Re: Why Would Aliens Hide?

Robin Hanson (
Sun, 28 Nov 1999 13:58:42 -0500

Robert Bradbury wrote:
> > ... Unexplained excess of dust production seems the opposite
> > of what one would expect from aliens greedily eating up all
> > the metals they can find.
>... an abundance of dust, is what you would
>expect if SIs are throwing away the most "useless" mass
>as thrust material. H you want to keep because it can
>produce energy, C you want to keep because it is a great
>construction material, O, Si or Fe on the other hand are
>of less value. So, if Amara would say the element abundance
>in interstellar grains seems to favor O, Si, or Fe over
>what would be expected for H/C, then I'd be willing to bet
>on propulsion exhaust.

This prediction doesn't seem to be confirmed by the data Amara pointed us to (Table 4, P. Frisch et al, "Dust in the Local Interstellar Wind" ApJ 1 Nov 1999.) If anything, Si seems to be the left out element, not C. (See section 6.4 of the paper.)

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