Torsten Hägerstrand (1916 - 2004) was a Swedish geographer who is mostly known for his work on migration, cultural diffusion and time geography (which will be explained later on). Hagerstränd was a student at the University of Lund and would stay connected to this university for the rest of his life. In 1957 he promoted and became a professor at the Lund University until his retirement in 1982 (Academic Dictionaries and Encyclopedias, n.d.). Hägerstrand got more honorary doctorates from other universities. With his publications he influenced the population (and cultural) geography. He introduced the diffusion models for example and his most important work the time geography (Britannica Academic Edition, 2012).
His most important publications are:
- Innovations förloppet ur korologisk synpunkt, 1953, Lund: Gleerup. Vertaald door Allan Pred in het Engels als Innovation diffusion as a spatial process, University of Chicago Press, Chicago, 1967
- Migration and area, in: D. Hannerberg, T. Hägerstrand and B. Odeving (eds), Migration in Sweden: a symposium, Lund Studies in Geography, Series B, no. 13, Lund, Gleerup, 1957, p. 27-158.
- On Monte Carlo simulation of diffusion, in: W.L. Garrison and D.F. Marble (eds), Quantitative geography, Vol. 1, Northwestern University Studies in Geography, 13, Evanstone, 1967, p. 1-33
- What about people in regional science? In: Papers Regional Science Association, 24, 1970, p.7-21
- Information systems for regional development – a seminar, Lund Studies in Geography, Series B, no. 37, Lund, Gleerup, 1971
- Diorama, path and project, TESG, 73, 1982, p. 323-339
(Academic Dictionaries and Encyclopedias, n.d.).
In his theory of time geography (Hägerstrand, 1970), Hägerstand shows how people travel and live through time and space from birth to death. People are not free to do so, they always have to deal with decisions they made earlier (historical setting) and some constraints. These constraints can be divided into three groups: capability constraints, coupling constraints and authority constraints.
Capability constraints are biological and instrumental of nature. An individual needs to sleep and eat sometimes and has the possibility to make use of a certain modality. For instance a person can´t travel through time and space, without making stops to eat.
Coupling constraints have to do with the presence of persons and/or materials required for certain activities. For example if you want to play soccer, you need to have a team to play with (and another opponent team).
Authority constraints refer to certain institutions which determine whether you can perform a certain activity or not. For instance opening times of stores determine when you can go shopping or a timetable for a ferry shows what time you can take a ferry to cross the fjord.
These constraints ‘define the time-space mechanics of constraints which determine how paths are channelled or dammed up’ (Hägerstrand, 1970, p. 11). The constraints create a three-dimensional prism, with time-space walls. This prism can change every day and influences the life path of individuals (Hägerstrand, 1970).
When people travel through space and time, they do that to complete projects. A project consists of series of tasks and leads to the achievement of a goal. Projects include people, resources, space and time and in order to complete projects, people must overcome their constraints. When participating in a project, an individual may be temporarily inaccessible to another individual. As a consequence, the latter may have to change his or her plans (his or her project). This is called a spread effect (Hägerstrand, 1970).
In his paper on everyday regionalisation, Werlen (2009) refers to the theory of time geography in the following way: “[…] it is emphasized that people cannot but always be embodied or situated in time and space, as in the formulations of Torsten Hägerstrand’s time-geography, and that through proximate face-to-face interactions, as well as now through mediated inter-actions over longer distances, they build up pictures of the geographies that they are inhabiting, suffusing them with meanings […] and therefore create a symbolically charged grounding […] that is central to all manner of ensuing economic, political, and cultural activities, events and processes.” (p.2).
Academic Dictionaries and Encyclopedias. (n.d.). Torsten Hägerstrand. Retrieved at 27 September 2010, from 
Britannica Academic Edition. (2012). Geography. Retrieved at 11 Oktober 2012, from
E-Geography. (n.d.). Hägerstrand. Retrieved at 11 Oktober 2012, from
Hägerstrand, T. (1970). What about people in regional science? Papers of the regional science associaton, vol. 24, pp. 7-21.
Haggerty, C. (2009). Time geography, social media and social exclusion. Retrieved at 11 Oktober 2012, from
Werlen, B. (2009). Everyday Regionalizations. Elsevier.
Edited by Renate van Haaren, --RenateVanHaaren 09:28, 11 October 2012 (CEST)