ABSTRACT
Suppose that we have denumerably many balls, numbered by the positive integers in sequence: 1, 2, 3, . . . , n, . . . . As described above, at half a minute to noon, balls 1 and 2 are thrown into the room and 1 taken out. Then at a quarter of a minute to noon 3 and 4 are thrown in, and 2 removed. At each stage we move half way in time towards noon from the last stage, throw in the next two balls and remove the lowest numbered ball. So every numbered ball gets removed at some stage. But at each stage there is one more ball in the room than there was before.
