Spaceman Spiff

I agree. But I was only considering measuring/observing the property not changing it. If E=mc2 , and we make m=0, then E=0 also. No energy => no motion @ 0 Kelvin. So the space-time (x, y, z, t) frame from which the observation is made would then be the rest frame. I have to think and research some more about my last question. Maybe I said it wrong... I know the concept I am trying to form, I need to figure out if it makes sense, and how to describe it.

I agree with your definition of binding energy. However, since fission induced by collision with a neutron is not the same as natural radioactive decay (alpha, beta, gamma), I stand by the arithmetic of the fission equation given (yes - the kinetic energy of the incoming neutron is being ignored). I am new to SFN, but i feel that we are moving away from (hijacking?) the intended theme/subject of this topic. It was last directly addressed (I think,) by MigL's intriguing post (quoted below). So the question I am submitting here for consideration is: Starting by positing E=mc2, and that mass and energy are simply properties of matter and radiation; Is E=mc2 simply equating the measurement of a specific property (energy) of something to another property (mass) using a conversion factor (c2)? If so, then I think that only works if both properties are of the same thing. Therefore, maybe matter does not actually change into radiation, instead what we experience as matter and radiation are 2 different "manifestations" of the same thing?

I am sorry. Maybe "disappears" was the incorrect word to use. I am referring to the change in total mass defect (and therefore binding energy) that results from the fission equation . The binding energies are: U-235 = 1784 MeV; Ba-142 = 1180 MeV; Kr-91 = 778 MeV. This results in 174 MeV excess energy released per nucleus of U-235. No I do not know the root cause of the resulting mass difference even though the numbers of protons & neutrons match, however the since both measured properties (mass defect & binding energy) equate using E=mc2 for each atom, I am reasonably certain that there is an equivalent difference in the total mass defect between the 2 sides of the fission equation.

So when we discuss E=mc2, what we are really discussing is the conversion of a particular property of one thing into another property of a different thing? So what about the conversion of the things (matter and radiation) themselves? Although now that I think about it a little, the only way to know that a thing exists is to observe/measure a property of that thing. So then - during an atomic fission event when a measured amount of mass disappears, and a measured amount of energy appears, does matter actually change into radiation, or are we just measuring 2 properties of the same thing?

If I understand Photon's analogy correctly, then "rabbit holes" are good, and It can/will go plenty deep for (x,y,z,t) spacetime - [and I have some ideas about that]. I believe your rabbit hole is just another name for the thread of knowledge. If I use the rabbit hole for Matter as an example, it would have started with things being "made" of some combination of fire, air, water & earth. Later we figured out molecules, then atoms, then atomic particles. Now I believe that that particular rabbit hole currently stops at quarks, but who's to tell that in in the not too distant future, quarks will no longer be considered the "fundamental/elementary" constituent of matter?