We are not alone. Credit: Joe McNally/Getty Images

March 27, 2023   9 mins

A year of spy balloons and UFOs in North America has sparked renewed interest in the possibility of extraterrestrial life — and not just among conspiracy theorists. Some of the world’s leading cosmologists are convinced that alien technology has already reached planet Earth. Harvard Professor Avi Loeb has spent years tracking mysterious objects in our solar system, and believes they could be fragments of an extraterrestrial civilisation.

In an interview with Florence Read, he explains his theory of the objects’ origin, why they were sent here, and how we should interact with aliens if we find them.

Florence Read: When was the first unidentified interstellar object detected in our solar system?

Professor Avi Loeb: It was spotted in October 2017 by a telescope in Hawaii. It was given the name ‘Oumuamua, which means “the scout”. And at first, of course, everyone thought it was a rock from another star that just happened to pass by.

The more we learned about it, the more it looked weird. It was tumbling every eight hours and the amount of sunlight reflected from it changed by a factor of ten as it was tumbling. So that meant that it had a very extreme shape. The best fit for the variation of reflected sunlight was that of a flat object, pancake-like, which is quite unusual.

And then, this object didn’t show any cometary tail — there was no evaporation from it visible — yet it exhibited an excess push away from the sun, by some mysterious force. I suggested that since the force is not the rocket effect of evaporating gases, it could be being pushed by the reflection of sunlight. But for that to be the case, the object had to be very thin, sort of like a sail being pushed by light. And, of course, if it happens to be that way, then it could be artificial in origin.

Nature doesn’t make sails that are propelled by reflecting light. In fact, the same telescope in Hawaii discovered another object which exhibited the same qualities as ‘Oumuamua: it was pushed away from the sun by reflecting sunlight, and had no cometary tail. And within a few weeks, the astronomers realised it was actually a rocket booster that was launched in 1966 by NASA, as part of a lunar lander mission. It was made of stainless steel, so it didn’t evaporate. It had thin walls, and that’s why it was pushed away by reflecting sunlight. Here’s an example of an object we know is artificial, because we made it. The question is: who made ‘Oumuamua?


FR: And your answer was: potentially extraterrestrial life?

AL: It’s a possibility. We don’t have conclusive evidence. My book, Extraterrestrial, describes the anomalies of ‘Oumuamua. But it didn’t come close enough to Earth for our telescopes and even radars to resolve it. We don’t know what, exactly, it looks like.

About a year and a half ago, I established the Galileo Project. One of the goals is to design a space mission that will come close to the next ‘Oumuamua. We have a “dating app” — the Vera Rubin Observatory in Chile — that will start operations within a year. It has a camera of 3.2 billion pixels, 1,000 times as many pixels than you have in your cell phone. It will survey the southern sky every four days, and has a good chance of finding more objects like ‘Oumuamua. We can review them, and swipe most of them to the left on this “dating app” — but if we decide that one of them looks like ‘Oumuamua, we might come close to it and take a close-up photograph. And if we see that it’s a rock, so be it — but it could also show some bolts and screws on its surface, and even a label, made on an exoplanet.

I should say that almost four years before ‘Oumuamua was discovered, the very first interstellar object was discovered, in the form of a meteor. ‘Oumuamua was the size of a football field, but in 2014 an object roughly half a metre in size exploded in the lower atmosphere of the Earth. The US Space Command confirmed that this object is interstellar. The data indicates that this object survived all the way down to the lower atmosphere of the Earth, where it was subjected to very extreme stress — it was tougher than iron meteorites. In fact, it’s 10 times tougher than all meteors ever identified in the same catalogue.

So the question is: was it from some unusual source very different from the solar system? Or was it artificial in origin? Maybe it was made of stainless steel, and was a spacecraft from another civilisation. We’re going to find out the composition — we are going to the Pacific Ocean this summer to look for the fragments leftover from this meteor. By collecting them from the ocean floor, we hope to figure out their composition and tell whether they were just a rock or part of a spacecraft.

FR: If it’s artificial, where might it come from?

AL: Freeman Dyson — a British-born scientist, very well-known about 60 years ago — suggested that a very advanced scientific civilisation would not just rely on the amount of energy coming from its star to the surface of its planet, but would surround the star with a megastructure that would harvest the energy of the star. It is called the “Dyson sphere”: it’s a huge engineering project to imagine. It could be made of tiles that are hovering above the star, just like very thin sails. But there would be very high stresses on the construction, and therefore it would be made of very tough material. Once the civilisation loses interest in the Dyson sphere, it might not maintain it, and then asteroids would hit it quite frequently and could destroy it within a billion years. So the pieces of a broken Dyson Sphere could float in interstellar space and they could account for the materials that we found in the interstellar meteor.

FR: But your theory about ‘Oumuamua is different — in your report you argue: “An artificial interstellar object could potentially be a parent craft that releases many small probes during its close passage to Earth.”

AL: A very good approach, to probe a large region of space, is to release many small probes — like a dandelion seeding its environment. If you have a probe visiting the habitable zone of a star like the Sun, the probe itself might be too big and move too fast to land on a particular planet. If you want to probe a lot of regions and a lot of planets, you might just spread dandelion seeds. In fact, just this year, we founded a new space corporation with my colleague, Dr Frank Laukien, that aims to use this approach for the Moon and Mars, instead of the traditional approach of using just one big probe and visiting one location.

FR: How do they propel themselves?

AL: It depends on the nature of the engine. The only type of engine that we employ so far for interstellar probes are chemical rockets that can push a probe up to about a thousandth of the speed of light. But there could be much better schemes. For example, a very distinguished British cosmologist named Hermann Bondi wrote a paper in 1957, suggesting that if you have a negative mass — we are used to positive masses, but a negative mass in principle is possible to construct — then the negative mass will push away, if you put the positive mass next to it. And the positive mass will pull the negative mass with it. So together, they would accelerate indefinitely up to the speed of light. That is a type of engine that we have never constructed, and could potentially be engineered, if we developed the physics behind it.

FR: So should we assume that an alien species could have far more sophisticated technology than we do?

AL: Yes, and the way I think of it, it’s just like going on a date. You can learn from the other person. We should look at it as an opportunity; we shouldn’t be fearful of it. We are probably not sophisticated enough to be a threat to whatever comes to visit us. But we can make money from it — if we learn how to replicate [the technology] here on Earth. We can get a leap into our future.

As for what they might be hoping to accomplish — if you stay on your planet, then you might be annihilated or destroyed by a single-point catastrophe — we will not know until we observe them. I don’t think it makes sense to establish a committee of experts, and decide what the protocol is for responding to visitors. We should just try and figure out what they’re seeking. I spoke to Henry Kissinger just last year, and I asked him — because he negotiated with other nations, where the culture is very different — what is the realpolitik of interstellar communication? And he said that first you want to learn what the other side is seeking, and only then develop a dialogue with them.

FR: Is there any evidence from observatories or telescopes that these probes are actually entering our solar system?

AL: The Government collects data as a result of national security concerns and the sensors the government is using are classified. If there is high-quality data, it’s not being released to the public. But an extraterrestrial technological object has nothing to do with national security. It doesn’t adhere to national borders, and therefore any knowledge about it should be shared by all humans. It shouldn’t be the privilege of the President of the United States. We know that we are not at the centre of the universe; we know that there are billions of other Earth-Sun systems in the Milky Way galaxy alone. We are not at the centre of the stage, and we just came to the cosmic play at the end ,over the past few million years. The play is not about us.

FR: Tell me what it’s like being an expert in aliens. It must be quite an odd field to choose as your specialism.

AL: The way to think of me is as a farm boy. I’m connected to nature more than people. I have no social media. I don’t care how many likes I get. I’m just trying to do what sounds like common sense — something today which is not that common (especially in academia). There are many of my colleagues working on extra dimensions of the multiverse who do fancy mathematics — and it’s their way of showing off that they are smart. But if there is an object from another civilisation that could change the future of humanity, it may not take fancy maths to realise that it’s not a rock. When there is data about something unusual, we’re supposed to be curious. There is uncertainty. You can be wrong. That’s part of the job description.

FR: What if you are a young junior professor, at a university like Harvard, when stepping outside the bounds of what’s considered acceptable science is too risky?

AL: If you look at the career of Pablo Picasso, you will find that early on, he was a realist. He tried to draw in the style of traditional painting. After he mastered that, he invented cubism, which was disruptive. So as a young scientist, you don’t want to disrupt the system. You want to learn first of all the basic principles of physics, and apply them along the themes that are defined by senior people in academia, so that you can get a postdoc position after your PhD. Eventually you’re promoted to tenure.

But what happens after people get tenure is they are even more obsessed with their ego. They want to get honours, awards — to be recognised by their peers — and they conform to the beaten path. I say that the road not taken is the most interesting thing to take, because it may have low-hanging fruit. So I advise young scholars: if you’re interested in innovation, once you get tenure, start to be creative: innovate, because that’s the whole purpose of academia. Betray the slogan of the Party in George Orwell’s 1984, “ignorance is strength”. That’s what academia should be about.

But unfortunately, it’s not. I heard, a few days ago, a very distinguished scientist, who said: “I don’t really want to know whether Covid-19 came from a lab leak, or the wet market in Wuhan.” Why would he say that? Because he doesn’t want the image of science to be tarnished, if it came from a lab leak. This is similar to arguing that “ignorance is strength”. Knowledge is strength, and the same is true about the nature of unidentified aerial phenomena, the nature of dark matter. Everything should be driven by our ambition to be knowledgeable, because then we can adapt even if reality doesn’t look as pretty as it should be. Let us see it.

FR: There is a genuine cohort of your colleagues who would say that there is 0% probability that aliens do exist. What do you think the probability is of life beyond Earth?

AL: Galileo was placed under house arrest just for suggesting that maybe the Earth moves around the Sun, and today he would have been cancelled on social media. If you were to ask those theologians, they would say there is zero probability that the Earth is not at the centre of the universe. Now, why would they say that? Because the church wanted to control people. There are always ulterior motives. I bet you that if we find a piece of technological equipment from another civilisation, people will say: “Of course, this was talked about for decades. There is nothing really new — we knew it all along.”

But if I had to guess, I would say not only that we are not alone, but that there were many technological civilisations before us that reached greater heights. We are probably not even close to the top half of their advances. They would have technologies that look like magic to us — like miracles in religious texts. It’s possible that that civilisation could create life in its laboratories. It would bring the concept of God, or something very capable, into reality — it will unify science and religion in some sense. I think it’s very likely that they were out there billions of years ago, maybe not right now. But they existed, and the only question is, when will we find the conclusive evidence beyond any doubt? And for that, we need to search. If there are objects of technological origin, we will find them.


This transcript has been lightly edited.

Flo Read is UnHerd‘s producer and a presenter for UnHerd TV.