Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization

First Edition

© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm


 

21.4.2 Galactic Trade Routes

Generally speaking, trade routes are fixed along the shortest possible physical pathway between the sources of the principal commodities shipped and the major centers of consumption.1169 Each regime of travel has a unique set of physical characteristics that dictate the distribution of optimum routes. On land, surface conditions such as mountain chains and passes, accessible waterways, impassable swamps and deserts are determinative. On the sea, the curvature of the Earth, ocean currents, wind patterns, and the presence of iceberg fields, monsoon tracks and other hazards to navigation are more critical. In the air, trade routes are fixed mainly by political considerations, distribution of major population centers, jet stream and other atmospheric conditions, and so forth. In the realm of interstellar commerce, too, a unique set of problems prove determinative.

Probably the single most important parameter in deciding which trade routes should be utilized by an extraterrestrial civilization is the level of sophistication of transportation technology. Starships restricted to speeds below 50%c will gain no benefits from relativistic time dilation. Time of flight between neighboring stellar systems in the Disk will average on the order of decades for the vessel’s crew. Even if physiological longevity is greatly extended, starships will probably have to call at inter mediate ports to take on fuel and fresh crews. Even vessels able to pull 99%c won’t do significantly better. For such starships, the time dilation factor will cut trip time down to about 14 shipboard years per 100 light-years of travel. While it is certainly possible to imagine traveling for decades without pausing to refuel, resupply, or recrew, the longer the flight time the less likely starships will not stop at intermediate points.

In other words, starships limited to 99%c or less probably will not be able simply to aim at target star systems anywhere in the Milky Way and journey directly towards them (though "leading the target", of course, to account for proper stellar motions during the journey). Rather, since the distances are so vast and the travel times so long for the crews, manned trading missions most likely must follow certain prescribed routes as they crisscross the Galaxy engaging in interstellar commerce. (Unmanned robot cargo ships are another matter -- they can be "aimed and shot.") Regular ports will be visited and many planetfalls made as starvessels "hop" from solar system to solar system along paths calculated to cost minimum time or energy. Eventually these may be legislated into law as a matter of convenience by the ET Interstellar Transit Authority.

Intragalactic trade routes may also be fixed in accordance with physical heterogeneities in the Galactic environment. For instance, hydrogen gas is an order of magnitude more plentiful along the spiral arms than in the interarm regions. Hence xenologists expect that Bussard ramscoop vehicles might adopt trade routes called "ring routes" by network theorists. Ring routes follow a clockwise or counterclockwise pathway around the circumference of the Galaxy (the arms of the Milky Way) and then follow a radial route inwards to the final destination. Using an external ring route the trip path will be about 250% longer than a simple direct (straight) route; using an optimized internal ring route, however, this excess distance may be reduced as low as 37%.2629

It will also be recalled that the number of habitable star systems (classes F, G, and K) is only a few percent higher in the spiral arms than in the interarm regions, so self-fueled starships will not tend to follow trade routes aligned with the Galactic spiral structure. To an economic galactographist, the Galactic Disk is essentially uniform with useful star systems. However, there are certain clumpings of stars which impart valuable heterogeneity to the intragalactic environment. One example of this is the galactic or "open" cluster.

Galactic clusters contain from a few dozen to nearly a thousand suns, usually confined to a more or less spherical volume ranging from 5-65 light-years in diameter. About 500 clusters are known (see table next page for a few of them), and it is estimated that there are about 20,000 scattered throughout the Milky Way.1945 While this imples a mean distance between them of about 1000 light-years, this figure is very misleading because clusters are largely confined to the spiral arms. Taking this into account, the true mean separation works out to perhaps 100-300 light-years.

Galactographic considerations suggest that civilizations located in clusters may form close-knit economic units. This is possible because solar systems in galactic clusters typically are separated by a mere 0.5 light-years, which is an order of magnitude closer than normal stars (such as our Sol) in the Galactic Disk. Interstellar trade routes may be designed as a series of overlapping arcs connecting series of galactic cluster trade associations around each spiral arm. (Each cluster may represent individual political units, small pockets of interstellar civilization scattered across the Galactic wilderness.)

There are many other nonuniformities in the galactic distribution of stars which may have economic implications for galactic governments. Stellar belts, associations, and galactic star clouds (bright "knots" of suns found in Cygnus, Scutum, Sagittarius, etc. in our own galaxy) are more diffuse aggregations than clusters but may serve to concentrate trading activity to some degree. Globular clusters, metal-poor and probably also planet-poor, may be exploitable without danger to sentient lifeforms (since such clusters most likely harbor none). With 104-106 Population II stars each, globulars (Table 21.5) represent rich lodes of fusionable hydrogen and a possibly very lucrative mining venture for industrious galactic entrepreneurs.

 


Table 21.5 Galactic and Globular Clusters as Interstellar Trade Route Nodes
(modified from Robinson3086)
Name of Cluster
Constellation Distance
from Sol
Diameter
of Cluster
Approximate
Age of Cluster
   
(light-years)
(light-years)
(years)
GALACTIC/OPEN CLUSTERS
Hyades Taurus 
130
15.1
4 108
Coma Coma Berenjces
260
22.7
4 108
Pleiades (M45) Taurus
410
14.2
2 108
IC 2391 Vela
490
6.4
3 107
Praesepe "The Beehive’ (M44, NGC 2632) Cancer
520
13.5
2 109
IC 2602 Carina
520
9.9
3 107
Perseus Perseus
560
38.7
3 107
M7, NGC 6475 Scorpius
780
11.4
2 108
Mel 227 Octans
780
13.7
4 108
NGC 2451 Puppis
980
10.5
7 107
IC 4665 Ophiuchus
1100
15.7
7 107
NGC 2516 Centaurus
1200
17.6
4 108
NGC 752 Andromeda
1200
16.2
3 109
Trapeziwn (NGC 1976/80) Orion
1300
19.0
1 106
NGC 3532 Carina
1400
21.9
4 108
IC 4756 Serpens
1400
20.9
9 108
NGC 2422 Puppis
1600
13.7
7 107
NGC 2232 Monoceros
1600
9.3
3 107
M23, NGC 6494 Sagittarius
1800
14.1
4 108
M6, NGC 6405 Scorpius
1900
14.1
7 107
Tr 24 Scorpius
1900
33.0
1 106
M25, IC 4725 Sagittarius
2000
19.9
3 107
M41, NGC 2287 Canis Major
2200
20.0
3 x 107
NGC 2264 Monoceros
2400
20.8
9 106
Tr 37, IC 1396 Cepheus
2400
41.6
1 106
NGC 2546 Puppis
2400
31.6
9 106
M67, NGC 2682 Cancer
2700
14.2
4 109
NGC 3114 Carina
2800
29.8
7 107
M35, NGC 2168 Gemini
2800
23.9
7 107
IC 2395 Vela
2900
17.1.
3 107
M37, NGC 2099 Auriga
4200
29.1
2 108
NGC 4755, "Jewel Box" Crux
4400
15.3
3 107
NGC 1912 Auriga
4500
23.4
2 108
Lagoon Nebula (M8, NGC 6523 & 6530) Sagittarius
4800
62.8
1 106
NGC 2362 Canis Major
5000
10.2
9 106
NGC 188 Cepheus
5100
20.6
5 109
NGC 3766 Centaurus
5300
18.6
9 106
Rosette (NGC 2244) Monoceros
5400
42.3
1 106
M46, NGC 2437 Puppis
5400
42.5
3 107
M11, NGC 6705 Scutum
5600
20.4
2 108
NGC 6231 Scorpius
5900
27.6
1 106
M16, NGC 6611 Serpens
6200
14.4
1 106
Tr 16 Carina
6400
18.5
9 106
NGC 6067 Norma
6900
31.9
3 107
NGC 869 [ the Double Open Cluster ] Perseus
7400
64.3
9 106
NGC 884     "       "          "         " Perseus
7900
68.6
9 106
NGC 7790 Cassiopeia
11,000
14.5
7 107
GLOBULAR CLUSTERS
NGC 6397 Ara
9,500
52.3
5 109
M22, NGC 6656 Sagittarius
9,800
74.6
7 109
NGC 6541 Corona Australis
13,000
88.1
5 109
M4, HGC 6121  Scorpius
14.000
92.2
9 109
NGC 104 Tucana
16,000
209
1 1010
NGC 5139 Centaurus
17,000
323
7 109
NGC 6752 Pavo
17,000
211
5 109
M55, NGC 6809 Sagittarius
20,000
120
5 109
P410, NGC 6254 Ophiuchus
20.000
95.3
9 109
M13, NGC 6205 Hercules
21,000
77.1
5 109
P412, NGC 6218 Ophiuchus
24,000
151
7 109
NGC 6723 Sagittarius
24,000
82.2
2 1010
M92, NGC 6341 Hercules
26,000
92.2
3 109
M5, NGC 5904 Serpens
26,000
82.2
5 109
NGC 2808 Carina
30,000
162
7 109
MIS, NGC 7078 Pegasus
34,000
93.7
4 109
M3, NGC 5272 Canes Venatici
35,000
93.5
7 109
M2, NGC 7089 Aquarius
40,000
79.4
5 109
NGC 1851 Columba 
46,000
153
7 109


 

Another major heterogeneous feature is the general density gradient of suns in the Galactic corpus. Stars are about an order of magnitude more numerous near the Core than in the outer Rim regions of the Disk. As we move inward from the Rim, number density rises continuously. Stellar metallicity is also about ten times higher in the Core than in the Disk, so more planets, lifeforms, cultures, and mining ventures are possible nearer the more central regions of the Galaxy. (This is also where globular clusters are most abundant.) Economic and sociopolitical activity is expected to concentrate towards the Core.

Galactic communication routes may tend more to be line-of-sight than trade routes. These systems may be organized hierarchically with extremely complex network designs.2991 One writer suggests the following:

Local terminals handling ten worlds are constructed in space, presumably circling a star for free energy. The civilizations in touch with each terminal might range from a few hundred to a few thousand light-years away. The terminal receives signals from each and rebroadcasts them to the other members; in addition, it bumps a duplicate of the signal to a junction station further up the network hierarchy. From the junction it receives, and passes along to its member worlds, the full output of the galactic network, a great glut of information, perhaps edited in advance for potential interest to each idiosyncratic world. The more complicated junction stations in turn report to a large central station. A network of one central station and 1000 junctions, each in turn corresponding with 100 local terminals, could handle 1,000,000 worlds. Each society then would require only a single antenna, aimed at its local terminal.2607

Other designs, perhaps analogous to the decentralized nonhierarchical military ARPANET system or the ALOHANET packet radio network, may be more practical for complex interstellar communications.2484,2483

 


Last updated on 6 December 2008