Re: Why Would Aliens Hide?

Robin Hanson (
Wed, 17 Nov 1999 11:54:00 -0500

Robert Bradbury wrote:
> > P(ower) you can extract from a star ...
> > If you have two stars, ... a certain amount M of metal available, ...
> max P(m1) + P(m2) such that m1 + m2 = M
> m1,m2 and m1 >=0, m2 >=0
> > You are suggesting that an optimum is m1 = 0 and m2 = M, putting all the
> > metal at one star ...
>The metal may have 2 [other] uses: computation, which presumably requires
>energy, or memory, which requires very little energy ...
>The computational throughput of a parallel processing "computer" system
>... best situation to setup is m1 at the thermodyanmic limits
>and m2 with the leftovers. For example, this could be m1 = 0.999(m1+m2)
>and m2 = 0.001(m1+m2). You can't use any more metal at m1 because
>you are using all the power of your star *and* are radiating at
>the lowest background temperature possible. You may develop
>m2 but it is hardly worth the trouble, ...
>I agree, if transport costs are high, you don't go harvest metals
>and ship them home. In the long run, you will orbit ... in the
>Galaxy, ... to locations (stars or gas clouds) where quantities
>of metals are available and transport costs are very low. ...
>It takes a small fraction of the metal in a system like ours to harvest
>all of the sunlight (and hide the star in the visible region). It
>[probably] takes more metal than we have available even after
>dismantling all of the planets to *optimally* use the energy the
>sun is producing. So we can rapidly evolve to the low-SI level with
>a hidden star but may take eons to evolve to high-SI levels.

Let me paraphrase to see if I understand you. You seem to be saying that creatures at one star care only about the energy and metals at that star. Thus the only interest they have in other stars is to collect metal from those stars and bring it back home. This interest is temporary, because eventually they have more metal at home than you can use, given their limited local energy. Also, they have no interest in the energy at other stars, because energy is too expensive to immediately transport or to store awaiting a low cost opportunity.

Empirically, I think this predicts that we will not see metal planets around visible stars. This is a prediction we should be able to verify in the next twenty years or so. I presume you use "metal" in the usual astrophysical sense of everything but H and He?

It also predicts we will not find effective ways to transport or store energy. But how hard would it be to surround a star with a parabolic mirror to direct starlight to a different system? Or to power a laser directed there? Perhaps you want to argue that the local demand for energy will also satiate, as well as the demand for mass.

More later.

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