Recall that a 2.2-pound rock has on the order of 1027 bits of information encoded in the state of its atoms and about 1042 cps represented by the activity of its particles. Since we are talking about an ordinary stone, assuming that its surface could store about one thousand bits is a perhaps arbitrary but generous estimate.68 This represents 10−24 of its theoretical capacity, or a memory efficiency of 10−24.69 We can also use a stone to do computation. For example, by dropping the stone from a particular height, we can compute the amount of time it takes to drop an object from that height. Of
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