1. AP Human Geography
GRAVITY MODEL

2. What is a model?
a representation of some phenomenon of the real-world made to facilitate an understanding of its workings
a simplification and/or generalization of a complex reality from which the incidental detail has been removed
an abstraction – not a reality

3. Types of geographic models
Mathematical
Graphic
Textual

4. What do you need to know about models?
The associated geographer
The “parts” of the model
The “assumptions” of the model
Critiques of the model
Applications of the model

5. Most Critical! A model IS NOT a “plan” to be followed in the future.
A model IS a “description” of what happened in the past.
A model IS NOT a critique of the present.
A model IS a pattern to which we can compare the present in order to see differences.

6. Tobler’s Law of Gravity
Waldo Tobler
"Everything is related to everything else, but near thing s are more related than distant things.”

7. Gravity Model Uses size of location and distance as factors for travel
Size of location takes precedent over distance
The gravity model can be used to estimate:
Traffic Flows
Migration between two areas
The number of people likely to use one central place

8. The GRAVITY MODEL of MIGRATION is a model, derived from Newton's law of gravity.
Newton's law states that: "Any two bodies attract one another with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them." 
The GRAVITY MODEL of MIGRATION is used to predict the degree of interaction between two places

9. When used geographically, the words 'bodies' and 'masses' are replaced by 'locations' and 'importance' respectively,.
Importance can be measured in terms of population numbers, gross domestic product, or other appropriate variable.

10. The gravity model of migration is therefore based upon the idea that as the importance of one or both of the location increases, there will also be an increase in movement between them.

11. The farther apart the two locations are, however, the movement between them will be less.
This phenomenon is known as distance decay.

12. The simplistic version of the gravity model of migration is as follows:
Mij = gravity model prediction of migration between origin i and destination j
Pi = population of origin State i
Pj = population of destination State j
dij = distance from origin i to destination j
Mij=
Pi*Pj
dij2

13. CITY ATLANTA NEW YORK CITY KNOXVILLE AUSTIN LOS ANGELES CHICAGO TULSA
POPULATION (2012)
ATLANTA
443,775
NEW YORK CITY
8,336,697
KNOXVILLE
182,200
AUSTIN
842,592
LOS ANGELES
3,857,799
CHICAGO
2,714,856
TULSA
393,987
COMPARE ATLANTA TO EACH OF THE CITIES LISTED

14. How might the calculations of distance you came up with differ from actual travel distances in real life?
What other factors might influence people to travel to one city or another (other than distance decay)?
How accurately do you believe the gravity model formula predicts actual migratory patterns between places? Explain.

15. Earnest Ravenstein (1885)
1) Most migrants only travel short distances to higher populated areas
2) Migrants created gaps through the flow towards the higher populated areas filling up space between origin and destination
3) Counter-current of migration at destination
4) Long distance migrants flock towards world cities or large industrial areas
5) The natives of towns are less migratory than those of the rural parts of the country
6) Females are more migratory than males
Until recently
Men, or couples w/o children, young adult or senior citizens, no dependents

16. Migration Issues Push factors Pull factors Forced Migration Refugees
Things that push people to move away from a location
Pull factors
Things that draw people to a location
Forced Migration
People forced to leave a given place permanently
Usually based on ethnicity, religion, ideology, etc.
Refugees
People leaving a location for fear of persecution or death
War-torn nations, religious persecution
Cuban refugees
Intervening obstacles
Things that block migration streams
Intervening opportunities
Things that attract people while in the migration stream

17. Cultural Hearths The center or starting point of a cultural trait
Regions can be defined by hearths
Examples?
Vatican City
Birth of Blues (Memphis, Tennessee)

18. Hierarchical diffusion Contagious diffusion Stimulus diffusion
Cultural Diffusion
Relocation diffusion
Hierarchical diffusion
Contagious diffusion
Stimulus diffusion
Expansion diffusion

19. Assimilation Acculturation
The spread of a cultural complex or a cultural trait from one location to another
The process of another culture embracing or adding that cultural trait to their cultural complex
Assimilation
A culture is completely dominated by another culture
Forced migration
Imperialization