[ExI] Where are they? was Re: 2^57885161-1

Eugen Leitl eugen at leitl.org
Wed Feb 20 16:09:16 UTC 2013

On Wed, Feb 20, 2013 at 07:39:32AM -0800, The Avantguardian wrote:

> >Intelligent species are a subset of all expansive species.
> True but non-intelligent post biota will likely be too busy eating one another to build Von Neumann probes.

They are not building von Neuman probes. They *are* von Neuman probes.
Why did the astrochicken cross the void? To get to the other star.
Sex needs to intelligence. The properties of the originating organisms
do not matter, as they're erased over time. Making you smarter
slows you down, so being smart is a negative fitness matric for

When humans travelled across the sea, they encountered islands
already full of life, albeit not human one. A fertile world abhors 
pockets of sterility.
> >My aquarium is not a democracy.
> Your aquarium also stands little chance of being detected by an ET civilization as well or colonizing the galaxy.

The galaxy is just one aquarium, as far as postbiota are concerned.
> >If we don't collape there will be measurable stellar dimming
> >in about a century scale, if not earlier.
> So how many long-period eclipsing binaries out there aren't really binary stars at all but are instead works in progress?

They're not binaries, they're going from a naked star with a planetary
system to a ~AU FIR blackbody effectively overnight (century scale).


IRAS-based whole-sky upper limit on Dyson Spheres

Richard A. Carrigan Jr

(Submitted on 14 Nov 2008 (v1), last revised 10 Mar 2009 (this version, v2))

A Dyson Sphere is a hypothetical construct of a star purposely cloaked by a thick swarm of broken-up planetary material to better utilize all of the stellar energy. A clean Dyson Sphere identification would give a significant signature for intelligence at work. A search for Dyson Spheres has been carried out using the 250,000 source database of the IRAS infrared satellite which covered 96% of the sky. The search has used the Calgary database for the IRAS Low Resolution Spectrometer (LRS) to look for fits to blackbody spectra. Searches have been conducted for both pure (fully cloaked) and partial Dyson Spheres in the blackbody temperature region 100 < T < 600 K. When other stellar signatures that resemble a Dyson Sphere are used to eliminate sources that mimic Dyson Spheres very few candidates remain and even these are ambiguous. Upper limits are presented for both pure and partial Dyson Spheres. The sensitivity of the LRS was enough to find Dyson Spheres with the luminosity of the sun out to 300 pc, a reach that encompasses a million solar- type stars.
> >> The universe is vast and you have sampled only a small speck of it. 
> >> It would be unwise to extrapolate that ridiculous sample to the universe at large.  
> >
> >Expansive life is impossible to miss across GLYr distances, unless
> >observability is censored by relativistic expansion + anthropic principle.
> >What we see is exactly what we can expect to see.
> If a civilization turned the Andromeda galaxy to computronium 2 Myrs ago, we wouldn't notice for another 500 kyrs. So don't wait up.

We won't notice, because the observation window (before you see something,
and before the blue rains start) is too damn short it's arbitrarily improbable.

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