Each year, when I have been teaching Ecology & Evolution I wonder if I am misguiding my students during the photosynthesis lessons. To augment the module, I bring in a dense Holly log, hold it up, and ask: “where did the mass of this come from?”. After leaving them hanging for a few days or weeks, we discuss it again and start to rule out some of their answers (water, “dirt”, sun, water…). I help them rule out the sun, because everyone knows that empty space does NOT have mass…so light can NOT have mass either, because the light would have to travel through empty space to get to Earth from the Sun. But what about Black Holes dah dah dah??? Where’s the “truth”?!