‘Oumuamua: A Hydrogen Iceberg?
centauri-dreams.org
centauri-dreams.org
I'd love to read it.
i.e. context: the paper summarised in the OP is his counter to a "hydrogen iceberg" challenge/alternative to his original "alien" paper.
Oumuamua as the space junk of an extra-terrestial society naturally appeals to me even if it's not a legitimate guess (I understand that technological artifact is only a legitimate guess if all other options are exhausted, Ok).
One question would be whether the "axiom of mediocrity" implies that Oumuamua's flyby of the sun was not the object's first flyby. Logically, if objects that can survive a million encounter with stars exist, they would seem a million times more common than objects that could survive one. Which would also be why you'd be more likely to find space junk than a working space craft.
That doesn't seem quite right. Wouldn't they be a million times more common relative to their overall proportion in the universe? Durable objects could be, say, one in a million, cancelling out the probability.
For a civilization that is approaching type II status or beyond, the energy required to accelerate an asteroid is likely trivial.
Why is it assumed that a "star faring society" must originate from a place of significant gravity?
I can understand heat and some way to gather the required chemicals (primordial ooze) together is required. But does it require much gravity really?
Setting aside the quandary of sufficient mass to support life evolution and development from 0 => faster-than-light (or some other interstellar) travel, there's the problem of liquid water. The lower the pressure it is under, the more quickly it will evaporate or even boil. Not only that, but dissolved gasses within the water will also boil out.
So, we're left with either imagining some means of having a large quantity and volume of mass configured in a way that maintains pressure without gravity, OR identifying an alternative set of chemicals for the properties that carbon, oxygen and water currently fulfill.
Water is especially useful due to being a dipole, and there are several other known compounds that are as well, but they are significantly more complex. I'm definitely not super informed in this area, but my understanding is there really aren't other options that are readily found in nature in regular quantities.
While I mentioned "primordial ooze" I was thinking of ooze as a random assortment of elements we may or may not know much about as my "keep your mind open to possibilities" attitude left it vague.
But by defining the Ooze(especially with probabilities of elements in the universe) you define the requirements - mainly liquid water.
And then conditions by which you have to keep a blob of water together and liquid in the harshness of space are more apparent.
As you say, in theory you could come up with weird physical structures to keep water liquid and together; or some other chemistry to fulfill the same roles.
But in practice, probability says "Liquid Water + Gravity".
It sounded reasonable, but I'm not good enough with science to know if it was legit.
...not to mention that you also have to do away with an oxygen rich atmosphere as well...
Places with low gravity, such as Io, could easily form life just like Earth did, and would have an easier time to get spaceward if evolution ever got that far.
That’s not how the statistics work.
Solid hydrogen is terribly difficult to study [1]. Solid hydrogen does not exist at pressures below 100 GPa (i.e. 1 million times higher than the atmospheric pressure). These pressures occur deep inside Jupiter, for example, but how do you get the "hydrogen iceberg" free?