Two closed systems, not one.

Energy does not get lost, but it doesn’t mean it all fits in one closed system.

Photo by Jordan Opel on Unsplash

The good thing about the First Law of Thermodynamics is that, when energy cannot get lost, we do not need to find it. We can start out our story of the material universe with the presence of energy even before there was matter. It was already there, folks! Stop looking. It never got lost.