WHY IS THIS PICTURE MOVING?

Let your gaze roam over the brown ovals: Only what your eyes fixate on is stable. Everything outside the focus seems to be strangely moving in waves. This optical illusion is called peripheral drift, and it is based on the brightness differences in the image and not on the colors used. The light and dark areas confuse the motion sensors in our brains and trick them into detecting undulation. Incidentally, this always occurs in the direction from dark to light.