make "our" mag like the
other S.-F. mags on the market, and I read Astounding
Stories because it is DIFFERENT, and I mean every one of
those capitals!--Ben Smith, Box 444, Billings, Mont.

Mr. Ernst's Answers:

(a) No, it has not been actually proved. It has been
indicated mathematically (by formulae based on conjecture),
but never actually solved--for the very good reason that it
is impossible to reproduce spacial conditions in earthly
laboratories. Know how an explosive force would react in
space? We don't even know positively what space is, let
alone how our chemicals and instruments would behave in it.

The majority theory is that explosive charges would propel a
rocket or space ship more effectively in the (theoretical)
emptiness of space, than in our atmosphere. But to my mind
it is quite possible that an explosion--a violent expansion
of gases causing rapid increase of pressures--would be
ineffectual where there are no pressures to be increased.
Might not the violently expanding gases fly forth from an
exhaust vent to expand instantly, frictionlessly and
impotently to the ends of the universe? In my story, "The
World Behind the Moon," I assumed that would occur. And no
man living is in a position positively to disprove it.

And, as a corollary, if a propulsion explosion cannot have
effect in empty space, as presumed in the story, the space
ship must enter atmosphere before it can stop by firing its
bow tubes. Otherwise, with the bow tubes shooting their
expanding gases futilely into nothingness, you could go into
"reverse" till the cows came home and the ship would hurtle
forward just the same.

(b) Friction of a bullet through a rifle barrel produces a
temperature considerably higher than "tropical."

(c) Again, no one knows spacial or planetary conditions. It
seems reasonable to assume that a planet's mass may have a
fairly direct bearing on the density of its atmosphere.
However, Venus, a smaller globe than Earth, is supposed to
have a denser atmosphere. For all we know to the contrary,
meteors no larger than pebbles may carry about with them
microscopic films of "atmospheres" of varying
densities.--Paul Ernst.

_Hitting Our Stride_

Dear Editor:

The more I read Astounding Stories, the more