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Speaker 1

00:00

The following is a conversation with Avi Loeb, an astrophysicist, astronomer, and cosmologist at Harvard. He has authored over 800 papers and written 8 books, including his latest called Extraterrestrial, the First Sign of intelligent life beyond Earth. It'll be released in a couple of weeks, so go pre-order it now to show support for what I think is truly an important book in that it serves as a strong example of a scientist being both rigorous and open-minded about the question of intelligent alien civilizations in our universe. Quick mention of our sponsors.

Speaker 1

00:36

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Speaker 1

01:02

As a side note, let me say a bit more about why Avi's work is so exciting to me and I think to a lot of people. In 2017, a strange interstellar object now named Amuamua, it's fun to say, was detected traveling through our solar system. Based on the evidence we have, it has strange characteristics which made it not like any asteroid or comet that we've seen before. Avi was 1 of the only world-class scientists who fearlessly suggested that we should be open-minded about whether it is naturally made, or in fact is an artifact of an intelligent alien civilization.

Speaker 1

01:39

In fact, he suggested that the more likely explanation, given the evidence, is the latter hypothesis. We also talk about a lot of fascinating mysteries in our universe, including black holes, dark matter, the Big Bang, and close to speed of light space travel. The theme throughout is that in scientific pursuits, the weird things, the anomalies, the ideas that right now are considered taboo should not be ignored if we're to have a chance at finding the next big breakthrough, the next big paradigm shift, and also if we are to inspire the world with the power and beauty of science. If you enjoy this thing, subscribe on YouTube, review on Apple Podcasts, follow on Spotify, support on Patreon, or connect with me on Twitter at Lex Friedman.

Speaker 1

02:26

And now, here's my conversation with Avi Loeb. In the introduction to your new book, Extraterrestrial, you write, this book confronts 1 of the universe's most profound questions, are we alone? Over time, this question has been framed in different ways. Is life here on Earth the only life in the universe?

Speaker 1

02:47

Are humans the only sentient intelligence in the vastness of space and time? A better, more precise framing of this question would be this. Throughout the expanse of space and over the lifetime of the universe, are there now or have ever been other sentient civilizations that, like ours, explored the stars and left evidence of their efforts? So let me ask, are we alone?

Speaker 2

03:13

That's an excellent question. For me, the answer is sort of clear because I start from the principle of modesty. If we believe that we are alone and special and unique, that shows arrogance.

Speaker 2

03:28

My daughters, when they were infants, they tended to think that they are special, unique, and then they went out to the street and realized that other kids are very much like them, and then they developed a sense of a better perspective about themselves. And I think the only reason that we are still thinking that we are special is because we haven't searched well enough to find others that might even be better than us. And I say that because I look at the newspaper every morning and I see that we do foolish things. We are not necessarily the most intelligent ones.

Speaker 2

04:02

And if you think about it, if you open a recipe book, you see that out of the same ingredients, you can make very different cakes, depending on how you put them together and how you heat them up. And what is the chance that by taking the soup of chemicals that existed on Earth and cooking it 1 way to get our life, that you got the best cake possible? I mean, we are probably not the sharpest cookie in the jar. And my question is, I mean, it's pretty obvious to me that we are probably not alone because half of all the sun-like stars we know now as astronomers, half of the sun-like stars from the Kepler satellite data have a planet the size of the Earth, roughly at the same distance that the Earth is from the sun.

Speaker 2

04:51

And that means that they can have liquid water on their surface and the chemistry of life as we know it. So if you roll the dice billions of times, just within the Milky Way galaxy, and then you have tens of billions of galaxies like it within the observable volume of the universe, it would be extremely arrogant to think that we are special. I would think that we are sort of middle of the road, typical forms of life, and that's why nobody pays attention to us. If you go down the street on a sidewalk and you see an ant, you don't pay attention or a special respect to that ant, you just continue to walk.

Speaker 2

05:28

And so I think that we are sort of average, not very interesting, not exciting, so nobody cares about us. We tend to think that we are special, but that's a sign of immaturity.

Speaker 1

05:38

And we're very early on in our development.

Speaker 2

05:40

Yes, that's another thing, that we have our technology only for 100 years, and it's evolving exponentially right now on a three-year timescale. So imagine what would happen in 100 years, in 1,000 years, in a million years, or in a billion years. Now, the sun is actually relatively late in the star formation history of the universe.

Speaker 2

06:01

Most of the sun-like stars formed earlier. And some of them already died, became white dwarfs. And so if you imagine that a civilization like ours existed around a typical sun-like star, By now, if they survived, they could be a billion years old. And then imagine a billion-year technology.

Speaker 2

06:22

It would look like magic to us, an approximation to God. We wouldn't be able to understand it. And so, In my view, we should be humble. And by the way, we should probably just listen and not speak because there is a risk, right?

Speaker 2

06:39

If you are inferior, there is a risk. If you speak too loudly, something bad may happen to you.

Speaker 1

06:46

You mentioned we should be humble also in the sense with the analogy to ants, that they might be better than us. So there's a kind of scale that we're talking about and in the question, you mentioned the word sentient. So sentience, or maybe the more basic formulation of that is consciousness.

Speaker 1

07:11

Do you think that this thing within us humans in terms of the typical life form of consciousness is the essential element that permeates, if there's other alien civilizations out there that they have something like consciousness as well? Or is this, I guess I'm asking, can you try to untangle the word sentient?

Speaker 2

07:33

Yeah, so that's a good question. I think what is most abundant depending on how long it survives. So if you look at us as an example, we are now, We do have conscious and we do have technology, but the technologies that we are developing are also means for our own destruction, as we can tell.

Speaker 2

07:55

You know, we can change the climate if we are not careful enough. We can go into nuclear wars. So we are developing means for our own destruction through self-inflicted wounds. And it might well be that creatures like us are not long-lived, that the crocodiles on other planets live for billions of years.

Speaker 2

08:19

They don't destroy themselves, they live naturally. And so if you look around, the most common thing would be dumb animals that live for long times, not those that have conscious. But in terms of changing the environment, I think since, I mean, humans develop tools, they develop the ability to construct technologies that would lift us from this planet that we were born in, and that's something animals without a consciousness cannot really do. And so I, you know, in terms of looking for things that are, that went beyond the circumstances they were born into.

Speaker 2

09:03

I would think that even if they're short-lived, these are the creatures that made the biggest difference to their environment, and we can search for them. Even if they're short-lived, and most of the civilizations are dead by now. Even if that's the case.

Speaker 1

09:18

That's sad to think about, by the way.

Speaker 2

09:19

Well, but if you look on Earth, there are lots of cultures that existed throughout time and they're dead by now. The Mayan culture was very sophisticated, died, but We can find evidence for it and learn about it just by archeology, digging into the ground, looking. And so we can do the same thing in space.

Speaker 2

09:38

Look for dead civilizations, and perhaps we can learn a lesson why they died and behave better so that we will not share the same fate. So I think there is a lesson to be learned from the sky. And by the way, I should also say, if we find a technology that we have not dreamed of, that we can import to Earth, That may be a better strategy for making a fortune than going to Silicon Valley or going to Wall Street. Because you make a jump start into something of the future.

Speaker 1

10:12

So that's 1 way to do the leap is actually to find, to literally discover versus come up with the idea in our own limited human capacity, like a cognitive capacity.

Speaker 2

10:23

It would look, it would feel like cheating in an exam where you look over the shoulder of a student next to

Speaker 1

10:28

you.

Speaker 2

10:29

But It's not good

Speaker 1

10:30

on an exam, but it is good when you're coming up with technology that could change the fabric of human civilization. But there is, in my neck of the woods of artificial intelligence, there's a lot of trajectories 1 can imagine of creating very powerful beings, the technology that's essentially, you can call superintelligence, that could achieve space exploration, all those kinds of things, without consciousness. Without something that to us humans looks like consciousness.

Speaker 1

11:06

And there is a sad feeling I have that consciousness too, in terms of us being humble, is a thing we humans take too seriously. That we think it's special just because we have it. But it could be a thing that's actually holding us back in some kind of way.

Speaker 2

11:22

It may well be, it may well be. I should say something about AI, because I do think it offers a very important step into the future. If you look at the Old Testament, the Bible, there is this story about Noah's Ark that you might know about.

Speaker 2

11:40

Noah knew about a great flood that is about to endanger all life on earth. So he decided to build an ark. And the Bible actually talks about specifically what the size of this ark was, what the dimensions were. Turns out it was quite similar to Umuamua that we will discuss in a few minutes.

Speaker 2

12:01

But at any event, he built this ark and he put animals on it so that they were saved from the great flood. Now, you can think about doing the same on Earth because there are risks for future catastrophes. We could have the self-inflicted wounds that we were talking about, like nuclear war, changing the climate, or there could be an asteroid impacting us, just like the dinosaurs died. The dinosaurs didn't have science, astronomy, they couldn't have a warning system, but there was this big stone, big rock that approached them.

Speaker 2

12:36

It must have been a beautiful sight. Just when it was approaching, it got very big and then smashed them, okay, and killed them. So, you could have a catastrophe like that, or in a billion years, the sun will basically boil off all the oceans on earth. Currently, all our eggs are in 1 basket, but we can spread them.

Speaker 2

12:57

It's sort of like the printing press, if you think about it. The revolution that Gutenberg brought is there were very few copies of the Bible at the time, and each of them was precious because it was handwritten. But once the printing press produced multiple copies, you know, if something bad happened to 1 of the copies, it wasn't a catastrophe. You know, It wasn't a disaster because you had many more copies.

Speaker 2

13:20

If we have copies of life here on Earth elsewhere, then we avoid the risk of it being eliminated by a single-point breakdown, a catastrophe. So the question is, can we build NOAAX spaceship that will carry life as we know it? Now, you might think we have to put elephants and whales and birds on a big spaceship, but that's not true because all you need to know is the DNA making, the genetic making of these animals, put it on a computer system that has AI plus a 3D printer, so that this CubeSat, which is rather small, can go with this information to another planet and use the raw materials there to produce synthetic life. And that would be a way of producing copies, just like the Gutenberg printing press.

Speaker 1

14:16

Yeah, and it doesn't have to be exact copies of the humans. It could just contain some basic elements of life and then have enough life on board that it could reproduce the process of evolution on another place.

Speaker 2

14:30

Right.

Speaker 1

14:31

So I mean, that also makes you sad, of course, because you confront the mortality of your own little precious consciousness and all your own memories and knowledge and all that stuff.

Speaker 2

14:39

But who cares? I mean, we are not

Speaker 1

14:42

so significant. I care about mine, right, and you care about yours.

Speaker 2

14:44

No, no, I actually don't. You know, if you look at the bigs, if you're an astronomer, 1 thing that you learn from the universe is to be modest, because you're not so significant. I mean, think about it, all these emperors and kings that conquered a piece of land on earth, and were extremely proud, you know, You see these images of kings and emperors that usually are alpha males, and they stand strong, and they're very proud of themselves.

Speaker 2

15:12

But if you think about it, there are 10 to the power 20 planets like the Earth in the observable volume of the universe. And this view of conquering a piece of land, and even conquering all of Earth, is just like an ant hugging a single grain of sand on the landscape of a huge beach. That's not very impressive. So you can't be arrogant.

Speaker 2

15:34

If you see the big picture, you have to be humble. You know, also we are short-lived, you know, within a hundred years, that's it, right? So what does it teach you? First, to be humble, modest.

Speaker 2

15:47

You never have significant powers relative to the big scheme of things. And second, you should appreciate every day that you live. And learn about the world.

Speaker 1

15:56

Humble and still grateful.

Speaker 2

16:00

Yes, exactly.

Speaker 1

16:01

Well, let's talk about probably the most interesting object I've heard about and also the most fun to pronounce.

Speaker 2

16:10

Oumuamua, yes. Oumuamua. Can you tell me the story of this object and why it may be an important event in human history and is it possibly a piece of alien technology?

Speaker 2

16:23

Right, so this is the first object that was spotted close to Earth from outside the solar system And it was found on October 19th,

Speaker 1

16:36

2017.

Speaker 2

16:37

And at that time, it was receding away from us. And at first, astronomers thought it must be a piece of rock, you know, just like all the asteroids and comets that we have seen from within the solar system. And it just came from another star.

Speaker 2

16:52

I should say that the actual discovery of this object was surprising to me because a decade earlier, I wrote the first paper together with Ed Turner and Amaya Moro-Martin that tried to predict whether the same telescope that was surveying the sky, Pan-STARRS, from Hawaii, would find anything from interstellar space, given what we know about the solar system. So if you assume that other planetary systems have similar abundance of rocks and you just calculate how many should be ejected into interstellar space, the conclusion is no, we shouldn't find anything with pan-stars.

Speaker 1

17:30

To me, I apologize, probably revealing my stupidity, but it was surprising to me that so few interstellar objects from outside this whole system have ever been detected.

Speaker 2

17:40

Or none. None has been.

Speaker 1

17:42

You do, well, maybe talk about it, that there has been 1 or 2 rocks since then?

Speaker 2

17:48

Well, since then there was 1 called the Borisov. It was discovered by an amateur Russian astronomer, Gennady Borisov, and that 1 looked like a comet. And just like a comet from within the solar system.

Speaker 1

18:05

But this is a really important point, and sorry to interrupt it. You showed that it's unlikely that a rock from another solar system would arrive to ours.

Speaker 2

18:14

Right, and So the actual detection of this 1 was surprising by itself, to me. Yes. So at first they thought maybe it's a comet or an asteroid, but then it didn't look like anything we've seen before.

Speaker 2

18:29

Borisov did look like a comet. So people asked me afterwards and said, you know, doesn't it convince you if Borisov looks like a comet, doesn't it convince you that Oumuamua is also natural? And I said, you know, when I went on the first date with my wife, she looked special to me. And since then I met many women, that didn't change my opinion of my wife.

Speaker 2

18:53

So, you know, that's not an argument. Anyway, so why did Oumuamua look weird? Let me explain. So first of all, astronomers monitored the amount of sunlight that it reflects.

Speaker 2

19:08

And it was tumbling, spinning every 8 hours. And as it was spinning, the brightness that we saw from that direction, We couldn't resolve it because it's tiny. It's about a few hundred feet, the size of a football field. We cannot, from Earth, with existing telescopes, resolve it.

Speaker 2

19:28

The only way to actually get a photograph of it is to send a camera close to it. And that was not possible at the time that Oumuamua was discovered because it was already moving away from us faster than any rocket we can send. It's sort of like a guest that appeared for dinner. And then by the time we realize that it's weird, the guest is already out the front door into the dark street.

Speaker 2

19:53

What we would like to find is an object like it approaching us, because then you can send the camera irrespective of how fast it moves. And if we were to find it in July 2017, that would have been possible because it was approaching us at that time. Actually, I was visiting Mount Haleakala in Maui, Hawaii, with my family for vacation at that time, in July 2017, but nobody knew at the observatory that the Ummu Ammua is very close.

Speaker 1

20:25

That's sad to think about that we had the opportunity at that time to send up a camera.

Speaker 2

20:29

But don't worry, I mean, there will be more. There will be more because I operate by the Copernican principle, which says we don't live at a special place and we don't live at a special time. That means if we surveyed the sky for a few years and we had sensitivity to this region between us and the sun, and we found this object with pan-stars, there should be many more that we will find in the future with surveys that might be even better.

Speaker 2

21:01

Actually, in 3 years' timescale, there would be the so-called LSST, that's a survey of the Vera Rubin Observatory, that would be much more sensitive and could potentially find an Oumuamua-like object every month. Okay, So I'm just waiting for that. And the main reason for me to alert everyone to the unusual properties of Umu Umu'a is with the hope that next time around when we see something as unusual, we would take a photograph or we would get as much evidence as possible because science is based on evidence, not on prejudice. And we will get back to that theme.

Speaker 2

21:38

So anyway, let me point out what is-

Speaker 1

21:39

Some of the properties actually. Yeah, the elongated nature, all of those kinds of things.

Speaker 2

21:44

So the light curve, the amount of light, sunlight that was reflected from it was changing over 8 hours by a factor of 10, meaning that the area of this object, even though we can't resolve it, the area on the sky that reflects sunlight was bigger by a factor of

Speaker 1

22:03

10

Speaker 2

22:05

in some phases as it was tumbling around than in other phases. So even if you take a piece of paper that is razor thin, there is a very small likelihood that it's exactly edge on. And getting a factor of 10 change in the area that you see on the sky is huge.

Speaker 2

22:22

It's much more than any, it means that the object has an unusual geometry. It's at least a factor of a few more than any of the comets or asteroids that we have seen before.

Speaker 1

22:32

You mentioned reflectivity, so it's not just the geometry, but the properties of the surface of that thing. Well, if you assume the reflectivity is the same,

Speaker 2

22:43

then it's just geometry. If you assume the reflectivity may change, then it could be a combination of the area that you see and the reflectivity, because different directions may reflect differently. But the point is that it's very extreme.

Speaker 2

22:59

And actually the best fit to the light curve that we saw was of a flat object, unlike all the cartoons that you have seen of a cigar shape. A flat object at the 90% confidence gives a better model for the way that the light varied. And it's also- So

Speaker 1

23:17

like flat, meaning like a pancake.

Speaker 2

23:18

Like a pancake, exactly. And so that's the very first unusual property, but to me it was not unusual enough to think that it might be artificial. It was not significant enough.

Speaker 2

23:32

Then there was no cometary tail, you know, no dust, no gas around this object. And the Spitzer Space Telescope really searched very deeply for carbon-based molecules. There was nothing. So it's definitely not a comet, the way people expected it to be.

Speaker 2

23:50

Can you maybe briefly mention what properties a comet that you're referring to usually has? Right, so a comet is a rock that has some water ice on the surface. So you can think of it as an icy rock. Actually, comets were discovered a long time ago, but the first model that was developed for them was by Fred Whipple, who was at Harvard.

Speaker 2

24:17

And I think the legend goes that he got the idea from walking through Harvard Square and seeing, during a winter day, and seeing these icy rocks, you know? So a

Speaker 1

24:28

comet is icy, and an Asteroid is not. It's just a rock.

Speaker 2

24:32

It's just a rock. Yeah, so when you have ice on the surface, when the rock gets close to the sun, the sunlight warms it up. And the ice sublimates, evaporates.

Speaker 2

24:44

Because The 1 thing about ice, water ice, is it doesn't become liquid if you warm it up in vacuum, you know, without an external pressure. It just goes straight into gas. And that's what you see as the tail of a comet. The only way to get liquid water is to have an atmosphere like on Earth that has an external pressure.

Speaker 2

25:08

Only then you get liquid. And that's why it's essential to have an atmosphere to a planet in order to have liquid water and the chemistry of life. So if you look at Mars, Mars lost its atmosphere and therefore no liquid water on the surface anymore. I mean, there may have been early and that's what the Perseverance survey, the Perseverance mission will try to find out whether it had liquid water, whether there was life perhaps on it at the time.

Speaker 2

25:36

But at some point, it lost its atmosphere, and then the liquid water was gone. So the only reason that we can live on Earth is because of the atmosphere. But a comet is in vacuum, pretty much, and when it gets warmed up on the surface, the water becomes, the water ice becomes gas, and then you see this cometary tail behind it. In addition to water, there are all kinds of carbon-based molecules or dust that comes off the surface.

Speaker 1

26:07

And those are detectable.

Speaker 2

26:09

Yeah, it's easy to detect. It's very prominent. You see these cometary tails that look very prominent because they reflect sunlight and you can see them.

Speaker 2

26:17

In fact, it's sometimes difficult to see the nucleus of the comet because it's surrounded and shrouded with, and in this case, there was no trace of anything. Now, you might say, okay, it's not a comet. So that's what the community said. Okay, it's not a, no problem, it's still a rock.

Speaker 2

26:32

You know, it's not a comet, but it's just a rock, bare rock, you know, okay, no problem. Then, and that's the thing that convinced me to write about it, and then in June

Speaker 1

26:43

2018,

Speaker 2

26:44

you know, significantly later, there was a report that in fact the object exhibited an excess push in addition to the force of gravity. So the sun acts on it by gravity, but then there was an extra push on this object that was figured out from the orbit that you can trace. And the question was, what is this excess push?

Speaker 2

27:08

So for comets, you get the rocket effect when you evaporate gas, you know, just like a jet engine on an airplane. A jet engine is very simple. You throw the gas back and it pushes the airplane forward. That's all, that's how a jet.

Speaker 2

27:22

So in a case of a comet, you throw gas in the direction of the sun, and then you get a push. So in the case of comets, you can get a push, but there was no cometary tail. So then people say, oh, wait a second, is it an asteroid? No, but it behaves like a comet, but it doesn't look like a comet.

Speaker 2

27:41

So what, well, forget about it, business as usual.

Speaker 1

27:44

So That's what they mean by non-gravitational acceleration. So that's interesting. So the primary force acting on something like just a rock, like an asteroid, would be, like you can predict the trajectory based on gravity.

Speaker 1

28:00

And so here there's detected movement that cannot be accounted purely by the gravity

Speaker 2

28:04

of the sun. And if it was a comet, you would need about a 10th of the mass of this comet, the weight of this comet, to be evaporated in order to give it. And there was No sign of that.

Speaker 2

28:15

No sign, 10% of the mass evaporating, it's huge. Think about it, a hundred meter size object losing 10% of its mass. You can't miss that. And the- So that's super weird.

Speaker 2

28:27

It's super weird.

Speaker 1

28:28

Is there a good, is there

Speaker 2

28:30

in your

Speaker 1

28:30

mind a possible explanation for this?

Speaker 2

28:31

You know, so I operated just like Sherlock Holmes in a way. I said, okay, what are the possibilities? And the only thing I could think, so I ruled out everything else, and I said it must be the sunlight reflected off it, okay?

Speaker 2

28:45

So the sunlight reflects off the surface and gives it a push, just like you get a push on a sail on a boat, you know, from the wind reflecting off it. Now, in order for this to be effective, it turns out the object needs to be extremely thin. It turns out it needs to be less than a millimeter thick. Nature does not produce such things.

Speaker 2

29:09

So, but we produce it because it's called the technology of a light sail. So we are, for space exploration, we are exploring this technology because it has the benefit of not needing to carry the fuel with the spacecraft. So you don't have the fuel, you just have a sail, and it's being pushed either by sunlight or by a laser beam or whatever. So perhaps this is a light sail.

Speaker 1

29:38

So this is actually the same technology with the Starshot project. Yes. So

Speaker 2

29:44

people afterwards say, okay, you work on this project, you imagine things. You know, obviously my imagination is limited by what I know. So I would not deny that working on light sails expanded my ability to imagine this possibility.

Speaker 2

30:01

But let me offer another interesting anecdote. In September this year, 2020, I mean,

Speaker 1

30:08

2020,

Speaker 2

30:10

there was another object found and it was given the name 2020SO by the Minor Planet Center. This is an organization actually in Cambridge, Massachusetts that gives names to objects, astronomical objects found in the solar system. And they gave it that name 2020SO because it looked like an object in the solar system and it moved in an orbit that is similar to the orbit of the Earth, but not the same exactly.

Speaker 2

30:42

And therefore it was bound to the sun, but it also exhibited a deviation from what you expect based on gravity. So astronomers that found it extrapolated back in time and found that in

Speaker 1

30:56

1966,

Speaker 2

30:57

it intercepted the Earth. And then they realized, they went to the history books and they realized, oh, there was a mission called Lunar Surveyor, Lunar Lander, Surveyor 2, that had a rocket booster. It was a failed mission, but there was a rocket booster that was kicked into space.

Speaker 2

31:17

And presumably this is the rocket booster that we are seeing. Now, this rocket booster was sufficiently hollow and thin for us to recognize that it's pushed by sunlight. So here is my point. We can tell from the orbit of an object, obviously this object didn't have any cometary tail.

Speaker 2

31:34

It was artificially made. We know that it was made by us. And it did deviate from an orbit of a rock. So just by seeing something that doesn't have cometary tail and deviates from an orbit shaped by gravity.

Speaker 2

31:50

We can tell that it's artificial. In the case of Oumuamua, it couldn't have been sent by humans because it just passed near us for a few months. We know exactly what we were doing at that time. And also it was moving faster than any object that we can launch.

Speaker 2

32:05

And so obviously it came from outside the solar system. And the question is, who produced it? Now, I should say that when I walk on vacation on the beach, I often see natural objects like seashells that are beautiful and I look at them and every now and then I stumble on a plastic bottle and that was artificially produced. And my point is that maybe Oumuamua was a message in a bottle.

Speaker 2

32:34

And we should, this is simply another window into searching for artifacts from other civilizations.

Speaker 1

32:42

Where do you think it could have come from? And if it's, so, okay. From a scientific perspective, the narrow-minded view, as we'll probably talk about throughout, is you kind of want to stick to the things that are naturally originating objects like asteroids and comets.

Speaker 1

33:05

Okay, that's the space of possible hypotheses. And then if we expand beyond that, you start to think, okay, these are artificially constructed, and like you just said, it could be by humans. It could be by whatever that means, by some kind of extraterrestrial alien civilizations. If it's the alien civilization variety, what is this object then that we're looking at?

Speaker 2

33:31

An excellent question. And let me lay out, I mean, we don't have enough evidence to tell. If we had a photograph, perhaps we would have more information.

Speaker 2

33:40

But there is 1 other peculiar fact about Oumuamua. Well, other than it was very shiny, that I didn't mention, we didn't detect any heat from it, and that implies that it's rather small and shiny. But the other peculiar fact is that it came from a very special frame of reference. So it's sort of like finding a car in a parking lot, in a public parking lot, that you can't really tell where it came from.

Speaker 2

34:11

So there is this frame of reference where you average over the motions of all the stars in the neighborhood of the sun. So you find the so-called local standard of rest of the galaxy, and that's a frame of reference that is obtained by averaging the random motions of all the stars, and the sun is moving relative to that frame at some speed. But this object was at rest in that frame, and only 1 in 500 stars is so much at rest in that frame. And that's why I was saying it's like a parking lot.

Speaker 2

34:45

It was parked there, and we bumped into it. So the relative speed between the solar system and this object is just because we are moving. It was sitting still. Now you ask yourself, why is it so unusual in that context?

Speaker 1

35:00

You

Speaker 2

35:00

know why? Because if it was expelled from another planetary system, most likely it will carry the speed of the host star that it came from. Because the most loosely bound objects are in the periphery of the planetary system, and they move very slowly relative to the star, and so they carry the, when they are ripped apart from the planetary system, most of the objects will have the residual motion of the star, roughly, relative to the local star.

Speaker 2

35:29

But This 1 was at rest in the locus. Now, 1 thing I can think of, if there is a grid of road posts, you know, like for navigation system, so that you can find your way in the local frame, then that would be 1 possibility.

Speaker 1

35:45

These are like little sensors of, that's fascinating to think about. So there could be, I mean, not necessarily, literally a grid, but just evenly, in some definition of evenly spread out set of objects like these that are just out there.

Speaker 2

35:59

A lot of them. Another possibility is that these are relay stations for communication. You might think in order to communicate, you need a huge beacon, a very powerful beacon, but it's not true.

Speaker 2

36:12

Even on Earth, we have these relay stations, so you have a not-so-powerful beacon, so it can be heard only out to a limited distance. But then you relay the message, and it could be 1 of those. Now, after it collided with the solar system, of course, it got a kick. So it's just like a billiard ball.

Speaker 2

36:31

We gave it a kick by colliding with, but most of them are not colliding with stars. So that's 1 possibility, okay? And there should be lots of them if that's the case. The other possibility is that it's a probe that was sent in the direction of the habitable region around the sun to find out if there is life.

Speaker 2

36:56

Now, it takes tens of thousands of years for such a probe to traverse the solar system from the outer edge of the Oort cloud all the way to where we are. And it's a long journey. So when it started the journey from the edge of the solar system to get to us now, we were rather primitive back then. We still didn't have any technology.

Speaker 2

37:15

There was no reason to visit. There was grass around and so forth. But maybe it is a problem.

Speaker 1

37:22

So you said 10,000 years, that's fastest, so it takes that long.

Speaker 2

37:25

Tens of thousands, yes. Tens of thousands of years. Yeah, and The other thing I should say is, it could be just an outer layer of something else, like something that was ripped apart, like a surface of an instrument that was, and you can have lots of these pieces, if something breaks, lots of these pieces spread out, like space junk.

Speaker 2

37:49

And you know, that.

Speaker 1

37:51

It could be just space junk from an alien civilization.

Speaker 2

37:56

Yes.

Speaker 1

37:57

So it's kind of. I should

Speaker 2

37:59

tell you about space junk. Let me. Yes, what do you mean by space junk?

Speaker 2

38:04

So I think, you might ask, why aren't they looking for us? 1 possibility is that we are not interesting, like we were talking about. In the ants' hypothesis. Another possibility, if there are millions or billions of years into their technological development, they created their own habitat, their own cocoon, where they feel comfortable, they have everything they need, And it's risky for them to establish communication with other, so they have their own cocoon and they close off.

Speaker 2

38:38

They don't care about anything else. Now, in that case, you might say, oh, so how can we find about them if they are closed off? The answer is they still have to deposit trash, right? That is something from the law of thermodynamics.

Speaker 2

38:52

There must be some production of trash. And we can still find about them just like investigative journalists going through the trash cans of celebrities in Hollywood. You can learn about the private lives of those celebrities by looking at the trash. It's fascinating to think, if we are the ants in this picture, if this thing is a water bottle, or if it's like a smartphone,

Speaker 1

39:19

Like where on the spectrum of possible objects of space, because there's a lot of interesting trash. So like how interesting is this trash?

Speaker 2

39:28

But imagine a caveman seeing a cell phone. The caveman would think, since the caveman played with rocks all of his life, he would say, it's a rock. Just like my fellow astronomer said.

Speaker 2

39:40

Right?

Speaker 1

39:41

So that's- Yes, exactly. That's brilliantly put. Actually, as a scientist, do you hope it's

Speaker 2

39:44

a water bottle or a smartphone? Because- I hope it's even more than a smartphone. I hope that it's something that is really sophisticated.

Speaker 2

39:52

That's funny.

Speaker 1

39:53

See, I'm the opposite. I feel like I hope it's a water bottle because at least we have a hope with our current set of skills to understand it. A caveman has no way of understanding the smartphone.

Speaker 1

40:04

It's like, it will be, like, I feel like a caveman has more to learn from the plastic water bottle than they do from the smartphone.

Speaker 2

40:11

But suppose we figure it out, if we, for example, come close to it and learn what it's made of.

Speaker 1

40:17

And I guess a smartphone is full of like thousands of different technologies that we could probably pick at. Do you have a sense of where, a hypothesis of where is the cocoon that it

Speaker 2

40:32

might have come from? No, because, okay, so first of all, you know, the solar system, the outermost edge of the solar system is called the Oort cloud. It's a cloud of icy rocks of different sizes that were left over from the formation of the solar system.

Speaker 2

40:55

And it's thought to be roughly a ball or a sphere. And it's halfway, the extent of it is roughly halfway to the nearest star, okay? So you can imagine each planetary system basically touching the Oort clouds of those stars that are near us are touching each other. Space is full of these billiard balls that are very densely packed.

Speaker 2

41:24

And what that means is any object that you see, irrespective of whether it came from the local standard, So we said that this object is special because it came from a local standard of rest. But even if it didn't, you would never be able to trace where it came from because all these Oort clouds overlap. So if you take some direction in the sky, you will cross as many stars as you have in that direction. Like there is no way to tell which Oort cloud it came from.

Speaker 1

41:52