Summary of “One space between each sentence, they said. Science just proved them wrong.”

Letters of uniform width looked cramped without extra space after the period.
Anything more than a single space between sentences was too much.
The original printing of the U.S. Declaration of Independence used extra long spaces between sentences.
Reading speed only improved marginally, the paper found, and only for the 21 “Two-spacers,” who naturally typed with two spaces between sentences.
Everyone tended to spend fewer milliseconds staring at periods when a little extra blank space followed it.
The study’s authors concluded that two-spacers in the digital age actually have science on their side, and more research should be done to “Investigate why reading is facilitated when periods are followed by two spaces.”
No sooner did the paper publish than the researchers discovered that science doesn’t necessarily govern matters of the space bar.
Johnson told Lifehacker that she and her co-authors submitted the paper with two spaces after each period – as was proper.

The orginal article.