Though the debate regarding whether it is correct to enter one or two spaces after a full stop/period appears to have abated, it remains a relevant topic. Perhaps even more so because an increasing amount of retired people have taken to public writing. Also, as explained further down, the subject has an impact upon the readability of books, both physical and digital. Authors need to be fully aware of this.
Historically there has been consistent discussion about which is correct with some even suggesting, and using, three or four spaces. It will help to have some understanding of why the concept of two spaces, in particular, has been largely accepted and adopted as the norm for some time.
Many, incorrectly, consider the advent of manual typewriters to have been the principle motivation for the adoption of two spaces after a full stop/period. However, the truth is, this simply reflected earlier typographical acceptances; two spaces were considered to provide clearer, visible, breaks between sentences. Nevertheless, why did users of manual typewriters decide to adopt the format? Principally because these machines used character monospacing. This is where each and every character is given equal spacing no matter the actual width of the character. As a result, a lot of white space was left between each letter making it harder to detect where one sentence ended and another began. Naturally, this impacted, negatively, upon the reading experience.
When electric typewriters and computers came into use proportional typesetting was adopted. This is where the spacing for each character is determined by the actual width of the individual character. For example, the thinner ones such as ‘I’ or ‘1’ where given less space than the broader ‘W’ or ‘M’. This provided a far more reader friendly presentation though the continuing use of two spaces after a full stop/period resulted in a visibly larger proportion of white. It was subsequently found only inserting one space markedly improved the reading experience and was therefore adopted by many, though not all, as the norm.
For authors a principle factor in determining the correct method, assuming they are not prepared to simply accept the general trend at face value, is how text looks in book print format. ‘Book print’ does not just mean physical books it is equally, if not more, relevant to digital books. Why? In book publishing, physical and digital, ‘justified’ formatting is often used within which spacing becomes an important issue. To have additional, unnecessary spaces, can and usually does impact upon appearance and readability. Besides there being too much white in both presentations, the formatting of digital books tends to be thrown out generally creating a very ugly appearance. In a very competitive market these aspects are important. If a reader cannot enjoy their read, they are very unlikely to either complete or recommend a book. Bear in mind mouth to mouth recommendations can make or break the success of a book or author. Neither are they likely to purchase another book by the same author or from the same publisher.
The aspect of retirees taking up writing was mentioned earlier. No doubt many where taught and brought up to always insert two spaces at the end of a sentence. To them it is the only correct method. However, as indicted above this is no longer accepted as being so and needs to be taken on board by all writers and authors. Some, not just retirees, will no doubt, and do, continue to argue two spaces is the only correct method. Some may even feel offended by the insistence for only entering one space, considering it a further example of society abandoning ‘correct’ grammar principles. Nevertheless, they do need to take on board the aspect of presentation and readability, especially when so much is now produced in digital, electronic formats where the aspect of spacing is of particular importance.