There are many ways to describe the first law of thermodynamics, and many ways to explain it. In this unique animation, chemist Andrea Sella recalls one of Richard Feynman’s descriptions of the law. In a classic analogy, Feynman imagines a child with a set of building blocks, and a mother struggling to ensure he doesn’t lose any. Each day, the total number of blocks remains the same, although some do stray from their original location.
This consistent fact – that the blocks cannot be created or destroyed – allows the mother to calculate how many blocks are in a box without even looking. And this consistent fact, that energy itself is also always conserved, lays the foundation for one of physics’ greatest rules.