In a recent blog, Jim remarked about how weird it was to think that he could remember his parents being the age he is now, and how surprising it is to realize that age doesn't necessarily bring certainty, contrary to popular myths of adulthood. (BTW, that's my paraphrase--Jim may have meant something entirely different.)
Since my mom and dad were, respectively, 38 and 40 when I was born, I'm only now getting to the point of being able to remember them at the age I am now. In fact, I recently came across this snapshot and realized that I'm the same age now that my mother was when this was taken. She looks a hell of a lot better at 42 than I do, by the way, and I can't even say that I've had four kids that ruined my figure like she could have (though clearly that wasn't even the case for her, dammit).
As you can see, this was shot the day of my sister's high-school graduation, which dates it to June 1970. My sister is thirteen years older than I am, and a few months ago while we were shopping in Pittsburgh someone assumed she was my mother (referring to me as her daughter). She was incensed, though I think it was a harmless assumption on the clerk's part. Still, I probably didn't help matters any when I remarked that people used to mistake the two of us for twins. D'oh! I really was trying to lighten the situation, but it was a thoughtless thing to say.
Still, it goes to show what a moving target the idea of age really is--though of course, that doesn't make the idea itself any less potent. Personally, I prefer the Tralfamadorian sense of time; as Kurt Vonnegut writes in Slaughterhouse Five, they "look at all the different moments just the way we can look at a stretch of the Rocky Mountains. They can see how permanent all the moments are, and they can look at any moment that interests them."
Like this one, for example.