Earth Science Today
Russ Colson
Minnesota State University Moorhead

Answer to thought-problem:  You rub your hands together to warm them in the cold of a Moorhead winter.  Which of the three sources of energy above is the main source of energy heating your hands?

Solar energy: Sunlight is absorbed by plants and converted to chemical energy (sugars etc.). The cow eats the plant. You eat the cow. Through a series of chemical and electrochemical steps, your body converts the energy to kinetic energy (moving your hands). Friction between your hands converts the kinetic energy to heat.

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