Eva is in a closed, dark room. She uses her arm muscles to turn on a lamp. When she moves her hand closer to the lamp, the light
heats her hand. The light bounces off the pages of a book and into her eyes. If this room is a closed system, what happens to the total amount of energy in the room?
Well, we know that the total energy in a closed system remains constant.
The problem with the story of Eva is that she is not in a closed system. If the dark room were really a closed system, then she could press the button or turn the switch all day, and the lamp could not light. It needs electrical energy coming in from somewhere in order to turn on.
Let's say that Eva used her arm muscles to strike a match and light the candle on the table. Then we would have have food energy, muscle energy, chemical energy in the match, chemical energy in the candle, heat and light energy coming out of the candle, heat energy soaking into her hand, light energy bouncing off of the book and into her eyes ... all going on during the story, and the sum total of all of them would remain constant.