Re: Dyson shells are possible

Robert J. Bradbury (
Fri, 17 Sep 1999 13:18:41 -0700 (PDT)

On Fri, 17 Sep 1999, Robin Hanson wrote:

> I referred in my paper to:
> Jun Jugaku and Shiro Nishimura. A search for dyson spheres around
> late-type stars in the solar neighborhood ii. pp. 707-710 in Cristiano B.
> Cosmovici, Stuart Bowyer, and Dan Werthimer, editors. Astronomical
> and Biochemical Origins and the Search for Life in the Universe,
> number 161. Editrice Compositori, 1997.
> The 1% isn't an assumption, but rather a measured bound on starlight
> reradiated at IR temps at these stars.

Yes, Jugaku & Nishimura have been searching for Dyson spheres for a long time. If you go back to their first paper, you will discover that they cite "Papagianis (1984, p. 268)" [The Search for Extraterrestrial Life: Recent Development] as the source for the 1% number. And if you look there, you will dicover that Papagiannis provides no calculations and *assumes* that you are using the mass in the solar system to construct "habitats" for humans. Most probably these habitats are modeled after those he discussed in "The Number N of Galactic Civilizations Must Be Either Very Large or Very Small", p 45 from Strategies for the Search for Life in the Universe [1980].

So Jugaku & Nishimura are using the Papagiannis assumptions. And you are using their assumptions. In light of nanocomputers, singularities, nanotechnology enabling dismantling planets, etc. those assumptions are silly.

> Are you suggesting that aliens may in fact be intercepting more than 1%
> of the starlight from these 100 nearby stars that Jugaku observed,
> but are reradiating it at near 3K?

I am suggesting that unless an alien civilization is severely mass constrained (much less matter at their disposal than say the planet Mercury), it will *likely* use all of that mass to intercept ~100% of the starlight *and* will reradiate as a black body in the infrared. The people who have gotten this right are Dyson, Kardashev, Slysh and a few other Russians. See for example any of the papers by Kardashev and in particular:
V. I.. Slysh, "A Search in the Infrared to Microwave for Astroengineering Activity", in The Search for Extraterrestrial Life: Recent Developments, M. D. Papagiannis (ed.), D. Reidel, Dordrecht (1985).

The Slysh paper explains in detail the frequencies, how far away we could detect them with the IRAS data, etc.

> Or are you suggesting that there are at least hundreds of other stars
> that have been completely enclosed and are reradiating at near 3K?

I'll only offer the observation that 90% of the mass in the galaxy is "missing", meaning *only* we can't see it using current instruments, *and* current instruments are virtually incapable of seeing objects emitting in the mid-far infrared region unless they are within a few light years.

> Under either of these scenarios you have to ask: why these aliens
> are leaving all these stars to throw their valuable hot photons off
> to infinity?

  1. It is possible that at the time we are at they are already harvesting 90% of the photons.
  2. H & He are not particularly good materials for building things (Solid H has the hardness of butter). It is possible that "stars" are the most efficient ways to convert H & He into C, O & Al, W, etc.
  3. The rapid "colonization" perspective requires the economic assumption that you justify the risks of colonization with a big payoff. If all civilizations eventually hit the singularity and eventually turn all of the matter in their solar system into a big hunk of computronium (using all of the star's energy), then the payoff of rapid colonization decreases *significantly*. There may be colonization, but it is likely to take place at a slow pace and for reasons like Ball's Zoo hypothesis, it may choose to ignore places where other intelligent life might develop.

> It would be very far from efficient to carefully manage the less than 1%
> of light you did intercept while completely ignoring the 99% you let go by.

Yep, thats why I think they harvest it all!

> And it would be far from efficient to so patiently manage one star while
> completely ignoring others nearby.

You have to ask yourself what the "currency" of advanced civilizations is. Is is matter, energy or "computational throughput"? You get more matter and more energy by exploring, but you derive little additional "computational throughput". You colonize a 2nd star and double the number of instructions you have, but the propagation delays synchronizing your two "processors" kill you. Even with very large collectors (telescopes the diameter of the moon), you will have to start putting a lot of your power into the lasers to send your "thoughts" across a light year. The more power you put into computation the less you have for local thought. The tradeoffs get *very* complex.