Comment by cptaj | Hacker News Reader

Comment by cptaj | Hacker News Reader

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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.

Well,

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.

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