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Extraterrestrial: On ‘Oumuamua as Artifact

The reaction to Avi Loeb’s new book Extraterrestrial (Houghton Mifflin Harcourt, 2021) has been quick in coming and dual in nature. I’m seeing a certain animus being directed at the author in social media venues frequented by scientists, not so much for suggesting the possibility that ‘Oumuamua is an extraterrestrial technological artifact, but for triggering a wave of misleading articles in the press. The latter, that second half of the dual reaction, has certainly been widespread and, I have to agree with the critics, often uninformed.

Image credit: Kris Snibbe/Harvard file photo.

But let’s try to untangle this. Because my various software Net-sweepers collect most everything that washes up on ‘Oumuamua, I’m seeing stark headlines such as “Why Are We So Afraid of Extraterrestrials,” or “When Will We Get Serious about ET?” I’m making those particular headlines up, but they catch the gist of many of the stories I’ve seen. I can see why some of the scientists who spend their working days digging into exoplanet research, investigate SETI in various ways or ponder how to build the spacecraft that are helping us understand the Solar System would be nonplussed.

We are, as a matter of fact, taking the hypothesis of extraterrestrial life, even intelligent extraterrestrial life, more seriously now than ever before, and this is true not just among the general public but also within the community of working scientists. But I don’t see Avi Loeb saying anything that discounts that work. What I do see him saying in Extraterrestrial is that in the case of ‘Oumuamua, scientists are reluctant to consider a hypothesis of extraterrestrial technology even though it stands up to scrutiny — as a hypothesis — and offers as good an explanation as others I’ve seen. Well actually, better, because as Loeb says, it checks off more of the needed boxes.

Invariably, critics quote Sagan: “Extraordinary claims require extraordinary evidence.” Loeb is not overly impressed with the formulation, saying “evidence is evidence, no?” And he goes on: “I do believe that extraordinary conservatism keeps us extraordinarily ignorant. Put differently, the field doesn’t need more cautious detectives.” Fighting words, those. A solid rhetorical strategy, perhaps, but then caution is also baked into the scientific method, as well it should be. So let’s talk about caution and ‘Oumuamua.

Loeb grew up on his family’s farm south of Tel Aviv, hoping at an early age to become a philosopher but delayed in the quest by his military service, where he likewise began to turn to physics. An early project was the use of electrical discharges to propel projectiles, a concept that wound up receiving funding from the US Strategic Defense Initiative during the latter era of the Cold War. He proceeded to do postgraduate work at the Institute for Advanced Study in Princeton, mixing with the likes of Freeman Dyson and John Bahcall, and moved on to become a tenured professor at Harvard. Long before ‘Oumuamua, his life had begun to revolve around the story told in data. He seems to have always believed that data would lead him to an audacious conclusion, and perhaps primed by his childhood even to expect such an outcome.

I also detect a trace of the mischief-maker, though a very deliberate one. To mix cultures outrageously, Loeb came out of Beit Hanan with a bit of Loki in him. And he’s shrewd: “You ask nature a series of questions and listen carefully to the answers from experiments,” he writes of that era, a credo which likewise informs his present work. Extraterrestrial is offered as a critique of the way we approach the unknown via our scientific institutions, and the reaction to the extraterrestrial hypothesis is displaying many of the points he’s trying to make.

Can we discuss this alien artifact hypothesis in a rational way? Loeb is not sure we can, at least in some venues, given the assumptions and accumulated inertia he sees plaguing the academic community. He describes pressure on young postdocs to choose career paths that will fit into accepted ideas. He asks whether what we might call the science ‘establishment’ is simply top-heavy, a victim of its own inertia, so that the safer course for new students is not to challenge older models.

These seem like rational questions to me, and Loeb uses ‘Oumuamua as the rhetorical church-key that pops open the bottle. So let’s look at what we know about ‘Oumuamua with that in mind. The things that trigger our interest and raised eyebrows arrive as a set of anomalies. They include the fact that the object’s brightness varied by a factor of ten every eight hours, from which astronomers could deduce an extreme shape, much longer than wide. And despite a trajectory that had taken it near the Sun, ‘Oumuamua did not produce an infrared signature detectable by the Spitzer Space Telescope, leading to the conclusion that it must be small, perhaps 100 yards long, if that.

‘Oumuamua seemed to be cigar-like in shape, or else flat, either of these being shapes that had not been observed at these extremes in naturally occurring objects in space. Loeb also notes that despite its small size and odd shape, the object was ten times more reflective than typical asteroids or comets in our system. Various theories spawned from all this try to explain its origins, but a slight deviation in trajectory as ‘Oumuamua moved away from the Sun stood out in our two weeks of data. That deviation also took it out of the local standard of rest, which in itself was an unusual place for it to have been until its encounter with our Sun caused its motion to deviate.

I don’t want to go over ground we’ve already covered in some detail here in the past — a search for ‘Oumuamua in the archives will turn up numerous articles, of which the most germane to this review is probably ‘Oumuamua, Thin Films and Lightsails. This deals with Loeb’s work with Shmuel Bialy on the non-gravitational acceleration, which occurred despite a lack of evidence for either a cometary tail or gas emission and absorption lines. All this despite an approach to the Sun of a tight 0.25 AU.

The fact that we do not see outgassing that could cause this acceleration is not the problem. According to Loeb’s calculations, such a process would have caused ‘Oumuamua to lose about a tenth of its mass, and he points out that this could have been missed by our telescopes. What is problematic is the fact that the space around the object showed no trace of water, dust or carbon-based gases, which makes the comet hypothesis harder to defend. Moreover, whatever the cause of the acceleration, it did not change the spin rate, as we would expect from asymmetrical, naturally occurring jets of material pushing a comet nucleus in various directions.

Extraterrestrial should be on your shelf for a number of reasons, one of which is that it encapsulates the subsequent explanations scientists have given for ‘Oumuamua’s trajectory, including the possibility that it was made entirely of hydrogen, or the possibility that it began to break up at perihelion, causing its outward path to deviate (again, no evidence for this was evident to our instruments). And, of course, he makes the case for his hypothesis that sunlight bouncing off a thin sail would explain what we see, citing recent work on the likelihood that the object was disk-shaped.

So what do we do with such an object, beyond saying that none of our hypotheses can be validated by future observation since ‘Oumuamua is long gone (although do see the i4IS work on Project Lyra). Now we’re at the heart of the book, for as we’ve seen, Extraterrestrial is less about ‘Oumuamua itself and more about how we do science, and what the author sees as a too conservative approach that is fed by the demands of making a career. He’s compelled to ask: Shouldn’t the possibility of ‘Oumuamua being an extraterrestrial artifact, a technological object, be a bit less controversial than it appears to be, given the growth in our knowledge in recent decades? Let me quote the book:

Some of the resistance to the search for extraterrestrial intelligence boils down to conservatism, which many scientists adopt in order to minimize the number of mistakes they make during their careers. This is the path of least resistance, and it works; scientists who preserve their images in this way receive more honors, more awards, and more funding. Sadly, this also increases the force of their echo effect, for the funding establishes ever bigger research groups that parrot the same ideas. This can snowball; echo chambers amplify conservatism of thought, wringing the native curiosity out of young researchers, most of whom feel they must fall in line to secure a job. Unchecked, this trend could turn scientific consensus into a self-fulfilling prophecy.

Here I’m at sea. I’ve been writing about interstellar studies for the past twenty years and have made the acquaintance of many scientists both through digital interactions and conversations at conferences. I can’t say I’ve found many who are so conservative in their outlook as to resist the idea of other civilizations in the universe. I see ongoing SETI efforts like the privately funded Breakthrough Listen, which Loeb is connected to peripherally through his work with the Breakthrough Starshot initiative to send a probe to Proxima Centauri or other nearby stars. The book contains the background of Starshot by way of showing the public how sails might make sense as the best way to cross interstellar distances, perhaps like Starshot propelled by beamed energy.

I also see active research on astrobiology, while the entire field of exoplanetary science is frothing with activity. To my eye as a writer who covers these matters rather than a scientist, I see a field that is more willing to accept the possibility of extraterrestrial intelligence than ever before. But I’m not working within the field as Loeb is, so his chastening of tribal-like patterns of behavior reflects, I’m sure, his own experience.

When I wrote the piece mentioned above, ‘Oumuamua, Thin Films and Lightsails, it was by way of presenting Loeb’s work on the deviation of the object’s trajectory as caused by sunlight, which he produced following what he describes in the book as “the same scientific tenet I had always followed — a hypothesis that satisfied all the data ought to be considered.” If nature wasn’t producing objects shaped like that of a lightsail that could apparently accelerate through the pressure of photons from a star, then an extraterrestrial intelligence was the exotic hypothesis that could explain it.

The key statement: “If radiation pressure is the accelerating force, then ‘Oumuamua represents a new class of thin interstellar material, either produced naturally…or is of an artificial origin.”

After this, Loeb goes on to say, “everything blew up.” Which is why on my neighborhood walks various friends popped up in short order asking: “So is it true? Is it ET?” I could only reply that I had no idea, and refer them to the discussion of Loeb’s paper on my site. Various headlines announcing that a Harvard astronomer had decided ‘Oumuamua was an alien craft have been all over the Internet. I can see why many in the field find this a nuisance, as they’re being besieged by people asking the same questions, and they have other work they’d presumably like to get on with.

So there are reasons why Extraterrestrial is, to some scientists, a needling, even cajoling book. I can see why some dislike the fact that it was written. But having to talk about one’s work is part of the job description, isn’t it? It was Ernest Rutherford who said that a good scientist should be able to explain his ideas to a barmaid. In these parlous times, we might change Rutherford’s dismissive ‘barmaid’ to a gender-neutral ‘blog writer’ or some such. But the point seems the same.

Isn’t communicating ideas part of the job description of anyone employed to do scientific research? So much of that research is funded by the public through their tax dollars, after all. If Loeb’s prickly book is forcing some scientists to take the time to explain why they think his hypothesis is unlikely, I cannot see that as a bad thing. Good for Avi Loeb, I’d say.

And whatever ‘Oumuamua is, we may all benefit from the discussion it has created. I enjoyed Loeb’s section on exotic theories within the physics community — he calls these “fashionable thought bubbles that currently hold sway in the field of astrophysics,” and in many quarters they seem comfortably accepted:

Despite the absence of experimental evidence, the mathematical ideas of supersymmetry, extra-spatial dimensions, string theory, Hawking radiation, and the multiverse are considered irrefutable and self-evident by the mainstream of theoretical physics. In the words of a prominent physicist at a conference that I attended: ‘These ideas must be true even without experimental tests to support them, because thousands of physicists believe in them and it is difficult to imagine that such a large community of mathematically gifted scientists could be wrong.”

That almost seems like a straw man argument, except that I don’t doubt someone actually said this — I’ve heard more or less the same sentiment voiced at conferences myself. Even so, I doubt many of the scientists I’ve gotten to know would go that far. But the broader point is sound. Remember, Loeb is all about data, and isn’t it true that multiverse ideas take us well beyond the realm of testable hypotheses? And yet many support them, as witness Leonard Susskind in his book The Black Hole War (2008):

“There is a philosophy that says that if something is unobservable — unobservable in principle — it is not part of science. If there is no way to falsify or confirm a hypothesis, it belongs to the realm of metaphysical speculation, together with astrology and spiritualism. By that standard, most of the universe has no scientific reality — it’s just a figment of our imaginations.”

So Loeb is engaging on this very charged issue that goes to the heart of what we mean by a hypothesis, about the falsifiability of an idea. We know where he stands:

Getting data and comparing it to our theoretical ideas provides a reality check and tells us we are not hallucinating. What is more, it reconfirms what is central to the discipline. Physics is not a recreational activity to make us feel good about ourselves. Physics is a dialogue with nature, not a monologue.

You can see why Extraterrestrial is raising hackles in some quarters, and why Loeb is being attacked for declaring ‘Oumuamua a technology. But of course he hasn’t announced ‘Oumuamua was an alien artifact. He’s said this is a hypothesis, not a statement of fact, and that it fits what we currently know, and that it is a plausible hypothesis and perhaps the most plausible among those that have been offered.

He goes on to call for deepening our commitment to Dysonian SETI, looking for signs of extraterrestrial intelligence through its artifacts, a field becoming known as astro-archaeology. And he considers what openness to the hypothesis could mean in terms of orienting our research and our imagination under the assumption that extraterrestrial intelligence is a likely outcome that should produce observables.

As I said above, Extraterrestrial should be on your shelf because it is above all else germane, with ‘Oumuamua being the tool for unlocking a discussion of how we do research and how we discuss the results. My hope is that it will give new public support to ongoing work that aims to answer the great question of whether we are alone in the universe. A great deal of that work continues even among many who find the ‘Oumuamua as technology hypothesis far-fetched and believe it over-reaches.

Is science too conservative to deal with a potentially alien artifact? I don’t think so, but I admire Avi Loeb for his willingness to shake things up and yank a few chains along the way. The debate makes for compelling drama and widens the sphere of discourse. He may well be right that by taking what he calls ‘’Oumuamua’s Wager” (based on Pascal’s Wager, and advocating for taking the extraterrestrial technology hypothesis seriously) we would open up new research channels or revivify stagnant ones.

Some of those neighbors of mine that I’ve mentioned actually dug ‘Oumuamua material out of arXiv when I told them about that service and how to use it, an outcome Ernest Rutherford would have appreciated. I see Extraterrestrial as written primarily for people like them, but if it does rattle the cages of some in the physics community, I think the field will somehow muddle through. Add in the fact that Loeb is a compelling prose stylist and you’ll find your time reading him well spent.


Comments on this entry are closed.

  • Keith Cooper February 23, 2021, 8:09

    Hi Paul, it’s not often at all that I say I would disagree with you, but I disagree here. You write that the spaceship hypothesis stands up to scrutiny as a hypothesis and is better than other alternatives in ticking boxes, but that’s just the thing: it doesn’t stand up, and that’s why the scientific community is reacting so strongly to this.

    (Disclaimer: I’ve not read Loeb’s book, but I’ve seen his papers on the subject and read the articles and interviews about him that have appeared to promote the book.)

    (I also think there’s a mixing of concepts here – as a hypothesis, it’s fine to ask the question, could it be a spacecraft, but for a hypothesis to become a theory it has to come under scrutiny and survive contact with the evidence.)

    In all the articles and interviews about Loeb’s book that I’ve seen, nobody seems to bother asking the very scientists who study comets and asteroids day in, day out, and who actually planned and performed the observations of ‘Oumuamua that Loeb is piggybacking his theory on, what they think. And it’s no real surprise that they are entirely comfortable with the evidence suggesting that ‘Oumuamua was some kind of comet. And I know one or two of those researchers personally, and I know they’d have been tremendously excited if it had been a spaceship.

    Here’s a summary of their findings, addressing all of the points that Loeb brings up: https://arxiv.org/abs/1907.01910

    For one, the 10:1 ratio in dimensions is at the upper end of the range that it could be, but it was the one that got quoted the most as it was one of the first estimates. Scientists seem to have settled on 6:1 as a minimum, which is still pretty extreme, but not unexplainable. Look at Arrokoth, that’s nearly 4:1. Not sure about 67P but that’s a bizarre shape too. I could easily imagine ‘Oumuamua as being a contact binary of two objects with ratios of 3:1. joined end to end. And we forget how bizarre Arrokoth was – two flattened, pancake-shaped objects stuck end to end. The law of averages suggests there’s bound to be objects even weirder in the Kuiper Belt – maybe even weirder than ‘Oumuamua in shape.

    It’s albedo is nothing special – based on Spitzer data it was calculated to be 0.1, and you’d expect a solar sail to be much shinier. As for the lack of detectable outgassing, though mysterious, it’s not unprecedented. Normally outgassing releases a lot of dust from the surface, but no dust was seen. However, some comets, for reasons not yet fully understood, preferentially eject larger grains than those that were searched for – ‘Oumuamua could have been like one of these comets. And some outgassing comets don’t release dust at all, so the lack of dust doesn’t necessarily mean there was not outgassing, Since the level of outgassing needed only be a few kilograms per second, it could have gone unnoticed, and observations were not comprehensive – the paper quoted above states that there were no observations sensitive enough to detect water outgassing, they were relying on cyanide gas detection as a proxy (none was seen, but it could have been at a level too low to detect).

    Yes, there are ifs, buts and maybes, but as Jason Wright is fond of saying, we’ve got to rule out every conceivable natural solution before considering that the alien one could be real. Boyajian’s Star is a really good example of how science needs to approach these subjects calmly and rationally. Loeb isn’t doing this, he’s not encouraging this sort of rigour. He knows what he’s doing – he can wind up the public and the media with this idea, and he knows that they’re going to believe him, and not take the time to explore all the caveats.

    And the irony is that the mass media, who are proclaiming this line about nobody taking SETI seriously and that somehow Loeb is the only person doing this, were only weeks before getting excited about BLC-1. Short memories.

    Asking the question, is ‘Oumuamua a spacecraft? is a perfectly acceptable hypotheses. No problem there. Where would SETI be without hypotheses like that, which appear a little outlandish? And what we learned from studying ‘Oumuamua can provide important constraints on observations for the future so that if or when a spacecraft does come along, we can better recognise it. Unfortunately, many of the public now believe that ‘Oumuamua is a spacecraft, and that damages future SETI research because they’ll either assume SETI scientists and astronomers are either blinkered or lying.

  • henry cordova February 23, 2021, 10:45

    I’ve lately become skeptical about the entire possibility (or should I say “probability”) of the existence of extraterrestrial technical civilizations. But the fact remains, that concept violates no known physical law and cannot be ruled out. Yomama came from a direction near the Solar Apex, and it was traveling at a sun-relative velocity of the same order of magnitude as the other stars dritfing along the local Standard of Rest. In other words, its kinematic behavior is perfectly consistent with a natural object, a comet or asteroid, gravitationally ejected from another solar system, perhaps billions of years ago. In spite of its peculiar observed dynamical behavior, or its bizarre optical appearance, it is simply traveling much too slow to be an interstellar spacecraft.

    Of course, we can devise convincing explanations for this, but they all sound contrived, an attempt to “save the phenomenon”. Perhaps it is a derelict, just drifting in the stream. The point is, its not acting like a spaceship, it doesn’t seem to be going anywhere in a hurry, although it could conceivably be part of the booster stage of one, jettisoned ballast, debris or it has had multiple stellar interactions that made it slow down and look like an ordinary rock.

    We simply don’t know enough about this thing to say what it is, so skepticism is perfectly justified. As for its reflective and optical properties, and its acceleration, well, we haven’t seen enough of these guys to come up with any generalities about them.

    I hope its an artifact, and I can’t rule it out, but I really doubt it.

    • Hamilton1 February 24, 2021, 12:53

      “In spite of its peculiar observed dynamical behavior, or its bizarre optical appearance, it is simply traveling much too slow to be an interstellar spacecraft.”

      You answered this issue in your next paragraph, but it still bears repeating. If the object had merely been dispatched from a mothership, then the slow speed is irrelevant. We don’t know much about ‘Oumuamua but we can at least avoid inventing easily refutable non-arguments.

      • Henry Cordova February 24, 2021, 21:54

        I guess you’ve just saved the phenomenon.

    • Law February 26, 2021, 12:51

      Even for ballast, it’s far too slow. Perhaps some sort of Outer Solar System probe (they say you’d build thousands of those), or a scrap of solar sail material, but yeah, I totally agree that the low relative velocity is a point against.

  • Brian Altmeyer February 23, 2021, 11:12

    My view from a distance is that the resistance Loeb talks about is more economic than ideological, though in practice that distinction often blurs.

    It goes like this: Imagine you have a 20/30-year career studying something interesting and respected but completely devoid of romance or adventure in the pop-sci imagination. Maybe you spent the past 10 years as the principal investor guiding a NASA probe mission that will, say, develop a firmer understanding of the solar magnetic field.

    Now imagine an alien artifact zips through the solar system, but in this scenario, it’s unequivocal. No room to safely tuck it away in a corner of speculation or unresolved dispute. What now happens to the funding for your project? What happens to the relevance of your past research?

    From a political perspective, your project’s priority just became zero, and it’s not at all clear that your knowledge is broad enough to tie in with the urgent new investigations that follow. You have gone from a position of respect and confidence to suddenly feeling like a grad student again.

    This is what Loeb is talking about: The suffocating irony of scientists being afraid of surprises rather than being hungry for them.

    And it is visible, even from the outside. Even on far less dramatic questions than alien technological intelligence.

    Mars exploration, for instance. NASA has been talking (and talking, and talking) about the microbe question since its inception, but no probe sent there has ever been designed to efficiently seek definitive answers.

    What happens instead is questions are kept narrower than necessary, and interpretations vaguer than necessary, treating each probe as an investment in future careers rather than seeking to maximize knowledge as quickly as possible. And as to Loeb’s point, not because they don’t want to know, but simply by Darwinian fact that this type of “shy” investigation is more likely to get funded than something more scientifically brutal.

    In other words, if a question can be answered by a single probe that costs $0.5B and can fulfill its goals in 3 years, but there is a way to parse it into smaller questions that together cost $20B and take 30 years, the latter will get the institutional support. The former will be politely considered but sidelined as too “ambitious,” even if it is objectively safer, faster, and cheaper on every level than what institutions go with instead.

    The way it looks, then, is that the “science economy” is plagued by confirmation bias and conflicts of interest, which then manifest as (seeming) intellectual cowardice and doublethink in mainstream debate.

    It would be like if you need to find out what’s happening to the Greenland glacier, and it’s decided the most prudent way to go about it is to send an “expedition” 5 miles outside of Montreal instead. Then, oh so bravely, to send the next project 10 miles out, and the one after that 15. To just go to Greenland would somehow be interpreted as a radical, anarchistic act.

    As someone who yearns for knowledge, this makes me cringe to see.

    The fact that an artificial hypothesis is even plausible for Oumuamua should be catalyzing drastic new efforts, not rationalizations and fears about what the media might say.

    If I had my way, there would be a global effort to develop technologies to go chase Oumuamua down and just answer the question directly.

    • Alex Tolley February 23, 2021, 13:29

      While I don’t much agree with your argument, reports on NSF and NIH research funding indicate that there is far too much support for low risk, incremental research, and too little blue-sky research. This is partly due to how funding and results are rewarded. The clear exception in the US is DARPA. The UK has just announced a similar approach. (The UK is even more conservative than the US in VC capital for new ideas. The idea of “disrupting” existing businesses was an anathema.)

      OTOH, it is easy to see why public funding is conservative. The well-commented issue of the search for life on Mars is an example. The Viking mission was direct, yet proved ambiguous at best. Nasa pivoted to a slower series of missions, threaded with the search for liquid water. But if a dedicated mission fails, that is a huge loss for other, far less risky, research objectives. Perhaps the best example is proposals for the FOCAL mission. The cost and time spent on sending a telescope to the FOCAL line to stare at just 1 star is a high-cost, high-risk project. Far better to do lots of cheaper studies to find a high probability life-bearing target before sending out such a dedicated probe. Similarly, trying to chase down ‘Oumuamua would be highly expensive, risky, and a great waste of effort if it turns out to be a comet. There are a great many far more interesting and deserving missions that could be funded – unless we are near-certain that ‘Oumuamua was indeed an alien spacecraft (Loeb agrees with this).

      I don’t know when the US became so conservative with public funding. I suspect the rise of opposition to government spending, and the [in]famous William Proxmire “Golden Fleece: awards pushed this conservatism. [Where is Proxmire when you need him for the Shelby Launch System”?] It seems that apart from DARPA, it is private spending that is leading the way for high-risk projects – like the Breakthrough initiatives, and New Space companies, exemplified by SpaceX. These harken back to the days of exploration funded by private groups, as well as the early days of aviation, such as Lindbergh’s famous solo, trans-Atlantic flight, and Amelia Earhart’s record-breaking endeavors. The Planetary Society’s attempts to launch a solar sail fit that category even though by the time they had success, they were beaten to the post by Japan’s JAXA.

      Searching for life in space is, so far, a very expensive set of projects. The question I would ask is, “Do they need to be so expensive, or could much cheaper approaches answer the questions”?

      • Brian Altmeyer February 24, 2021, 8:44

        Agree, blue-sky research is undervalued. Humanity keeps running into this paradox, that there cannot be a fully rational way to justify seeking the unknown, but science is meant to both do that and be rational about it.

        Too often it answers the paradox by misapplying the Hippocratic ethic, thinking science is obliged to protect the comfort or social status of institutions.

        To double the sad irony, we find that the greatest scientific windfalls in history were not driven from within the scientific community at all. They were driven by unquantifiable and arbitrary motives: Entire oceans and continents traversed simply because people wanted their food to taste better or last a little longer (spice trade); or humans in orbit and on the Moon for national ego (Space Race).

        So it can be irksome how little the scientific community understands and acknowledges the wave it rides. For instance, the Mars program does not have the status it does because of what it can teach us about Earth’s formation or microbes, which are the questions the community chooses to focus on. Rather, it has the status it does because civilization has an instinct that we’re going to spread there, and wants to put eyes on the future.

        As an institution, the scientific community is very uncomfortable with these motives. It’s uncomfortable with the visceral version of itself: The hunger to interact with and discover the universe as a living part of it, rather than as a narrow laboratory experiment with highly rationalized methods and goals.

        And that’s fine as long as that preference itself is kept rational rather than becoming a moral axiom. Otherwise we end up with surreal “sheep specs” type arguments (see the HBO movie “The Pentagon Wars”, it’s hilarious).

        I disagree that arriving at Oumuamua only to find it a weird type of comet would be wasted effort. We would have a powerful new propulsion technology that could be applied generally to future exploration, and in addition have discovered an exotic new type of natural object. Apart from never finding it (which is what will happen anyway if we do nothing), those great results would be the *worst*-case scenario.

        The payoff of it actually being artificial would be that the relationship between politics and science changes very quickly, and in a much more sustained and fundamental way than the Space Race.

        Speaking to cost and risk, as hard and expensive as propulsion technology is to develop, I honestly don’t see that capability costing outside the ballpark of ambitious international programs we already do. Probably it would be some kind of electric propulsion advanced from existing tech: Something we want to do anyway, just on an accelerated timescale.

        The nightmare scenario is that we’re a little disappointed, like when the first flyby images of Mars came back. But that hasn’t stopped us from going back, and certainly not from using the lessons learned along the way.

    • Ron S. February 23, 2021, 13:33

      “In other words, if a question can be answered by a single probe that costs $0.5B and can fulfill its goals in 3 years, but there is a way to parse it into smaller questions that together cost $20B and take 30 years, the latter will get the institutional support.”

      Can you give an example of this having happened?

      • Brian Altmeyer February 24, 2021, 9:15

        The succession of Mars rovers is the archetype for it.

        Even after it was plain from orbiters that Mars has plenty of water today, there was this narrative that water is elusive, and that they needed to gradually build up an understanding of the planet’s primordial geochemistry to characterize the potential for ancient or current life.

        It’s not wrong, but it is somewhat arbitrary and evasive. You want to study fish populations in the Pacific, so the idea is…go study fish fossils in Arizona for a few decades first to establish “context.”

        Again, they’re not wrong. They’re doing real science. It’s just a very, very shy approach.

    • charlie February 23, 2021, 16:55

      “As someone who yearns for knowledge, this makes me cringe to see.”

      Therein lies your problem right there. And to not put a to find a point on it it comes down to the word: yearn. I don’t know your age, nor your economic status, nor your family status, or even your professional
      status-but as an older man I can tell you that as you get older and the ways of the world weigh down on you, you’ll find out (I believe) that the far more pedestrian worries begin to take precedence over rather abstract notions in science. For the greater part of the population the world, just getting through the day and not having some weight of the world problem coming down on your head means that you had a successful day. I don’t mean to sound cynical here but in the current climate we see not just here in the United States but throughout the world even in developed nations it’s getting harder and harder to make ends meet. Personally I would rather see money diverted into more day-to-day concerns such as robotics and better and more improved medicines. And I feel others if you were to press them on the issue would tend to agree.

      So, pouring money in any fashion into chasing down what is probably in all likelihood nothing but some kind of rock passing through the solar system is not exactly top of the agenda type of issue. But I do understand your point, I just don’t think that you realize quite yet what kind of problems you will be facing in the not too distant future that you will make you almost undoubtedly push such fanciful notions out.

      • henry cordova February 23, 2021, 20:54

        I would be all in favor of more resources directed to solving real-world practical problems, rather than lofty philosophical dreams. But experience has shown that money saved by scrubbing space missions does not get automatically diverted to feeding people, educating children and curing diseases. We live in a society that has no problems lavishing billions on consumer toys, theme parks and sporting events, or into propaganda campaigns that promote these inaninities…not to mention the enormous expenditures we devote to armaments.

        So if we can con the cretins that we elect to public office or place in positions of commercial power into financing some of our philosophic, scientific and artistic hobbies, then I say go for it. Its money well spent, and someday it will probably yield a “practical” payoff. Whatever the hell that means.

      • Brian Altmeyer February 24, 2021, 9:40

        The yearning for knowledge is no more arbitrary or naive than seeking money, power, status, or beauty. It is simply another human motive, and shared by people of all ages, all backgrounds, and all practical circumstances.

        But it is objectively the most net-positive impulse, seeking to elevate human existence rather than merely preserve it (though it’s the best at that too).

        If a society is capable of investing in such things at all, then it has every rational reason to value bold science. History is unequivocal: The return on investment is massive, and effectively perpetual.

        You mention robotics: Guess what a space probe is? As for medicines, there is never any shortage of investment in that field. What is lacking is the inspiration for social commitment to the STEM that underpins them, so they don’t just devolve into fraudulent stat games by Big Pharma.

        A humanity with far horizons is much more committed to its own health and honor than one caught up in “problems down here” fallacies.

    • Joe H. March 2, 2021, 22:54

      “If I had my way, there would be a global effort to develop technologies to go chase Oumuamua down and just answer the question directly.”

      Is this at all feasible? Given how fast it’s moving and how much time has past, this idea sounds like science fiction. Do we even have enough data to plot the trajectory accurately? Nevertheless this would be a great topic for a future Centauri Dreams article. Everyone could just cut loose with their wildest ideas about how to intercept Oumuamua within a reasonable time frame . It would accomplish Loeb’s goal to get scientists and engineers to think more boldly.

  • Steve Kilston February 23, 2021, 12:21

    Excellent post, Paul! Many years ago I. J. Good assembled a fine book called The Scientist Speculates. Very thought-provoking.

  • Michael February 23, 2021, 12:46

    Could these stellar wonderers have large amounts of helium and hydrogen impinged into them and when heated released as a practically invisible gas.

    • Bryan Kelly February 23, 2021, 14:13

      You are on to something there, but it’s not gas that’s released, just the heat and other radiation it traps. Rutherford’s barmaid may well inform Avi that Oumuamua is indeed a light pump, absorbing and emitting photons as-needed, as opposed to a sail. Then she’d probably go on to explain it’s likely a Vantablack, graphene and hydrogenated graphene, i.e., graphane-layered metamaterial or equivalent, and not a film. Some guy looking for Guiness 0.0 but settling for Kaliber told her that rumor.

      • Douglas Robert Loss February 23, 2021, 19:19

        All of which would appear to support the “artifact” hypothesis…

  • Andrei February 23, 2021, 12:48

    Very good text this time by highlighting the problem of speculating openly on scientific matters. Some do it to gain attention which could lead to research grants, others for personal promotion, even when it is done in good faith – it can lead to embarrassing or even damaging results.
    The cult of believers who jumped on Oumuamua as ‘proof’ of their lunacy is a prime example of this.
    I am the first to advocate that scientific news should be brought to as many as possible. But sadly, with the collapse of the educational system in many countries, we need to exclude speculation. As many cannot distinguish between that and actual research results.
    And since we’ve found that Arrokoth / ‘Ultima Thule’ also had one odd flattened shape, it might be a common shape for objects that spend long time in deep space.
    There might be nothing unusual about Oumuamua’s flattened shape – regardless if it happen to be of hydrogen ice or not.

  • Raffaele Antonio Tavani February 23, 2021, 13:14

    Articolo molto equilibrato, e ricco di riflessioni profonde. Di questo tipo di articoli, ne abbiamo molto bisogno.
    Saluti, a tutti i frequentatori di questo blog scientifico, da Raffaele Antonio Tavani

    Google Translate:

    Very balanced article, and full of profound reflections. We need these kinds of articles very much.
    Greetings, to all the visitors of this scientific blog, from Raffaele Antonio Tavani

  • Ashley Baldwin February 23, 2021, 13:39

    It’s a polemic liberally garnished with irony.

    Gets my vote.

    How come the ‘extraordinary claims require extraordinary evidence ‘ pole vault bar was never applied to the self serving / circular argument nonsense that was ‘Rare Earth’ ?

    The book with the oxymoronic title.

    Conceived by messers Ward and Brownlee, sometime collaborators with notorious ID proponent Guillermo Gonzalez.

    Extraordinary claims require extraordinary evidence – but ludicrous claims obviously require none. Just a faith based anthropocentric narrative.

    Why not just bring back Ptolemy and the inquisition ?

    • Alex Tolley February 23, 2021, 14:34

      Or :

      “That which can be asserted without evidence, can be dismissed without evidence.”
      ― Christopher Hitchens

      • Ashley Baldwin February 23, 2021, 18:57


  • Mike Serfas February 23, 2021, 13:47

    I would like to think that aliens could come up with better than a flyby mission. Don’t they know enough orbital mechanics to arrange a close encounter with Jupiter?

    I can think of another astronomical object in a much better position to keep an eye on what the humans are up to. If astronauts do set up camp on the Moon, we should have them feel around the surface for seams and hidden hatchways. :)

  • DCM February 23, 2021, 13:57

    It’s a ROCK! An F-ing ROCK!

    • Michael February 23, 2021, 14:35

      He thinks it could be a ROCK-ET-…A F-ing ROCK-ET-

    • ljk February 25, 2021, 10:52

      The Universe is a big scary place, made even more so by its seeming indifference. Aliens with all their potential unknowns and motives are even scarier.

      In comparison, inanimate rocks drifting at seeming random through the stars are much more comforting. It’s all about the feels before the science, let’s admit this here.

      Humans have yet to really leave the cave, including when that cave is expanded to a big round rock eight thousand miles across.

  • Gary Wilson February 23, 2021, 14:53

    We don’t absolutely know what it is but it looks an awful lot like a rock to me too. Occam’s Razor for me here. :)

    • Andrei February 23, 2021, 18:25

      Hear hear! Absolutely from me also – on Occam’s razor.
      ….and the need to avoid meaningless speculation,

    • Douglas Robert Loss February 23, 2021, 19:23

      To be completely fair, no one has actually seen it. All we’ve seen is a single- (or a very few-) pixel reflection which varied regularly in it’s brightness. So rock or not, who can say? But from the picture the answer is, not enough data.

      • DCM February 24, 2021, 5:56

        Speculation is OK but it’s based on whatever one’s personal and cultural assumptions are till tested.
        It’s understandable that we’d be searching for life elsewhere but anything not precisely defined is an inkblot test of our own assumptions and aspirations. The latter are usually a hope that some super advanced creatures will show up and solve all our problems for us.

  • ljk February 23, 2021, 14:55

    Despite how modern folks tend to perceive our forefathers and foremothers as having a vitriolic reaction to the idea of extraterrestrial beings, the truth is they often considered the concept not only without fear but a logical extension of God’s powers. Why would He make all these worlds and not populate them with more creatures to worship Him?


    Even my catechism book from 1969 says that aliens could certainly exist because God can do anything he wants anywhere, any time, and any place – so who are we to limit His powers?

  • ljk February 23, 2021, 15:25

    Astronomer Avi Loeb Says Aliens Have Visited, and He’s Not Kidding

    In conversation, the Harvard University professor explains his shocking hypothesis—and calls out what he sees as a crisis in science

    By Lee Billings on February 1, 2021


    Some salient quotes from above:

    People ask why I get this media attention. The only reason is because my colleagues are not using common sense. Contrast string theory and multiverses with what I and many others say, which is that based on the data from NASA’s Kepler mission, roughly half of the galaxy’s sunlike stars have a planet about the size of the Earth, at about the same distance of the Earth from the sun, so that you can have liquid water on the surface and the chemistry of life as we know it. So if you roll the dice on life billions of times in the Milky Way, what is the chance that we are alone? Minuscule, most likely! To say that if you arrange for similar circumstances, you get similar outcomes is, to me, the most conservative statement imaginable. So I would expect most people to endorse that, to hug me and say, “Great, Avi, you’re correct. We should look for these things because they must be very likely.” Instead what I see is a backlash that shows a loss of an intellectual compass—because how else can you explain working on string theory’s extra dimensions or the multiverse when we have no clue for their existence? But that is considered mainstream? That’s crazy.

    And in terms of risk, in science, we are supposed to put everything on the table. We cannot just avoid certain ideas because we worry about the consequences of discussing them, because there is great risk in that, too. That would be similar to telling Galileo not to speak about Earth moving around the sun and to avoid looking in his telescope because it was dangerous to the philosophy of the day. We should not want to repeat that experience. We need an open dialogue among scientists where people present different ideas and then allow evidence to dictate which one is right. In the context of ‘Oumuamua, I say the available evidence suggests this particular object is artificial, and the way to test this is to find more [examples] of the same and examine them. It’s as simple as that.

    So how do you change this situation? I think the answer is to bring it to the public as much as I can.

  • Floyd Mathews February 23, 2021, 18:04

    I agree, it is a great book, although a little too much material about Loeb’s own personal career and family history.

    However Loeb did make a good presentation of his two main points:

    1. Oumuamua observations were intriguing, to say the least. Especially it’s acceleration after perigee.

    2. The mainstream scientific community still remains a little bit afraid to raise or even consider controversial ETI hypotheses.

    Carl Sagan’s memorable quote was “Extraordinary claims require extraordinary proof.”

    Compare that to any inmate convicted on the simple ACCUMULATION of multiple circumstantial evidences, but not one piece of direct evidence?

  • Douglas Robert Loss February 23, 2021, 19:29

    When I read the book and came across the passage about mainstream theoretical physics accepting unproven (and likely untestable) theories as irrefutably true, I was strongly reminded of Lee Smolin’s 2006 book, “The Trouble With Physics.” When I read that I was struck by how much the M-theory (string theory) contingent of theorists had in common with a cult. And that impression hasn’t lessened in the meantime. It’s similar to the whole dark matter/dark energy search, which is taking on stronger and stronger similarities to the whole luminiferous aether belief of the late 19th century.

  • Edwin February 23, 2021, 20:51

    Hi Paul and Commentators

    Yes this is interesting and I enjoyed the reading and comments as always now if only I had the spare time to read the book!

    Cheers Edwin

  • Martin February 24, 2021, 4:39

    I (briefly) looked at the paper claiming an oblate ellipsoid was a better fit than a prolate ellipsoid. I came away unconvinced, but of the general impression it could be either. All of the artists’ impressions though show it as a prolate ellipsoid, and it’s a good thing, as otherwise the conversation would go something like this: “It’s a derelict flying saucer! No! Stop! Put down that astrolabe!”

  • Robin Datta February 24, 2021, 8:29

    I retired well over a decade ago. Off-label presrcibing was an accepted practice and even led to new treatments. This was comparable to speculation off the beaten track in other parts of science. The effort to curb such presrcibing with the promotion of lucrative though mediocre alternatives in countries with the wherewithal has effects that show up in the data.

    • Alex Tolley February 24, 2021, 12:43

      Don’t underestimate the efforts of pHarma to undermine these advantages. The most blatant case I have come across is the use of an NSAID that has benefits for Multiple Sclerosis (MS). The NSAID was very inexpensive. However, by making a prodrug that metabolized to the same NSAID at the same effective dose, the company was able to get a license for use in MS to charge 10s of thousands of dollars per year, and effectively prevent the off-label use of the NSAID in the EU.

      It would not surprise me if some company was trying to reformulate a dexamethasone pill for use in Covid to charge a high price for this very fortuitously effective treatment, now that we are expecting variants to keep appearing and become endemic.

      The other driver of finding new uses for old drugs is that the industry is reaching the end of the road for ingestible compounds (the famous Lipinsky “Rule of Five”). Repurposing older drugs with tweaks, especially for chronic and “First World” diseases is an easier route to successful commercialization than finding new compounds to interfere with existing or new targets.

  • ljk February 24, 2021, 14:27

    Paul, thank you for writing this. You have said much of what I wanted to say regarding Avi Loeb and his ideas on Oumuamua. They are fundamental to the advancement of science into the 21st Century; they are not the work of a crackpot despite how some are attempting to smear what they do not like or grasp. If anything, they prove Loeb’s points and motives.

    It is an amazing and not a happy occasion how many have missed the point about what Loeb is trying to do regarding our first identified interstellar visitor. While I understand why the well-meaning layperson might reject his ideas as they attempt to follow the scientific method, I think the professional community has other underlying motives in addition to being methodical.

    I get one reason why the scientists and academics might not be happy with Loeb’s declarations: Science in general is taking a big hit by a disturbingly large section of the population that neither comprehends or trusts science. They likely see Loeb claiming a celestial object that was barely detectable an alien space vessel as akin to the UFO cults and therefore tacitly supporting those who are opposed to science.

    The other thing is they just don’t like the idea of aliens in general. The possibility of other minds in the Universe are fine so long as they remain both fictional and very, very far away. Why do you think SETI began and is so rooted in searching for aliens not visiting us in person in starships but on distant worlds in other solar systems.

    I was present at a SETI meeting held at Harvard University in 2000 where the prominent-in-their-fields speakers trashed the idea of interstellar travel with one slide showing a ridiculously over-complicated star vessel where they verbally took it apart in terms of why no one is crossing the galaxy, then proceeded to “prove” why all aliens with sufficient technology will be sending radio waves among the stars and only for altruistic science.

    It was amusing, by the way, how these hypothetical aliens were “allowed” to conduct METI, while humanity is just supposed to be quiet and listen for these assumed invitations.

    Aliens mess with humanity’s comfort zones, forget any possibilities that they might be hostile threats to us. But, boy oh boy, does that old trope get brought up when the situation requires an extra measure to bring the point home.

    Stephen Hawking is famously brought up because he thought advanced aliens would roam the galaxy in huge WorldShips, finding new solar systems to exploit and strip of their resources before moving on. Hawing may have been a genius, but his extraterrestrial motives are little different from similar ideas brought up practically since the concept of space traveling aliens was founded.

    The Universe at large, and any intelligences within it, probably could not care less about human wishes and desires. They will show up when they show up, whether we are ready for them or not. Loeb has shown that our paradigms, biases, and fears have kept us from the rare opportunity to investigate an object that could indeed be an alien interloper.

    Finding proof that other minds beyond Earth exist could change us all for the better and make us true Citizens of the Cosmos. As we have seen, however, change doesn’t come easy with a species that did not even realize it was on a finite planet floating in space around an ordinary star until just a few drops of time ago.

    Let us hope we wake up before it is too late. Perhaps a bit more attention to the whole forest rather than a few of the trees for a change.

    • Robin Datta February 25, 2021, 0:30

      2,000,000 years ago our genus Homo showed up; 300,000 years ago our sapiens (paucisapient?) species was on the roster. And most of our progress was in less than the last three millennia.

      A billion-year old alien lineage (split into many species over that time) with 100% closed loop recycling of matter (excepting nuclear fusion and fission processes), with an almost imperceptible flow of energy, would be as inclined to teach us their technology as we would be to teach algebra to a bullfrog.

      • ljk February 25, 2021, 11:03

        Such beings don’t even need to be anywhere near that ancient, just different. And aliens are very likely not like us in most ways. This isn’t Star Trek or Star Wars.

        Look at how we are just starting to wake up about the true intelligence of cetaceans and cephalopods. Because until recently they were just animals swimming in the oceans to be used as we saw fit.

        Oh heck, look at how many humans have treated other humans just because a few outward features do not exactly match theirs. No fins or tentacles required for bias and prejudice.

        • Alex Tolley February 25, 2021, 13:42

          I don’t want to preempt Robin’s reply, but I think you are missing the point. Robin is effectively reiterating the point that we are ants next to a motorway and that motorists have no interest in communicating with ants (unless they are named E O Wilson). And while I haven’t tried teaching my cat algebra, I am fairly sure he would be less interested than the average US 1st grader even if he has the capability to understand and learn the basics.

          While I appreciate the intelligence displayed by the cephalopods, they have had 100s Myr to evolve a technological civilization but have failed to do so. They stayed in the oceans and were bypassed by the vertebrates in terms of capabilities and intelligence.

          While I tend to think ETI will be machine-based, they will have required an evolved, biological species to create them. Technology, at least as we know it, requires living in an atmosphere that allows the forging of metals to transcend chipped flints. That requires controlled fire. To live in an atmosphere requires being able to support the body against gravity, which on Earth requires a skeleton, whether internal or external (the latter requiring a dense, O2 atmosphere as in the Carboniferous). So despite Wayne Barlowe’s floating Eosapiens, I don’t see how the cephalopods could have ever evolved into a technological civilization. While I do appreciate Haldane’s

          The universe is not only stranger than we imagine; it is stranger than we can imagine.

          I think we have to be careful not to go overboard and throw all logic out the window when speculating about ETI. While I sincerely hope [post-]humans become a spacefaring, indeed interstellar, species, the limits of our biosphere suggest we may not be able to achieve this, and that over the long term, we may fall back to a simpler, sustainable, civilization instead, or simply go extinct. Either we quickly achieve Cabal’s aims, or we slowly fall back to Passworthy’s. I believe that neither will happen and that the continued rapid drive to miniaturized intelligence and machines will be the spacefaring future. They are just at the beginning of their “Cambrian explosion” and subsequent evolution. Ribbit, ribbit.

          • Michael February 25, 2021, 16:43

            Alex the cephlapods get along on 1 gram of oxygen per cubic meter of water at 15 C. That’s over a thousand times less than we have. They have not done bad at all.

          • ljk February 25, 2021, 17:19

            Quoting you:

            “While I appreciate the intelligence displayed by the cephalopods, they have had 100s Myr to evolve a technological civilization but have failed to do so. They stayed in the oceans and were bypassed by the vertebrates in terms of capabilities and intelligence.”

            While I do not assume that octopuses have secretly built starships and are currently roaming the galaxy with them (but oh wouldn’t that be amazing?), I would like to use the quote by Douglas Adams below from his famous SF novel The Hitch-Hiker’s Guide to the Galaxy to illustrate the point that just because a species hasn’t built much compared to humanity does not automatically imply that they are therefore less advanced…

            “For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons.”

            We have ideas of progress that come from centuries ago and largely from a few dominating cultures. There could certainly be ETI who are much smarter than us and decided long ago to stay home and live lives of the mind.

            The whole point by Loeb is not whether Oumuamua is really artificial or not, but whether we are going to start opening up to such possibilities and then search scientifically accordingly. What I said above originally stands, especially regarding human attitudes towards aliens.

            • Alex Tolley February 25, 2021, 21:26

              While I love Adams’ humor, I do not believe mind alone is enough. Humans have built civilization and knowledge using tools and various cognitive supports. We can transmit knowledge and build upon it. We can see the invisible with microscopes and telescopes. Even the most powerful brains in vats cannot do that and would be largely limited to the discoveries of Ancient Greece, unable to advance. The Greeks were just as intelligent as we are, but they were limited in what they could do, and as a result, remained a relatively impoverished civilization compared to ours. Big-brained, aquatic creatures might be able to build an interesting civilization, but like the Greeks, it would be limited. They, like the Greeks, could never leave their homeworld. They would be prey to any number of natural disasters that could wipe them out.

              Hyper-intelligent beings that have no extensive technology, or have largely abandoned it, strikes me as a yearning for Eden, or a return to a simple, rural lifestyle. I don’t buy that vision.

              As for starfaring cephalopods, I recall Stephen Baxter writing about squid as astronauts. I can certainly imagine a technological civilization uplifting cephalopods so that they can become a technological civilization. They might be like Daleks, supported by machine carapaces, able to develop an advanced civilization even though as individuals without their technology they would be helpless. [At least the original version. Modern versions of Daleks seem to be quite capable even naked.]

      • Robin Datta February 25, 2021, 23:43

        The nature of possible but yet undetected sentience can be categorized à la Rumsfeld into the known unknowns and the. unknowns.

        The known unknowns take from our knowledge of the earth’s biota of from which we were derived and of which we are a part, and project from it with permutations, combinations upto and including the wildest of imaginings. This includes stripping away the biology and embedding the mind in some other substrate, electronic or otherwise.

        With regard to unknown unknowns, they are beyond speculation, and will remain so unless they have enough in common with us through phhysics, chemistry and/or psychology to be perceptible to us perchance or per volition.

        The attitude towards them can be categorized according to abilities (“they’re ants, we’re humans” vs. “we’re ants, they’re human”) and intent (“we’ll help them”, “they’ll help us”, “live peaceably with/without helping each other”, blending together (machine civilisations), and conflicts, brief, intermittent, long, with/without conquest, absorption/assimilation or extermination.

  • Gary Wilson February 24, 2021, 15:51

    The lack of availability of solid experimental evidence often leads to what begins as mild speculation in science but then sometimes grows to wild speculation. I can see Loeb’s concerns about the work physicists are doing in both string theory and dark energy and matter. But I see similarities to those concerns in his own speculations about Oumuamua! Can he not see that also? However I do defend his right to propose various speculations, but I would not call them testable hypotheses.

  • Mike Serfas February 24, 2021, 16:06

    I have to admit I was impressed by the H2 hypothesis, and am reluctant to give up on it. I know this paper ( https://arxiv.org/abs/2006.08088 ) was raised against it, but what if that paper’s model is just wrong? If an iceberg of frozen hydrogen forms over an immense span of time, in the presence of starlight, do we know it couldn’t undergo a process of surface evolution like desert pavement, leaving the hydrogen protected by layers of resistant material, but releasing gas from a natural vent near the axis of rotation?

    Active course correction is characteristic of an alien space probe, but it is more impressive if it is, say, hovering over New York, heading to Alpha Centauri, or at least trying to make a flyby past a planet. A tiny correction that might be explained by light-sail like properties of an asteroid on a voyage to nowhere … why did they bother at all?

  • Harold Shaw February 25, 2021, 0:30

    What are the odds the first interstellar object discovered is a spaceship? Weird natural objects will outnumber spaceships by at least 100 to 1. Could even be as high as 1000 to 1.

    • law February 26, 2021, 13:02

      Depends. A ten-gram scrap of solar-sail could easily be a hectare across. Solar sails necessary to move multimillion-tonne asteroids could easily mass tens, hundreds of thousands of tonnes, with a million square kilometers of area (practically the area of Ceres). Fragments of solar sails for intra-system exploration and civilization could be pretty common – they’re big thin shiny objects for their mass.

      By comparison, a hundred-meter long thin rock might mass ten thousand tonnes, a hundred thousand tonnes – a million times more than an equivalent solar sail.

      But again, the scale of the universe and emptiness of the galaxy suggests that civilization is uncommon, and even solar sails are probably outnumbered a billion to one by natural objects.

  • DCM February 25, 2021, 4:50

    I still doubt aliens have visited us. We may even be the first to even consider interstellar travel.
    It’s the constant refrain about aliens coming to help or “rescue” us that makes the notion doubtable to me. It seems to have been universal to expect sky gods to do so. In any event, aliens likely differ from us more than do lobsters or pine trees.
    I’m reminded of something I read some years ago that throws light on expectations and things like flying saucer cults. In World War II a large (for the era) bomber flew over then unreached by outsiders parts of New Guinea. Maybe in the 1960s, 1970s the inhabitants were contacted who had seen the plane — which had precipitated a number of religious movements, based of course entirely on the indigenous peoples’ religions if sparked by the overflight.
    The movements had no direct connection to the airplane or the crews’ motives, much less the war raging nearby; they were totally limited to the local cultures even though sparked by the bomber.
    If, indeed, aliens have flown over Earth the result has been the same here and has little to do with the beings or their robots in the craft. More likely these are sparked by misperceived meteorological events, but they are in any event more about us than about THEM.

  • RAS February 25, 2021, 7:33

    I agree there’s a lot of economics in this. It’s like when the Common Cold Unit was closed down in the U.K. by the government of the time because it wasn’t perceived to be doing useful research or rather cost effective research especially into Coronavirus as they weren’t perceived as an issue or to even be dangerous. It was only when SARS & MERS turned up some started to think again but that was only a few because it wasn’t seen as a funding priority. Those who hold the purse strings are always overly conservative and this is often to the negative of good science.

  • torque_xtr February 25, 2021, 8:02

    Relaxing cautions can lead to increase in expectations, by orders of magnitude, from what real picture. What if only one in ten thousands of similar objects is artificial? And ‘Oumuamua is only a magnetized splinter of a Psyche-like body, with even bigger aspect ratio, peppered by dust and pushed by solar wind against it’ s magnetosphere?

    Still worth a chase, though. At very least we’ll see something very unlike our own asteroids, do some science on the way, and get a good training for some next encounter. Imagine that in 15 years we detect a weak laser line in an interstellar object’s spectrum, while previous 7026 detected by LSST showed nothing surely unusual, but still haven’t flown even a megawatt-class nuclear electric engine to space!

  • Steve Muise February 25, 2021, 9:19

    William of Ockham stated that “entities should not be multiplied without necessity”, and Loeb’s spaceship hypothesis fails that test.

    The observed data from Oumuamua may fit the spaceship hypothesis, but the observed data is fairly sparse, and Loeb’s hypothesis requires the existence of a really big necessary entity: a technical civilization other than our own. To my way of thinking that would require exponentially more data and a much more complex explanation, and thus Loeb’s hypothesis fails the Occam’s Razor test.

    This isn’t to say that Oumuamua ISN’T an artificial object, merely that Loeb’s hypothesis requires a lot more data than is currently available, and should probably be ranked near the bottom in a list of possible explanations.

    • ljk February 25, 2021, 10:58

      As I said above and am repeating here, stop focusing on the tree and look at the whole forest.

      • Steve Muise February 25, 2021, 13:30

        In this case there is no forest to focus on, only a solitary tall plant which we can’t identify standing in the middle of an endless stretch of prairie.

        • ljk February 25, 2021, 16:44

          My “forest” is not a flotilla of supposed Oumuamuas, but rather the overall picture of what could be out there in terms of intelligent life and their instrumentalities and why.

          • Alex Tolley February 25, 2021, 21:02

            As real as a pantheon of gods civilizations once believed in? Are highly advanced ETIs really that much different from gods living in unreachable realms, mostly indifferent to humanity, but occasionally meddling in our affairs? Are we just dressing up their presence with clever logic, probability math, and other mind tricks to convince ourselves they must be there, a techno twist on religion?

            If we discover life then the probability increases that ETI is out there. But that is not a forgon conclusion based on guesses of the probability of intelligence emerging, civilization arising, and finally becoming star faring themselves.

            Let’s use our technologies to search for signs of life and civilization, but be prepared to accept that maybe we are currently the only extant technological intelligence in the galaxy.

  • ljk February 25, 2021, 13:00

    I think there is some relevance here with this article as scientists strive to make everything similar to the outward simplicity of E=mc2 at the cost of uncovering the complexities of reality…


  • Deleo February 25, 2021, 13:28

    I did read Avi’s book. I have seen some criticism that the book didn’t go into enough detail about Oumuamua, and it contained to many backstories about his personal life.

    I think this criticism is a little harsh. I though the book was well written, and geared towards a widespread audience. It was not meant for a scientific journal. That being said, I still am not convinced that Oumuamua is alien technology.

    Oumuamua was an incredibly rare object. Everyone can agree on that. But it may not be as rare as we think. With better telescopes more objects like this may be discovered.

    I think this article below is the most likely explanation for what Oumuamua was. If it was a nitrogen iceberg from the outer layers of our solar system. If true, that would be a cool enough discovery in itself.


  • ljk February 25, 2021, 13:40

    If Aliens Exist, Here’s How We’ll Find Them

    Two esteemed astrophysicists peer into the future of space exploration.


    FEBRUARY 24, 2021


    To quote:

    Conjectures about advanced or intelligent life are shakier than those about simple life. Yet there are three features that may characterize the entities that SETI searches could reveal.

    • Intelligent life is likely not to be organic or biological.

    • It will not remain on the surface of the planet where its biological precursor emerged and evolved.

    • We will not be able to fathom the intentions of such life forms.

    • Alex Tolley February 25, 2021, 17:31

      Rees and Livio have written a cogently argued essay, much of which I agree with. However, early on they say that exploration will remain a risky endeavor and that we should not think of tourism. On this, I disagree. Any risky endeavor can be made far less risky as technology is developed. Once diving was very dangerous, now it can be done with SCUBA gear in relative safety. One can even go underwater in tourist submarines. You couldn’t get me near an early 20th-century airplane, but I am more than comfortable in a jet airliner. I see no a prior reason why space technology will not allow safe tourist trips to the Moon and beyond. The limitations beyond the Moon are time. One factor improving safety may be a space-based infrastructure of inorganic intelligence to watch over us.

      One thing to think about. When a new technology superseded an older one, there tends to be a late flowering of the old technology before it disappears. Will the genetic engineering of our biological bodies to adapt to environments away from Earth create new species of humanity that are the biological equivalent of this late flowering before the inorganic intelligences supersede us?

      • ljk February 26, 2021, 11:09

        You are right about tourism. People pay tons of money to climb Mount Everest, which is still far more dangerous than a current trip to space. People will want to explore the Final Frontier BECAUSE it is inherently dangerous.

        Good question on your last comments. I suspect there will be a variety of “answers” to how people want to evolve next, especially when we are able to control our destinies through technology and genetic engineering. Some will want to enhance their organics, while others will go full Artilect.

        The beings we meet in space, or the ones who leave Earth and the Sol system to spread into the galaxy, will probably be largely technological with maybe a little radiation-hardened organics thrown in.

        I always see Orion’s Arm as a more modern take as to who and what we will be and meet out there some day….


      • law February 26, 2021, 13:06

        Peter Watts has the right idea. We’ll run into highly fecund, long-hibernating, fast-moving species first. They’ll inevitably have the greatest ranges galaxy-wide, like dandelions and seafaring coconuts, compared to nuts that do not fall far from the tree or groves of trees that extend roots slowly outward.

  • Harold Shaw February 25, 2021, 15:16

    There is a difference between seeing the forest and insisting any given tree is an Ent.

    Embrace the premise of spaceships or, as I do, spaceship people and we must question the efficacy of sending a probe to any object in the solar system or sweeping an object with radar. The existence of Ents demands we explore more cautiously. If you reflexively reject this idea you are only seeing the grove, not the forest.

  • Patrick Underwood February 26, 2021, 0:24

    Can someone help me with this one? If the object was varying in brightness every eight hours, and therefore probably tumbling, how did it get that net acceleration away from the Sun? I guess a net velocity vector could be summed from a bunch of random ones, but it doesn’t make sense to me that the resultant would be along its previous path instead of in some other random direction. (My physics classes were a long time ago, so I’m probably not understanding something here.)

    • Alex Tolley February 26, 2021, 11:34

      Thrust aligned with its spin axis works just fine. Ehether the object is oblate or prolate to account for its light curve, its spin axis would be through the equator, not the poles.


  • AlexTru February 26, 2021, 4:46

    Wishful thinking of Avi Loeb brought him to a conspiracy theory .
    I do not know how to distinguish his speculations from “classical” UFOlogy…
    Even Sagan’s approach seams to Loeb too conservative…
    Long live flying saucer-Oumuamua!

  • Jagged Orbiter February 26, 2021, 6:30

    A probe design to catch the next interstellar interloper:

    ‘USNC-Tech is proposing a compact 20 kWe, 500 kg dry mass, radioisotope-electric-propulsion spacecraft design powered by a novel Chargeable Atomic Battery (CAB) that is capable of ∆Vs on the order of 100 km/s with a power system specific mass of 5-8 kg/kWe. A spacecraft powered by this technology will be able to catch up to an extrasolar object, collect a sample, and return to earth within a 10-year timeframe. The data collected from samples and data from interstellar objects has the potential to fundamentally change our view of the universe and our place in it. Two of these objects ‘Oumuamua and C/2019 Q4 (Borisov) have passed through our solar system in the past three years, and we must be ready for the next one. The core innovation of this spacecraft architecture that makes this amazing mission possible is the CAB, which has a power density of over 30 times that of Pu-238. The CAB is easier and cheaper to manufacture than Pu-238 and the safety case is greatly enhanced by the CAB’s encapsulation of radioactive materials within a robust carbide matrix. This technology is superior to fission systems for this application because fission systems need a critical mass whereas radioisotope systems can be much smaller and fit on smaller launch systems reducing cost and complexity.’

    • Alex Tolley February 26, 2021, 12:02

      This is a NIAC 1 proposal, whose key technology, the CAB, has not been developed. The submission is from the lead CAB developer at Ultra Safe Nuclear. Their near information-free website might just tell you something about the company. Let’s see how they fulfill their NIAC 1 proposal and if it is renewed for NIAC II.

      For a device to have 30x the power density of Pu-238 and is cheaper to manufacture suggests that they are using a more common (or more easily manufactured) radioactive material with a much higher conversion efficiency.

  • Robin Datta February 26, 2021, 10:23

    A clarification –
    The nature of possible but yet undetected sentience can be categorized à la Rumsfeld into the known unknowns and the unknown unknowns.

    The known unknowns we take from our knowledge of the earth’s biota from which we were derived, and of which we are a part. We project from it with permutations, combinations upto and including the wildest of imaginings, even to stripping away the biology and embedding the mind in some other substrate, electronic or otherwise.

  • Beverly Baney March 1, 2021, 7:44

    From all of the responses you have provided the proof as to why Professor Loeb is needed in every educational curriculum. I am saying. Look at the thinking that has been presented that would not have been shared. LET’S CONTINUE TO SHARE!

  • ljk March 1, 2021, 14:30

    A Review of “Extraterrestrial” by Prof. Avi Loeb

    FEBRUARY 28, 2021


    On October 19th, 2017, astronomers from the Haleakala Observatory in Hawaii announced the first-ever detection of an interstellar object in our Solar System. In honor of the observatory that first spotted it, this object (designated 1I/2017 U1) was officially named ‘Oumuamua by the IAU – a Hawaiian term loosely translated as “Scout” (or, “a messenger from afar arriving first.”)

    Multiple follow-up observations were made as ‘Oumuamua left our Solar System and countless research studies resulted. For the most part, these studies addressed the mystery of what ‘Oumuamua truly was: a comet, an asteroid, or something else entirely? Into this debate, Dr. Shmuel Bialy and Prof. Avi Loeb of the Harvard Institute for Theory and Computation (ITC) argued that ‘Oumuamua could have been an extraterrestrial probe!

    Having spent the past few years presenting this controversial theory before the scientific and astronomical community, Prof. Loeb has since shared the story of how he came to it in his new book, Extraterrestrial: The First Sign of Intelligent Life Beyond Earth. The book is a seminal read, addresses the mystery of ‘Oumuamua, and (most importantly) urges readers to take seriously the possibility that an extraterrestrial encounter took place…


    To quote:

    “To be clear, my attitude at the time was simply That might work. The astronomical world had been presented with an exciting discovery, an interstellar object, about which we had collected a trove of confounding data. We confronted facts that were hard to match to a hypothesis that accounted for all of them. When I proposed that Bialy and I explain ‘Oumuamua’s deviation by way of sunlight, I was following the same scientific tenet I had always followed – a hypothesis that satisfied all the data ought to be considered.”

    It was only after they checked the numbers, and confirmed that they worked, that the interstellar probe theory really began to form. The next step was to compute what an interstellar probe would look like in terms of size and composition, thickness, and reflectivity. In the end, all of the evidence proved to be consistent. As Loeb explained it, it all rested on the notion that ‘Oumuamua wasn’t natural in origin:

    “The lightsail inference may seem outlandish,” Loeb summarized, “but getting to it did not require any wild leaps. Shmuel and I went down a logical path. We followed the evidence, and, in the grand tradition of the
    detective work of science, we hewed closely to a maxim of Sherlock
    Holmes: “When you have eliminated the impossible, whatever remains,
    however improbable, must be the truth.” Hence our hypothesis:
    ‘Oumuamua was artificial.”


  • Michael Fidler March 3, 2021, 2:32

    Concepts for future missions to search for technosignatures.


  • ljk March 3, 2021, 12:25

    The SETI Institute will have a live talk on everyone’s favorite real interstellar visitor this Thursday, March 4 – link provided below.

    The talk summary seems to be in response to Dr. Loeb’s book. Take a big guess which side TSI falls on.

    The Nature of ‘Oumuamua

    Scheduled for March 4, 2021


    SETI Institute

    There are a lot of theories out there. Join SETI Institute research scientist Matija Ćuk to explore the various hypotheses suggested by astronomers, including himself. Matija will also explain why the scientific community favors the idea that there is a natural explanation for ‘Oumuamua’s origin.

    Learn more about the SETI Institute and stay up-to-date on awesome science:

    – Subscribe to our YouTube channel at https://www.youtube.com/c/SETIInstitute/​
    – Watch our streams over on Twitch at https://www.twitch.tv/setiinstitute​
    – Listen to our podcast, Big Picture Science http://www.bigpicturescience.org/​
    – Subscribe to our newsletter https://seti.org/signup​
    – Buy merchandise from Chop Shop https://www.chopshopstore.com/collect…​

    Don’t forget to like and subscribe! Ring the bell for notifications of when we go live.

  • ljk March 3, 2021, 12:32

    If warp drive or its equivalent ever is possible, then the idea of Oumuamua as a deep space probe passing through our star system may become very quaint…


  • ljk March 4, 2021, 17:27


    ‘Oumuamua: our first interstellar visitor

    ‘Oumuamua zipped through the inner solar system in 2017, revealing just how little we know about planetary systems beyond our own.

    By Alison Klesman | Published: Wednesday, February 5, 2020


    To quote:

    ‘Oumuamua’s acceleration was in the direction opposite the Sun; it was also related to its distance from the Sun, growing weaker as their separation increased. “There were a number of things that can cause acceleration in that direction,” Meech says.

    The team investigated eight of those causes, including friction or drag changing its trajectory, the possibility that ‘Oumuamua was actually two or more objects tugging on each other, a strong magnetic field within ‘Oumuamua interacting with the solar wind, and pressure from solar photons pushing on ‘Oumuamua to speed it up.

    One by one, they ruled out these scenarios. Friction or drag would pull it toward the Sun, not speed it up in the opposite direction. Images of ‘Oumuamua showed no additional objects large enough to affect its motion in the way astronomers saw. And even a high magnetic field would not cause enough interaction with the Sun’s charged particles to push ‘Oumuamua as observed. For solar photons to push ‘Oumuamua hard enough, the space rock would need an incredibly low density, like that of aerogel, a substance that can be up to 900 times less dense than water.

    Or, speculated Shmuel Bialy and Abraham Loeb of the Harvard-Smithsonian Center for Astrophysics, ‘Oumuamua could be incredibly thin with a large surface area — like a solar sail.

    Although the idea that ‘Oumuamua is an alien spacecraft or abandoned extraterrestrial technology is certainly exciting, Meech and others argue it is extremely physically unlikely, especially given that one explanation the team investigated did work quite well: “The only thing that was left, which was the most logical, is that it’s outgassing,” Meech says.

  • James Jason Wentworth March 5, 2021, 3:39

    One of the late Freeman Dyson’s colleagues (I can’t remember which) complained that he–as Avi Loeb is now being complained about–was “the sort of scientist who, when a theory is beginning to solidify [as the data accumulate] like a rime of ice on the surface of a lake, takes delight in tossing a rock [new data] to shatter it, making a new theory necessary.” Why that is a bad thing is beyond me; even though it creates more work for the scientists, they should welcome that (even for purely practical, economic reasons, relating to having and keeping their jobs [it’s probably more fun than teaching classes at their universities]); kudos to Avi Loeb for also being such a scientific rabble-rouser (I’m sure that Dyson appreciated him as a kindred spirit), and:

    Ernest Rutherford’s statement that “a good scientist should be able to explain his ideas to a barmaid” was no put-down to barmaids. (In both his time and now, it was/is a job requiring a high level of both physical and cognitive skill; in Germany [and undoubtedly in other countries, especially in Europe], a barmaid must often carry two literal handfuls of mugs, one’s handle on each finger, each often holding a different liquor, and deliver them all unerringly to their respective buyers without spills, for her entire shift–that is why they were and are well-paid, and in high demand.) Rutherford was referring to what, today in business, is referred to as the “elevator pitch”; a good scientist should be able to explain briefly–in a clear, concise, and (most importantly) ^understandable^ way–his or her ideas to any non-scientist.

  • ljk March 10, 2021, 14:11

    Alien Life and Interstellar Travelers: An Interview with Avi Loeb

    Is ‘Oumuamua an asteroid, a comet, or a probe sent by an extraterrestrial civilization? Prof. Avi Loeb is in favor of the latter.

    By Matthew S. Williams

    March 09, 2021


    To quote:

    As Professor Loeb explained in an article published in Scientific American (Nov. 20th, 2018), ‘Oumuamua presented six major anomalies that scientists were hard-pressed to find a natural explanation for.

    To summarize them briefly, during the 11 days that it was visible to our instruments, data gathered on ‘Oumuamua indicated that it was either extremely elongated (like a cigar) or more likely disc-shaped. It was also highly-reflective and deviated from a path dictated by our Sun’s gravity, which was a result of its acceleration.

    The kinematics of ‘Oumuamua indicated that it must have originated in a very special frame of reference (consistent with 1 in 500 stars in our galaxy) and that it would have taken a very powerful kick to knock it out of its parent star system.

    Last but not least, the very fact that it was detected implied that there is a huge population of interstellar objects, which would be possible if every star in our galaxy ejected one quadrillion (1015) objects in their lifetime.

    While not impossible, Loeb cites previous and subsequent studies where the researchers attempted to place constraints on the likely number of interstellar objects in our galaxy. As he indicates, these produced estimates that fell short of 1015 by several orders of magnitude.

    Any one of these anomalies could be explained in terms of a 1 in 10, 1 in 100, or 1 in 1000 chance of probability. But considered together, the odds of such an exotic object showing up in our Solar System and behaving as it did were about 1 in a million!

  • ljk March 11, 2021, 13:37

    Sure it’s just one data point at the moment, but there is at least one species in the galaxy that sends vessels to other worlds:


    And at least five (more if you count their final rocket stages) are leaving the Sol system.

  • ljk March 13, 2021, 22:38


    Given the difficulties and risks of space travel, extraterrestrials with advanced technology may have visited Earth only one in a million years, researchers say

    MARCH 13, 2021


    You may also enjoy these accounts of why we do not see the aliens:

    1.Are the Aliens We Never Find Obeying Star Trek’s Prime Directive? The Directive is, don’t interfere in the evolution of alien societies, even if you have good intentions. Hence the Zoo hypothesis. Assuming the aliens exist, perhaps it’s just as well, on the whole, if they do want to leave us alone. They could want to “fix” us instead…

    2.How can we be sure we are not just an ET’s simulation? A number of books and films are based on the Planetarium hypothesis. Should we believe it? We make a faith-based decision that logic and evidence together are reasonable guides to what is true. Logical possibility alone does not make an idea true.

    3.Did the smart machines destroy the aliens who invented them? That’s the Berserker hypothesis. A smart deadly weapon could well decide to do without its inventor and, lacking moral guidance, destroy everything in sight. Extinction of a highly advanced civilization by its own lethal technology may be more likely than extinction by natural disaster. They could control nature.

    4.Researchers: The aliens exist but they are sleeping… And we wake them at our peril. The Aestivation hypothesis is that immensely powerful aliens are waiting in a digitized form for the universe to cool down from the heat their computers emit.

    5.Maybe there are just very few aliens out there… The Rare Earth hypothesis offers science-based reasons that life in the universe is rare. Even if life is rare in the universe, Earth may be uniquely suited to space exploration, as the Privileged Planet hypothesis suggests.

    6.Does science fiction hint that we are actually doomed? That’s the implication of an influential theory, the Great Filter hypothesis, as to why we never see extraterrestrials. Depending how we read the Kardashev scale, civilizations disappear somewhere between where we are now and the advanced state needed for intergalactic travel.

    7.Space aliens could in fact be watching us. Using the methods we use to spot exoplanets. But if they are technologically advanced, wouldn’t they be here by now? The Hart-Tipler conjecture (they don’t exist) is, of course, very unpopular in sci-fi. But let’s confront it, if only to move on to more promising speculations.

    8.Is the brief window for finding ET closing? According to some scenarios (the Brief Window hypothesis), we could be past our best-before date for contacting aliens. Of course, here we are assuming a law of nature as to how long civilizations last. Can someone state that law? How is it derived?

    9.What if we don’t see aliens because they have not evolved yet? On this view, not only did we emerge during a favorable time in the universe’s history but we could end up suppressing them. The Firstborn hypothesis (we achieved intelligence before extraterrestrials) lines up with the view that humans are unique but sees that status as temporary.

    10.The aliens exist—but evolved into virtual reality at a nanoscale. That’s the Transcension Hypothesis, the latest in our series on science fiction hypotheses as to why we don’t see extraterrestrials.
    On this view, after a Singularity the ETs become virtual intelligences, exploring inner space at an undetectably small scale.

    11.Is intelligent life in the universe living in interior oceans of planets and moons? The Ocean Planets Hypothesis is that intelligent beings may flourish in the interior oceans of the moons of gas giant planets — or within exoplanets — but they are trapped there.
    If intelligent life forms are trapped in the interior oceans of rocky moons and planets, Earth is a special planet—much better suited to space exploration.

    12.Is real-world space travel just too daunting for ET? That’s the Percolation Hypothesis as to why we don’t make contact with aliens. They can’t overcome the laws of physics, any more than we can. If there is a purpose behind the universe, maybe the aliens and we weren’t intended to meet. That’s worth considering, given the physics barriers.

  • ljk March 13, 2021, 22:44

    Interview: Christopher Morrison and the Interstellar Sample Return Mission

    This week I talk to Christopher Morrison from USNC about their recently awarded NIAC Grant. Their grant will investigate the feasibility of a radioisotope-electric propelled spacecraft that could intercept and retrieve a sample from a future interstellar asteroid or comet.


  • ljk March 15, 2021, 10:27

    There Should be About 7 Interstellar Objects Passing Through the Inner Solar System Every Year



  • ljk March 16, 2021, 17:02



    16 March 2021

    WASHINGTON—The first known interstellar object to pass through our solar system is likely a piece of a Pluto-like planet from another solar system, according to a new study published as a pair of papers today in the Journal of Geophysical Research: Planets, AGU’s journal for research on the formation and evolution of the planets, moons and objects of our solar system and beyond.

    The results may help scientists learn about the stuff exoplanets are made of and the evolution of solar systems beyond our own.

    “This research is exciting in that we’ve probably resolved the mystery of what ‘Oumuamua is and we can reasonably identify it as a chunk of an ‘exo-Pluto,’ a Pluto-like planet in another solar system,” said Steven Desch, an astrophysicist at Arizona State University and an author of the new study. “Until now, we’ve had no way to know if other solar systems have Pluto-like planets, but now we have seen a chunk of one pass by Earth.”

    Full article here:


    To quote:

    ‘Oumuamua’s characteristics suggest it is likely made of solid nitrogen, like the surface of Pluto, according to the authors.

    “It was likely knocked off the surface by an impact about half a billion years ago and thrown out of its parent system,” said Alan Jackson, an astronomer and planetary scientist at Arizona State University and coauthor of the new study. Jackson will present the research on Wednesday, 17 March at the 52nd Lunar and Planetary Sciences Conference.

    ‘Oumuamua likely wasn’t flat when it entered our solar system, but melted away to a sliver, losing more than 95% of its mass, during its close encounter with the Sun, according to Jackson.

    “Being made of frozen nitrogen also explains the unusual shape of ‘Oumuamua. As the outer layers of nitrogen ice evaporated, the shape of the body would have become progressively more flattened, just like a bar of soap does as the outer layers get rubbed off through use,” Jackson said.

  • rastronomicals March 26, 2021, 16:15

    I’m currently working my way through Extraterrestrial, and found the comment section here very interesting. I was hoping to gauge the reaction to Loeb’s book in a space that was very knowledgeable but not necessarily professional, and I think Centauri Dreams probably qualifies.

    I had picked up the book not so much because of aliens as because Loeb has become a fascinating figure to me.

    What’s his game? By going on Joe Rogan and doing an AMA on Reddit, it’s pretty clear that self-promotion is part of the plan for him, but why would social media stardom be important to him, when he has an h-index through the roof and a job like chair of the Harvard astronomy department?

    In the book, he makes sure to make the point, to apologize, seemingly sheepish: these media appearances, they’re part of the job. But he also, one notes, makes sure to mention the appearances in the first place.

    That ego could be the fount of this media blitz he’s gone on in defense of his idea, for one of his academic accomplishments, it’s almost uncanny to me.

    Yet if Loeb’s ego is unseemly, the reaction of other scientists in his field has been even less virtuous. The primary complaint seems to be ‘I was minding my own business, looking at light curves, and was then made to explain the reason why this object is probably natural to someone who doesn’t know any better.’ I mean, yeah, maybe you were, but isn’t that your job as a scientist?

    And aggravation isn’t the only reaction to Loeb. Ethan Siegel has been positively *rabid*.

    In the end, there’s no way Loeb could possibly be so wrong in his hypothesis that Siegel’s rantings against him could be justified. ‘Oumuamua may or not be a light sail, but it seems pretty clear to me anyway that there’s enough there to at least entertain the possibility. Which is exactly what Loeb’s detractors aren’t doing. And you can’t say that Loeb doesn’t predict that behavior throughout his book.

    I’ve noted the recent hypothesis from Jackson and Desch, and I see that it addresses the high-albedo issue and gets it right regarding color. But it doesn’t explain the smooth acceleration curve and I wonder how the nitrogen pancake doesn’t smack of the same desperation–anything but a technosignature!–that the hydrogen iceberg had.

    This skepticism notwithstanding, I recognize that Loeb himself never addresses the idea of nitrogen ice, being content, if I’m right, to simply suggest that nothing natural would be so pure of carbon.

    I also noticed Loeb’s reaction to the Jackson-Desch work in Scientific American, and I thought it was graceful–certainly more graceful than anything Siegel’s written.

    Again, not done with the book, but I think so far I will cautiously say that Loeb is in fact feeding his ego, but that doesn’t seem to invalidate the possibility that he’s also right about several things.

    • Paul Gilster March 26, 2021, 20:16

      Dr. Loeb has a new paper, out just today, I believe, on the nitrogen ice question. I haven’t read it yet.

  • ljk April 6, 2021, 13:07

    Anything but aliens – and I am not just referring to the reaction to Oumuamua as an artificial probe or leftover starsail, etc.


    [Submitted on 23 Feb 2021]

    Oumuamua Is Not a Probe Sent to our Solar System by an Alien Civilization

    Ben Zuckerman

    Oumuamua, the first known object of extrasolar origin seen to enter our Solar System, has multiple unusual characteristics that, taken together, are very difficult to explain with conventional astronomical entities like asteroids and comets. Consequently, it has been hypothesized that Oumuamua is an interstellar probe that was constructed by an alien civilization.

    We demonstrate that the accomplishments that can be achieved with large space telescopes/interferometers in the alien’s planetary system will completely quench any motivation for construction and launch of an Oumuamua-like probe. The absence of any such motivation proves that Oumuamua is not an alien creation.

    Comments: Submitted for publication in the AAS journals. The Zuckerman (1981) reference is available in pdf format on request to the author

    Subjects: Popular Physics (physics.pop-ph); Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:2103.05559 [physics.pop-ph]
    (or arXiv:2103.05559v1 [physics.pop-ph] for this version)

    Submission history

    From: Benjamin Zuckerman [view email]

    [v1] Tue, 23 Feb 2021 02:48:05 UTC (86 KB)


  • ljk April 16, 2021, 13:14

    What Should We Do if Extraterrestrials Show Up?

    It’s hard to say at this point, but a crucial first step is to establish whether they exist so any future arrival won’t come as a complete surprise

    By Avi Loeb on April 15, 2021


    To quote:

    Are we the smartest kid on our cosmic block? To find out, we should keep our eyes open and search through our telescopes for items from our nearest neighbors, taking proper precaution about a vessel masquerading as a Trojan Horse. There might be plenty of small, fast-moving objects that are constantly traveling through the solar system and that we fail to recognize given the limited sensitivity of our telescopes. It would be interesting to search for them in future data streams from the Large Survey of Space and Time (LSST) on the Vera C. Rubin observatory, which will start monitoring the Chilean sky in less than three years. In addition, my student Amir Siraj and I have shown that a global network of several hundred optical cameras on Earth can identify flares from interstellar meteors entering the Earth’s atmosphere at an unusually high speed of up to the speed of light.

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) discovered gravitational waves only after the National Science Foundation (NSF) invested $1.1 billion in it. Similarly, we should expect to find extraordinary evidence for ETs only after we invest major funds in a search. It would be most appropriate to allocate taxpayer funds to the search for our cosmic neighbors, given the major impact that such a discovery would have on society—far exceeding the implication of discovering gravitational waves.

    Putting our hands on a piece of alien technology would change the way we perceive our place in the universe, our aspirations for space and our philosophical and theological beliefs. Our psychological shock would resemble the one encountered by my daughters when they met kids smarter than they were on their first day in the kindergarten.

    Or we could choose to stay ignorant about our neighbors until they show up. This would be equivalent to my daughters choosing to stay at home. The possible existence of ETs will not go away if we ignore them, just like the Earth continued to move around the sun after religious authorities refused to look through Galileo’s telescope. The dinosaurs dominated the planet for many millions of years, but their reign was abruptly ended 66 million years ago, when the giant Chicxulub rock showed up on the sky, on a collision course with Earth.