
Was Oumuamua an Alien Solar Sail? - wallace_f
https://phys.org/news/2018-11-oumuamua-extraterrestrial-solar.html
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neuronic
> As for what an extra-terrestrial light sail would be doing in our solar
> system, Bialy and Loeb offer some possible explanations for that. First,
> they suggest that the probe may actually be a defunct sail floating under
> the influence of gravity and stellar radiation, similar to debris from ship
> wrecks floating in the ocean. This would help explain why Breakthrough
> Listen found no evidence of radio transmissions.

Wouldn't it be advantageous for Oumuamua's creators to simply collect data,
leave the observed systems alone and start transmitting when those clueless
Earthlings aren't listening anymore? This thing was noticed only at 0.25 AU
_post_ flyby. It is sort of terrifying that someone might have sent this...

Anyways, I am highly skeptical. For all we know, this was a slightly out-of-
the-ordinary rock that swung by Sol. Our current inability to explain its
behaviour due to lack of data immediately has people screaming "Aliens!".
Well, one notable issue here is that the "Aliens!"-conclusion is not due to
evidence for the fact (detected transmissions, clear artificial behaviour or
surface structures) but lack of evidence against it. One natural cause for the
acceleration when moving away from the Sun as well as the fast spin would be
outgassing, but:

> In addition, they cite other research that showed that if outgassing were
> responsible for the acceleration, it would have also caused a rapid
> evolution in 'Oumuamua's spin (which was not observed).

Are we sure we didn't just fail to detect it? As nature would have it,
improbable configurations might have been at work here and multiple streams of
outgassing may have stabilised spin?

~~~
wallace_f
>Are we sure we didn't just fail to detect it?

I would be interested in knowing more about the possibility of that from
people who study comets.

The alternative theory is the object is an extremely thin sheet (0.3mm thick),
which is what these scientists suggest as the best fit for the data. That
would be a really thin slice of space rock.

~~~
candiodari
How about from the people who study chance ?

The issue with rare events is that you can never estimate the probability
curves. This has the strange result that each one looks unique, complex and
very much non-random ... despite potentially being very common, simple and
random.

We have one example from an unknown distribution. You can always read a lot
into it's exact properties ... but there's nothing to be read, because we
don't have the variation on those properties. So this could have been a very
common run-of-the-mill interstellar asteroid ... and it could have been an
alien explorer. We don't know, and we probably won't know. Well, I guess in
the second case we'll eventually realize.

~~~
wallace_f
Good ideas. But what I meant was about the possibilities of outgas-propellent
existing without them being observable.

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KnightOfWords
As I understand it, Oumuamua spectra is very similar to that of a D-type
asteroid. It appears to be covered by a dull red organic gunk (tholins), which
would make a very inefficient solar sail.

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akshayB
Is it easier to colonize asteroid belt since water and minerals are easily
available?

Gravity still is a problem, but all the resources needed to build colony and
sustain life are easily available on lot these asteroids. Also water is great
for shielding solar radiation which means on some of these asteroids
underground colonizes can pose a lower hazard compared to solar radiation on
planets like Mars or our moon.

~~~
Chris_Chambers
Is gravity actually a problem if the colony is underground and the asteroid is
spinning?

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ajmurmann
Spinning would only result in a ring inside the asteroid having the desired
gravity. Still might be pretty good though. Not sure what the cost would be to
create the desired spin for a reasonably sized candidate asteroid.

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wallace_f
I wonder why this post got deranked so fast? Was it user flags or mod
decision?

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fraqed
Previous HN discussion:
[https://news.ycombinator.com/item?id=18338927](https://news.ycombinator.com/item?id=18338927)

~~~
wallace_f
Thank you

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ChikkaChiChi
Would it make sense for an advanced civilization to hollow out asteroids to
create interstellar ships?

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ajmurmann
Probably not, since The quality of the material likely isn't very high and
you'd end up with pretty sick walls which result in lots of mass to
accelerate. Maybe that's not true for all asteroids and it might differ
between solar systems.

~~~
loa-in-backup
parent probably meant *thick walls, but I bet modern lingo like "sick walls"
would also apply, as it's a very "rad" idea.

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qubax
Part of me wishes it was true. But part of me also knows that betteridge's law
of headlines is as reliable as newton's laws of motion for everyday life.

~~~
ericb
> Part of me wishes it was true.

Me too, on one level, but we should be careful what we wish for. If it was an
alien solar sail, there's not much in earthly history of two cultures at
different levels of advancement meeting that lends much hope for a long-term
happy outcome of an intergalactic encounter.

~~~
BrandoElFollito
True.

Then at least we had in both cases humans for whom there is God that they will
ultimately share similar cultures ("do not kill when not needed", "may share
similar feelings",...)

With aliens this is a whole different perspective. I am personally not excited
to find out how our worlds may or may not be compatible.

