Stefan writes from Orleans, Ontario: "I am studying energy in school (in Canada). I know many things have potential energy, but I am wondering: Is all matter made of energy, including rocks or a wooden table for example."

Answer: You stumped me. I must admit that don't know the answer to your question. I do know about some Web sites that may be helpful. I have attached a few links below - including one from Canada - about Energy, Matter, Dark Matter and the Universe.