Cambios fisicoquímicos y estructurales experimentados

Metaphor function has been linked to text genres in various studies (Musolff 2010; 2016; Musolff and Zinken 2009). Charteris-Black (2004), for instance, investigated the ideological function of metaphor in political speeches where the ideological function features as key. Metaphor use in different scientific genres (research articles, educational texts, popular science texts) has also been explored (Boyd 1993; Baake 2003; Brunette and Caignon 2004; Cameron and Stelma 2004; Semino 2008; Herrmann 2013; Deignan Littlemore and Semino 2013). Cameron and Deignan (2004), for instance, explored the use of metaphors in what they call “educational discourse” that includes popular science texts and classroom conversations and argue that educational metaphors fulfil four different functions: explanatory function, illustrating function, summarising function and an argument/convincing function.

A wider range of metaphor functions has also been identified by Goatly (2011) who lists thirteen metaphor functions in discourse. Goatly (ibid.), however, does not specify in his study whether the different metaphor functions are linked to specific genres.

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This variety of metaphor functions is often presented in the literature as metaphor “categories”. Boyd (1993), for instance, claims that there are two main categories of metaphor in scientific discourse: theory-constitutive metaphors and exegetical metaphors. The notion of categories is criticised, namely by Semino (2008:134), who suggests that Boyd’s distinction does not capture two different categories of metaphor, but rather two different functions a metaphor can perform when used in particular scientific texts and genres.

Boyd’s metaphors categories, or rather functions are explained, in some detail, in what follows as they represent the two key functions of metaphor in specialised scientific articles and popular science articles. As will be seen later in this chapter, the core difference in the use of these two functions between the two genres of research articles and popular science articles resides in the dominance of one or the other function in each genre rather than in the exclusion of one or the other function.

3.2.1 Theory-constitutive metaphor

By theory-constitutive metaphor, Boyd (1993) means metaphors that are inherent to a particular scientific theory or model. He argues that such metaphors are theory-constitutive because they cannot be replaced by a literal expression. A number of theories are built upon such metaphors. For instance, the ‘string theory’ in A&A is built upon the ‘string’ metaphor. Strings are thought to be the tiniest elements of the universe; they derive their name from an analogy with the strings of musical instruments. ‘Strings’ are thought to vibrate and oscillate in the way a stringed instrument does. Boyd (1993) holds that metaphor is not only used to coin new words to denominate newly discovered entities but it actually constitutes theories and creates new knowledge by creating new similarities. A number of theories are built upon metaphors; the ‘code’ and the ‘translation’ metaphors in genetics are other examples of metaphorical scientific models (Brunette and Caignon 2004). The use of metaphor is seen by Baake (2003) as a characteristic of the early stages of a scientific theory. Such a metaphor may disappear later when knowledge about the phenomenon is developed enough to be described in a literal way, which means in a more objective and neutral way (Baake 2003; Bailer-Jones 2000, 2002; Bicchieri 1988; Hoffman 1980; Knudsen 2003; Oliveira 2009). This idea is consistent with the claim about the role

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of metaphor in science. Baake (2003:56) considers metaphor as ‘one of the several tools for producing theory, along with mathematics, empirical research, and intuition’. Baake (2003) refers to the relation between the scientific discovery and the creation of knowledge, but questions whether science discovers intrinsic facts about the world or whether, through the process of scientific discourse, it creates those facts. He holds that knowledge creation is a process whereby discovery (the act of observation) occurs concurrently with creation (the act of reflection upon what is observed). As noted above for Boyd (1993), Baake (2003) supports the theory-constitutive role of metaphor in science and the contribution of metaphor to knowledge production.

However, the metaphor does not always play a positive role, according to some studies. It happens that when theories develop, metaphors that constitute them may become irrelevant; this is the case, for instance, of the ‘code’ metaphor in genetics. Knudsen (2003) argues that despite the fact that the ‘code’ metaphor was found to be inaccurate because it was associated with the wrong chemical entity, it is still pervasive in genetics where it is no more seen as a metaphor but as a conventionalised term. Despite the role of metaphor in explaining abstract notions to learners mainly in education institutions (Garland and Ratay 2007), there are few studies about the role of metaphors in the field of Astronomy and Astrophysics characterised by its complexity and level of abstraction as claimed by McCool (2008:14) in the following statement;

Effective science communication requires a return to the mind of a beginner. This is a critical detail to remember because astronomy is, above all else, a remarkably complex subject. Since astronomy is initially a study of the abstract, observations of mysterious targets in the archives of time, we slowly forget our initial self. Novelty gives way to expertise. The problem is that effective astronomy communication requires a kind of scientific translation, a process made possible only by understanding the novice stargazer. And one of the best ways to accomplish this goal is communicating through analogy and metaphor (McCool, 2008:14).

To back up his strong claim, McCool (2008, 2009) reviews some popular metaphors in Astronomy And Astrophysics such as Kepler's metaphor of ‘the music spheres’ and argues that metaphor and analogy can be “vehicles” that help us to “grasp difficult astronomical concepts” (2008:15).

Boyd contrasts the theory-constitutive metaphor with pedagogical or exegetical metaphor, which is used for explanation and illustration. In contrast with the theory-constitutive

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metaphors, Boyd (1993) argues that pedagogical metaphors can be replaced by literal expressions.

3.2.2 Pedagogical or exegetical metaphors

A pedagogical metaphor, as its name indicates, is widely used in texts for educational purposes such as textbooks or in particular contexts such as classrooms (Cameron 2002, 2003) or popular science texts (Semino 2008, 2011, Deignan et al., 2013). However, this type of metaphor can also be found in scientific texts such as research articles as explanation procedures are not confined to popular science texts. As noted, Boyd holds that such metaphors can be replaced by literal expressions:

Certain metaphors, which might be plausibly termed exegetical or pedagogical metaphors, play a role in the teaching or explication of theories which already admit of entirely adequate nonmetaphorical (or, at any rate, less metaphorical) formulations (Boyd 1993: 485).

Because the concept of ‘pedagogical metaphors’ is central to the present study, it is further detailed in the next section where metaphor function is explained in relation to the concept of ‘genre’.