 1.951–1117. The final part of book 1 is a leap from the invisibly small to the unimaginably large. The universe is infinite, he argues, consisting of infinitely extended space and an infinite number of atoms. Some philosophers, he adds, mistakenly picture our world as formed around a spherical earth, itself located at the universe’s centre. Although Lucretius does not say so, the juxtaposition of these two themes was natural because the latter thesis—a version of the Platonic one that privileged our own world as unique—was the main rival to that of the universe’s infinity. Modern readers may therefore well sympathize with the motivation of Lucretius’ critique of it, even if at the same time regretting his too ready dismissal of the ridiculous image of animals walking upside down in the antipodes, where it is day when it is night here (1.1058–67).