For the final Natural Science & Mathematics (NS&M) Colloquium lecture of the semester, Dr. Larry Weinstein, a physics professor from Old Dominion University and co-author of Guesstimation: Solving the World’s Problems on the Back of a Cocktail Napkin, presented “The Art of Guesstimation: How to Use Mathematics and Common Sense to Estimate the Answers to an Almost Unlimited Range of Questions.”
“If the sun were made of gerbils, the Earth would be incinerated,” said Dr. Weinstein to a laughing audience of professors, physics and non-physics students, and St. Mary’s County community members. “I don’t know the energy output of a gerbil, so I’ll consider the energy output of a human, about 1 Watt per kilogram.”
Dr. Weinstein continued to work on the estimation by considering that a gerbil’s most likely energy output would be 10 times that of a human, considering that the animals have a lower amount of insulation.
From there, Weinstein considered the energy output of the sun and its mass (about 0.0001 Watts per kilogram) and determined that the same mass of gerbils would give off about 10,000-100,000 times more energy.
While an extreme example, Dr. Weinstein used the gerbil calculation to show that using basic mathematics and some general understanding of the universe would allow anyone to estimate the answer to almost any question. In light of St. Mary’s strong opinions toward environmental preservation and awareness, Weinstein limited his questions mostly to energy conservation, covering topics from the efficiency of electric cars to windmills replacing gasoline.
“Let’s say there are about 100 nuclear power plants in the U.S.,” said Dr. Weinstein. “If each produces about 1 gigawatt of power, that would collectively be about 1 terawatt of power.” A windmill, given a constant gust of 20-mph winds, would generate about 2 megawatts of power, meaning that it would take 500,000 windmills to equal the power of 100 nuclear power plants.
Several of Dr. Weinstein’s estimations shed light on the fact that certain alternative energy sources on the market are not enough to replace the strongly efficient ones that damage the environment, increasing the need for other methods. Electric cars cannot be given a reasonable amount of battery power to equal the burning efficiency of gasoline, and even solar panels on all roofs of U.S. houses would barely be enough to sustain U.S. electrical needs.
“Even if I can’t point people in the right direction, I can at least point them away from the wrong ones,” Dr. Weinstein said in response to a question from the audience.
Before signing copies of his new book, co-authored by Old Dominion University mathematics professor John Adam, Weinstein made a concluding statement about guesstimations: “Think about the answer, break up the question, and dare to be imprecise.”
“I thought it was a good presentation,” said junior Brian Tennyson, a physics major who attended the event. “He really covered how the science of estimation works.”
“One of the most important abilities for people to have is to do these sorts of calculations,” said Dr. Charles Adler, chair of the physics department and organizer of the NS&M Colloquium series. “Quite often, you have to make estimates like that.”