One or Two Spaces?

So I finally got an answer to the question I know you've ALL been wondering about: how many spaces after a period?? Thank you, Grammar Girl. You wanna know? I'll tell you in a minute.

See, I always thought the two spaces thing was so weird. I didn't even find out until about a year ago that people did this. I never learned this, but apparently people everywhere were taught growing up to put two spaces between sentences. Like this. Weird. And it's not even a generational thing necessarily, because my mom was taught to do it, but so was my ex-boyfriend. Somehow I missed the boat.

Stylebooks (AP, Chicago) say not to do it. And Grammar Girl told me why this morning (I read her daily devotionals). She says that when you're using a typewriter, go ahead and put two spaces. This is because typewriters use monotype font, where each character is the same width (i and m take up the same space, for example, because all the letters have serifs). On computers, however, i and m are proportional—fontmakers have made up for this width difference, so two spaces are not necessary.

Long explanation, short answer. I feel validated. Cheers all around.