From: Anders Sandberg (asa@nada.kth.se)
Date: Thu Oct 24 2002 - 14:15:10 MDT
On Thu, Oct 24, 2002 at 09:07:17AM -0700, Charles Hixson wrote:
> Anders Sandberg wrote:
>
> >Thermodynamics makes things troublesome. While you can convert matter to
> >energy, there will always be entropic losses and efficiency is never
> >100% even if the conversion is. As a first approximation a black hole
> >
> I thought that the matter-antimatter reaction was 100%, is this wrong?
> (Of course, keeping any sizeable amount around isn't going to be free,
> but one could say the same for a black-hole.)
Matter-antimatter reactions are *in principle* 100% efficient at
converting matter to energy, but this efficiency is different from the
thermodynamic efficiency of a process to extract useful work (which has
to be less than 100% efficient). The first is a statement about how much
matter would remain, the second a statement about how much entropy costs
you have to pay.
Actually, banging matter and antimatter together is not going to convert
them into energy in a neat way. Individual particles annihilate each
other, producing pairs of gamma photons (that is the 100% part). But
these photons can both create new particle-antiparticle pairs and bounce
off other particles, shooting them away. So the result is more like a
hot plasma than a perfect conversion.
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
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