This article positions A Portrait of the Artist as a Young Man through the lens of scientific discourses of astronomy, in particular in relation to popularizations of the science of entropy and its literary impact. It is argued that scientific readings of Joyce’s texts have tended to focus too much on ‘Ithaca’ and ‘Night Lessons’, to the neglect of key scientific metaphors for creativity and subject formation utilized in A Portrait. Focused close readings of the later chapters of A Portrait allow the author to make a case for reading Joyce’s use of the bildungsroman form in parallel with theories of cosmic evolution and decay. Science fiction, such as the work of H.G. Wells, and the poems of Yeats’s apocalyptic collection The Wind Among the Reeds, are offered as important points of comparison for Joyce’s transformation of astronomical ideas into literary texts. A final, more playful, section explores the politics of alien life in Mulrennan’s story of an old man who imagines ‘queer creatures’ in Chapter V of A Portrait.