I went to a 90’s-themed dance party on Saturday, hosted by one of my most fun-loving Seattle friends.

Remember the 1990s? With its Spice Girls, Dr. Dre, Britney Spears, Nirvana, Alanis Morissette, Jay-Z, Mariah Carey, Lauryn Hill, TLC?

What struck me the most about this party was that:

1) The 1990’s are far enough away now that we can have a themed-party centered around them. (I wore a choker necklace and Mary Jane’s. One girl dressed like Ginger Spice.)

2) Without fail, every time a new song came on, someone in the room would say something like, “No way. This wasn’t the 1990s. This song is only like (insert number less than 10) years old.”

Or, one person kept cracking me up with, “Naw. This song is contemporary. I just listened to that last week.”

At one point, I said, “You know, 2001 was 10 years ago.” Everyone expressed wonder over the sentiment.

Most of us at the party were in our 20s, 30s and 40s. Why do we reflect on the passage of time, and gasp?

Maybe it’s reaching a point where events that happened so many years ago are vivid in memory, not blurred like the soft-edged reflections of childhood.

But I think it’s deeper than that.

Time is really hard to understand — like money and health, there’s never enough of it, we’re never satisfied with it, and it is ever-fleeting.

My former astronomy professor, Richard Berendzen, opened up his class with this on the first day:

Time. We kill time, spend time, lose time, make time, beat time, take time, waste time; but we virtually never consider time, much less understand it. Yet to view events properly and possibly even to perceive ourselves in rightful context, let us go back in time, even to its beginning.

Time, you may know, is the fourth dimension. While we can move whichever way we want in the first three dimensions, in the fourth, there is but one way and one speed:

Forward, at 60 minutes per hour.