The answer is supposed to be: they weigh the same. A pound.
But it seems like feathers are light, and a pound of feathers would be easier to move. Maybe “heavy” means: possessing heft. Hard to heave. Hard to give the old “heave-ho.” So the pound of feathers might be lighter than the pound of lead.
Or maybe the pound of feathers is impossible to heave! Unless they are squashed together in a sack somehow, large quantities of feathers are neither heavy nor light. They’re not heavable. Moving them is a complex engineering challenge, much more so than lead. So the question of “which is heavier” has no answer. Or the answer is “What do you mean?”
But what about the response — heavy doesn’t mean “hard-to-heave”. Heavy means — if you put it on a scale what would the scale say? That’s the know-it-all answer that the asker of the trick question has in his back pocket.
So on the know-it-all’s construal the question “which is heavier a pound of feathers or a pound of lead” is about what scales would say. What the question really means is “If you took an amount of feathers that caused a scale to read “one pound” and the amount of lead that caused a scale to read one pound and put them on two scales, which scale would read more?”
Could that be what the question means?
Obviously not! Because the answer to the question “Which of two scales that read the same would read more?” is obviously neither! That’s not a trick question.
And the question “Which is heavier, a pound of feathers or a pound of lead is a trick question.
So the know-it-all is wrong.