[ExI] Silence in the sky—but why?

[Eugen Leitl]

On Mon, Aug 26, 2013 at 06:42:46PM +0100, BillK wrote:

> Forget the rest of the universe. Let's just look at our galaxy.

No, let's not forget the rest of the universe. 
Because some 10 GLYrs are a lot of real estate.

> 100,000 light years diameter, 100 to 400 billion stars.
> 
> As we are still here, you must be claiming that no other space
> expansive species has arisen in our galaxy as it wouldn't take very

We're not an expansive species. Yet. We have a fighting chance
to become one.

> long to eat the Milky Way. Many stars in our galaxy are billions of
> years older than our sun.

You don't need just old stars, you need a suitable metallicity,
habitable zone, no extinction events, lucky evolution (it's not
obvious why we should be here at all, rewind the evolution and
something else entirely emerges), you need a species with stability
and enough smartness to reach machine-space (we're close, but
we're by no means there). You can't put a probability to any of
these steps as long as you don't have at least a second, unbiased
(so no causally entangled life in this solar system will do)
sample to compute how probable expansive species are.

>From the looks of it, we are terribly rare. Just how rare we don't
know, until we find another sample.
 
> >
> > You can't observe very well if you're dead. I keep saying it, but
> > you don't seem to register it for some reason.
> >
> 
> I agree! So you are saying we must be the first space species in our
> galaxy. That's a big claim.

No, that's not a big claim. Even a single species across 10 GLYrs won't
fail to observe itself. Everything else is a big claim, though.
 
> > No. We're seeing the early beginnings as early beginnings. We do not
> > know how remote areas look right now. Relativistic observers are hard
> > to observe due to the anthropic effect. You don't see them coming until
> > they're almost here, and they leave no pre-expansive observers in their
> > wake any more than a colony of E. coli leaves pristine agar behind.
> > (But other species that thrive on E. coli will follow).
> >
> 
> The Milky Way is in the Local Group of galaxies, Up to about 11
> million light years away. So we would be well able to see if any of

11 megayears is really negligible.

> them were being eaten. Unless it all started less than 11 million
> years ago - a tall order!.

You will not see a relativistic front until it's knocking on your
door.

> Age of universe - 14 billion years. Solar System - 4.5 billion years

Most of it sterile. You can model high-metallicity early-generation
stars, but these are really rare to count. What's the cutoff edge is
is hard to tell.

> old. Humans - a few million years.

This planet is only good for less than half a gigayear.
 
> 
> >
> > It requires a lot of IQ of you want to build a dog, in fact,
> > it's so hard, we can't do it yet. Yet dogs breed fine.
> >
> >
> 
> But dogs don't build starships.

You're still thinking like a human. Pioneers don't build starships, they
*are* starships. And so will we, shortly. Either that, or we blow our chances.
If 2050 doesn't look much, much worse than today our chances are good.
If we're still around mostly as is by 2100 we've made it through the
population bottleneck.