Shimrod, no honest scientist would begin to give you definition with an ironclad guarantee for light, or any other part of the electromagnetic spectrum. Truth is, they really don't know what it is. They can tell you some of the ways it behaves in our four dimensional existence but on the quantum level it get verrrrry strange. Throw in a few measures of dark energy, dark matter, the essence of string theory, what the limit of the universe may be, what precipitated the Big Bang, if indeed there was one (it has come under doubt of late!) and a few other conundrums, the enigma, wrapped in a riddle (the original description of a Quasar) and then tell me what you mean by physical.

In the nuts and bolts "soulless" universe, when you die your basic chemical composition assumes a random and inert (other than chemically) form, sans efforts of those beauticians of the dead---morticians. Your conscious mind ceases to to exist as the electrical energies in your brains become random (whatever that really means). From your perspective, the universe ceases to exist and the unknown and unknowing infinity from whence you came reclaims your temporary consciousness.

Have you had a night when you did not dream? Where were you? Who or what are you during that time? How is it that you are still you when you awake? No, that is not true. You are ALMOST the same person who went to sleep the night before, but you have changed, physically, mentally. Some changes are big and some little. For most folks death is a big change, or at least a surprising one but for others it is only a slight shift from their present mode. For many, it is a welcome relief from a lifetime of pain and if you have ever lived you know that life IS pain.

If you have lived right, after you die you are missed by some. You don't have a heart unless you have loved someone other than yourself. If you managed to get outside yourself and touch someone else you have done a good thing and you will be remembered for one generation only; then you are gone from living memory. If you have made a significant contribution to mankind then your secondhand memory will persist for a little longer. If you have slaughtered millions during your time on this planet, you may be remembered for even longer as a great leader like Julius Caesar or as the embodiment of evil like Adolf Hitler. Who knows? and to you it will make absolutely no difference, at least not in THIS dimension.

Sweet dreams.