A rubber ball is bouncing on a flat surface. Every time it bounces, it loses energy, while the sound of the ball hitting the surface accelerates (because the intervals of the ball impacting the surface become shorter with each bounce). The ball seems to be accelerating when, in fact, it is slowing down. I know the evidence for an accelerating expansion of the universe and what I have just written are not linked, but I find the similarities interesting. In the ball's case, it is just an illusion.