Which of the following statements is NOT true about Milankovitch Cycles?
a. Milankovitch calculated his theory of the timing of ice ages on earth based on the gravitational interactions between earth, the sun, and the other planets which cause cyclical variations in the earth's orbit around the sun
b. Milankovitch's theory of the ice ages was not proven until ocean sediment cores became available many decades after he published his theory
c. Milankovitch believed that ice ages were mostly caused by variations in the sun's energy output
d. Milankovitch made his calculations without using computers