I've just been to Wiki to explore one of philosophy's most tantalising questions:
""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.
What is the difference between what something is, and how it appears? - e.g., "sound is the variation of pressure that propagates through matter as a wave"Perhaps the most important topic the riddle offers is the division between perception of an object and how an object really is. If the tree exists outside of perception (as common sense would dictate), then it will produce sound waves. However, these sound waves will not actually sound like anything. Sound as it is mechanically understood will occur, but sound as it is understood by sensation will not occur. "
Sound is a form of energy, just like electricity and light. Sound is made when air molecules vibrate and move in a pattern called waves or sound waves. An action (such as our falling tree) produces soundwaves which travel to the ears and then relayed into signals inside the brain.Like touch, audition requires sensitivity to the movement of molecules in the world outside the organism. Both hearing and touch are types of mechanosensation. It basically amounts to the idea that if no-one were around to listen to the falling tree, it would not make a sound, you would just have vibrating molecules. Vibrating molecules do not make a sound until they are emitted by the brain. Is this suggesting then that the Universe is indeed silent, and that the only sound which takes place is inside our minds? If this is the case, then it stands to reason that each and every sound that we have ever percieved is actually a part of our brains. The brain thus presents itself as somekind of cosmic hammond organ.
This of course must stand the same for touch, for an object is neither inherently rough or smooth, but simply a message relayed to my brain from my skin. If an object possesses absolutely no qualities whatsever, then it can only be my mind which is creating all affirmations about it. The mechanosensation of hearing and touch open up any number of avenues about all that we thought we knew about memory. For we don't simply remember a sensation that we have felt - we are everything about the sensation, and all it encompasses.