Galileo and Wagon Wheels

By R.

Galileo...noted the curve now known as the cycloid, traced out by a point on the rim of a wheel as it rolls along a horizontal path... [H]e abandoned study of the curve, suggesting only that the cycloid would make an attractive arch for a bridge... Carl B. Boyer, A History of Mathematics. Wiley & Sons, 1989. p. 327

cycloid traced by point on a moving wheel
cycloid traced by point on a moving wheel