In this chapter we will examine some immediate consequences of the axioms of , and develop some qualitative understanding of these before we mathematise things in the .

In Chapter 2 we saw that people often creatively use different kinds of resources to communicate different meanings at different times and with different people, and in Chapter 3 we considered different ‘varieties’ of language associated with different groups of people. In this chapter we will focus on people’s practices of mixing together more than one ‘language’, ‘dialect’, or register when they communicate and some of the reasons for these practices. We will provide an overview of the different ways these practices of ‘mixing resources’ have been conceptualised in sociolinguistics, including code switching, crossing, and translanguaging. The focal topic for this chapter is language in education, where we will explore issues around mixing and switching linguistic resources in classrooms.

Throughout this book we have talked about how different resources (‘languages’, ‘dialects’, ‘styles’) are valued differently in different societies. The value assigned to different resources manifests not just in structural inequalities (see Chapter 2), but also in the pervasive everyday attitudes people have about particular ‘languages’ and ways of using language, and the acts of ‘othering’ and aggression that sometimes result from these attitudes. In this chapter we will focus on the study of language attitudes, exploring how and why people respond to other people’s communicative practices in negative or positive ways. The focal topic explores how the linguistic practices of certain groups of people are represented, mocked, and appropriated in ways that perpetuate racism and marginalisation.

In the , we have learned how to describe motion; we now want to explain it. In newtonian mechanics, we do this by defining quantities such as momentum, energy, force and so on. To what extent can we do this in the context of relativity, with our new 4-vector tools?

This chapter focuses on the mobility of communicative resources and the way they interact with and are influenced by different resources they come into contact with as a result of this mobility. It explores the different ways sociolinguists have addressed mobility, from more traditional approaches that focus on ‘language contact’ to more contemporary ones which attempt to trace the trajectories along which people and resources ‘flow’ through global networks. It then examines the communicative practices of global hip-hop artists as a case study in language and globalisation. The focal topic for this chapter is migration, specifically the communicative challenges migrants face and the strategies they deploy when they move from one place to another.

Having described motion, we can now explain it. We introduce the conserved 4-momentum, and with it the ideas of energy-momentum, conserved mass, and scattering.