One space or two?
The eternal question of one space or two spaces after a period can be answered with one simple word: one.
When the typewriter was first invented, it was advisable that the use of the 'em-quad' or 'm-quadrant' (which is the full width of the letter 'm') was necessary to separate sentences. Many style guides up until the 1940s used this as a standard. However, by the 1950s, these style guides began to disappear in favor of single-spacing after the sentence.
But still, why?
During the 1960s, new machines allowed for double-spacing to seem wasteful and production costs were reduced with single-space. Then, technology introduced an automated type setting where a line break could occur when there were two spaces, leaving an undesirable empty space at the beginning of the new line.
Double spacing today mean little in comparison to the hand-crafted typeface of yesteryear, but it's still regarded as old-fashioned. Many publishing houses will make a writer fix their spacing before print. On TECS, we enjoy both single-spacing and double-spacing, but we thought you'd like to know how that came about.
[Written by @Tanya]