Here are some extensions to that question:
- How can you tell the interval between two guitar strings, even if you have no musical training? (You can use a ruler if you want.)
- How can you find the half way point on a string even without the ruler?
- Why are the lower-pitched strings thicker?
- Now suppose you are standing in a hard, cement tube (like a sewer) whose ends are both closed. How can you use the guitar to measure the length of the tube?
- How could you use a metronome to measure the length of the tube?
- How could you use the guitar to find the half way point of the tube, as well as the one third point, one fourth point, etc.?
- How could you accomplish the same thing with the metronome? (Or maybe two metronomes?)
- Can you modify the techniques of the last few points to work when the tube is open on both ends, or open on one and and closed on the other?
- Why can you even tell different pitches apart when listening to them? Two different pure tones both just shake your eardrum back and forth. One might do it faster, but it’s not like your neurons are going to send 2000 messages per second to your brain for a 2000Hz tone and 3000 for a 3000Hz tone. Also, you need to be able to distinguish many frequencies at the same time in order to tell different overtones apart. How could one simple ear accomplish all that?