 Suppose we have a jar—a very large jar—with the capacity to hold infinitely many balls. We also have a countably infinite pile of balls, numbered 1, 2, 3, 4, …. First we drop balls 1–10 into the jar, then remove ball 1. (This adds a total of nine balls to the jar.) Then we drop balls 11–20 in the jar, and remove ball 2. (This brings the total up to eighteen.) Suppose that we continue in this way ad infinitum, and that we do so with ever-increasing speed, so that we will have used up our entire infinite pile of balls in finite time (Figure 1.3.1). How many balls will be in the jar when this supertask is over?