Prof Avi Loeb on what 'Oumuamua tells us about the problem with modern physics © ESO/M Kornmesser

Podcast transcript: Prof Avi Loeb on ‘Oumuamua

Read the transcript of our Science Focus Podcast with Prof Avi Loeb – scroll down to listen to the episode.

Jason Goodyer Hello and welcome to the Science Focus Podcast. I’m Jason Goodyer, commissioning editor at BBC Science Focus Magazine. Today I’m speaking to Avi Loeb, professor of theoretical physics based at Harvard University. Today, we’ll be talking about his new book, Extraterrestrial: The First Sign of Intelligent Life Beyond Earth. Hi, Avi.

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Avi Loeb Hi. Thanks for having me.

JG Oh, you’re very welcome. Thanks. Thanks very much for joining us. So, yes, as I said today, we’re talking about your book, Extraterrestrial, and we’re going to, you know, we get a lot of books coming into the office or homes now, I suppose, but not so many like this one. So it took me a little bit by surprise. So at first I was under the impression I was going to get a very, very rigorous sort of explanation of this fascinating interstellar object, ‘Oumuamua, which we’ll get into later.

JG But it’s kind of having read the book is more a sort of part memoir, part meditation on your experiences in your life working with science, and also, partly your views on how science and scientists should approach problems. I mean, would you say that’s fair?

AL Yeah, I think all of these aspects are intertwined. And it’s sort of like a living organism has a lot of things, you know, and you can’t just isolate one from the other. 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 works in reality and not necessarily portrayed to the public. So it’s 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.

JG Right. That’s a great analogy. So the sort of the kind of hook in this is this fascinating object named ‘Oumuamua 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?

AL Right. So on 19 October 2017, the telescope on Mount Haleakalā in Hawaii, named the Pan-STARRS, 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 at the periphery have ice on the surface or if any of them gets close to the Sun, the ice would warm up by the sunlight hitting it, and then it will end up in vapour and shrouded with dust.

So we end up with this cometary tail surrounding these icy rocks and the most of the objects lost by other stars would come from the periphery because of passing stars 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 Spitzer Space Telescope looked very sensitively around it and couldn’t find any carbon based molecules or dust. So it’s not a comet.

OK, so then the suggestion was, well, maybe it’s just the rock without any ice on the surface. Now, the object was tumbling every eight hours, and showed variations in its brightness by a factor of 10 or more. And since we are looking at the reflected sunlight from the object. It implied that the area that 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. The factor of change is quite extreme and it 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 actually the best fit to the variation in the light was that of a pancake shaped object. So it was a flat object and 90 percent 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 had in the rocket. So the only way to explain it in my mind was a 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’re making them for space exploration. And there was actually an object just a few months ago that was discovered by the same telescope Pan-STARRS. 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. But then the astronomers extrapolated its orbit back in time and realised, oh, it’s actually a rocket booster from a 1966 launch. And we know that it’s hollow and 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 tail. So here is a demonstration that an artificial object that we produced that was thin enough shared the same properties as ‘Oumuamua. The only question is who produced ‘Oumuamua?

JG Your calculations about the trajectory, about the luminosity, about the general behaviour of the subjects led you to conclude it was in fact an artificial object?

AL That’s right. So I realised that about eight months after the object was discovered, and at that point I decided maybe to write the scientific paper summarising why I believe it’s artificial. And of course, there was a huge pushback. And there is still. I mean, people attack me even personally, which I’m willing to bite that bullet. 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 are faced with anomalies, you are trying to find explanations. And let’s try and see if there is an explanation from a natural origin. I’m completely in favour 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, a chunk of frozen hydrogen. And then if the hydrogen evaporates just like a comet, hydrogen is transparent. So you can’t see the cometary tail that would explain why we don’t see it. But the problem with that is that we wrote the paper after that with my colleague I one showing that a 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 in the first place in molecular clouds. We demonstrated that as well. So that doesn’t seem likely.

And then there was a suggestion that maybe it’s a collection of dust particles held together in a loose configuration, just a very porous material, like a cloud of dust, 100 times less dense than air. My issue with that is when it gets close to the Sun, like ‘Oumuamua 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.

And then the third possibility suggested was, oh, maybe it’s very elongated because it’s shrapnel, it’s a piece of debris of something bigger that got disrupted when it passed close to a star. The problem with that scenario is that you end up with shrapnel, which is elongated usually because of the gravitational tidal force. And the object was most likely pancake shaped, not cigar shaped. 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. Now people are opposed to the mere discussion or having on the table that option of it being artificial. That’s in my mind strange. I left a seminar room where there was a talk about ‘Oumuamua and a colleague of mine that worked on rocks in the Solar System for decades said “‘Oumuamua is so weird. I wish it never existed.”

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. If you want to stay in your comfort zone, then just don’t look, just stay ignorant. You can enjoy life. You can eat good food. You can speak with friends. Just ignore all the facts around you. Many people do that, by the way. But as a scientist, you have an obligation 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.

JG I think quite a lot of people listening won’t be familiar with the concept of light sails. So can we can we just explain exactly what that is and why it fits the bill?

AL So light is made of particles in principle that are called photons. And you can think of them as billiard balls bouncing and when they bounce off a mirror, they just give a little push. And so the idea of a light sail is to take advantage of that push. So, for example, you could make the sail sufficiently thin, such that the reflection of light 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. Since light takes four years to get there, you need the spacecraft to move at a 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. The advantage of this method is that the spacecraft does not carry fuel so it can be very lightweight.

In the context of Starshot, just to give you an example, we’re talking about a sail that weighs only a few grams, and is roughly the size of a person, being pushed by 100 gigawatt laser. Over a few minutes, it will reach a fifth of the speed of light, over a distance that is five times the distance to the Moon. And you can attach electronics to such a sail so that you will have a camera navigation device, communication device.

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

JG So, just to sort of summarise what you’re saying, there could in fact be an artificially produced lightsail made by an extraterrestrial civilisation that has now become defunct and somehow wound its way into the Solar System?

AL It could also be a surface layer that is torn off 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 causes, 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 in around the orbit of the Earth, around the Sun. Lots of them, so that when the next interstellar object is spotted, one of the cameras will be close enough to take a close up photo. A picture is said to be 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. And I wouldn’t need to write the book if we had a picture. And that’s what I really want.

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 ‘Oumuamua. We found one after a few years of surveying the sky with Pan-STARRS. If we continue to survey 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 ‘Oumuamua-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? Let’s just let’s just take a photograph of them. And, you know, maybe one out of a few would be a plastic bottle on the beach. You know, most of the time on the beach we find the rock and every now and then a plastic bottle that tells us there is a civilisation out there.

JG So what are our sort of current limitations in detection capabilities. Obviously now it’s long gone.

AL Yeah, there is there is no point in obsessing about ‘Oumuamua because it’s now a million times fainter than it was close to the Sun. And we cannot chase it because any spacecraft would have to carry a large telescope. And as I said before, there must be a lot of objects like this already within the Solar System. A rough estimate would be of order quadrillion, like 10 to the power of 15. There are lots of them. And just like a lot of ants in the kitchen you know, we just need to find more of the same and then take a closer up 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 civilisations, because traditionally we’ve been looking for 70 years for radio signals, and that’s equivalent of 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 Postal Service is very slow, you might get a letter from 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 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 are 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 people talk about which is more direct communication here. You just need to know how much trash you have there is in space. It’s sort of like asking how many plastic bottles you have on the beach per unit area. So what’s your chances are one of them would be next to your legs. That’s basically the premise.

JG So, yeah, some people say, oh, that that sounds very, very out there. I did, but in fact, we humans have sent Voyager. It’s now outside of our own Solar System. So it’s it’s a completely plausible, completely normal idea. Right. But, as you say, lots of people for some reason, they resist this this option, this idea of it being from an extraterrestrial civilisation. Why do you think that is? Why is there that resistance that you do clever maths and make all sorts of other other hypotheses, but just refuse, no, just completely outrule that will from the outset? I think that’s a very strange way of thinking.

AL 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. And 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 through ideas that flatter their ego. You know, that, 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, they were infants, and they tended to think they are the smartest in the world. And when they went to the kindergarten, they realised 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 referred to, or in general, people prefer to believe that they are special and unique.

And it started with Aristotle saying that we are the centre of the Universe. You know, it’s a natural tendency of humans to always think and I think it’s a 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 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 dates back to the ancient Greeks, the human body has a soul and therefore should not be operated on. And imagine if scientists were to say, OK, 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?

The point is that if science can apply this 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 form. You know, it must clarify what 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? 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 the whole culture, you know, 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, you know. 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 that when they try something, they are not always right. And they make mistakes. They do things and they get bruises. OK, 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 they’re 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 you will not have an image that you are always right. But the objective is not to get prizes and awards recognition, honour society, the objective is to understand nature. And unless you take risks and innovate, you will never do that and you have to put skin in the game. But there is this culture of physics right now. It’s very comfortable, right? They say, oh, there is no way to test these ideas empirically. That’s what we can do, mathematical gymnastics. And you just demonstrate that we are smart and they give each other awards, we give each other honours just based on the fact that they demonstrate that they’re smart. 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 that your skills and how smart you are by mathematical gymnastics without being tested against experiment. 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 the evidence on an idea that is not speculative, which is, you know that we know that half of all the stars like the Sun have a planet the size of the Earth, at roughly the same separation. And so you basically arrange for similar circumstances for 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 of astronomy and rather than be shoved to the periphery claiming that is speculative right now. By the way, after my book appeared, and I voiced my opinions, I heard from a number of people that said, you know… 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’re afraid to speak out. They’re afraid to follow their interest or to innovate because of the implications of their jobs, jobs in the future. And you would think that we learn from experience. Science should be open minded.

That, in fact, should encourage innovation and not groupthink, 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 a bestseller in multiple countries around the world that 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 are asking me to speak because there was nobody that was willing to take the brunt. You know, when I was in the military at the young age, there was this saying that sometimes a soldier needs to put his body on the barbed wire so 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 civilisation, it’s the biggest question that science can address, because it changed our perspective about our place in the Universe, our aspirations for the future. What else could be more important than this, knowing whether there are smarter kids on our block?

JG I was going to ask next, in the book, like I was saying, there’s an autobiographical aspect to it. Sure, you know, you start off when you were a child on the farm, etc., and then you got how you became to be became interested in different aspects. So it’s like quite a lot of different aspects of science. So I was going to ask, you kind of touched on that, but what is it especially? You seem especially interested in extraterrestrial intelligence and what is it about them that’s so fascinating to you?

AL 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 ourself. And, 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 neighbourhood 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 matter. 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 axions, weakly interacting massive particles. None of them were found over the past few decades, hundreds of millions spent to see 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 of a thousand times lower. A thousand times. Just think about it. How is it possible that the questions 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 and black holes in the past.

That’s why I have no, you know, no issues coming up front and discussing the search for intelligence in the same ways. To me, it’s an integral part of science. And I don’t see why my colleagues are just completely, you know, off where they should be. You know, the mainstream is exactly the opposite position of where it should be. It’s just one of those instances that by chance, they arrived, as the result of ‘Oumuamua, arrived to a place.

And I notice that, you know, there is a lot to be fixed there. A lot is done wrongly. And people just don’t realise 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? OK, even if we find it, it would 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 in the atmosphere of other planets.

Now, think about oxygen, so that billions of dollars, you know, people are asking for observatories that would 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 the Earth.

So if you don’t find oxygen on the planet, it doesn’t say that there is no life here. Obviously, we know that, you know, 50 per cent of the Earth like situations each other. 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 molecules would definitely be an indication for what it is, you know, these complex molecules that we produce in refrigerating systems, in industries that would indicate an industrial civilisation 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 are looking also for industrial pollution, but you will never find that in the documents advocating for those billion dollars instruments, and I ask myself, why would that be the case? Why would you sign this on purpose, not even mention that? And to me, that’s just inappropriate. And something has to be changed here. You know, the public gets it. But science got to a point where it’s more about groupthink. It’s more about the number of likes you get on Twitter.

It’s more about getting one person awards and avoiding risks in the context of theoretical physics, not putting skin in the game, not asking the right questions necessarily that the public cares about, but more the questions that will make you appear smart, you know, whether it’s a rock or artificial doesn’t require sophisticated maths. Right. But whether we are living in four dimensions or 10 dimensions does require sophistication. So what the community prefers to do as part of the mainstream activity is do the sophisticated gymnastics of, you know, 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, as the philosophers did, that they don’t want to look through his telescope because they know the answer, 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, just say, oh, I don’t want to discuss it. You know, you just maintain your ignorance. And it’s unfortunate because, you know, our civilisation, 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 block.

JG So say you’ve got control of all of the world, at least a substantial, substantial budget for projects, 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?

AL 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, crossings close to one one of the cameras and take photographs of those and look for the plastic bottles amongst 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 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. Don’t need to go large distance. You don’t need to be a huge facility to detect something that is very faint. You just put, you know, the detectors in your backyard and look for objects that there are from the street, you know.

And instead of going to the street, you know, they save you the time because it takes even for ‘Oumuamua, it took more than 10,000 years to cross the Solar System all the way from the edge of the Earth. And that’s a long time. And instead of us spending the time travelling 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 window into extraterrestrial intelligence that was never explored before. And that’s why I’m excited about us opening our eyes, you know, calling our attention to opportunities. And of course, if one of these objects does look really intriguing and we land on it, you can learn a hell of a lot of things about the technology that was developed to produce that object and what it means. What was the intention of the object in the first place? Maybe we can see a site like a stamp stating where it was produced, like USA on some of the spacecraft that made it to the Moon, or there would be something maybe written on it or some information we can you can find it. 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 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, the detector 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.

So, of course, as you put a lot of cities, you can see them at 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. And, 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. And so there are different aspects of technological signatures because one can look for including, as I said before, the industrial pollution. And then I would go for that as my second priority. And finally, you know, there should be other civilisations 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 lights. And 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.

JG Yeah, that’s brilliant, but just sort of go back something I was going to ask you. So obviously our own interstellar project, Voyager, if you were to see it close up, it’s very clearly not a naturally occurring object. So why is it that we have this confusion about ‘Oumuamua. Is it just the pure fact that we couldn’t get any decent enough picture of it?

AL 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. Right. 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 reflections of the surface. But I think a picture is really the best tool for us to learn about what is what it looks like. And of course, you can do a lot of other things with our best telescopes in terms of, you know, studying the object as it moves and exactly figuring out what kind of force is pushing 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.

JG So just go back to your great analogy, your plastic bottle washed up on the beach and say, how many of these do you think that could be out there? You know what are our chances to say, you know, best case scenario is set up with all of these detectors? Well, how good do you think our odds are?

AL Oh, well, if ‘Oumuamua was a member of the population of objects that were on random trajectories, in other words, they were not targeting the central region of the Solar System, but just moving around and the Sun bumped 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 them. 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, that we want to do the archaeology.

And by the way, even if it’s natural in origin, ‘Oumuamua, the suggestions made were that it was something that we had never seen before. So we will learn something new no matter what. And even if it’s natural, we 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.


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