Finally, an answer to the age-old (and quite geeky) question—should you double space after a period? No! So why do so many people swear that you should? Well, long story short, most typewriters used monospace fonts (meaning letters that each took up the exact same width). Typists were trained to insert an extra space to give a period some room before adding in the next capital letter.
But that was a long time ago. Technology has evolved a lot since then. Fonts are now designed proportionately. Your computer now knows that an ‘i’ takes up less room than an ‘m’, and adjusts the space to fit accordingly. For this reason, inserting a double space after a period today is a big fat waste of time. And it doesn’t look too good either.
Full story at GOOD.
More on typography for font fanatics.