Much of my time at work is spent writing technical procedures. Many of these procedures are shared between several engineers, which results in conflicting formatting and typography. My perpetual struggle is with coworkers who put two spaces after each period.
Like them, I also used to insert two spaces after a period. This was how I was taught in my high school typing class (one of the most useful classes I've ever taken, and that includes college and grad school). However, in my technical writing course at BYU, we were told to use only one space. It was explained to us that all novels, professionally published books, and technical journals use a single space since the double space wastes room (which costs money). Ever since then, I've followed the one-space rule.
Recently, an article was brought to my attention in which technology writer Farhad Manjoo confirms what my technical writing professor told us. According to the article, the one-space rule was settled upon by typesetters in Europe and the United States in the early 20th century. However, because of the monospaced type of manual typewriters, which would give a skinny letter like "i" the same space as a wider letter like "w", it was difficult to distinguish the spaces between letters from the spaces between sentences in typewritten documents. Thus, the two-space practice was borne. The necessity of the two spaces became obsolete in the 1970s when electric typewriters allowed the use of proportional fonts.
Since the reason for using two spaces ended nearly 40 years ago, typographers argue that only one space should be used. In an amusing bit, Manjoo shares the opinion of one typographer:
"Forget about tolerating differences of opinion: typographically speaking, typing two spaces before the start of a new sentence is absolutely, unequivocally wrong," Ilene Strizver, who runs a typographic consulting firm The Type Studio, once wrote. "When I see two spaces I shake my head and I go, Aye yay yay," she told me. "I talk about 'type crimes' often, and in terms of what you can do wrong, this one deserves life imprisonment. It's a pure sign of amateur typography."It's not just a matter of opinion, the author argues, it's actually a specified practice in several professional manuals:
Every major style guide—including the Modern Language Association Style Manual and the Chicago Manual of Style—prescribes a single space after a period. (The Publications Manual of the American Psychological Association, used widely in the social sciences, allows for two spaces in draft manuscripts but recommends one space in published work.)In other words, "If you type two spaces after a period, you're doing it wrong."