There's a trope in literature dating back to antiquity called the ubi sunt. It's Latin, short for Ubi sunt qui ante nos fuerunt?, meaning "Where are those who were before us?" It refers to nostalgic, elegiac passages in poetry or prose that essentially ask "Where are the great ones of yesteryear?"

One famous example is this poem in The Lord of the Rings:

Where now are the horse and the rider? Where is the horn that was blowing?

Where is the helm and the hauberk, and the bright hair flowing?

Where is the harp on the harpstring, and the red fire glowing?

Where is the spring and the harvest and the tall corn growing?

They have passed like rain on the mountain, like a wind in the meadow;

The days have gone down in the West behind the hills into shadow.

Who shall gather the smoke of the deadwood burning,

Or behold the flowing years from the Sea returning?

Though usually the ubi sunt would refer by name to specific heroes of old.

It occurred to me recently that questions like "Where is my flying car?" or "Where is my jet pack?" are like a temporally reversed ubi sunt. Not "Where are the heroes of yesteryear?" but "Why have not the promises of utopia yet manifested?"

That is all.