[ExI] Silence in the sky—but why?

Eugen Leitl eugen at leitl.org
Mon Aug 26 16:32:24 UTC 2013

On Mon, Aug 26, 2013 at 05:08:51PM +0100, BillK wrote:
> On Mon, Aug 26, 2013 at 3:53 PM, Eugen Leitl wrote:
> > Any nonrelativistic expansion will be completely overgrown by
> > relativistic expansion. As relativistic travel isn't hard (for
> > small probes, anyway), this means you can consider nonrelativistic
> > expansion an early, transient phase which is hard to observe.
> > Unless you're the point of origin.
> >
> If a galaxy can be swarmed in 10 million years, then why haven't we
> been invaded multiple times?

Because we're not in anyone's smart light cone.

And it's not that you can *remember* having never been born,
and *multiple times* at that... 

> By non-relativistic *and* relativistic expansion.

The best chance to observe expansion is to be expansive yourself.
Expansive observers are not extinguished by a passing wave of other
observers, and they traverse much of the visible universe, eventually
observing everything there is to observe, including other expansive
observers. Pioneer species are succeeded by the other kind.
> > We're not talking about just single galaxies, but patches of
> > real estate GLYrs across. Stellar systems would go dark very
> > quickly, so by the time you see half of the sky going dark
> > (FIR) your own system is already toast. Not a damn thing
> > you can do about it, unless you're already expansive.
> > So time interval from observer to expander is very short
> > (few centuries in our case), and hence you need to be arbitarily
> > unlucky in order to see half of the sky go dark.
> >
> > What we're seeing is exactly what we should be seeing.
> >
> No it isn't. That should have happened *billions* (not millions!) of
> years ago, if it is going to happen at all.

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. 
> >
> > No, the entire visible universe would made from ~AU FIR blackbodies,
> > but this is not something you could observe, as you would have never
> > happened in the first place. As you're alive and observing, this
> > indicates that we're not in anyone's smart lightcone.
> >
> But timescales say that should have happened long ago. We see the
> whole universe from the early beginnings up to a few light years from

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).

> us and there is no sign of conversion to blackbodies anywhere, at any
> stage of the universe growth. Our solar system is comparatively young
> in the grand scheme of things.

95% of all stars that will ever be already are. We're not young,
we're the right sort of metallicity and live in a great neighborhood.
You should see some of the others, except that you can't, because
bad neighborhoods kill you. Stone cold dead.
> >
> > 'Intelligence' doesn't decide a damn thing, out of control and
> > statistics decides everyting.
> >
> Now you're just being silly. I do believe interstellar travel and
> eating the galaxy requires 'intelligence'. Not necessarily benevolent

No. It only requires intelligence once, at the origin.

> intelligence, but you need a bit of IQ to build starships.

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. 

Why did the astrochicken cross the galaxy? To get to the other side.
Hardly sparkling conversationists, though. That's okay, it's not
their evolutionary niche, after all. 

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