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A Harvard Astronomer on the Interstellar Object ‘Oumuamua (newyorker.com)
191 points by jelliclesfarm 30 days ago | hide | past | web | favorite | 146 comments

There's definitely not enough evidence to say Oumuamua is an artifact of an alien civilization. But there isn't enough evidence to say it isn't either. Moreover, as far as I know, there is enough evidence to be pretty sure every other significant celestial body is not an alien artifact. So it's higher on the scale than anything else.

The argument I've heard is that it is a disabled alien probe. This makes sense given that any device sent into space will probably last much longer as space junk than as a working device. So, the density of alien space junk would be higher than the density working artifact. Thus, if this thing were to turn out to be disabled alien probe, it would be more or less what you'd expect to see occasionally if alien civilizations of our level existed in some moderate density (note, most of "Fermi Hypothesis" possibility arguments involves hypothetical higher levels of civilization, which seems to me a rather thin argument).

There is definitely not enough evidence to be pretty sure every other celestial body is not an alien artifact.

Just a few weeks ago New Horizons was doing a flyby of kuiper belt object Ultima Thule. Before the flyby, this object was merely a couple of pixels in any of our instruments.

In fact, it exhibited odd light curves that seemed very unlikely for a regular asteroid. This also prompted comparisons to Rama, just like Oumuamua did. Its straight out of the book.

So up until the first pictures were downloaded, we definitely did not have enough data to disprove an alien artifact hypothesis. Turned out to be just another asteroid (a pretty interesting one, but no green men)

Ultima Thule was a studied object, targeted by an serious AF NASA interplanetary mission, and we knew jack shit about it. There are millions of other kuiper belt objects out there and we know absolutely nothing about them.

So yeah, Oumuamua is pretty much part for the course in that regard.

One major difference between Oumuamua and Ultima Thule, is that Ultima Thule is very accurately following a known gravitational trajectory. Oumuamua is not, and that factors greatly into the astronomer's point of view.

Also, from the article, while traversing the solar system Oumuamua apparently changed velocity in a way not explained by local gravity or gas discharge. U.Thule may have had odd lighting, but I don't recall hearing it moved in an odd way.

"The most unusual fact about it is that it deviates from an orbit that is shaped purely by the gravitational force of the sun. Usually, in the case of comets, such a deviation is caused by the evaporation of ice on the surface of the comet, creating gases that push the comet, like the rocket effect. That’s what comets show: a cometary tail of evaporated gas. We don’t see a cometary tail here, but, nevertheless, we see a deviation from the expected orbit. And that is the thing that triggered the paper. Once I realized that the object is moving differently than expected, then the question is what gives it the extra push. And, by the way, after our paper appeared, another paper came out with analysis that showed very tight limits on any carbon-based molecules in the vicinity of this object."

No one has claimed that Oumuamua is likely an alien device. It has been cited as a possibility and that possibility is being touted as justification for doing more to study such objects.

Most of these comments are arguing against a claim that has not been made.

Well, apart from the interiviewee in the article that this conversation is about who certainly seems to make that claim. From the interview:

> "It is much more likely that it is being made by artificial means, by a technological civilization."

That's not a general conclusion he's pushing, it's what he thinks would be a likely conclusion if two other hypotheticals are met:

"if it is indeed less than a millimetre thick, if it is pushed by the sunlight, then it is maybe a light sail"

It's not clear at all that he think it's likely that it's less than a millimeter thick or that it is a light sail. That's simply "the only thing that came to his mind" to explain the additional force(s) working on it.

Ok how about the introductory paragraph that states

> The following October, Avi Loeb, the chair of Harvard’s astronomy department, co-wrote a paper (with a Harvard postdoctoral fellow, Shmuel Bialy) that examined ‘Oumuamua’s “peculiar acceleration” and suggested that the object “may be a fully operational probe sent intentionally to Earth’s vicinity by an alien civilization.”

or another spot where he says

"Every now and then we find an object of artificial origin. And this could be a message in a bottle, and we should be open-minded."

Seems to me like he is saying it could be worth considering that maybe this is an alien object.

The goalposts are moving. Yes to "worth considering" but that's not what I was responding to above ("is likely an alien device" ... "certainly seems to make that claim").

I'm not trying to move the goal post. I'm only taking umbridge with the fact the previous poster said "No one has claimed that Oumuamua is likely an alien device". The person interviewed in the very article this discussion is about seems to think that maybe it could be. So we are talking semantics between "likely" and "possibly".

"likely", "maybe", "possibly" can all be used differently.. Especially if you take it out of context of the rest of the article.

> Man that food sure looks tasty.

> You haven't even tasted it! Why are you saying it's tasty?

There are absolutely no claims that it's an alien artifact. What he is doing is providing reasons for why checking out similar solar visitors is something we need to do.

Here's my layman's understanding of the semantics between likely and possibly:

Likely: greater than 50% probability

Possibly: greater than 0% probability

Saying something is likely is a pretty strong claim. You can make meaningful decisions based on such knowledge.

“Every now and then we find an object of artificial origin.” Did he just admit we have found aliens before? What other artificial objects or origins have we ever found?

" It is very similar to when I walk on the beach with my daughter and look at the seashells that are swept ashore. Every now and then we find an object of artificial origin. And this could be a message in a bottle, and we should be open-minded. So we put this sentence in the paper. "

That quote is specifically in answer to it being a millimeter-thick light sail. An object that size that is only a millimeter thick... yeah, I might agree with his "much more likely" characterization, if the object has that shape.


Given extremely ambiguous information, the chance of something like Oumuamua being an alien probe depends very strongly on the chance of an alien civilization producing something like this. And those chances are beyond anyone knowing. The Bayesian priors are just unguessable.

As I understand it we more about Ultima Thule than that. First, it is in orbit around our Sun. Further that orbit is very close to the ecliptic (low inclination). Further there are many such objects of various sizes in the Kuiper belt.

All of those things are easily explained by it having formed at the same time as the other Kuiper objects formed and in the same way. It makes it significantly unlikely that it flew in from far away, decelerated into orbit in the Kuiper belt, and then changed its orbit to match the ecliptic.

And even though it was but a few pixels, by calculating its mass using its orbital parameters its density can be deduced to be similar to other belt objects (rock and ice rather than metals). Which further enhances the 'its a normal object' hypothesis.

It is possible of course, that an alien civilization designed a probe that would mimic the composition of a Kuiper belt object and flew it here, and then inserted it into its orbit, and then flew away, so that it could sit there and do what ever it does. But that is not the most likely answer :-)

    > Ultima Thule was a studied object, targeted by an serious AF NASA interplanetary mission...
It was targeted by New Horizons project well after the spacecraft lauched in 2006. Ultima Thule was only discovered in 2014 !!

Sadly for Oumuiamua, this thing was detected far too late to do intensive observations, it's on the way out of the solar system if I understand correctly.

Wouldn't a disabled probe present a statistical problem? A disabled probe likely means we weren't the intended target of the probe. Considering how quickly we found this thing after we have acquired the ability to find them it either means we are incredibly lucky and we just happened to see an extremely rare event, the probe was targeted towards our solar system, or interstellar space is full of these probes making them incredibly common sights. If you can statistically rule out the first explanation and a disabled probe rules out the second, what is left besides that third option which is inherently much harder to believe?

If this work the work of an alien intelligence it seems unlikely that it wouldn't have been targeted at our solar system. Space is so vast that accidentally running into a solar system other than then one you intended is stupefyingly unlikely, especially at the speeds this object was traveling.

Another interesting point is that if it is an alien probe it would have had to been sent long before human civilization began unless the aliens are parked practically on our doorstop.

I'm not arguing that this is an alien probe, but I don't think being disabled rules out the possibility of the flyby being intended. We don't know exactly how long our probes will last, that depends on radiation and other factors. The trajectory could have been plotted to keep slingshotting around different stars long after the expected lifespan of the probe had elapsed, just in case it lasted longer than that.

I like this characterization of it. Basically we can't prove that it isn't an alien artifact yet, which is impressive given all the things that we can state conclusively are not alien artifacts.

When Voyager 1 and 2 fly through some distant star system millennia from now, it will be pretty clear they aren't space junk. But it is also true that our species will no longer exist either.

I base that on the following conjecture, if we were to become capable of travelling among the stars with relative ease, then we'll go collect these two little artifacts and put them in a museum. But if we go extinct, these ships will continue on their way forever. So any alien that comes across them can know we're extinct.

> I like this characterization of it. Basically we can't prove that it isn't an alien artifact yet, which is impressive given all the things that we can state conclusively are not alien artifacts.

That seems like the height of human hubris - we are stuck on a little rock in the corner of the galaxy, but somehow assume we are authorities on things astronomical.

> I base that on the following conjecture, if we were to become capable of travelling among the stars with relative ease, then we'll go collect these two little artifacts and put them in a museum. But if we go extinct, these ships will continue on their way forever. So any alien that comes across them can know we're extinct.

You're assuming that we will at some point have the ability to catch up to them - we may develop interstellar flight, but it may be stuck in very slow speeds, we may never catch up to them with our giant colony ships as we sleep away the eons.

>That seems like the height of human hubris - we are stuck on a little rock in the corner of the galaxy, but somehow assume we are authorities on things astronomical.

The basic idea of science is that it's possible to do better than "assume we are authorities..." I don't want to come across as unsocial but in dismissing astronomy without knowing enough about it you may be guilty of some hubris yourself.

I'm not dismissing astronomy at all. I'm saying that if we can't explain something, that doesn't mean it can't be explained in some other mundane way. When we look at a problem and go "well, we don't really know what caused it, therefore aliens" seems ridiculous when there's unlimited things that could be the cause, just because we aren't aware of those causes.

I'd like to conjecture that even if we did develop interstellar travel, we will let them travel.

Now instead of collecting them, we will mostly build a mobile museum, to show the then humans, achievements of early humans, still moving through space.

Eventually we will get so advanced we wont really worry about collecting them at all, for the same reasons, the current humans don't go looking for the first wheel ever made.

Is it necessarily true that our species will not exist when Voyager 1 and 2 fly through in a galaxy far far far away a long long time in the future?

Are you talking about Terran homosapiens specifically and the consideration that once we populate other planets that we'll become genetically different enough to no longer be considered the same species - or do you think we'll never get up there?

A couple of things; time and circumstances.

First we know there are many ways in which life on the planet can be eradicated that are not yet preventable by humans. Asteroid impact, solar flare, volcanic eruption, and climate change, while humans also can kill ourselves off with a large exchange of nuclear weapons. So if you plot the chance of our existing over time, as long as we stay a single planet species that plot heads to zero long before Voyager interacts with another star system.

Then we have Voyager, which will take 17 thousand years (and some change) to go one light year. Nearest star system is Alpha Centauri at just over 4 light years away so conservatively 80 thousand years before Voyager gets there (assuming it is on a path that takes it to Alpha Centauri)

Doing the math, the probability that humans exist in 80 Kyrs versus human ability to travel at a significant speed (say > 0.5c) between the stars vs human nature to retain artifacts when they can from historic events.

It is a thought exercise, which I doubt we'll live to see any affirmative answer to :-)

Voyager 1 is going 38,610 mph, 2 is slightly slower than that.

Andromeda, one of our closest galactic neighbors is 220,000 light years away.

Imagining that Voyager 1 is going in the right direction and ignoring that the Andromeda is going to collide with us regardless, that works out to 3,821,000,000 years to get there. And that's for a very very close galaxy, on an astronomical scale.

Pretty optimistic to think we'll be around on that time scale, but I suppose it could happen.

Aren't both Voyagers still gravitationally bound to our galaxy? They have escaped the sun but not milky way. In this case they will never leave our galaxy.

Good point. A quick google gives 537 km/s as the Milky Way's escape velocity, or 1,201,000 mph. Not going fast enough for that.

Moot point for Andromeda since that's coming here, but it'll never ever get to any other galaxies.

Voyager’s stated velocity is relative to the solar system, which imparts its own velocity relative to the Milky Way to Voyager. Another quick google suggests Sol is swinging around the galaxy at 200 km/s so Voyager’s 17 km/s is really nothing.

Also depends on whether Voyager's velocity is in a useful direction, it could just as easily be counterproductive. But not much difference either way.

But might they not travel through another star system in this galaxy before getting anywhere near another galaxy?

"Voyager 1 will eventually come within 1.6 light-years of the star Gliese 445 — in astronomical terms, this will be a near-miss. But don't hold your breath; the "encounter," for lack of a better term, won't occur for another 40,000 years.

After that, it gets a little difficult to predict Voyager's journey, as chaotic motions within the galaxy make accurate predictions of stellar movements challenging. But given the wide swaths of empty space between the stars, the spacecraft's visit near Gilese 445 is probably the closest that Voyager 1 will approach another star, ever."


OP said star system. You’re quoting distances to another galaxy.

I’m responding to

>Is it necessarily true that our species will not exist when Voyager 1 and 2 fly through in a galaxy far far far away a long long time in the future?

Thanks for your answer btw, it was exactly what I was looking for as I didn't know the speeds of the Voyagers.

The one making the claim has the burden of proof. And following Hitchen's Razor: What can be asserted without evidence, can be dismissed without evidence.

Saying that is an alien probe it's not an argument, just an untested hypothesis. What follows on the paragraph is an argument, albeit a bad one.

> The one making the claim has the burden of proof.

This is nonsense. Every claim has an corresponding claim of its negation. Which one has the burden of proof?

What evidence do you have that it's an asteroid?

Scientifically speaking, that it's an asteroid is the default or null hypothesis. That it's an alien artifact is the alternate hypothesis.

The burden of proof is on the latter, this is just SoP in science. Otherwise we end up with a world full of superstition, as it was for most human history.

We have no evidence yet of other intelligent life in the universe. But we know there are quadrillions of asteroids all over the place, some of which pass by us every so often.

Occam's razor, correctly stated, says that, all else equal, the explanation that relies on the fewest assumptions is most likely the true one. Given our lack of evidence for intelligent life, and preponderance of evidence of asteroids, the former explanation requires far more assumptions than the latter.

By definition it’s not an asteroid, it’s a celestial body but we don’t have a classification for it since we never seen one before.

It is also not a comet, so the null hypothesis is that it’s a rocky natural object but it doesn’t mean it’s an asteroid.

The best classification we might have for it is a distant detached object (DDO) but since it’s likely not part of our solar system it can’t be classified as a detached object by the current minor planetary object classification system we have either.

Fair enough. Should probably just generalize that's some kind of naturally occurring thing that's not the result of alien intelligence.

You are mixing multiple interrelated ideas (and to be fair so was the person you are replying to).

In most cases the "claim of negation" is the default position (related to the null hypothesis). If I claim there are invisible faeries that hold us to the earth. The negation of that claim is that there aren't. But this sort of reasoning only applies to things like debate and philosophy.

Science is fine with the unknown, claims must meet the burden of proof to be considered more than a speculation. Hence a "claim of negation" isn't scientific, because you instead present observation and calculation which makes the claim invalid in the first place. The default state being that no claim (we call these hypothesis) is valid. Sometimes this means that there are many competing partially valid hypothesis. One can't prove a negative, so instead science deals in hypothesis and only ever judges the positive claim against what we know. I can't emphasize this enough, there is no such thing as a negative claim in science: just a claim that we don't know the answer yet because no current hypothesis are convincingly valid.

People aren't claiming it's an asteroid, because that has a specific definition it doesn't match. Note in the article he talks about comets as one thing some people think it is. In the title of the article it's "Interstellar Object" which I don't think anyone is disputing.

The hypothesis he is putting forward is reasonable though. At least as well as any other hypothesis. We don't really have proof (observations) either way (and like a good scientist he spends a lot of time pointing out how we should be ready next time) so no hypothesis can meet a burden of proof at the moment. But then science doesn't really use a concept of "burden of proof", that's a legal concept. Instead we simply work with our least wrong models - even our best theories are not proven - which are judged by how well they predict the world.

And in this example the hypothesis "aliens did it" answers a lot of questions in a reasonable way. But then so does "nature did it" but some of the answers and mechanisms are less convincing in that case. And I think the point the interviewee is making is that we should be ready to better answer that question next time an object like this comes by because the answer "nature did it" is somewhat unconvincing for this object.

The null hypothesis is like the empty set: there's no claims inside it. The negation of a claim is another claim independent of the first.

Suppose I show you a jar containing a large number of coins and I claim the number of coins is even by just looking at the jar. Do you have evidence that I am correct? No! Just by looking at it I can't possibly know the exact number of coins. But this means that the logical negation of my claim is true ( the number of coins is odd?). Also no! Again, I can't know the exact number of coins by just looking at it.

So although there are only two possibilities, I have no evidence at all. And this means the only claim I can make is the null hypothesis: I don't know.

Absence of evidence is not, itself, an evidence of absence. In other words, if I don't have evidence that you committed a murder, it doesn't mean you're innocent. It means just that: I don't have evidence to convict you, and I must dismiss the case.

I didn't mix anything up, and your comment agreed with mine and expanded upon it (and I thank you for that).

I agreed with your conclusion but not your methodology nor terms nor those of the person you were responding to.

Exactly what J Harlen Bretz (the Missoula Floods guy) said when other geologists said he needed to figure out where all that vast volume of water came from. 'Not my problem.'

Secondly, science doesn't prove. It creates models, and finds the ones that stand up to close scrutiny. Bretz provided massive evidence for his flood model. Those who chose to ignore him chose to ignore the evidence ... whatever their names were.

I didn't claim it's an asteroid. What I said, actually, is that any hypothesis asserted without evidence, and the autor of the post affirms that we have no evidence for the claim that it is an alien probe, can be dismissed without evidence.But to be fair, anyone claiming it's an asteroid must provide evidence supporting his/her claim. Otherwise it can also be dismissed without evidence.

The one making ANY claim has the burden of proof. The null hypothesis is the default whenever there's no evidence supporting any claim. It is basically a fancy way of saying we don't know what it is.

Other similar things are asteroids. It's doing a thing an asteroid would do.

It's much more likely that it's ejecta from some event from outside our solar system. Or a redirected Oort body.

> There's definitely not enough evidence to say Oumuamua is an artifact of an alien civilization. But there isn't enough evidence to say it isn't either.

This is why the Occam's razor rule is important. He formulate a (weird) hypothesis, he thought 3 or 4 ways to prove that the hypothesis is false, then he failed to prove that the hypothesis is false. Then the conclusion is???

The possibilities are:

* A weird asteroid

* A disabled alien probe

* A functional alien probe

* Something more weird

All four variants have almost the same level of support now. But using the Occam's razor we should favor the first one until more evidence is discovered.

Why should we favour the first one?

Imagine our best understanding of cosmology suggested that some interstellar object, which we'll call "foobars" for the sake of this argument, existed in high amounts. However, we weren't totally certain that foobars existed, or exactly what they would look like if they did.

In this case, when we discovered a new, weird and unexplainable phenomenon, would there really much pushback when somebody proposed that foobars might be the cause?

Well, according to the Fermi Paradox[1], there's seems to be a very good chance, statistically speaking, that alien life is common in our galaxy. So, when a phenomenon is observed with highly unusual characteristics, why should an alien origin be considered unlikely or fringe explanation?

I think people dismissing or diminishing the possibility of an alien explanation should also be required to provide a reasonable, evidence-based explanation for the Fermi Paradox.

[1] https://en.wikipedia.org/wiki/Fermi_paradox

> Why should we favour the first one?

If confirmed, which of the following two will get to the first page of all newspapers in the world:

* Scientists find a rock in space

* Scientists find a alien starship in space

The "default" selection is the other, unless someone provides overwhelming evidence.

> In this case, when we discovered a new, weird and unexplainable phenomenon,

It's probably a rock with some ice.

> Well, according to the Fermi Paradox,

The Fermi paradox starts from the assumption that we should expect a big number of advanced civilization in the Milky Way, but we really don't have the smallest cue about how the number should be. We have a estimations from millions of millions to much less than one. We just don't know. We only know that we didn't find an alien civilization yet. We didn't even find alien life yet. So you can't use the Fermi paradox as a proof or supporting evidence that an unknown object has alien origin.

The density of interstellar alien space junk is almost certainly much, much lower than that of natural interstellar objects. So there is a very strong prior that this is likely a natural object.

I highly recommend the PBS Space Time video on this topic linked in another comment.

Depends on your priors for the parameters in the Drake equation.

The shape seems to be the most interesting part about it. If it were deliberately manufactured by a sentient alien civilization, why choose that specific shape? A light sail based probe doesn’t seem to be a sufficient enough explanation for the shape.

> If it were deliberately manufactured by a sentient alien civilization, why choose that specific shape? A light sail based probe doesn’t seem to be a sufficient enough explanation for the shape.

Why not? Assuming a civilization is (or was) technologically advanced enough, they would probably be doing lots of things we couldn't understand, especially given how little we know about this thing. He wasn't saying it was definitely, or even probably, a light sail, just that we should entertain the possibility.

Besides, we don't actually know what the shape is, only that its changes in brightness would be consistent with an elongated object, which is the simplest explanation. Or, maybe the object is perfectly spherical but the brightness changes are due to seeing a light sail at different angles, which is extremely unlikely but within the realm of possibility.

Point is the shape is unknown. A cigar shape is one possible explanation that fits the light curve data; a solar sail is another.

Only the solar sail shape could explain how the object accelerated without outgassing

I'd say its unexpected change in velocity is the most interesting part about it.

Antennas for sending data back need a large area parabolic dish. Solar panels also need a large area. Large area seems like a likely feature of any probe.

for a "naturally occurring" process to create something we could suspect as a lightsail, I wonder about something, perhaps a comet, blowing a bubble. That is a layer of something what could form a membrane over something that could off gas. Both triggered by heat. Bubble is created and pops or deflates and the skin blows around for ever.

How much would it cost to go grab this thing and plonk it onto the moon for studying, in the event the object is harboring a contagious disease? Could a private company accomplish this?

Nothing like that has ever been done, and the object is potentially huge and heading away from us at speed. I doubt even a photo intercept is now feasible at all.

That is unfortunate. That makes me curious about Voyager 1/2. We put drawings and objects on it for other civilizations to study. I wonder if they will have a similar dilemma; in that, it is moving too fast.

If you can detect voyager, you’d be advanced enough to be able to catch it, as you’d be almost on top of it.

We can barely see Ultima Thule as a pixel, which is closer, and the size of a city. Voyager is the size of a pinto.

Getting a probe going fast enough to catch it is currently beyond us; never mind bringing it back. But if we start burning money now we might have a chance for (at least a better peek) at the next one

Curious if any billionaires have rock collections. This should qualify as a rare rock.

We could get a probe to encounter it, however it would be a high speed encounter - far faster than new horizons encounters. Interception seems off the table currently.

You mean to build a spacecraft capable of getting there in the time available, and assembling a company to do the necessary operations of launching the spacecraft and managing its operations, and funding those operations, etc.?

What would be that private company's incentive?

Honestly I am not sure. Perhaps if they suspected great mineral value, or perhaps using that as a PoC to prove they can do it for future military contracts, but I don't know.

There are many projects I can't wrap my head around due to the great costs. When I suggest we should not spend trillions on going to mars without having a specific need to do so, people reject that notion.

>there is enough evidence to be pretty sure every other significant celestial body is not an alien artifact.

How the heck do we know that? We have no idea what "alien technology" might be or what the result of it might look like.

Well, I think everyone is pretty sure that there is no intelligent alien life in our solar system, since everything we can see is either a rock, or ball of gas or ice. The only things we can detect outside the solar system are stars and maybe some of their planets, or things much bigger than stars, all of which we are also pretty sure are naturally occurring given their scale. That doesn't leave a lot else that we have observed outside of this Oumuamua object and maybe a few stray radio signals that we can't account for.

PBS SpaceTime's excellent coverage of Loeb's paper: 'Oumuamua Is Not Aliens


>When you look at all the stars in the vicinity of the sun, they move relative to the sun, the sun moves relative to them, but only one in five hundred stars in that frame is moving as slow as ‘Oumuamua. You would expect that most rocks would move roughly at the speed of the star they came from. If this object came from another star, that star would have to be very special.

If we're to assume that this is something that was expelled from a remote solar system, wouldn't you then also assume that there had to be some explosion or collision to get this thing on its current course? And wouldn't that account for a speed that doesn't match nearby objects?

As your quote indicates, it's not just not going at the speed of any nearby star, it's going at the particular speed of the galaxy (or galaxy's average rotation). If an object were expelled randomly by a nearby star, it's speed would be: star's speed + random extra boost. The chances this would exactly the galactic speed seems small.

Kinda a weird speed for an alien artifact too, though. One would expect for it to be launched. Humans may in some sense have a small time horizton, but you have to have an absurdly long time horizon to fling probes out into the universe at the local average speed and expect them to encounter anything, since by definition of "local average speed" that's literally the speed least likely to encounter anything. In some sense, that's actually literally the least likely velocity I'd expect to be an alien result.

(And it's also conceivable that humans have bizarrely long time horizons, if the future of all intelligence is moving into a machine intelligence on a computational substrate as fast as possible. If intelligences subjectively experience hundreds or thousands or millions of times faster, it's like dropping the speed of light by the same factor, and it still takes all the same amount of energy to launch probes. I'm not saying this is inevitably true, but I do think there's an excessively strong bias to assume that humans are as bad as possible in every possible way.)

It's exactly what you would want to do if you didn't want someone who found it to be able to tell where it came from

For that, you just need the velocity vector not to be in the very narrow class of vectors that point back at you. There's no need to put it in "galactic neutral", especially given that, as I said, that's literally the worst possible speed to get anywhere. That's just one possible choice from the almost-every-possible-vector selection set that will work to disguise your origin.

Of course, we also have the question of why you would care to disguise your origin for a "space probe" traveling at such a slow speed. (Pretty much every conceivable mechanism that could have something traveling at any appreciable speed and that slowed it down anytime in the recent past would be very easily detectable. Of course you can invoke inconceivable mechanisms, but as I often say, you have to understand you have left rationality and logic behind when you do that; if we're going to say this object has a magic drive that decelerates without any detectable emissions, we might as well ask why it's not just using an FTL drive, or why any alien civilization is bothering to "probe" us when they've long since landed at Area 51 and have long since been running our civilization anyhow as our secret leaders.)

Whipping it around a nearby unoccupied star would be an easy way to obscure its origins. Just their bad luck that Sol turned out to be occupied, by a primitive civilization that might be able to act on knowledge of its origin vector in a few centuries or millennia.

It looks slow to us, but it might be that whatever method it uses to skip big distances doesn't steer, so the only way to get pointed somewhere else is a close approach. And, of course, the method doesn't work in a gravity well, so it has to coast until it's a few hundred AU out.

Will enough records be preserved through the coming dark ages (after the ecosystem collapses) for the raccoons or macaques or whatever inherits the earth to act on them?

The raccoons and macaques will likely have their own close approaches to observe and trace back.

Kinda a weird speed for an alien artifact too

It is a weird speed for a probe that has been recently launched to be going. It is the speed you'd expect "junk" that has been floating in speed for long time to be going, getting slingshotted from star to star until it's speed adds up to the average of the wide area it's in.

Of course, does being bounced from star to star mean the thing was built for that or is it just something could happen at random.

But given a long enough time and an object with a low enough ballistic coefficient I'd expect it to come to rest with respect to the interstellar medium, maybe. I don't know if that works out quantitatively in this case.

Well, it also is very likely to go at a speed that makes it easy to spot (easy for its class), because otherwise we would have seen the easier ones first (except if this one is a super fluke and we’ll never see its like again)

But not for the odd shape, or for the apparent change in acceleration with out any off-gassing.

The title's use of "Harvard" is interesting in that it hints at appeal to authority.

Imagine that the astronomer were based at Lackawanna College. Would that information be worth conveying through the title?

"Lackawanna College Astronomer on the Interstellar Object ‘Oumuamua"

I doubt it. The problem with appeal to authority is that there's no place in science for it. Not only that, appeal to authority undermines science itself.

As Carl Sagan put it in The Demon-Haunted World:

Arguments from authority carry little weight – authorities have made mistakes in the past. They will do so again in the future. Perhaps a better way to say it is that in science there are no authorities; at most, there are experts.


In a way, quoting Carl Sagan is an appeal to authority in itself. If the same words were said by /u/RandomRedditUser, the quotation would carry less weight.

You could also see the "Harvard Astronomer" and "Carl Sagan" here as appeal to expertise, for which university association is an imperfect proxy.

I see how it could be interpreted that way. But my purpose was to credit the author and his book.

Had I left the quote without attribution and claimed it as my own, I'm sure someone would have suggested I should take a refresher on plagiarism. Ditto had I paraphrased Sagan without attribution.

If I had merely given the quote without a link or context, I'd run the risk of perpetuating false quotes.

Had /u/RandomRedditUser written the text instead of Sagan, I would have cited it in the same way.

I'm not criticizing the way you quoted Sagan; what I'm trying to say is that there's no escape from any kind of "appeal to authority".

There's too many people saying too many things that are too expensive to evaluate on their own merits; we all use heuristics to filter and rank stuff. Appeal to authority/expertise is one of those (and, as all heuristics, imperfect).

This is not an appeal to an authority, though (which you acknowledge with your "hints at" comment). An argument from authority is of the form "this guy is at Harvard, therefore his argument is correct."

What is happening here is that the popular press is using the professor's association with Harvard as a heuristic to determine whether or not to take him seriously enough to publish his arguments. To a first approximation, this is a reasonable thing to do, because it's using the prior probability of someone having something interesting to say to guide your choice of where to devote your scant attention.

By no means is this a substitute for an actual substantive evaluation of the claims being made; when that happens, you have fallen prey to the appeal to authority fallacy.

This is news, not science. The science will come after.

If Linus Torvalds makes a bold prediction about Linux, it carries more weight. Likewise here.

The creator of a work has unique rights over that work. There are literally authorities on created works. They are the "authors."

I think what Sagan is getting at is that no such relationship between scientists and science exists. Although the author of a scientific paper can be an authority on it, that authority doesn't extend to the subject of the paper.

if I want to convince somebody of something scientific, I point them at a textbook written by an authority (say, Bruce Alberts, who wrote Molecular Biology of the Cell). For each fact in the book, it contains citations to the original scientific publications (most of whom were written by authorities, but some simply by experts).

Probabilistically, it seems like authorities are the least likely to be wrong.

Oumuamua probably isn't artificial, but observations of objects like it and Tabby's star, fast radio bursts and contact binary systems* will likely increase as our instruments and data parsing improve. So, if aliens are the cause of any these or some repeated, anomalous future observations, it's only a matter of time before we all but confirm we are not alone.


My favorite speculation is that Oumuamua is a spent deceleration stage for a larger inbound multi-stage interstellar rocket. It would probably be a nuclear fusion rocket or similar. Previous stages flew past us and we didn't notice. The next stages(s) and/or the payload should arrive shortly. Since it's decelerating the next stage will be traveling slower.

Something like that would probably be bright enough for us to see it by now if we looked, and we probably did because of our interest in Oumuamua.

Assuming it's not intentionally obscured.

If I were building an interstellar vehicle to send to/past possibly hostile alien worlds, it wouldn't have headlights.

You can't do stealth in space. Thermodynamics won't let you. If you're using a whole lot of energy you will light up in the infrared.

Parent's point is valid except for the fact that they might not be lighting off the deceleration stages one after the other. There could be a time gap, and maybe a significant one. Gaps between firings would be likely because that's one way you could steer. You could time firings to aim for e.g. an orbital insertion around Jupiter, which would be easier since Jupiter is so massive. You could also use Jupiter or another gas giant to aerobrake with some kind of ablative shield like in the film 2010. It's fairly likely that whatever physicists' nightmare propulsion system an expendable interstellar rocket stage would use would be something that is hard to turn off once you light the candle, so each stage might be an all or nothing thing.

It would be interesting to use the JWST, an infrared telescope, to look at areas of the sky where an inbound craft coming along this sort of interstellar trajectory might be. A probe or spacecraft would have to have its own power source. This would be way dimmer than a lit deceleration stage, but JWST might be able to see it. If it's using energy at all it must have radiators due to the second law.

Of course if this hypothesis were valid and they lit another deceleration stage, it would absolutely be visible if we looked in the right place. It would be very very bright in the infrared and probably in visible light too. Hell if it's something insane like an antimatter driven fusion rocket you might be able to see it with the naked eye.

If it is decelerating toward us it will have to be dumping significant amounts of hot propellant at least roughly in our direction. You can't obscure that with known physics as far as I'm aware.

If you're going to involve unknown physics, the theory becomes a lot more unlikely.

That's actually a fun thought... once you've got your probe up to a third of the speed of light or whatever... how are you going to slow down again in order to actually do anything useful?

Or maybe this is a solar sail that was part of an ACCELERATION stage for a probe that already passed through our solar system millions of years ago.

If we were to do an interstellar ship with current physics it would probably rely on:

- Preacceleration strategies that speed up the craft without using its onboard/deceleration reaction mass/fuel (gravity whips, launching lasers for a solar sail, cannon-fired fuel pods)

- Pulse nuclear acceleration using "preseeded" fuel pods launched ahead of the craft and captured as the craft caught the pod

- ion drive once the preseeded fuel pods weren't practical anymore

- ion drive, solar sail, and pulse nuclear and more gravity whips to slow down

Pulse nuclear/orion ships are the only thing that gets close to specific impulse and performance to get to Alpha Centauri in anything reasonable. It becomes a LOT more feasible if fuel pods are prelaunched, or seeded by a leading disposable fuel seeding ship (it doesn't have to slow down, it can just, uh ...

.... fly through the target system once it's done.


This kind of makes me want to play KSP again...

I'm not a rocket scientist (heh) but I'm imagining a many-stage nuclear rocket. You'd have a whole bunch of acceleration stages followed by a much smaller number of deceleration stages followed by the payload. You wouldn't need as many deceleration stages since you've already spent all the mass in your acceleration stages.

Building such a thing in space would involve sending up the stages themselves with some kind of heavy lift vehicle, assembling them in orbit, and firing it. The number of stages you could assemble would be quite large since there's no air resistance or (relative) gravitational stress in space. You'd just have to not exceed the tensile strength of the material during acceleration. You could put together 100 stages or more I'm sure. It's one rather brute force but workable way of reaching some nontrivial fraction of the speed of light.

Someone should do the math on this for fission (NERVA-like), thermonuclear pulse (Orion), and pure fusion.

“...at least a quarter of the stars in the Milky Way galaxy have a planet like Earth, with surface conditions that are very similar to Earth, and the chemistry of life as we know it could develop.”

I was rather surprised by this claim. Isn’t it currently beyond our ability to detect earth-sized planets around other stars? Isn’t it also beyond our capability to directly detect surface conditions on planets around other stars?

This is actually a really weird claim. We know now thanks to Kepler that many stars have planets just like our Sun does, but so far we've only been able to see large gaseous planets and a few rocky ones that can be as large as 1.5x Earth.

25% sounds way too high. We have not even found many stars like our own with rocky Earths like our own yet. I am certain we will eventually find them, but I think the number of rocky planets with oxygen atmosphere and liquid water is going to be under 1%.

Life is most likely rare but abundant- 1% of 100 billion is a butt-ton of Earths

It is not beyond our ability, as "detecting earth-sized planets" was the explicit mission of the Kepler spacecraft.

I guess I should ask a different question then. Have we detected any earth-sized planets? I can only remember hearing about super-earths and gas giants, and I generally read the exoplanet discovery announcements when I see them.

We have indeed. This page has some that are also in the habitable zone: https://en.wikipedia.org/wiki/List_of_potentially_habitable_...

Note that, while some are super-earths, others like Kepler-438b or the planets in the TRAPPIST-1 system are Earth-sized or smaller.

Possibly an extrapolation from Kepler data, which can only see planets orbiting at the right angle. If it were to be looking at an extra-solar system "top down" then it wouldn't find any planets.

For astronomers "earth like" is just about anything within an order of magnitude of earths size and within the very vague habitable zone, it doesn't say anything about it's surface conditions.

You should be able to look up the exact numbers here[0]. Figure 1 in this paper[1] shows a radii histogram of kepler sub gas giant exoplanet candidates.

[0] https://exoplanetarchive.ipac.caltech.edu/

[1] https://arxiv.org/pdf/1806.05909.pdf

If this unusual object were an artifact and our solar system wasn't it's destination the most positive evidence for it's artificial nature would be it's onward destination.

As yet I haven't seen any extrapolations of its post-encounter track.

thank you Dr. Loeb for giving this the attention it deserves. oumuamua demonstrated that we aren't equipped to respond fast enough to these types of objects. we need plans in place that addresses the latency of fast moving objects so that we can prioritize them for study and not be left wondering...

I'm not exactly sure why you are being downvoted at the time of my reply. Surely being prepared for this situation will give humanity benefits regardless of any actual contact with alien civilizations. Similar to how having environmental friendly tech is a net plus regardless of your stance on global warming.

Why? We haven't even finished studying all the slow-moving nearby objects.

The following October, Avi Loeb, the chair of Harvard’s astronomy department, co-wrote a paper (with a Harvard postdoctoral fellow, Shmuel Bialy) that examined ‘Oumuamua’s “peculiar acceleration” and suggested that the object “may be a fully operational probe sent intentionally to Earth’s vicinity by an alien civilization.”

The referenced paper is here:

Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration?


Having already read multiple articles about Oumuamua, the only thing this particular article added to my knowledge is that Isaac Chotiner is not a particularly good interviewer.

>> Loeb has long been interested in the search for extraterrestrial life, and he recently made further headlines by suggesting that we might communicate with the civilization that sent the probe. “If these beings are peaceful, we could learn a lot from them,” he told Der Spiegel.

Such as why it's a bad idea to communicate with alien civilisations, particularly ones that appear to be more technologically advanced than ours.

The whole case sounds just crazy publicity stunt.

After reading more, I think Avi Loeb had a valid reason to speculate and put it out there even the numbers have large uncertainties and put the article out because the argument is good enough even with the large uncertainties. It's the fault of the general public if they get carried away.

(If I would bet, I would say the probability is less than 0.00001 that the hypothesis is correct.)

Dr Avi Loeb is one of those rare individuals in his field who doesn't believe in "settled science" as opposed to others in his field.

"settled science". Love that term.

This guy will need to have a chat with a plasma physicist, one of these days, if he wants to get to the bottom of this.

When he does, he will then need to keep it to himself, because there's no quicker route to ostracism, in astronomy, than to start talking about electromagnetics.

What's the future for the study of Oumuamua? Apparently, it should be beyond the orbit of Saturn by the end of this month. Will we _ever_ know what it is definitively, or is it too late?

I would like to understand this better myself. If we dedicated some resources and say... a year until launch, could humanity (current state of tech) build something that could catch up to this thing in a reasonable (2, 3-5 year?) timeframe?

Unlikely that we will ever know for this specific object, but hopefully we will be more poised for future study ;)

Oumuamua is moving way too fast for anything to catch up to it anytime soon. If I remember correctly it's moving about as fast as New Horizons in the 23km/s speed range. You would need lots of years to catch up to it!

Is the object too small and/or traveling too fast that we can never get better photos of it? I am assuming we can still predict where it should be even after it left our system?

It was detected too late (already 0.22 AU from Earth and moving away) and it is tiny, only about 100m. We will never get any photos from it.

we [as a species] already have probes landing on interplanetary bodies; and have made considerations to manipulate trajectories of such.

I would entertain the possibility the object in question could be just such a hacksteroid of mostly cosmic origin with some tech pushing it around.

some good news. if it's a solar sail it means that their technology doesn't include em drive warp speeds and all that fancy stuff so it will take them a long time to come and kill us all

I am making a note to read the paper because this interview was a disaster. The interviewer asked a personal question about religious beliefs and denies that the question was inappropriate after putting him on the defensive by questioning his reasoning from a decidedly uninformed perspective. Why not survey others in the field and voice their objections instead of condescending to the interviewee? This reads like some weird gotcha journalism... in The New Yorker of all places.

If you as an interviewer ever say "Hold on. Let me finish", you have failed and should rethink your methodology. It was embarrassing to read.

Thank you. I'll read it. I have heard multiple interviews of Loeb on youtube.[0] I like that he doesn't hide away the potential for wonder in astrology/cosmology. In that way he reminds me of Sagan a great deal. Sagan faced some ridicule as well in his time, so go figure.

[0] https://www.youtube.com/channel/UCz3qvETKooktNgCvvheuQDw/vid...

For some reason, it seems a widespread habit to drift from astronomical or quantum discussions into religion. So widespread that we see Apollo astronauts reading Genesis and Youtube search results on those topics return a jumble real science with mysticism.

Yet this seems to happen much less for, say, chemistry, geology, materials science etc. (nor software questions mercifully)

It's not quite clear why (western?) minds are wired this way. Particularly since chemistry was tied up with mysticism for centuries yet subatomic science is brand new.

But it would be nice if at least professional interviewers would avoid straying into non-sequiturs.

> This reads like some weird gotcha journalism... in The New Yorker of all places.

Why is that surprising to you?

It's amusingly similar to the discussions here about astronomy: based on observations and predictions, if one were looking for gotcha journalism, one would probably point a telescope for the gotcha wavelength at the New Yorker.

It is all speculation and no proof, but a good advertisement for the cited scientist.

Being a Harvard astronomer in and of itself doesn't make one's arguments any stronger. What a silly headline.

I down-voted you, and here's why:

1. An appeal to authority is a logical fallacy. However, authority does serve a purpose. People will take Harvard astronomers more seriously than backyard astronomy enthusiasts. Therefore his credentials are relevant.

2. No one, at any point, makes an argument that you should believe anything he claims on his credentials alone.

3. In this world of click-bait headlines and ad-revenue-driven content, this doesn't even qualify as close to click-bait. It doesn't even say UFO, or alien, or artifact, or anything controversial. The title of the article is literally what it is. It is a Harvard astronomers thoughts on an object in space.

> 1. An appeal to authority is a logical fallacy. However, authority does serve a purpose. People will take Harvard astronomers more seriously than backyard astronomy enthusiasts. Therefore his credentials are relevant.

You're basically saying "appeal to authority is a logical fallacy but it's an OK fallacy"

We should judge his opinion on the validity of his claims, not on the credentials he carries. If the backyard astronomer makes a more cogent argument, we should prefer that over the Harvard astronomers. Ideas have merits, credentials don't.

Carl Sagan famously said

    One of the great commandments of science is, "Mistrust arguments from authority." ...
    Too many such arguments have proved too painfully wrong.
    Authorities must prove their contentions like everybody else.

Your entire comment is off-topic.

You ignored points #2 and #3 and misrepresented #1. That's a classic straw-man fallacy.

I did not say "it's an OK fallacy", so do not put those words into my mouth. I said authority serves a purpose. It can serve as a signal, used to filter out noise. His arguments must, of course, stand on their own. If you actually read the article, you'll find he makes some good arguments.

In fact, neither this headline nor this article even make the "appeal to authority" fallacy in the first place. So why harp on it?

> Your entire comment is off-topic.

How so? I'm literally talking about the article.

> You ignored points #2 and #3 and misrepresented #1.

Point #2 wasn't worth addressing, but I'll do it just in case.

> 2. No one, at any point, makes an argument that you should believe anything he claims on his credentials alone.

Nor did I say anyone made that argument. Irrelevant.

> 3. In this world of click-bait headlines and ad-revenue-driven content, this doesn't even qualify as close to click-bait. It doesn't even say UFO, or alien, or artifact, or anything controversial. The title of the article is literally what it is. It is a Harvard astronomers thoughts on an object in space.

Nor did I say the article was clickbait. I mere pointed to the fact that the choice of words for the headline implies appeal to authority, though I did not say that in so many words.

Finally, I did not misinterpret #1. Let's revisit what you said

> 1. (...) People will take Harvard astronomers more seriously than backyard astronomy enthusiasts. Therefore his credentials are relevant.

Let's break this down:

(A) People will take Harvard astronomers more seriously than backyard astronomy enthusiasts.

This is precisely stating that people are subject to appeal to authority. You are saying someone's credentials confers their opinion with greater weight than if such opinion was anonymous, so you are agreeing with my original point.

But let's for a moment ignore the fact that we wish (A) wasn't true.

(B) Therefore his credentials are relevant.

It seems like you were trying to imply that because (A) is true, then (B) must true.

Your argument is tantamount to: If people believe in the value of credentials, then credentials are valuable.

In a more generic sense, if people believe in X to be valuable, then X must be valuable.

That's only true if you assume X has no inherent value but only that value which others confer to it. I would disagree with that assumption.

> So why harp on it?

I'm harping because the headline perpetuates the fallacy that credentials mean something. Maybe they do in practice as you said it yourself, but that's entirely besides the point. I'm arguing they shouldn't.

I'm also harping because it's a free "country".

This is the guy that believes aliens created a solar sail-powered pancake-shaped spacecraft 600,000 years ago just so it could fly by us and say hi, right?

That's not what he said at all?

No, it is what he said.

In this article, he mentions a dead alien civilization sending it. He also mentions the pancake shape.

In this other article[1] he mentions it taking 600,000 years to reach us from Vega.

In this article[2] he mentions the solar sail.

You can find it all on the Wikipedia page[3]. But thanks for the downvotes, guys.

[1] https://www.skyandtelescope.com/astronomy-news/astronomers-s... [2] https://www.haaretz.com/world-news/.premium.MAGAZINE-if-true... [3] https://en.wikipedia.org/wiki/ʻOumuamua

Down-votes are not for factually correct or incorrect comments. They are for comments that either do or do not contribute to the discussion.

Saying that he believes that "aliens created a solar sail-powered pancake-shaped spacecraft 600,000 years ago just so it could fly by us and say hi" is incredibly dismissive, and also a misrepresentation of his views, and his point.

Those are his views. I didn't misrepresent them, I stated them plainly. As a result, it sounds like a stupid idea. That is my contribution to the discussion. Not liking this contribution, or not agreeing with it, doesn't mean it's not a contribution. The downvotes are because people don't like it.

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