What comes down but never goes up?

How to think about it

1. Think of things that come down from the sky: rain, snow, leaves, sunlight.
2. Ask which of them never goes back up. Leaves can be thrown upward, and birds fly both ways.
3. Rain falls from clouds and soaks into the ground or runs into rivers. Nobody sees rain going upward.
4. The water does return to the sky later, but as invisible vapor, not as rain, so the riddle holds.

Why “Rain” is the answer

Rain falls from clouds and only ever travels downward as rain. The water cycle does carry water back up, but by then it has become vapor, not raindrops, so the riddle stays true in everyday terms. The question is a companion to “what goes up but never comes down”, and the two make a nice pair to solve together.

Common wrong answers

• Snow. Snow also falls and does not go back up, so it is a fair alternative; rain is the usual answer.
• A ball. A ball comes down after you throw it, but you threw it up first.