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 rhanson@gmu.edu http://hanson.gmu.edu
Asst. Prof. Economics, George Mason University
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