Re: Dyson shells are possible

Robin Hanson (
Fri, 17 Sep 1999 17:10:43 -0400

At 01:18 PM 9/17/1999 -0700, you wrote:
> > I referred in my paper to: Jun Jugaku and Shiro Nishimura. ...
> > 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 ...
>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.

Jugaku & Nishimura may have used Papagianis 84 to *motiviate* their choice of a cutoff to search for, but the data they get does not *assume* this cutoff. The ask directly whether more than 1% of the starlight from each star is coming out at IR temps, and they find no.

> > 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?
>a) It is possible that at the time we are at they are already harvesting
> 90% of the photons.

This doesn't answer the question about the 10% we see.

>b) 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.

This is irrelevant regarding the lost photons. Even if you don't want to build with star material, and even if you want stars to make metals, why let all those photons go?

>c) 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*. ...
>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 seem to be saying that you *know* that *all* advanced aliens want *only* "computational throughput", *and* that colonization cannot typically offer such throughput well. I'm skeptical about both claims. Almost all creatures today do not value only computational throughput; why should we expect such creatures to dominate the future? And I'm sure we could ifeden.computational problems that are so hard that one could compute them more quickly by sending out probes to turn the universe into computers, rather than just using one system to compute with. How can you know that advanced creatures aren't interested in such problems?

>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.

Even slow colonization is a problem, given how old the universe is. And are we to conclude that all the stars we see are zoos containing life? And all aliens everywhere have the same taste in zoos?

Robin Hanson Asst. Prof. Economics, George Mason University MSN 1D3, Carow Hall, Fairfax VA 22030
703-993-2326 FAX: 703-993-2323