A game-like activity using dice-like cubes can bring population growth home to all students, scientists, and nonscientists alike, while demonstrating many aspects of probability and uncertainty that are too often ignored in the physics curriculum. The activity can proceed at a variety of levels of sophistication and complication, from a simple demonstration of exponential growth through an elaborate modeling of life expectancy, advanced versus primitive societies, family planning, birth rate,

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... d population momentum. Variations can demonstrate radioactive decay, resource depletion, and the approach of a thermodynamic system to statistical equilibrium. Humankind needed about 5 million years to reach, in 1825, a population of one billion. We reached our second billion by 1930, our third by 1960, and our sixth by 1999. Populations of individual nations such as the United States show similarly surprising growth. A population's annual number of births tends to be proportional to its size, a feature that can be taken as the defining characteristic of exponential growth. Stated differently, populations tend to grow by a constant percentage per year rather than by a constant amount per year. Exponential growth can be surprising. All of us, scientists and nonscientists, had better understand these surprises. Al Bartlett 1, 2 has taught us the significance of exponential growth, and how to teach it to our students. Bartlett's work has inspired many others, including myself in this paper, to expand on this topic. 3 At least two introductory physics texts for nonscientists present this topic. 4, 5 13.