How can I explain physics to the science illiterate?

I like answering scientific questions on various
SF online forums. But it can be so vexing sometimes.

The topic on one forum turned to the hydrogen economy
and antimatter power. I mentioned that those were
not primary power sources, since there are no
hydrogen wells nor antimatter mines. I stated that
they are power transfer technologies, not power
sources. This was because they cannot be found
in nature, but had to be manufactured.

A nice gentleman who was sadly totally scientifically
illiterate asked:
If the manufacturing process requires less energy than the output, it
becomes a fuel, right? Is there some reason to think antimatter
production can't cross that threshhold?

I sat there reading that while thinking "Great. They are not
teaching the second law of thermodynamics in school anymore.
Where do I start?"

I gave a link to a site explaining the second law, and
saying that if you could manufacture the stuff using less
energy than it released, you'd have the makings of a
perpetual motion machine of the second order, which is
impossible.

I then made the mistake of mentioning that with antimatter
in particular, the law of baryon number conservation ensures
that equal amounts of matter and antimatter have to be
produced, so the highest efficiency of any antimatter
maker machine would be 50%.

The nice gentleman then chimed in with:
But are we confident that's the only way to manufacture antimatter?

How does one respond? To me, this looks much worse than
simple ignorance of the second law of thermodynamics. It looks
like a lack of ability to generalize from the specific to
the general. How do you teach that? Should I even try?

I gave him a dogmatic assertion that the law will guarantee
that it will be 50% efficiency regardless of the manufacturing
technique, and left it at that.
.

Relevant Pages

  • Re: Energy and momentum conservation in space propulsion
    ... Would the result you derived above indicate that the power ... As we've already discussed, the amount of kinetic energy required to accelerate something is frame dependent, so this means that the energy-momentum converter has some bizarre properties. ... the biggest possible bang upon the surface of some planet, ... an amount of antimatter, a device to convert this antimatter to useful ...
    (rec.arts.sf.science)
  • Re: Jettison the warp core!
    ... If you lose power, you're in deep shit. ... you probably won't get a few minutes warning to ... arrange for the antimatter to be removed from the ship. ...
    (rec.arts.sf.science)
  • Re: New and Improved Antimatter Spaceship for Mars Missions
    ... This begs the question - If enough antimatter can be made to power a trip to ... mars for $250M, then how much antimatter has already been made to power city ... killer weapons that fit in a watch??? ...
    (sci.space.policy)
  • Re: No Nukes in Space
    ... > I prefer that you use antimatter as was discussed with the DS1 project. ... That technology will not be practical without a massive ... source of power to generate, very inefficiently, the ... conventional nuclear fission for the first few decades. ...
    (sci.space.policy)