In the ninth installment of the "Pi in the Sky" illustrated problem set, students use the mathematical constant pi to solve real-world science and engineering problems. Students will use pi to detect frost in lunar craters, determine the density of Mars' liquid core, calculate the powered output from a dam, and find out how far a spacecraft travels as it returns data to Earth. Materials Pi in the Sky 9 poster – Download PDF Pi in the Sky 9 handouts – Download PDF Pi in the Sky 9 answer key – Do