Last week I asked the question: "What is an idea?"

I posted this image of a lightbulb:

But: Why are we still using the lightbulb for ideas (after all it is 140 years old!) AND what was used before? A candle? Will the symbol change to an LED any time soon?
What do you think: Does the lightbulb metaphor work for you?

Two things about this metaphor work especially well for me:

(1) First there is darkness (= questions) and then there is light (= ideas)

(2) The lightbulb lights up instantly, similar to an idea forming: One moment your are still wrecking your brains over the problem, the next the solution is clear, almost in an instance.