Comment by exratione | Hacker News Reader

Comment by exratione | Hacker News Reader

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The real issue is not that we haven't been visited (for which read, we exist, because the matter of the solar system wasn't turned into computronium by some group billions of years ago), but that everything we see is a wilderness. All of the observable universe appears natural in every place we can assess whether or not it is natural. No dyson spheres in evidence, no class 3 civilization in any of the nearest 100,000 galaxies, etc, etc.

This makes no sense given that we exist, and the laws of physics show no indications that we are a special case, or that transforming the universe into intelligent matter is impossible. All it takes is one small group in one species to create the self-replicating probes that dismantle every natural grouping of matter to create more efficient arrangements to support more intelligence, and on a small timescale compared to the age of the universe entire galaxies are turned from wilderness to structure.

https://www.exratione.com/2015/05/the-cosmological-noocene/

"Per our present understanding of physics and intelligent economic activity, we will turn every part of that great span into our descendants if not diverted or stopped by some outside influence, stars and all. The cosmological noocene, an ocean of intelligence. That the natural universe remains present to be used by us indicates that something is awry, however, that some vital and important understanding is missing, and as a species we are still just making the first fumbling explorations of the bounds of the possible with regards to what it is that we don't know."

There are two main assumptions in those "where are they?" Scenario. One is that self replicating probes are feasible and the other is that ots practical for them to travel interstellar distances.

I think the problem of designing and building self replicating probes, capable of recreating themselves from asteroidal matter, is greatly underestimated. We currently have little to no idea how to design such a thing, and no real idea what the lower bound on the mass of such a thing might be.

The next problem is nterstellar travel. The difference un scale between traveling to the moon and travelling to a nearby star is about the same difference in scale between throwing a rock down a typical garden and launching astronauts to the moon. The Daudalus project did down good work on this and their very modest proble of just a few tons, doing a flyby of a nearby star, took a large to portion of the mass of Neptune to construct in terms of fuel. The resources available in a typical planetary system might not be up to the job.

I don't honk magic future technology hand waves these problems away. Any future technology will have to work with the same elements on the same periodic table we have now, manipulating the same physical forces we work with now. We can't wish magic unobtainable into existence and the limits of what is achievable with matter and energy are already pretty much computable.

So it really may well be that going sustainably interstellar might be impractical.

The mass number you through out (large portion of the mass of Neptune) seemed really off to me so I looked it up and found some comparisons.

For a flyby: Daedalus mass = 5.0 * 10^7 kg (500 kg of scientific equipment)

With a slowdown to stay in the system: Daedalus mass = 10^10 kg

Mass of Neptune: 10^26 kg

So even for an extended stay, the mass of the Daedalus is no where close to a significant portion of Neptune.

I looked for equivalent mass objects, here is a few:

1.4 * 10^18 = all oceans on earth combined

10^12 kg = 1.4km diameter asteroid (Icarus)

3.5 * 10^10 kg = 0.5 x 0.3 x 0.2 dimension asteroid (Itokawa)

Estimates put the number of asteroids larger than 1km diameter in the belt between mars and Jupiter at 750,000

These are just straight mass conversions, no idea about the real content of fuel. If all those asteroids were straight fuel then you could launch upwards of a million Daedalus class ships that stay in the orbit of their target star.

I was thinking of the successor project, Icarus. It's not the mass of the probe, it's the mass of the gas giant's atmosphere you need to process to extract the Helium-3.

Maybe they have been turned into structure and intelligence, but we can't see it because it's operating in ways that are invisible to us.

The fallacy is that aliens must be using *technology that can be recognised as technology by early 21st century humans."

I suspect this is a low bar.

For all we know galaxies have already been transformed, and the curious science we're seeing - not least dark matter and/or dark energy - are the result.

Perhaps alien technology is non-material, and probes aren't any more necessary to aliens than head hunting is to us.

If you can manipulate spacetime and quantum phenomena directly, you're probably not going to spend a lot of time turning your star system or your galaxy into a showy megastructure.

One pretty sensible argument is that life/intelligence takes a lot of time to develop. I.e. we aren't the upstart humans encroaching on Ancient Aliens, we are Ancient Aliens. If we are among first intelligence to develop, then of course, we won't see signs of intelligent life.

Except the universe has been around 13 billion years, and our solar system has only been around 3-5 billion, so it seems unlikely we are the first.

Our life requires elements heavier than iron, which means stars had to have come and gone for our life to exist. Given that stars didn't exist until the universe was a few hundred million years old, and that stars last a few billion years before exploding, there's only around one or two billion years of head start for anything similar to us to have started existing before we did.

First where? Universe? Supercluster? Local group? Galaxy?

It does seem unlikely that we are the first. But if it takes the average galaxy 20 billion years to evolve stable interstellar life, we may never hear from the others - even if there are millions of other civilizations in the universe.

The question here isn't the odds of interstellar life evolving. The question is how frequently interstellar life evolves in neighboring regions of space at similar times while displaying mutually recognizable signs of intelligence.

> All it takes is one small group in one species to create the self-replicating probes that dismantle every natural grouping of matter to create more efficient arrangements to support more intelligence

The "paradox" ultimately comes down to a lack of data. If the milky way evolves interplanetary civilizations every 5 billion years, it's clear the odds are stacked against ever meeting another living civilization... especially if FTL is impossible and transporting large masses at C is not viable.

The assumption that life naturally lead to computronium and self-replicating structures also seems unfounded.

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