Interstellar travel

Safety in numbers
Feb 21st 2002 | BOSTON
From The Economist print edition


If future humans colonise space, they may take a few
lessons from the past

HOW many people are needed in a spaceship? Regular readers will
know that The Economist's answer to this question is: “none;
space exploration is better done by robots”. But this is true only if
scientific information is the goal. If the aim is colonisation, then
both men and women are necessary.

In a session on interstellar travel at the AAAS festival in Boston,
John Moore of the University of Florida, Gainesville, asked what
human population would be necessary for a colonising mission to
another solar system.

It would be a long trip. Several bright physicists have spent their
leisure hours designing propulsion systems that could send a craft
to a nearby star in less than a human lifetime. One popular solution
is to unfurl a light sail that would capture the energy beamed at it
from a powerful laser in orbit around the sun. The problem is that
deceleration at the other end takes so much time and energy that
such a system is suitable only for ‘fly-by' missions. A manned craft
could take centuries to arrive, and would therefore require some
sort of self-contained colony in which people could survive,
reproduce and lead something approaching normal lives. The
technical, ecological and financial problems of building such a
colony ship would be enormous, of course. But even if they were
overcome, the society inside would itself have to be viable.

Dr Moore, an anthropologist, set himself the task of designing such
a society. He saw the crux of it as a compact between the
generations to produce an acceptable crop of spouses for the
future. By ‘acceptable' he meant sufficient in number (a minimum
choice of ten suitable members of the opposite sex), and of
suitable age (within three years of the individual doing the
choosing) and consanguinity (not closer than second cousins). A
computer model of his devising showed that an initial group of
150-180 people was just big enough to fulfil these criteria. Even
when the model was run for 60-80 generations—equivalent to a
journey time of 2,000 years—the compact could hold.
Coincidentally (or perhaps not) the figure of 150-180 is the number
of people which psychological testing has shown that an individual
can know well enough to have a permanent social relationship
with. It is also the maximum size that anthropologists find for clans
of hunter gatherers, villages in pre-industrial societies, and even
infantry companies in armies. Dr Moore's woolgathering might
therefore have illuminated an important aspect of humanity's past,
as well as pointing to its possible future.

Quelle: Economist (nur mit Abo)

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