Shapeshifting Energy

Every useful device in your life is an energy converter. Your phone converts electrical energy to light, sound, and heat. Your car converts chemical energy to kinetic energy and heat. Your body converts chemical energy in food to movement, thought, and warmth.

Here is the critical insight: every transformation loses some energy as waste heat. No conversion is perfectly efficient. A chain of conversions loses energy at every link — sunlight to plant to cow to steak to your muscles strips away energy at each step.