How about this: with every breath, you inhale a million billion billion atoms of oxygen. When you exhale, these atoms take a couple of years to be uniformly mix

How about this: with every breath, you inhale a million billion billion atoms of oxygen. When you exhale, these atoms take a couple of years to be uniformly mixed in the atmosphere. Chances are you a breathing oxygen that was once in the lungs of, say, Shakespeare! (though, also, in dog farts). Before that, this same oxygen was created by fusion in the inside of a star, which died so we could live.