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time-space convergence

  A decrease in the friction of distance between places (see distance decay). As the definition suggests, the concept originated within spatial science. It was first formulated by D. Janelle (1968), who defined the convergence rate between two places as the average rate at which the time needed to travel between them decreases over time: the measure was supposed to be \'mathematically analagous to velocity as defined by the physicist\'. In a subsequent, more extensive essay, Janelle (1969) attributed time-space convergence to technical change: \'as a result of transport innovation, places approach each other in time-space\'.

Janelle showed that time-space convergence is usually both discontinuous in time — hence the convergence curve in figure 1 is not smooth but jagged — and also uneven over space: \'any transport improvement will tend to be of greatest advantage to the highest-ordered centre that it connects\' (Janelle, 1968). Forer (1974) noted that the converse is also true — that time-space convergence is partly a function of the hierarchical structure of settlement — so that Janelle\'s (1969) model of \'spatial reorganization\' entailed \'cyclic causality\' in which \'places define spaces\' and spaces in turn progressively \'redefine\' places.

{img src=show_image.php?name=bkhumgeofig74.gif }

time-space convergence 1: Edinburgh to London, 1658-1966 (after Janelle, 1968)

The concept was extended by Abler (1971), still largely within the framework of spatial science, who distinguished distance-convergence from an equally important cost-convergence: taken together, these were supposed to be \'two basic determinants of human spatial behavior\'. Abler identified a pervasive tendency in the modern world for the friction of distance to decrease (cf. modernity; modernization). And since the friction of distance is a fundamental postulate of classical location theory, central place theory and diffusion theory — it is, after all, what makes the identification of regular patterns possible — then time-space convergence \'scrambles\' and \'plays havoc\' with these standard geometric models (see also Falk and Abler, 1980). Hence time-space convergence has been wired to a concept of plastic space: \'a space defined by separation in time or cost terms, a space which the progressions and regressions of technology make one of continuous flux\' (Forer, 1978).

Forer (1978) also noted a \'lack of response to Janelle\'s ideas\', and attributed this in part to their links with \'the larger canvas of economic history and the long-term development of society\'. Ironically, however, it is precisely those links that turned out to be most important. Pred (1973) had already provided an exceptionally imaginative reconstruction of the changing time-lags within the circulation of public information through major newspapers published on the eastern seaboard of the United States between 1790 and 1840. Although his studies mapped the geography of time-space convergence and its hierarchical structure, and made explicit reference to Janelle\'s contributions, Pred was plainly as interested in the politico-economic and cultural implications of time-space convergence as he was in the geometric structures that preoccupied the original architects of the concept. Some of them eventually moved in a similar direction to explore the wider implications of contemporary time-space convergence for capitalist globalization (see Janelle, 1991). For precisely this reason, calibrations of time-space convergence are now more likely to be situated within the conceptual fields of time-space compression or time-space distanciation that speak directly to such concerns. (DG)

{img src=show_image.php?name=bkhumgeofig75.gif }

time-space convergence 2: Cost-space divergence: postal rates in Great Britain, 1710-1840

References Abler, R, 1971: Distance, intercommunications and geography. Proceedings of the Association of American Geographers. 3: 1-4. Falk, T. and Abler, R. 1980: Intercommunications, distance and geographical theory. Geografisker Annaler 62B: 59-67. Forer, P. 1974: Space through time. In E.L. Cripps, eds, Space-time concepts in urban and regional models. London: Pion, 22-45. Forer, P. 1978: A place for plastic space? Progress in Human Geography 2: 230-67. Janelle, D. 1968: Central place development in a time-space framework. Professional Geographer 20: 5-10. Janelle, D. 1969: Spatial reorganisation: a model and concept. Annals of the Association of American Geographers 59: 348-64. Janelle, D. 1991: Global interdependence and its consequences. In S.D. Brunn and T. Leinbach, eds, Collapsing space and time: geographic aspects of communications and information. London: HarperCollins, 49-81. Pred, A. 1973: Urban growth and the circulation of information: the United States system of cities 1790-1840. Cambridge, MA: MIT Press.

Suggested Reading Janelle (1968, 1991). Pred (1973).



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