[ExI] Tabby's star

Keith Henson hkeithhenson at gmail.com
Sun Dec 11 20:30:09 UTC 2016

Chris, these are really good questions.  Sorry I don't have good answers.

Re Dyson spheres, I don't think you want to waste material by changing
it's orbit so we could be looking at spread out former planets.  You
also have sticky problems with crossing orbits unless you stick to the
ecliptic.  These kind of patchy Dyson dots would hardly be visible.  I
am also not sure there is enough material in the solar system to build
something that would entirely shut off the star's light, especially
when you go out to 10 AU or more to get the temperature down.

Many years ago, when he first started comprehending nanotechnology,
Eric went off looking for galaxies with a bite out of them behind a
wave of life that was using all the energy from their stars.  He
didn't find any.  On the other hand, there is this:


The real mystery remains, if they exist, why don't they travel?  Is
the attraction of artificial realities a universal trap that keeps
*everyone* from sending out probes?  It didn't seem right to Anders.
I agree with him, discovery of aliens would prompt a difficult
reassessment of such thinking.

Best wishes,


On Sun, Dec 11, 2016 at 10:33 AM, Chris Hibbert <hibbert at mydruthers.com> wrote:
> Rafal wrote:
>> Let's assume that the volume of space the has been searched by our
>> telescopes well enough to detect all Dyson sphere building efforts is a
>> cube 4000 ly on a side, centered at Earth, or 64 billion cubic light
>> years.
>> If this is true, then the expected average density of such Dyson spheres
>> is
>> 1 per 64 billion ly, assuming lack of correlation between Earth and the
>> Tabby aliens.
> It seems we'd need to add an attenuation factor for the fact that we're not
> on the plane of the ecliptic for most stars. My guesses would be that we
> haven't actually done a consistent survey in all directions equally, and
> that only some percentage of stars doing this kind of hypothesized
> construction would actually present the kind of dimming we see from Tabby's
> star. So the number of stars in our "neighborhood" might be much higher.
> And as for whether there would be expected to be other evidence for
> civilizations at this level of technology, occluding your starting star is
> something you can do soon after your singularity, presuming you decide
> building computronium is an early goal. Regardless of goals, and presuming
> that FTL isn't going to make interstellar distances less of a hurdle, it's a
> while longer before we see multiple stars going out together.
> Or am I mis-reading Keith's description? Keith does this story you're
> spinning imply that the construction is ongoing as we watch? I think the
> story about the 15% dimming over the last century means that this is current
> construction. If we were seeing objects that had been around for a while, we
> might guess that the civilization had been around longer, and (given
> astronomical time scales) they should have reached some nearby systems, at
> least with their von Neumann probes.
> Do we need a story where civs that have been at this longer have built Dyson
> spheres and are hard to detect, and we're only going to see ones that are in
> the process of building as we watch?
> Chris
>  --
> C. J. Cherryh, "Invader", on why we visit very old buildings:
>       "A sense of age, of profound truths.  Respect for something
>       hands made, that's stood through storms and wars and time.
>       It persuades us that things we do may last and matter."
> Chris Hibbert
> hibbert at mydruthers.com
> Blog:   http://www.pancrit.org
> http://mydruthers.com

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