When a guitar's string is plucked, what causes the actual sound we
hear - the movement of the string, or the displacement of air caused by the
string? Would we be able to hear sound on the moon, where there is no air?
The sound of the guitar string we hear is due to the disturbance that
travels through the air as a longitudinal wave. The air acts as the medium
of sound transfer. On the moon, where there is no atmosphere to speak of,
there is no medium to transfer the sound. Although plucked, the sound does
not have a medium in which to travel, so would not have a sound. Inside
the pressurized Lunar Excursion Module, you would hear the instrument just
fine. Outside, it would be silent.
---Nathan A. Unterman
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Update: June 2012