There’s a question going around on Twitter, courtesy of the writer Matt Whitlock: “Without revealing your actual age, what’s something you remember that if you told a younger person they wouldn’t understand?”

This simple query has received, at this date, 18,000 responses. Here is just a tiny selection:

Etcetera. You are welcome to peruse the replies looking for your precise moment in time to be pinned to the screen, wiggling.

It is obvious that most of the relics of earlier eras that stick with people are technological, or at least about the material culture of technology.

It is banal to note that these technological eras are becoming shorter. No one expects today’s social networks or electronics to last as long as AM radio or the internal combustion engine or even three-channel broadcast television. That’s not how products work anymore. Many things are designed for obsolescence and the rest end up there anyway with frightening speed.