8 ms·

I don't find the author's reasoning in the related article[1] that its not a solar sail very convincing. I am not an astrophysicist, but, the author plainly ad

by eof 8y ago

I don't find the author's reasoning in the related article[1] that its not a solar sail very convincing. I am not an astrophysicist, but, the author plainly admits that the measurements are within expected bounds of a solar sail. Instead, the argument is surrounding the psychology of the hypothetical creators of said solar sail, or plausible ways we missed some data. Since we are just speculating at this point, who am I to say? But to answer some specific criticisms: - Perhaps the brightness/darkness cycles were the sail turning on and off as a mechanism to control velocity - 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. Either so we might notice it, or so it can collect data while here a bit better. I am having a hard time understanding how rare an event this space-foam-fractal theory is predicting, but if it's extremely rare a solar sail seems a completely reasonable hypothesis still. 1. https://www.syfy.com/syfywire/is-oumuamua-an-interstellar-spaceship-im-still-going-with-no https://www.syfy.com/syfywire/is-oumuamua-an-interstellar-sp...

dwaltrip 8y ago
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.
- pbhjpbhj 8y ago
  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.
  - dwaltrip 8y ago
    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.
  - gowld 8y ago
    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.
  - stouset 8y ago
    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.
    - pbhjpbhj 8y ago
      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.
- deleted 8y ago
  [deleted]
lubujackson 8y ago
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!
- SahAssar 8y ago
  > 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).
- saagarjha 8y ago
  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.
  - jabits 8y ago
    >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.
    - henriquemaia 8y ago
samstave 8y ago
I just dont understand how a solar sail would function outside the reach of our solar system... assume you have a sail that is equidistant between any stars - but some are bigger than others - and assum that the direction youd like to head, is backed by the weakest or smallest star. How will you get the energy youd be hoping for from these stars? How to orient? Or how to head the direction you want if there arent enough stars behind you to provide the thrust you want/need?
- TheOtherHobbes 8y ago
  You wouldn't. Solar sails need a handy nearby star, or a less handy giant laser. You won't get much acceleration from distant and/or dim stars. (Without a giant laser.) Interestingly, Oumuamua is at the high end of in-system solar sail velocities, and extremely slow for powered inter-system travel. The velocity profile matches a natural solar sail drifting rather randomly through space or - if you're going to go with "aliens", for the lulz - a probe deployed on the outskirts of the solar system with a low velocity. It doesn't match the profile of a powered inter-system solar sail.
- Jeff_Brown 8y ago
  On a real sailboat, you can go in lots of directions, not just the one the wind is pointing at. You can even go somewhat against the wind. In a lightsail, if I understand this diagram correctly[1], the imparted momentum is proportional to the sum of the angle of incidence and the angle of reflection. (Which, come to think of it, is exactly how billiards works.) Therefore the sail travels perpendicular to its orientation, no matter where the incoming light came from (as long as it came from that side -- I'm guessing the other side is not reflective). https://en.wikipedia.org/wiki/Solar_sail https://en.wikipedia.org/wiki/Solar_sail
reaperducer 8y ago
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.
Trombone12 8y ago
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.
- eof 8y ago
  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.
  - Trombone12 8y ago
    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.
simonh 8y ago
>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.
- flukus 8y ago
  > 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.

by eof 8y ago

dwaltrip 8y ago

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.

pbhjpbhj 8y ago
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.
- dwaltrip 8y ago
  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.
- gowld 8y ago
  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.
- stouset 8y ago
  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.
  - pbhjpbhj 8y ago
    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.
deleted 8y ago
[deleted]

lubujackson 8y ago

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!

SahAssar 8y ago
> 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).
saagarjha 8y ago
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.
- jabits 8y ago
  >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.
  - henriquemaia 8y ago

samstave 8y ago

I just dont understand how a solar sail would function outside the reach of our solar system... assume you have a sail that is equidistant between any stars - but some are bigger than others - and assum that the direction youd like to head, is backed by the weakest or smallest star. How will you get the energy youd be hoping for from these stars? How to orient? Or how to head the direction you want if there arent enough stars behind you to provide the thrust you want/need?

TheOtherHobbes 8y ago
You wouldn't. Solar sails need a handy nearby star, or a less handy giant laser. You won't get much acceleration from distant and/or dim stars. (Without a giant laser.) Interestingly, Oumuamua is at the high end of in-system solar sail velocities, and extremely slow for powered inter-system travel. The velocity profile matches a natural solar sail drifting rather randomly through space or - if you're going to go with "aliens", for the lulz - a probe deployed on the outskirts of the solar system with a low velocity. It doesn't match the profile of a powered inter-system solar sail.
Jeff_Brown 8y ago
On a real sailboat, you can go in lots of directions, not just the one the wind is pointing at. You can even go somewhat against the wind. In a lightsail, if I understand this diagram correctly[1], the imparted momentum is proportional to the sum of the angle of incidence and the angle of reflection. (Which, come to think of it, is exactly how billiards works.) Therefore the sail travels perpendicular to its orientation, no matter where the incoming light came from (as long as it came from that side -- I'm guessing the other side is not reflective). https://en.wikipedia.org/wiki/Solar_sail https://en.wikipedia.org/wiki/Solar_sail

reaperducer 8y ago

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.

Trombone12 8y ago

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.

eof 8y ago
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.
- Trombone12 8y ago
  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.

simonh 8y ago

>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.

flukus 8y ago
> 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.