 Suppose an infinite lattice of particles of the same mass are arranged so that there is a distance of ½ between the first and the second, a distance of ¼ between the second and the third, a distance of ⅛ between the third and the fourth, and so on. Now imagine that a new particle of the same mass collides with the first particle in the lattice, as in Figure 1.4.1. If it is a perfectly elastic collision, then the incoming particle will come to rest and the velocity will be transferred to the struck particle. Suppose it takes ½ of a second for the second collision to occur. Then it will take ¼ of a second for the third to occur, ⅛ of a second for the fourth, and so on. The entire infinite process will thus be completed after 1 second.