Harvard Astronomer On Why Aliens Aren't Science Fiction

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An artist's impression of ʻOumuamua, the first known interstellar object to pass through the solar system. (ESO/M. Kornmesser via Wikimedia Commons)
An artist's impression of ʻOumuamua, the first known interstellar object to pass through the solar system. (ESO/M. Kornmesser via Wikimedia Commons)

On a special edition of Endless Thread, host Ben Johnson (@TheBrockJohnson) talks to superstar astronomer Avi Loeb. They discuss mysteries surrounding the interstellar space object known as 'Oumuamua, why it could be a probe sent by an alien civilization, and how the scientific community should be more willing to acknowledge and embrace uncertainty.

This conversation is the second part of Endless Thread's (@Endless_Thread) coverage of 'Oumuamua and aliens. Check out the 'Oumuamua-inspired sci-fi radio drama "Stuck Between The Rock And Deep Space" for more.


  • Avi Loeb is the Frank B. Baird, Jr., Professor of Science at Harvard University and chair of Harvard's Department of Astronomy. He has published four books and over 650 papers on a wide range of topics, including black holes, the first stars, the search for extraterrestrial life and the future of the Universe. In 2012, TIME magazine selected him as one of the 25 most influential people in space. Visit his website for more info.

Interview Highlights

On The Mysteries Surrounding 'Oumumua

Avi: For one, when it spun around over a period of eight hours its brightness changed by a factor of 10. And that's much more than any object born in the solar system, such as asteroids or comets, that change by at most a factor of three or so. [Another weirdness is] the mere fact that it was discovered, [which] implies that the population of such objects is much more abundant than we anticipated. Unless of course it's on a very specialized orbit such that it's not a member of a population of random objects.

Ben: So the suggestion here is that there should be a ton of these and they should be somewhat observable, unless these objects are on a very special kind of predetermined mission.

Avi: Exactly.

"I don't see extraterrestrials as more speculative than dark matter or extra dimensions. I think it's the other way around."

Avi Loeb

On Criticism Received For Suggesting 'Oumuamua Could Be Alien Probe

Avi: To me, the entire discussion about 'Oumuamua is very similar to an imaginary scene where you see a cave person being shown an iPhone. And this cave person would look at it and think that it might be a rock. And then would show it to other members of his or her tribe and the people there would still say, "No, it's probably a rock and how dare you say something else, how dare you talk about something that is different than a rock because rocks are everything that we are familiar with." And so, to me, not even putting [aliens] on the table for discussion is a crime! Because if you look at the history of science, you know, Galileo Galilei argued that the Earth moves around the sun and he was put under house arrest for that. Now, this of course didn't change the facts. It doesn't matter what is being said on Twitter, what is being said in other social media or among scientists. This thing is what it is, right? And, you know, the Earth still moves around the sun irrespective of what the church said a while ago. And the fact that Galileo suffered for it has no relevance to nature.

On Uncertainty In Scientific Research

Avi: The most common phase in doing scientific research is dealing with uncertainty because we don't have enough evidence, enough data, to figure out the truth. And most of the time we are just conjecturing, assuming things and trying to figure out what is the truth. And it's similar to the work of a detective that comes to a crime scene and tries to figure out what's going on. And many of my colleagues say, "No, we should close ourselves in a room and communicate to the public only when we know the answer." I think that's actually the wrong approach because the populist movements that you see nowadays, they regard academia as the scientific elite, for example, because we come out with our results when they are finalized. [It's] sort of like lecturing to students in a classroom. I think we would get much more credibility if we were to show the process of uncertainty and the fact that scientists do not agree with each other when the evidence is not clear.

On Why Aliens Are More Than Science Fiction

Avi: I don't see extraterrestrials as more speculative than dark matter or extra dimensions. I think it's the other way around ... And the reason is that we exist and that we know that about a quarter of all the stars in the Milky Way galaxy have conditions similar to those on Earth.

Ben: This is essentially [the argument] that it's a mathematical impossibility for intelligent life not to exist.

Avi: Yeah, I mean if you roll the dice enough times obviously you'll get similar results. I don't think that we are special. My premise is based on cosmic modesty. And I think anyone that tries to argue that we are alone in the universe is showing arrogance. And moreover, I think that if we find an indisputable signal from an advanced civilization, we would realize that we are not the smartest kid on the block. That there are things far beyond what we are able to produce out there.

Ben: And 'Oumuamua sort of came by Earth on its way out?

Avi: Very close! Within a sixth of the Earth-Sun distance, and only then we could see it. So just imagine how much traffic may exist in interstellar space that we are not aware of. And my hope is that when we are able to exit the solar system, we’ll get a message back saying, "Welcome to the Interstellar club." ... It will change our perspective on reality.


Ben: I like the idea of this as a club that we would join, sort of like leveling up

Avi: Well that’s the optimistic view. Another viewpoint is that we don't recognize the risk and it might not be a pleasant surprise.

On Why He's An Optimist

Avi: I'm an optimist because I think in the big scheme of things, nothing matters. I think the universe is so big and there are many planets like the earth — more of them in the observable volume of the universe than there are grains of sand in all beaches on Earth. And, therefore, I'm not particularly attached to myself. I'm willing to take risks in my research because I see the big picture ... Let's just figure out the truth.

"It's similar to the work of a detective that comes to a crime scene and tries to figure out what's going on."

Avi Loeb, on scientific research

On Whether We Are Living In A Computer Simulation

Avi: I don't find this idea very appealing.

Ben: Appealing or likely?

Avi: I would find it likely if we see a bug, if we see stripes in the images that indicate something to do with the software malfunctioning. Otherwise it looks like reality to me and, you know, perhaps a student that failed an exam would prefer to think otherwise.

On Whether Time Travel Is Possible

Avi: That actually is a possibility that we should consider. It leads to logical inconsistencies, for example a child can go back and kill his parents and that is impossible potentially. But perhaps when he pulls the trigger nothing fires. So it's possible that physics allows for time travel in a way that will be self-consistent, [but] we don't know for sure. There are some theorems, some conjectures, but we don't know for sure.

On Whether There Is A Multiverse

Avi: It’s a possibility but I don't like it because it leads to intellectual laziness ... If you allow everything to happen, and moreover you have no way of testing it because you can't leave the boundary of our universe, then I regard this philosophical idea without any foundation in physics.

On Whether Life On Earth Came From Somewhere Other Than Earth

Avi: That's quite possible. In fact, we know that all forms of life on Earth have the same chirality, it's all left handed, the molecules [are] arranged in some special way. And one way to do that is by bringing life from outside and planting it here. What could do that? A piece of rock that flew from Mars, for example, landed on Earth. And we know that such rocks exist that could have carried life in it. But another possibility is directed seeding of life. You can imagine another civilization sending out life in tubes or producing life on a planet by sending 3D printers. And so it's completely possible. I wouldn't say it's likely but it's possible.

On God And Intelligent Design

Avi: I don't think reality is designed very intelligently, if you look at it. There are many things that could have been done better. And, as a result, I wouldn't assign it to a divine entity of perfect qualities because there are so many things that are just done wrong.

Ben: Which you could also call bugs in the system, which could also be proof that we're all living in a computer simulation!

Avi: Well, then I don't have high respect for the architects.

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Josh Crane Producer, Podcasts & New Programs
Josh is a producer for podcasts and new programs at WBUR.



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