Halvmörk
Encyclopedia
Halvmörk is the name of a fictional planet, scene of Harry Harrison
's SF
novel Wheelworld. It is the third planet of Beta Aurigae
.
Like many names in Harrison's work, Halvmörk is taken from a European language, here Swedish
. It literally means "half-dark". This may be related to the fact that due to extreme temperature differences human life is possible only in a small twilight zone round the wintry pole.
Halvmörk's orbiting period (year) is a little over eight Earth years. Its orbit is extremely elliptic, and the inclination of its axis is 41°, so seasonal changes have an enormous effect on the weather. The rotational axis is inclined
in the direction of the small axis of the orbit, so the periastron and the apastron coincide with the equinox
es.
As a result the twilight zone remains largely constant for most of the year, when the planet is far from its sun. During this time a colony of humans grows grain in the twilight zone. When the planet approaches its periastron or its apastron the colony migrates to the other pole, using enormous insulated trucks and the planet's sole road, built especially to be used once in four years.
The novel does not seem to take into account that due to the ellipticity of the orbit the planet would be in a near-equinoxe position during most of the orbiting period, which would mean that both poles would enjoy a mild twilight. If the orbit were less elliptic there would be no arctic twilight zone at all but polar nights and days of varying length, like on Earth. So it is hard to imagine the astronomic circumstances needed for Harrison's interesting plot.
Harry Harrison
Harry Harrison is an American science fiction author best known for his character the Stainless Steel Rat and the novel Make Room! Make Room! , the basis for the film Soylent Green...
's SF
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
novel Wheelworld. It is the third planet of Beta Aurigae
Beta Aurigae
Beta Aurigae , traditionally named Menkalinan, is a white subgiant ternary star system approximately 85 light-years away in the constellation Auriga.- Nomenclature :...
.
Like many names in Harrison's work, Halvmörk is taken from a European language, here Swedish
Swedish language
Swedish is a North Germanic language, spoken by approximately 10 million people, predominantly in Sweden and parts of Finland, especially along its coast and on the Åland islands. It is largely mutually intelligible with Norwegian and Danish...
. It literally means "half-dark". This may be related to the fact that due to extreme temperature differences human life is possible only in a small twilight zone round the wintry pole.
Halvmörk's orbiting period (year) is a little over eight Earth years. Its orbit is extremely elliptic, and the inclination of its axis is 41°, so seasonal changes have an enormous effect on the weather. The rotational axis is inclined
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
in the direction of the small axis of the orbit, so the periastron and the apastron coincide with the equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...
es.
As a result the twilight zone remains largely constant for most of the year, when the planet is far from its sun. During this time a colony of humans grows grain in the twilight zone. When the planet approaches its periastron or its apastron the colony migrates to the other pole, using enormous insulated trucks and the planet's sole road, built especially to be used once in four years.
The novel does not seem to take into account that due to the ellipticity of the orbit the planet would be in a near-equinoxe position during most of the orbiting period, which would mean that both poles would enjoy a mild twilight. If the orbit were less elliptic there would be no arctic twilight zone at all but polar nights and days of varying length, like on Earth. So it is hard to imagine the astronomic circumstances needed for Harrison's interesting plot.