Blau Space Briefly Explained

Everything exists somewhere. That is, for anything to exist it has to have a place to exist. So we invented physical space, with three dimensions (ignoring time, and any other dimensions that may or may not exist). Physical space is a convenient place to put things, but it really is just a way to understand how things are related to each other. It's a way to know what things are close to each other, and what things are far apart.

Researchers in the physical sciences have physical space to put things in. Physical space appears to have three dimensions to determine where things are. Social scientists need a bigger space. Or, more accurately, they need more dimensions. Physical space is part of the space of the social world, but it's not all of the space. Two people can be standing right next to each other (on the subway, for instance), but be miles apart socially. If we take the three dimensions of physical space, and add a handful of other dimensions (social dimensions like income, education, gender, ethnicity, language, to name just a few), we get social space. To know where someone is located in social space, we need to know not only where they are located in physical space, but also where they are located on these other dimensions.

Social space is sometimes called "Blau space", after the sociologist Peter Blau, who wrote about the role of individual and social characteristics in organizing social patterns. People don't interact with each other randomly, there is a pattern, and that pattern is determined by where their characteristics locate them on social dimensions. In other words, interaction is determined by location in Blau space.

The physical sciences have a concept that helps us understand how things interact with one another in space: gravity. (Actually, there are a number of forces used to describe interactions between elements in physical space, and they all have the property that their effect decreases as distance increases). Gravity is a force which affects every pair of things in physical space, but not uniformly, its force is stronger the closer two things are together. Blau space has a similar essential force, called homophily. Homophily, from the latin(?) roots homo, meaning "similar," and philos meaning "having a strong affinity or love for", describes the tendency for people with similar characteristics to be more likely to interact with one another than people who are very different. Homophily is also known through the common saying "birds of a feather flock together." Homophily simply says that the closer two people are in Blau space, the more likely they will interact with each other. (1)

Social distance is essentially the same as distance in physical space, it just uses more dimensions. Fortunately, distance in multiple dimensions is easy to calculate, simply sum the squares of all the distances in each dimension, then take the square root. Unfortunately, social distance isn't that simple, since its dimensions are measured in different units. The three dimensions of physical space all have the same units, but how do you compare years of age to dollars of income to miles? Introducing new dimensions introduces many more questions. Are these other dimensions uniform, or warped? For example, is a difference of one year of age the same regardless of the absolute ages? For example, is the difference between 9 and 10 the same as between 64 and 65? Probably not. To make things worse, the dimensions may interact. Is the difference between 13 and 14 years the same for a male vs. a female? Definitely not. Distance and the force of homophily in Blau space is still not well understood and there remains much research to be conducted. Nevertheless, the concepts of Blau space and social distance can be used to understand social life, and even manipulate it.