Gravity and the human migration

Created by Rafael
On Jul 11, 2017
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Objectives of the project

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Meet the team

This project was designed by PhD students from the UCL Mathematics Department: Nikoleta Kalaydzhieva, Pietro Servini and Rafael Prieto Curiel

Creating a large map of Africa

Using a grid we projected the edges of Africa into a bed sheet

Drawing the contour of Africa

The contour helps obtaining a precise shape of the continent

Different shadings in the aerial representation of the map

A relevant part is to show the different climate conditions by using different colours on the aerial representation of the map

Adding the finishing touches to the map

The aerial map of Africa

Urbanisation in Africa

An overlooked fact is that some African cities are considerably large and are growing at a fast rate. For example the largest cities, El Cairo and Lagos have more than 17 million inhabitants. This is roughly twice the population London has.

Selecting the cities to display

The largest cities were picked for the display, although some cities were not considered due to their proximity to other (larger) cities, for instance, Alexandria, although its metropolitan area has 5.3 million inhabitants, it wasn't displayed since El Cairo (18.7 million inhabitants) was selected first.

Representing the size of 23 cities in Africa

The population of the city is represented by the weight/size of each pouch. Each pouch contains weights (beans) and is wrapped in aluminium foil and identified with a name tag.

Gravity model of migration

One of the most relevant models to explain migration and trade is based on Newton's Law of gravity and is therefore called a gravity model. In recent years, the impact of a larger economy, population or market has been used to explain the additional attractiveness of larger places, taking into account the cost of distance. See for instance A theoretical foundation for the gravity equation (J.E. Anderson, 1979) and A gravity model of immigration (Lewer and Van den Berg, 2008)

The installation of the project

The location of the marks we created correspond to the geographical location of each of the 23 cities we selected in advance.

Locating the weights on each location

Using hooks we attach the pouches to their marked location on the map. This shows how the "weight" of each city pulls down the map creating a valley of size directly proportional to the "size" of the city.

The largest cities from underneath

The largest cities in Africa, El Cairo, Lagos and Kinshasa are considerably more populated than the rest and so their pouches are heavier than the rest

From a flat Earth to social forces

The map gets distorted as each pouch representing a city pulls it down. The bigger the distortion the larger the city.

Explaining the map from above and from below

During the exhibition...

The project was presented in front of an audience of Year 10-Year 12 students. Five sections were presented to each group:

  1. Identify Africa and the location of the largest cities of the continent
  2. Make the correspondence between city size and pouch size
  3. Audience participation for obtaining a map distorted by the weights of the 23 cities
  4. Use pulses to represent how trade and migration are affected by the size of the city (larger is more attractive) and the distance from the origin (closer is better).
  5. Explain that, beyond sensationalism, media and wrongly perceived ideas, data shows that migration (either legal or illegal, national or international, conflict-induced, disaster-induced, highly skilled or any other type) is mostly a local phenomena

Observing the map from above and below

By lifting the map we show the impact of different city size (weights) on the deformation of the map.

Impact of gravitational forces applied to city size

Observe the impact that the weights have on the deformation of the map, makes it easier to understand the relevance of city size in social life.

Things move!

With the help of our audience, we see how migration and trade occur due to the deformations of the map which is created by the gravity forces.

Migration creates larger cities

Migration, mainly from nearby towns and countryside, has created larger cities that keep on growing.

Challenging perceptions of migration

The migration debate is frequently carried with disregard of the facts. We used the last few minutes of the presentation to encourage a data-driven debate of societal issues and to challenge their beliefs about migration.
For example, less than 4% of the world migrates and nearly 99% of those who actually migrate, remain within the same country (internal migration).
And from those who migrate outside the country (international migration), half choose another African country as their destination.