This should be an easy question: What’s the diameter of a vinyl record? “Well,” you’ll say, “it’s 7 inches for a single and 12 inches for an album.” To which I will reply, “Yes. And…?” When we made the transition from Thomas Edison’s cylinder to Emile Berliner’s rotating disc about 120 years ago, the standard diameter for these newfangled things was generally 7 inches. No reason; it just seemed like a nice size.
But in 1901, some wise ass decided that 10 inches was a better size. A wider record meant that the grooves could be spaced out more widely; wider-spaced grooves meant that the grooves could be deeper; and deeper grooves meant that more information could be stored within then, leading to better sound. But if 10 inches was good, 12 inches had to be better, right? That size started making its appearance in about 1903 and for some reason spun at 60 RPM instead of the generally agreed-upon 78-ish RPM. More next time.