"In physics, a moiré pattern is an interference pattern created, for example, when two grids are overlaid at an angle, or when they have slightly different mesh sizes. The term originates from moire, a type of textile, traditionally of silk but now also of cotton or synthetic fiber, with a rippled or ‘watered’ appearance."
To see this moire circle animated, go to this link and hold your cursor over the image.
http://www.cutoutfoldup.com (lots of fun stuff to check out)
To see the moire circle above animated (really cool), go to this link and hold your cursor over the image.
Watered Silk or Moire
Another great blog page:
The history of moire fabric
"The History of Art...." inner boards, with green watered (moire') silk endpapers and inset inner-board panels; wide dentelles with four widely-spaced gilt rules, and a further double-rule at board edges. © Jeff Stikeman