A coffee cup mystery
Take a coffee mug, and place it on the table in front of you with the handle at 12 o'clock (for those of you who can only read digital clocks, that means the handle is pointing away from you).
Go on, go find one, I'll wait ...
...
Got it? OK, now ...
Gently (don't blame me if you break it!) tap it with a spoon at the 3 o'clock position (extreme right). Then at 9 o'clock (extreme left), Then 6 o'clock (closest to you).
Each time you get a single, clear note.
Now try halfway between all those points. For the clock minded, that's 01:30, 04:30, 07:30 and 10:30. You get a different, single clear note.
Now try elsewhere. Everything you get is one, the other, or a blend. You don't get any new notes, just a mix of the two we've already found.
And for those of you who think you have the answer, why is the frequency difference between the notes always the same ratio, regardless of the cup/mug you try?