My 10-year-old son and I visited a famous University to listen to a professor talking about his project, which he promised to lower household energy consumption.
"Think about it," the professor said, "why do we have to heat the entire house in winter while we only want to make people live comfortably? My project will develop a portable air-conditioner that only warms the air 1-2 millimeters away from a person. Thus, a person can feel warm even when the rest of the house is cold. In addition, the energy used by the air-conditioner is completely generated as a by-product of human activities, such as walking."
When I and other adults were all fascinated by the smart idea proposed by the professor, my son raised his hand. "Sir, don't we alreay have such things?", he said calmly, "they are called clothes".
