• Question: If a tree falls in the forest, but nobody hears it, does it make a sound?

    Asked by 782yttc52 to Anna, Hayley, Iain, Rebecca on 15 Jun 2015.
    • Photo: Iain Bethune

      Iain Bethune answered on 15 Jun 2015:

      The tags says Philosophy, I’ll take a purely physical explanation. If sound is the motion of molecules of air in the form of a pressure wave, then that occurs irrespective of if someone is there to hear it. The laws of nature that govern the event – gravity, conservation of momentum & energy – hold whether or not any of us is there to directly observe.

      Of course if you define sound to be the stimulus on your ear-drum interpreted via the nervous system and the brain, then maybe not!

      Final thought – if no-one ever saw the tree, who’s to say it fell in the first place…

    • Photo: anon

      anon answered on 15 Jun 2015:

      I love this question – it is indeed very philosophical and you could discuss it for ages 🙂 Some people say that a tree is only a tree if people are there to see an identify it. Therefore, it if fell and nobody heard it, the sound wouldn’t exist either. Others say that the tree exists independently from our perception (even if we don’t see it or hear it fall, it is still a tree and it is still falling) – those people would also argue that it still makes a sound (in a purely physical way, as Iain described).

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