(a) The pebble seems to move in a circular path when we are sitting outside the circular disc.
(b) The pebble seems to be stationary in front of us when we are standing at the centre of the disc.
(a) The pebble seems to move in a circular path when we are sitting outside the circular disc.
(b) The pebble seems to be stationary in front of us when we are standing at the centre of the disc.