I am an invisible barrier that can stop a speeding train if placed correctly, yet a butterfly can pass through me without slowing down. I have no mass, no height, and no width. What am I?
A boundary line or border
A line drawn on the ground or a national border has no physical dimensions or mass, but can legally or conceptually stop a train, while animals cross it freely.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Hard. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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