It's a happy birthday to Christie Brinkley, who turns 56 today. She's no actress, although her appearance in National Lampoon's Vacation certainly made an impression. Chiefly, though, Brinkley was known to guys who came of age in the 1980s and early parts of the 1990s as a model for Sports Illustrated's annual swimsuit issue (her romance with rock 'n' roll piano man Billy Joel didn't hurt in this regard either, upping her profile and keeping her in the public light). No crazy-busty chick, Brinkley and her sunny persona presented a confounding and seemingly at-odds image for plenty of teen and twentysomething guys — the knockout model as relatable girl next door.

And in photos like the one above, the leggy looker (she's 5'9") cemented the virtues of bared neck, shoulders and more for a generation of hormonally-charged dudes. Maybe the Internet, with its readily available explicit images, has changed that for the current generation. But movies (and magazines) used to not be above trading in sexiness without any preoccupation with actual sex. The bared female back is a big part of that — a subdued and at times almost startling inversion of what men, in all our visual orientation, most typically focus on. Of course, the ass pear doesn't hurt either.