In this chapter we will consider different modes of communication other than language, such as images and emojis. We will also consider the different media that serve as carriers for communicative resources, and how they can affect the way these resources circulate, how they can be used, and by whom. We will also discuss how media, especially digital media, can affect the formation of different kinds of communities, and how different kinds of texts and other communicative resources circulate through these communities. Finally, in the focal topic we will discuss the role different modes and media play in the stigmatisation of the communicative practices of particular individuals or groups and the promotion of particular ideologies such as sexism and racism.

Understand the importance of events within Special Relativity, and the distinction between events and their coordinates in a particular frame; and appreciate why we have to define very carefully the process of measuring distances and times, and how we go about this.

In this introduction we will explain how sociolinguistics is relevant to helping us to solve real-world problems. We will also explore some of the challenges we face when we talk about concepts such as ‘language’ and ‘society’, and introduce some of the more recent concepts, theories, and practical tools that sociolinguists have developed to talk about and analyse the relationship between language and social life.

In , we used the axioms ofto obtain the Lorentz transformation. That allowed us to describe events in two different frames in relative motion. That part was rather mathematical in style. Now we are going to return to the physics, and describe motion: velocity, acceleration, momentum, energy and mass.

In this chapter we will delve deeper into the connection between language and social meaning by exploring the traditional concern of sociolinguists with what is known as language variation. Variation means difference, so people who are interested in language variation are interested in how language use differs among different groups of people and the social meanings those differences might index. We will take a critical look at the different ways scholars have studied language variation, exploring how even small alterations in the way people talk can signal belonging or not belonging to a particular group, and we will also examine the social processes through which certain ways of speaking come to be associated with certain kinds of people. In the focal topic section we will look more closely at the issue of ‘belonging’.

This chapter focuses on the relationship between language and the material world. The material world includes public spaces and built environments, our bodies, and the objects that we use on a daily basis. We will start by exploring different kinds of public signs that are displayed in the physical environment, showing how things like posters, notices, billboards, advertisements, street names, and graffiti both reflect sociolinguistic realities and serve as resources for enacting those realities. We will then turn our focus to the relationship between language and the body. The ultimate aim of this chapter is to demonstrate that our bodies and the world around us are as important for performing social identities and managing social relationships as the words we speak. At the end of this chapter, in the focal topic, we will explore the significance of signage and embodiment in situations of conflict and political protest.

We are now able to deduce the Lorentz transformation, relating two inertial frames. We examine three paradoxes, namely the famous twins paradox, the pole-in-the-barn paradox, and the so-called Bell's spaceships paradox. We also take another look at the relationship with electromagnetism.

We look at the immediate consequences of the two axioms, and discover, qualitatively and then quantitatively, the phenomena of length contraction and time dilation.

We survey relativity's contact with experiment and observation, briefly discussing the classical tests of SR and of GR, and including a discussion of the famous 1919 Dyson-Eddington observations of the bending of starlight during the solar eclipse. In the latter, we look at the historical and social pressures on the scientists involved, and what effect these have on the processes of theory choice.

A brief recap of some mathematical topics.

Inwe saw how observers could make measurements of lengths and times in frames which are in relative motion, and reasonably disagree about the results – the phenomena of length contraction and time dilation. In , we were able to put numbers to this and derive a quantitative relation, Eq. (), between the duration of a ‘tick’ of the light clock as measured in two frames. We want to do better than this, and find a way to relate the coordinates of any event, as measured in any pair of frames in relative motion. That relation – a transformation from one coordinate system to another – is the Lorentz transformation (LT). The derivation inhas a lot in common with the account given in .