Capitalization of the word universe

Solution 1:

Perhaps it is just due to the popularisation of science? It makes sense that in the latter years of modern history, more and more people would become familiar with words such as universe due to widespread discussion of extraterrestrial physics and science fiction or due to their learning about scientific theories relating to the universe such as the Big Bang. Capitalisation is often used to denote specialist terminology, and so as the term universe became a word of more and more common usage, its capitalisation was gradually dropped. This is just my theory, however I believe it may have some grounding.