It’s official: Pluto has been downgraded to dwarf planet status. Mnemonic devices and classroom paper mache exhibits world-wide will be subject to immediate recall.

Why do we all naturally feel a twinge of pain at this? It’s a technical development in a field most of us have nothing to do with, affecting a place we’ve never seen and never will. Here’s my guess:

For people born in the 1950s, 60s and 70s exploration of the universe was the most exciting and dramatic thing conceivable, and Pluto was the outer edge of that frontier. While we’ve had unimaginable technological advances since then, neither cellphones, nor email, nor the internet, nor even google awakens the world of fantasy that space did.

Nowadays, that excitement has to a great degree died away. I took my son to the Air and Space Museum last Spring, thinking he’d have a spark of the amazement that I remembered from my childhood visits there. But now, instead of a futuristic wonderland, its become a history museum. It still exhibits the space adventures of the 1970s which were mysterious and pioneering then, but are now conjure the pages of old childhood social studies books and the scratchy sound of out of date audio and videotapes.

Maybe the thrill of outer space was bound to be fleeting. But the downgrading of Pluto is a reminder of how long gone it is.