An ngrams analysis doesn't show a significant increase in the use of "observable universe" after 1990. https://books.google.com/ngrams/graph?content=observable+

An ngrams analysis doesn't show a significant increase in the use of "observable universe" after 1990. https://books.google.com/ngrams/graph?content=observable+universe&year_start=1930&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cobservable%20universe%3B%2Cc0 https://books.google.com/ngrams/graph?content=observable+uni... . While it does increase, it seems to continue the trend which started in the 1940s. Here's an example of Asimov using "Observable Universe" in "Asimov on Numbers" (1977): https://books.google.com/books?id=el0PAQAAMAAJ&q=observable+universe&dq=observable+universe&hl=sv&sa=X&ei=_jTlVKfiL4TCywOz7ICQCw&redir_esc=y https://books.google.com/books?id=el0PAQAAMAAJ&q=observable+... .