Energy and Mass. WTH is that all about? Energy is a concept more than anything else. We humans can perceive it in some ways: HEAT is a form of energy; our senses detect it. LIGHT is a form, we see it. Electrical energy, Magnetic energy, Gravitational energy, we know about, but of those, only Gravitational can we "feel". In a way, via our body weight. So, ENERGY is situational, intangible to our everyday feelings. But MASS is easily felt, seen, understood. "Anything which has weight and occupies space has MASS". So the pencil on your desk has mass. When I was in the 5th grade, my Science teacher, Mr. Kavina, told us as he held up a pencil, that if we could convert all the mass in that pencil to ENERGY, we could power our home for a hundred years! Since that proclamation, which I recall like it was yesterday, that nagging thought has prevailed in my mind for a lifetime. Many things got in the way of pursuing study of this, of course. Personal shit. A murder-suicide, divorce, relocation several times, unrelenting fear of inability to remain above water, I have never accepted a dime of welfare $$. Getting off course a bit...... Albert Einstein proposed that ENERGY and MASS are EQUIVALENT! (?!?) He put forth the then incredible formula stating ENERGY = MASS times SPEED OF LIGHT SQUARED; E = M C C. The Physics world was stunned. Disbelieving, it attempted to unseat the new madman Physicist. That relation between Mass and Energy has now been confirmed as correct many times. What does it mean? It confirms that if we unlock the confining bounds of the atom, enormous amounts of energy can be the result of conversion of very small amounts of mass. (The pencil = incredible power). AFAIK, very few human induced mass to energy transforms have involved complete conversion. The atomic bombs of WW-II converted a few pounds of Uranium and Plutonium to pure energy, destroying whole cities, but still left behind a few pounds of residue: NOT ALL THE MASS was converted to energy. Instead, the by-products were undesirable: radioactive isotopes of newly-formed elements resulting from the conversion. Those devices were FISSION devices. Now, the FUSION devices take HYDROGEN gas and FUSE it with HYDROGEN gas, to form HELIUM gas, with the liberation of even more energy than the FISSION devices. And, you're left with Helium. Still not the proverbial Pencil = Huge Energy. I am only able to understand this all at a minor level, but I believe the scientists knew about, and proved, that one kind of nuclear transformation resulted in absolute completion of Einstein's prediction: ALL the MASS is converted to ENERGY in one kind of nuclear reaction. That is the "pair-annihilation" reaction", where two violently opposing atomic particles, the ELECTRON and the POSITRON, encounter one-another with the result that both disappear instantly and violently, leaving behind only pure energy. This last description is highly valuable. The pair-annihilation reaction is usefully applied in today's Medical World. It is called a PET scan. Positron Emission Tomography. See it in every modern hospital. Today's most accurate means of diagnosis internally, and the most expensive. PET scan technology is a spin-off of nuclear medicine technology we would likely NOT HAVE today, had those pioneers at Los Alamos not prevailed. Just sayin. Frank