e/If a tree falls in a forest

Information
has gloss	eng: "If a tree falls in a forest and no one is around to hear it, does it make a sound?" is a philosophical riddle that raises questions regarding observation and knowledge of reality.
lexicalization	eng: If a tree falls in a forest
instance of	(noun) a difficult problem brain-teaser, riddle, conundrum, enigma

Media
media:img	Coastal redwood.jpg