Designing Aliens (con't)
It's tempting to make the Whrloo homeworld
a low gravity planet, another easy route to flight, but the
problem is that as the gravity gets lower so does the atmospheric
pressure. The only option is to pile on still more gases, but
at this point we're going to have to figure out where to get
them. Also if the gravity gets low enough the atmosphere will
start to leak into space. We've already established that Whrloo
is an old world, so it needs to be big enough to hang on to
its atmosphere for the long term. The math is fairly involved
and depends in part on the molecular weight of the gases involves,
but the end result is that a planet needs to have at least half
a G of gravity to be able to hang on to gases heavy gases like
oxygen and nitrogen. So we'll make the surface gravity half
a G. This makes their world almost twice as big as Mars, and
also serves to lighten the Whrloo's carapaces. Now all we have
to do is scramble to figure out how to get all those gases on
to such a small world.
One easy answer is a collision like the one
that formed our own moon. Imagine a super-earth, twice as big
(and eight times heavier) than our own. If this world were a
little bigger or a little farther from its star it might become
a gas giant, but as it is it's developed a thick nitrogen envelope,
ten times thicker even than Venus's. Something with twice the
mass of earth slams into it, early in its history while its
system is still condensing. This titanic collision blasts half
of its mass into orbit, including a lot of its atmosphere. Most
of this material is lost, but enough coalesces to form the world
of the Whrloo, and it picks up a lot of the atmosphere before
the solar wind blows it away. Our world is a moon. It will quickly
become tidally locked to it's primary. The Whrloo, like the
Puppeteers, won't know about tides. They won't even know about
the primary, thanks to the heavy clouds, and the dense atmosphere
will tend to even out the weather. One day will be much like
the next, no matter where you go on the planet. It may be that
they won't even discover the stars until the Kzinti arrive,
at which point it will be far too late…
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| The War Starts in -871 Days |
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Cover Story:
Stephen Hickman
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On the Wars:
Toni Weisskopf
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