[ExI] Interstellar FedEx
Anders Sandberg
asa at nada.kth.se
Mon Sep 28 23:01:32 UTC 2009
Continuing my scratching at this problem; now I found a paper that
supports my intuition that there has to be a cost, but I'm unhappy with
their method too!
"Write or Radiate?" by Christopher Rose
www.winlab.rutgers.edu/~crose/papers/vtc03_2.pdf
demonstrates that under many conditions sending inscribed information is
energetically more efficient than radiating it. He also gets an energy
cost equal to the kinetic energy of the particle, but he derives it using
a frankly bizarre statistical argument.
http://www.winlab.rutgers.edu/~crose/cgi-bin/cosmic4.html
has a lot of related links. Including this fun paper from Annals of
Improbable Research:
http://www.improb.com/airchives/paperair/volume11/v11i4/sluggish-data-11-4.pdf
(the South African demonstration with pigeons gives independent support
http://tinyurl.com/kne2xs )
More seriously, this seems to imply that if you need to ship around a lot
of entropy, sending it by shipping matter may be the best strategy (lasers
have a pretty lousy heat capacity). If the matter has specific entropy S
bits/kg and mass m, then the cost of sending it somewhere at speed v will
be 0.5mv^2. So I get a cost of v^2/2S Joule per bit. So I can get very low
costs by decreasing v, at the price of having more matter in transit - at
v=0 there is no cost, but I am essentially just piling up entropy around
myself. Hmm, so what is the most entropic kind of stable matter?
--
Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University
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