Why the 45?
One of my friends at work mentioned that 45s -- 7-inch records that turn at 45 rpm -- were invented for jukeboxes. I challenged that, saying that RCA was caught flat footed by Columbia's introduction of the Lp in 1948 and rushed out an incompatible format, and that the large center hole was to build a more reliable changer. He disagreed and I countered that I'd dig up RCA's paper where they "prove" that 45 rpm is the best speed for a record, with no mention of jukeboxes or the "single" that later became the main use of 45s. Needless to say, this took me down the rabbit hole of old papers, recorded here. The RCA paper is at one my favorite resources, worldradiohistory.com : B. R. Carson, A. D. Burt, and H. I. Reiskind, "A Record Changer and Record of Complementary Design," RCA Review, Jun 1949, page 173 (page 17 in the PDF). https://worldradiohistory.com/ARCHIVE-RCA/RCA-Review/RCA-Review-1949-Jun.pdf and RCA's patent https://patentimages.sto...