The MLA handbook has some interesting information about spacing after the period. Here is section 3.2.12 "Spacing after Concluding Punctuation marks" in my physical copy of the sixth edition.
Publications in the United States today usually have the same spacing after a period, a question mark, or an exclamation mark, or an exclamation point as between words on the same line. Since word processors make available the same fonts used by typesetters for printed works, many writers, influenced by the look of typeset publications, now leave only one space after a concluding punctuation mark. In addition, most publishers' guidelines for preparing a manuscript on disk ask professional authors to type only the spaces that are to appear in print.
Because it is increasingly common for papers and manuscripts to be prepared with a single space after all concluding punctuation marks, this spacing is shown in the examples in this handbook. As a practical matter, however, there is nothing wrong with using two spaces after concluding punctuation marks unless an instructor requests that you do otherwise. Whichever spacing you choose, be sure to use it consistently in all parts of your paper--the works-cited list as well as the main text. By contrast, internal punctuation marks, such as a colon, a comma, and a semicolon, should always be followed by one space.
Publications in the United States today usually have the same spacing after a period, a question mark, or an exclamation mark, or an exclamation point as between words on the same line. Since word processors make available the same fonts used by typesetters for printed works, many writers, influenced by the look of typeset publications, now leave only one space after a concluding punctuation mark. In addition, most publishers' guidelines for preparing a manuscript on disk ask professional authors to type only the spaces that are to appear in print.
Because it is increasingly common for papers and manuscripts to be prepared with a single space after all concluding punctuation marks, this spacing is shown in the examples in this handbook. As a practical matter, however, there is nothing wrong with using two spaces after concluding punctuation marks unless an instructor requests that you do otherwise. Whichever spacing you choose, be sure to use it consistently in all parts of your paper--the works-cited list as well as the main text. By contrast, internal punctuation marks, such as a colon, a comma, and a semicolon, should always be followed by one space.