[dvh]

Here's my favorite "alternative" explanation of moiré:

sin(a) * sin(b) = 0.5 * (cos(a - b) - cos(a + b))

You may remember this formula from high school. The arguments a and b are basically frequencies. When you multiply two frequencies a and b, you will get their difference cos(a - b) and their sum cos(a + b). If two frequencies are similar (e.g. 101Hz and 100Hz) you get one very low frequency (101Hz - 100Hz = 1Hz) and the other one will be much higher number (101Hz + 100Hz = 201Hz). It's hard to see that higher frequency 201Hz, you have to come really close, but it is easy to see that low frequency, that 1Hz would manifest as 1 dark blob across entire area.