Hacker News Reader

It's far more likely to be a poorly understood natural phenomenon that we will later make sense of. It would be the millionth example of that, compared with the _first ever_ example of life not from Earth (capable of building interstellar tech!). We need very, very strong evidence to overcome this hurdle.

We know for a fact that the universe is filled with strange and interesting dynamics (not involving alien life forms) that we don't always understand at first. We don't yet know where else life may exist in the universe, if at all.

Alien life would be a natural phenomenon, ultimately; on a deep analysis any phenomenon is natural.

We make a differentiation between phenomenon wrought from cognition, but that cognition is - at least in part - a natural phenomenon too.

Is this distinction founded in dualist philosophies(mind-body and/or material-spirit)? Does it make sense to make for monistic materialists?

We might not ultimately recognise alien construction as coming from some intellect, plenty of creatures create structures on Earth (as do physical processes) with high complexity that are not considered to result from cognition.

We don't need to play this pointless semantics game every time the word "natural" is used.

There is an inarguable qualitative difference between the types of objects and materials that can be produced from undirected mechanical and chemical processes and those that can be produced through the work of intelligent, living beings.

In picking this semantic nit, you've completely ignored the actual point made by the GP: we've seen countless examples of new and strange phenomena that end up being described by undirected physical and chemical processes. We have yet to find anything that requires intelligent life to explain, like an interstellar skyscraper would.

It was more a "oh, this is a cool idea [to me, at this instant]".

Particularly I like that it sent me in to thinking of an alien life form that could, maybe like ants, construct a large scale "artefact" - like a solar sail - that we would recognise as being wrought by intelligent life but would actually be the result of some sub-intelligent life form.

I like Fritjof Capra's rendition of Gaia hypothesis (as an idea), but had never really extended the idea of self-ordering, or complex-ordering, to how we might interact with alien constructions.

>In picking this semantic nit, you've completely ignored ...//

Just my reaction to it.

I meant the term "natural" only as a short hand for anything that isn't alien technology. I do agree that even civilization and technology can be viewed as natural.

It's context-depednent. Unnatural doesn't need cognition-dependence, but merely higher complexity than usual -- an arthropod skeleton floating in space is unnatural, in the context of an asteroid, because asteroids are though of as "nartually" arising collisions of rocks, gravity, solar radiation, and the like, but not not the complex processes of animal life.

Uh, what? Plait makes the important point that the light curve is hard to explain without tumbling, and if the "sail" is tumbling the entire acceleration calculation presented in the paper is shit. Kind of a big deal.

Light curve is hard to explain without tumbling, and my suggestion is it could be explained by the solar sail changing it's reflectiveness purposefully.

At that level of detail you could just be chanting "god did it" over and over, it comes out to about the same explanatory power.

>Perhaps the 25km/s speed being a crawl for interstellar travel was because it was meant to slow down while passing through our solar system…

We know how much it’s acceleration as affected by solar pressure because we measured it, and it was very low, similar in scale to that caused by off-gassing of comments. Tiny both by interstellar travel standards, and in terms of its actual velocity.

The way you use ‘solar’ sails for interstellar travel is to propel them using a fixed laser at their point of origin, and possibly another laser to slow them down at their destination. Actual light pressure from a star is way too low to give them useful velocity for interstellar journeys.

> The way you use ‘solar’ sails for interstellar travel is to propel them using a fixed laser at their point of origin, and possibly another laser to slow them down at their destination.

What if someone sent out a bunch of these things to wander the galaxy until they encounter a civilization cable of detecting it and slowing it down? Perhaps it was even sent purposefully after signs of life were detected on earth. That seems like a feasible communication method with today's tech, the galactic equivalent of a station wagon full of hard drives.

I don't find the author's reasoning in the related article[1] that its not a solar sail very convincing

Imagine a pre-industrial civilization that finds a ship's sail that was lost at sea washing up on its shore.

I don't believe the solar sail hypothesis, but I like the fantasy it provokes in my mind.

It's the "I don't want to say aliens because no one will listen to you if you say aliens" conundrum, which does a disservice to the science by pooh-poohing any intelligence-spawned possibilities while wildly speculating on naturally-caused possibilities.

The reality is this is an extremely alien object, no matter if it was formed by intelligent beings or spun off from a star. Maybe this is a solar sail or maybe it is a giant snowflake.

And, contrary to the author's hand-waving, there is nothing that says an enormous, impossibly thin solar sail can't be formed by randomly bashing an infinity of rocks together over a near-infinity of time - after all, LIFE ITSELF comes from just such an action, so pretty much anything is in play if that is the standard!

> here is nothing that says an enormous, impossibly thin solar sail can't be formed by randomly bashing an infinity of rocks together over a near-infinity of time

Nobody is saying that it is impossible, the author is simply saying that it seems unlikely that is the origin. It's Occam's razor, whereby the simplest solution seems to not be alien intelligence or serendipitous solar sails, but rather something that we have seen appear naturally (fractals).

> after all, LIFE ITSELF comes from just such an action, so pretty much anything is in play if that is the standard!

That's how an instance of life came about. A very simple, most likely extremely short-lived, not at all efficient form of life. The advancement to Eukaryotes took ~2 billion years from there, and multicellular life took about another billion years. These happened not by random bashing, but selection pressures.

While a solar sail could happen completely randomly, 'life itself' isn't really a good comparison, since that's not really how it happened. At least not any form of life that is really recognizable as life.

everything is randomly bashing things together; every human is randomly bashing things together. we are similar, but have billions and billions of tiny differences that make up the specific things about us.

everything has selection pressures too: just like life forms exist and thrive in different environments, dust behaves differently at different temperatures and gravities.

life as an event, and specific things that happen thereafter are no less “random” than specific chunks of rock/dust in specific configurations

> life as an event, and specific things that happen thereafter are no less “random” than specific chunks of rock/dust in specific configurations

No. Incremental changes over millions of generations in response to environmental pressures are not "random".

This sliver of dusty ice may have formed in a one-in-a-million random chance, but there's no process that selects for this.

Life is a pretty rare occurrence, as far as we're aware. So I think I can forgive the author for not being sold on the "aliens" conclusion just yet–it's probably a good idea to look for alternative conclusions that might be more likely first.

>Life is a pretty rare occurrence, as far as we're aware.

I don't know where you get this from...just because we have not observed it directly? Based on everything we have learned so far about life here on Earth, it seems entirely reasonable to think that life would be very common throughout the universe.

If our nearby system (star, planets, and all in between) is to serve as an observation parameter to determine the probability of the occurrence of life, life in not very common.

Yes, it is true that you have plenty of life here, but you have it only on a very (and I mean very) thin layer on this floating rock. It seems a lot on the surface (pun intended), but it actually isn't.

It's reasonable to think life is very common. It's also reasonable to think that life might be very rare in the universe, or that we could be alone. Science, so far, hasn't really narrowed down orders of magnitude on some of the potential Great Filters. So it doesn't have that much to say about this question, yet.

(And, if you are willing to invoke some form of the anthropic principle, maybe a universe that can support even one instance of intelligent life is itself incredibly rare in some landscape?)

Are you conflating "common" with "possible"? Study of exonoplanets finds earth-like ones relatively rare, and being Earth-like is still a far cry from.

There may be a large number of life-hposting planets in the Universe, while still fitting current data that they are extremely rare as a fraction of, for example, the region of space reachable by humans, by floating space rocks, or perhaps even the Earth's light-cone.

Something being reasonable to think (while it's also reasonable to think the opposite, no less) and being aware that something is a fact are two very different things.

It's the "I don't want to say aliens because no one will listen to you if you say aliens" conundrum, which does a disservice to the science by pooh-poohing any intelligence-spawned possibilities while wildly speculating on naturally-caused possibilities.