Lex asked me tonight why we never run out of air on this planet. I answered with blah about exchanging oxygen and carbon dioxide with plants and all that. He says, “I know, I know, but…” and proceeds to clarify his point. If we breath in one “air” (which equals one oxygen and one carbon dioxide), use the O and exhale the CO2, which leaves one CO2 floating out there. A plant “breaths” in one “air”, uses the CO2, and exhales the O, leaving one O floating out there. The O and the CO2 find each other and merge. I’m with him so far. Then he says, “But that means there were two “airs” breathed in and only one breathed out. Why don’t we run out of air?” I really wanted an intelligent answer, but… I had nothing! I tried to make some blah blah guesses, but you can’t pull that wool over Lex’s eyes. I told him maybe his teacher knows, or daddy, because daddy knows everything. He said, “No he doesn’t. I bet he doesn’t know what it feels like to be inside a black hole.”

Just a usual bedtime with my boy. He’s ten and already a deeper thinker than I am. Tomorrow I’ll tell him to ask Alan.