full transcription of this episode [this will open in a new window] Listen to more episodes of the Science Focus Podcast: Dr Douglas Vakoch: Should we try to contact aliens? Bergur Finnbogason: Project Discovery and its search for exoplanets Dr Erin Macdonald: Is there science in Star Trek? What if the Earth’s magnetic field died? – Jim Al-Khalili Building a base on the Moon, and crafting believable sci-fi – Andy Weir Dr Becky Smethurst: How do you actually find a black hole? Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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So, hello and welcome to the Science Focus podcast. I'm Jason Goodyear, commissioning editor at BBC Science Focus magazine. Today I'm speaking to Avi Lope, professor of theoretical physics based at Harvard University. Today we'll be talking about this new book, Extraterrestrial, the first sign of intelligent life beyond death. Hi, Avi. Hi, thanks for having me.

Hi, you're very welcome. Thanks very much for joining us. So, yeah, as I said, today we're talking about your book extraterrestrial. And we get a lot of books coming into the office or our homes now, I suppose. But not so many like this one. it took me a little bit by surprise. So at first, I was under the impression I was going to get a fairly, fairly rigorous sort of explanation

of this fascinating interstellar object, which we'll get into later. But it's kind of, having read the book, it's sort of part memoir, part meditation on your experiences and your life working within science, and also partly your views on how science, and scientists should approach problems? I mean, would you say that's fair?

Yeah, I think all of these, all of these aspects are intertwined, and it's sort of like, you know, a living organism has a lot of things, you know, and you can't just isolate one from the others. And what I'm trying to present is not an idealistic view of how things are done in science, but rather, you know, how it's in reality and not necessarily portrayed to the public.

So one of the main issues that I'm trying to bring up is that scientists should be more straightforward about how the sausage is made. Right, that's a great analogy. So the kind of hook in this is this fascinating object named Amuamura that appeared in, I think, 2017. So just briefly, for those that haven't heard, I'm sure most people have,

but can you just tell us what that is and why it was so significant. Right. So in October 19th, 2017, a telescope on Mount Tehalla in Hawaii named the Pan Stars discovered the first object near the earth

that came from outside the solar system. And we know that because it moved too fast to be bound to the sun. Now, astronomers suspected that it must be a comet because most of the objects in the solar system are at the periphery. have ice on their surface. So if any of them gets close to the sun,

the ice would warm up by the sunlight, heating it, and then it will end up in vapor and shrouded with dust. So you end up with this cometary tail surrounding these icy rocks. And most of the objects lost by other stars would come from the periphery because of passing stars that tear them away from their parent star. And you would expect the population of interstellar icy rocks. So the first suggestion was it must be a comet.

And the only problem was that it didn't look like a comet. It didn't have a cometary tail. There was no gas surrounding it. And in fact, the space of space telescope looked very sensitively around it. It couldn't find any carbon-based molecules or dust. So it's not a comet. Okay. So then the suggestion was, well, maybe it's just a rock without any ice on the surface.

Now, the object, as it was tumbling every eight hours, showed variations in its brightness by a factor of 10 or more, actually. And that implies, since we are looking at reflected sunlight from the object, it implied that the area that it occupies on the sky varied by a factor of 10 as it was tumbling. And think about a piece of paper that is razor thin. The chance of you seeing it edge on is very small. So a factor of change is quite extreme. means that the object was at least 10 times longer than it was wide projected on the sky. And that's what led to this cartoon version of the object looking like a cigar, even though we didn't really have an image of it because it was too small for our telescopes to resolve.

But it was a cigar projected on the sky. It was actually the best fit to the variation in the light was that of a pancake-shaped object. So it was a flat object at a 90% level, most likely flat. And then it exhibited an extra push away from the sun, which could not be due to the evaporation of gas like you have in a rocket. So the only way to explain it in my mind was reflection of sunlight. But for that to be effective, you needed the object to be very thin, sort of like a sail that you find on a boat where the wind pushes it, except here it's the sunlight pushing it. But nature doesn't make light sails.

They are artificial, if real. We are making them for space exploration. And there was actually an object just a few months ago that was discovered by the same telescope, Pan Stars, and it was bound to the sun, and it was given the name 2020 SO by the minor planet center, as if it's an astrophysical object.

And then the astronomers extrapolated its orbit back in time and realized, oh, it's actually a rocket booster from a 1966 launch. And we know that it's hollow and that the surface is thin. And we noticed that it exhibited an extra push away from the sun as a result of reflecting sunlight. And there was no cometary tale. So here is a demonstration that an artificial object

that we produced that was thin enough shared the same properties as a muamua. The only question is, who produced a muamua? So just like going back to that a bit, so your calculations about the trajectory, about the luminosity, about the general behavior of this object led you to conclude that it was in fact an artificial object. So I realized that about six months or actually a little more eight months after the object was discovered. And at that point, I decided maybe to write a scientific paper summarizing why I believe it's, artificial. And of course, there was a huge pushback, and there is still. I mean, and people

attack me even personally, which, you know, I'm willing to bite that bullet, and as long as it doesn't kill me, it will make me stronger. But I should say that since I wrote that paper, there were a few scientists that I regard highly because they actually paid attention to the anomalies that I pointed out. So rather than just make general statements like most people do, those scientists were following the scientific process, which is when you're faced with anomalies, you're trying to find explanations. And let's try and see if there is an explanation from a natural origin. I'm completely in favor of that, and I appreciate very much the work done by those scientists that published about five papers on alternatives. And there were basically three suggestions that were made. One, that it may be a hydrogen, iceberg, you know, a chunk of frozen hydrogen. And then if the hydrogen evaporates, just like in a comet, hydrogen is transparent, so you can't see the cometary tape.

That would explain why we don't see it. But the problem with that is that we wrote a paper after that with my colleague, Thin Huang, showing that hydrogen and hydrogen iceberg would evaporate very quickly as a result of absorbing starlight along its journey. And it's not at all clear that it can be produced. produced in the first place in molecular clouds. We demonstrated that as well. So that doesn't seem likely.

And then there was a suggestion, maybe it's a collection of dust particles held together in a loose configuration, just like very porous material, like a cloud of dust, a hundred times less dense than air. So think about it a hundred times. And then getting my issue with that is when it gets close to the sun like Muammuamua was, it would be heated by hundreds of degrees. And a cloud of dust that is 100 times less dense than air would not have the material strength, in my view, to sustain this heating. So anyway, the idea was that the sunlight would push it.

It would be lightweight and drift the way Muammu did. And then the third possibility suggested was, oh, maybe it's very elongated because it's a shrapnel. It's a piece of debris of something bigger that got this. when it passed close to a star somewhere. The problem with that scenario is that you end up with shrapnel that is elongated, usually because of the gravitational tidal force. And the object was most likely pancake shape, not cigar shape. And also the chance of coming close to a star is very small.

So I said to myself, look, after two years, that's the best that the community could come up with as an alternative to artificial. In my view, the artificial is more likely. and there is no clear evidence that it's not artificial, therefore I wrote this book suggesting. Now, people are opposed to the mere discussion or having on the table that option of it being artificial. And that's, in my mind, you know, strange because, you know,

I left a seminar room where there was a talk about Omoa-Mu-A and a colleague of mine that worked on rocks in the solar system for decades, said, oh-Mu-A-Mua is so weird, I wish it never existed. And yeah, to me it was appalling. How can scientists say that? Because, you know, when you're faced with anomalies that take you out of your comfort zone, it's actually a very good thing because it means that you're learning something new. Unless you want to, if you want to stay in your comfort zone, then just don't look, you know, don't look for the telephone.

Yeah, just stay ignorant. You know, behave. You can enjoy life. You can eat good food. You can speak with friends. Just ignore all the facts around you. I mean, many people do that, by the way. But as a scientist, you have an obligation, you know,

to follow the evidence and see where it leads you. And if you are denying that privilege, you are not true to your obligation. And that's the problem I have with the scientific community. Yeah, absolutely. So you just mentioned, just going back a little bit, you mentioned this idea of the light sale. This is kind of a key point. And I think quite a lot of people listening won't be.

familiar with the concept of light sails. So can we just explain exactly what that is and why Umuamu fits the bill? Sure. So light is made of particles in principle that are called photons. You can think of them as billiard balls bouncing. And when they bounce off a mirror, they just give it a little push. And so the idea of a light sale is to take advantage of that push. So for example, they make them the same.

sail sufficiently thin such as the reflection of lights gives it enough push to move it forward. And of course, sunlight is not very powerful, but in principle if you have a very powerful laser beam, you can reach very high speeds. That's what we are aiming to do in the Starshot project. The goal is to reach the nearest star, Proxima Centauri, within a couple of decades. And to get there, I mean, since light takes four years to get there, you need the spacecraft to move at the fifth of the speed of light. And that means that the best way to achieve that is by pushing a sail with light, because light moves at the speed of light.

And the advantage of this method is that the spacecraft does not carry the fuel. So it can be very lightweight. And in the context of starshot, just to give you an example, we're talking about a sail that weighs only a few grams. and it's roughly the size of a person being pushed by a hundred gigawatt laser over a few minutes, it will reach a fifth of the speed of light. And over across a distance that is five times the distance to the moon. And you can attach electronics to such a sale so that you will have a camera, navigation device,

communication device. Of course, in the case of Oumuwa, it was not moving that fast. And it's quite possible that it was completely dysfunctional, you know, because it was tumbling. And, you know, what do you expect from a piece of equipment floating in space for billions of years? You know, think about New Horizons, Voyager 1, Voyager 2, when they will be billion years old. They will not be functional anymore. So there should be a lot of trash in space that is not working anymore.

So potentially, then, just to sort of summarize what you're saying there, Umuamua could in fact be an artificially produced light sale by an extraterrestrial civilization that has now become defunct and somehow wandered its way into the solar system. Exactly. And it could also be a surface layer that was torn apart of a spacecraft or anything that is thin. But the key here is whether it's artificial or natural. That's the key question. And my point is all the natural proposals, the proposals associating it with a natural origin, they all contemplated something that we have never seen before. So here is my point.

Let's deploy cameras around the orbit of the Earth, you know, around the sun, lots of them. So that when the next interstellar object is spotted, one of the cameras would be close enough to take a close-up photo. And, you know, a picture is said to be better than worth a thousand words, right? In my case, a picture would be worth 66,000 words, which is the number of words in my book. I wouldn't need to write the book if we had a picture, and that's what I really want. So, you know, when I go to the kitchen and find an ant, I get alarmed because I know that there should be many more ants out there. And the same should be true about the Muamua. we found one after a few years of serving the sky with pan stars.

If we continue to survey for a few more years, we'll find another one. And there is the Vera Rubin Observatory that will come into play in less than three years. It will have much greater sensitivity and could find an Oumu or Mua type object every month. So we will have a lot of opportunities to check if I'm right or wrong. I don't understand why, even if you're conservative and you say it's never aliens, why have a prejudice to start with if we will have a lot more objects? Let's just take photographs of them and maybe one out of a few would be a plastic bottle on a beach. Most of the time on a beach we find a rock.

And every now and then a plastic bottle that tells us there is a civilization out there. So what are our sort of current limitations in our sort of detection capabilities? obviously now it's it's long gone but you know yeah there is there is no point in obsessing about umuamua because it's now a million times fainter than it was close to the sun so and we cannot chase it really because anything that will chase any spacecraft will have to carry a large telescope and and as I said before there must be a lot of objects like it already within the solar system you know of other a rough estimate would be of other quadrillion like 10 to the power 15 there are lots of them and they just like a lot of ants in the kitchen, you know, and we just need to find

more of the same and then take a close-up photo or even land on one of them or, you know, basically study them, whatever looks artificial. And that would be a completely new way to learn about other civilizations because traditionally we've been looking for 70 years for radio signals. And that's equivalent to trying to speak with someone on the phone. You need the counterpart to be alive when you're speaking on the phone, right? But if you're waiting for a letter in the mail and the post service is very slow, you might get a letter when the person who sent it died already. So the point is the advantage of looking for physical objects is that you are basically summing over the entire history of cultures that used to exist. And most of them are dead by now.

So with the Mayan culture on earth, you know, we can't have a conversation because they're gone by now, but we can find relics they left behind in archaeological digs. And so I call it space archaeology. We can find those relics in space. And it's a completely different approach. Doesn't at all connect to the Drake equation that people talk about, which is more for radio communication. Here you just need to know how much trash you have there is in space.

It's sort of asking how many plastic bottles you have on the beach per unit area. So what's your chance that one of them will be next to your legs? You know, that's basically the point. So yeah, some people might say, oh, that sounds very out there idea. But in fact, we humans have sent Voyager is now outside of our own solar system, right? So it's a completely plausible, completely normal idea, right? But as you say, lots of people, for some reason, they resist this option. this idea of it being from an extraterrestrial civilization.

Why do you think that is? Why is that resistance? You can conjure all sorts of other, you know, do clever maths and make all sorts of other hypotheses, but just refuse that, no, just completely outrule that one from the outset. I think that's a very strange way of thinking personally. It is a very strange way of thinking. And, you know, I try to apply as much common sense as possible. and I just don't understand why for others it's not common sense.

But the way I see it, there are two main issues that come to mind. One is people claim that, you know, people prefer to ideas that flatter their ego. You know, for example, the idea that we are unique and special is much more appealing because it elevates our status relative to everything else in the universe. And, you know, my daughters, when they were at home, very, very, infants, they tended to think that they are the smartest in the world. And when they went to the kindergarten, they realized that's not so. There are other kids out there.

And, of course, they would have preferred to stay at home. If I were to ask them, they would prefer to stay because that was flattering their ego. So that's one aspect of it that scientists prefer to, or in general, people prefer to believe that we are special and unique. And it started with Aristotle saying that we are at the center of the universe, you know. And it's a natural tendency of humans to always think. And I think it's lack of maturity because by now my daughters after going to the kindergarten are much more mature than, you know, these scientists that say, oh, we are unique.

Anyway, the second issue is that there is all this literature on science fiction and on unidentified flying objects that some scientists feel that will stain their image if they were to subscribe to it or be associated with it. But here is my point that in the dark ages, there were people claiming that the human body has a soul. Actually, it dates back to the ancient Greeks. Human body has a soul, therefore, should not be operated. Okay. And imagine if scientists were to say, okay, this is nonsense, but there is this, all this nonsense being said about the human body,

we don't want to study anatomy whatsoever. Where would modern medicine be without anatomy? me. The point is that if science can apply the scientific method using the state-of-the-art tools to a question that is of importance and interest to the public, it must do so to clear the fog. You know, it must clarify, you know, in the context of, are we alone, are we the smartest kid on the block? There is an obligation to answer this question. Why shy away from it and say, we don't want to deal with that? I mean, that makes no sense. Now, it makes even less sense if you think about what the physicists are doing these days? What are they doing? You find a whole

group of people in theoretical physics that was starved of any experimental data for decades working on ideas that were never compared to experiments, such as extra dimensions, the multiverse, string theory, and when one of the ideas was tested supersymmetry, there was no evidence found for it in the Large Hadron Collider. So here is my point. Unless you put skin in the game. And by the way, kids do that. They get bruised because they put skin in the game. You know, when they try something, they don't.

So they are not always right and they make mistakes. They bump into things and they get bruises. Okay, so that's part of learning, right? And in science, the way to get bruises is by making predictions that are falsified by experiments. That's the way of putting some skin into the game. But I feel that this is a necessity of learning about the world. You know, you have to make mistakes.

because you don't always know in advance what's right. The problem is it will stand your, okay, so you will not have an image that you were always right. But the objective is not to get prizes, awards, recognition, honor society. The objective is to understand nature. And unless you take risks and innovate, you will never do that. You have to put skin in. So there is this culture of people working on ideas that cannot be tested experimentally. And it's very comfortable because you can basically demonstrate your skills and how smart you are by mathematical gymnastics without being tested against experiments. So these ideas may not apply to describing reality, but nevertheless, they can gain

recognition and awards. And it's a new age in theoretical physics where the necessity to compare to experiments is not there. And what I find strange is that people resist the notion of trying to collect evidence on an idea that is not a speculative, which is, you know, we know that half of all the stars like the sun have a planet the size of the Earth, roughly at the same separation. And so you basically arrange for similar circumstances to those on Earth that would lead to liquid water on the surface, potentially, and the chemistry of life, as we know it.

And if you arrange for similar circumstances, you might as well get similar outcomes. That's the most common sensical view to have. And I would imagine this notion to be in the mainstream of astronomy. And rather than be shoved to the periphery, claiming that it's speculative. Right now, I heard, by the way, after my book appeared and I voiced my opinions, I heard from a number of people that said, you know, I'm in some of the way, and some of the way, and some of them are very senior. They say, I'm extremely interested in what you say, and I completely agree with what you say, but I cannot express it publicly because it would damage my career. And, you know,

the biggest impact is on young people. They are afraid to speak out. They are afraid to follow their interests or to innovate because of the implications to their jobs in the future. And you would think that we learn from experience that science should be open-minded, that in fact should encourage innovation and not group think, and that ideas that are important to the public will be pursued. You know, the public funds science. So how can scientists say,

let's not consider this possibility at all if the public is so excited about it? And by the way, the success of my book, it's now bestseller in multiple countries around the world just a week or two after its publication. It's clear that the public is excited. The public was starved by the scientific community on this issue.

And here I come and just talk about it, and immediately the public is excited. And that's the reason why people ask me to speak, you know, because there was nobody that was willing to take the brunt. You know, when I was in the military at a young age, there was this saying that sometimes a soldier needs to put his body on the barbed wire so that others can pass through. And that's the way I feel, you know, the barbed wire does cause me pain. but I feel that I'm serving an important purpose to allow the younger people of tomorrow to discuss this issue freely. And frankly, I think for us as a civilization, it's the biggest question that science can address because it will change our perspective about our place in the universe, our aspirations

for the future. What else could be more important in this knowing whether there are smarter kids on our block? So yeah, that sort of leads on nicely to what I was going to ask next. Like in the book, it's kind of, like I was saying, there's a autobiographical aspect to it for sure. You know, you start off when you were a child on the farm, etc. And then you go how you became interested in different aspects of science, like quite a lot of different aspects of science. So I was going to ask, so you kind of touched on there, but what is it especially, you seem especially interested in extraterrestrial intelligence. And what is it about now?

That's so fascinating to you. Oh, it's the fact that it basically touches on our core existence, right? We are intelligent and there is a direct impact on the way we think about ourselves. You know, if you look at the mirror, that's one way of learning about yourself. But all you see is yourself. If you search for other intelligent beings out there, You know, they might be smarter than we are much more advanced. It might look like magic to us.

We could learn new things. It's sort of like going into your neighborhood and finding kids that, you know, have nothing to do with your family. And it opens up your eyes in a way. So it's really fascinating to think about, like, who cares about the physical objects out there? You know, hundreds of millions of dollars were spent on the search for dark metal. we don't know what most of the matter in the universe is. It's called dark matter just to label our ignorance. And there were suggestions for various types of particles, you know, like axioms, weakly interacting massive particles.

None of them were found over the past few decades, hundreds of millions spent to check if they exist. Nobody complains, of course, because we are trying to figure out, you know, you're taking some risks and, you know, very often you don't find anything. But at the same time, the search for technological signatures was funded at the level that is a thousand times lower, a thousand times. Just think about it. How is it possible that the question is so fundamental to humanity would be completely unfunded? And then anyone discussing that would be ridiculed. You know, I worked on dark matter. I worked on cosmology on black holes in the past. That's why I have no issues coming up front and discussing the search for intelligence in the same way. To me, it's an integral part of science. And I don't see why my colleagues are just completely off where they should be. The mainstream is exactly in the opposite position of where it should be. It's just one of these instances that by chance I arrived as a result of UMUAMUA,

I arrived to a place and I noticed that, you know, there is a lot to be fixed here. A lot is done wrongly and people just don't realize that. But it's a huge issue because, you know, how can it be that the search for the most fundamental question that we have is funded at the level that is a thousand times less than the search for dark matter and 10,000 less than future searches for primitive life, microbial life. okay, even if we find it, it will just say microbes exist somewhere else. It's not like, you know. And so that is now accepted to be part of the mainstream, to look for oxygen and methane

and methane in the atmospheres of other planets. Now, think about oxygen. So there are billions of dollars, you know, people are asking for observatories that will cost billions of dollars to build that will potentially, within decades, find evidence for oxygen. Now, in the atmosphere of another planet. Now, if you look at our planet, the only planet where we know life exists as of now, oxygen did not appear in the atmosphere for two billion years. So roughly the first half of the lifetime of the Earth, there was not much oxygen, even though there was a lot of microbial life on the surface of Earth. So if you don't find oxygen on a planet,

It doesn't say that there is no life there. Obviously, we know that 50% of the Earth-like situations would show that. And then the second point is if you do find oxygen, it wouldn't be conclusive because you can make oxygen by natural chemical processes. Now, what kind of molecule would definitely be an indication for life? Well, CFCs, you know, these complex molecules that we produce in refrigerating systems, in industries that they would indicate an industrial civilization. And nature does not produce these molecules.

So I'm just saying use the same instruments that you're asking for and just motivate it as if you're looking also for industrial pollution. But you will never find that in the documents advocating for those billion dollars instruments. And I asked myself, why would that be the case? Why would scientists on purpose not even mention that? And to me, that's just inappropriate and something has to be changed here. And, you know, the public gets it. But science got to a point where it's more about group thing.

It's more about the number of likes you get on Twitter. It's more about getting honors and awards and avoiding risks in the context of theoretical physics, not putting skin in the game, not asking the right questions necessarily the public cares about, but more the questions that will make you appear smart. Whether it's a rock or artificial doesn't require sophisticated math, right?

But whether we are living in four dimensions or ten dimensions does require sophisticated math. So what the community prefers to do as part of the mainstream activity is do the sophisticated gymnastics of mathematics just to demonstrate that we are smart. But, you know, nature is whatever it is, you know, if you ignore it, it will stay the same. So saying, for example, to Galileo that

the philosophers did that they don't want to look through his telescope because they know the answer that the earth moves, that the sun moves around the earth. That didn't change the fact that the earth moves around the sun and it just maintained their ignorance. And I say the same thing about extraterrestrial life. You know, if you just say, oh, I don't want to discuss it. You know, you just maintain your ignorance. And it's unfortunate because, you know, it's unfortunate because, Because, you know, as a civilization, the way we view our place in the world, would change one way or another if we find that there are smarter kids on the blog. So what would be, say you've got control of all of the, or at least a substantial budget for a project. and you want to say, right, let's have a serious go at finding extraterrestrial life.

What would be the best way to go about it, in your opinion? Well, in my view, the first thing I would do is space archaeology. In other words, deploy cameras throughout the region of the Earth's orbit around the sun and just wait for interstellar objects crossing close to one, one of the cameras and take photographs of those and look for the plastic bottle among the rocks. You know, just do that and do that for a while and see how many we can identify that look artificial based on a photograph. I don't think anyone would argue if the picture looks different than rock, a rock.

I mean, we can argue about what it means and what the purpose of this object is, but the distinction between an artificial object and a natural object would be quite clear, especially if it's extremely thin. So that would be my first priority doing in our backyard archaeology because that's easy. You don't need to go a large distance. You don't need to be a huge facility to detect something that is very faint. You just put the detectors in your backyard and look for objects that arrive from the street. you know, and instead of going to the street, you know, they save you the time because it takes,

even for a more than 10,000 years to cross the solar system all the way from the edge of the ore cloud. And that's a long time. And instead of us spending that time traveling away from the solar system, we can just examine those objects that made the trip and spend those long periods of time, maybe even billions of years, getting to us. And we can learn something from examining them. And I just think it's a fascinating new window into extraterrestrial intelligence that was never explode before.

And that's why I'm excited about the Muamu. It's opening our eyes. You know, it's calling our attention to this opportunity. And of course, if one of these objects does look really intriguing and we land on it, we can learn a hell of, you know, a lot of things about the technology that was developed to produce that object and what it is. means, you know, what was the intention of the object in the first place? Maybe we can see a sign, you know, like a stamp stating where it was produced, like USA, USA on some of the, you know, spacecrafts that made it to the moon, or there would be something maybe written on it or some information we can find. And I think it's just fascinating to explore, to do archaeology. So that would be

my first priority. Then, of course, second priority is looking for art. artificial lights on the night sides of planets. You know, just like we illuminate during the night, we illuminate cities. You know, if you have enough cities on the dark side, you could detect it from a distance. I mean, I actually wrote a paper saying that the city of Tokyo can be seen all the way to the edge of the solar system where Pluto is, for example. If you had a city like Tokyo on Pluto, then the Hubble Space Telescope, could have detected it.

Of course, if you put a lot of cities, you can see them to much greater distances. And my point is, let's search for artificial lights. The other thing we can search for are photovoltaic cells on the day side of a planet that are used to make electricity from the starlight that is impinging there. Then you can look for big structures,

you know, either a swarm of satellites hovering around the planet when it transits a star, maybe you can see evidence for that. Or you can look for megastructures, big structures. And, you know, so there are different aspects of technological signatures that one can look for, including, as I said before, the industrial pollution. And I would go for that is my second priority. And finally, you know, there should be, you know, if other civilizations are using beams of light, let's say, laser light, to launch.

light sails, then you could search for the leakage of that light from the beam around the light sail when it sweeps across our sky and it would appear as a flash of light. So we can look for flashes of light that are suspicious. So yeah, that's brilliant. But just sort of going back, something I was going to ask you earlier. So obviously our own interstellar probe Voyager, it's very, if you, if we, if you, if you, to see it close up, it's very clearly not a naturally occurring object. So why is it that we have this confusion about Amuamua?

Is it just a pure fact that we couldn't get a decent enough picture of it? Yeah, we just didn't have enough data about it. It doesn't need to be a picture. I mean, astronomers thought at the time that it must be a rock or an icy rock and therefore did not collect as much data as needed to study more detail. But if we see another weird object like it, we could potentially collect all the data possible. And that means taking a spectrum of the reflected light from the object,

maybe learning about the surface more than we did, the material on the surface, the reflectivity, the reflectance of the surface. But I think a picture is really the best tool for us, to learn about what it looks like. And of course, you can do a lot of other things with our best telescopes in terms of studying the object as it moves and exactly figuring out what kind of force is pushing it and how does it change over time.

We can just do a more detailed study of the next object. But the pinnacle would be, of course, getting a photograph. So just sort of going back to your, which is a great, great analogy, your plastic bottle washed up on the beach analogy. So how optimistic are you that how many of these do you think that could be out there? You know, what are our chances, say, you know, best case scenario, we set up all of these detectors or whatever. How do you reckon, how good do you think our odds are? Oh, well, if Umuamua was a member of a population of objects that were on random trajectories, in other words, they were not

not targeting the central region of the solar system, but just moving around and the sun bumped into one of them, then you should have one such object roughly at any given time within the orbit of the Earth around the sun. Because, you know, we found one over a few years within a fraction of that volume, and so that's roughly the estimate. And therefore, there should be a lot of,

lot of them. So if we just deploy enough cameras and wait for a few years, we will definitely have one of the cameras being very close to one of them. And one can go through a calculation of deciding exactly how many cameras to put and so forth. I mean, the cost is not great for a camera. And it's just that we have to decide that this is a priority and that we want to do the archaeology. And by the way, even if it's natural in origin or muamua, the suggestions made were that it was something that we have never seen before. So we will learn something new no matter what. And even if it's natural, we'll figure out something new about the factories that make these natural objects that we haven't imagined before. And that's why I think science will benefit either way.

Thank you for listening to this episode of the Science Focus podcast. That was Harvard University's professor Avi Loeb, talking. about his new book, Extraterrestrial, the first sign of intelligent life beyond death. Thank you for listening to the Science Focus podcast from the BBC Science Focus magazine team. With the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world.

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