Spaceman Spiff

2 hours ago, MigL said:

Changing one property, changes a lot of others.

I agree.  But I was only considering measuring/observing the property not changing it.

2 hours ago, MigL said:

Taking away a particle's inertial mass constrains it to move at c and have no valid rest frame.

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.

2 hours ago, MigL said:

So I don't really see how you can call them different manifestations of the 'same thing'.

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.

7 hours ago, Sensei said:

Nuclear binding energy that you mentioned ~1.7 .. 1.8 GeV is energy required to split nucleus of Uranium-235 to the all free protons and free neutrons.. 

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).

On 3/22/2019 at 7:34 AM, MigL said:

Mass and energy are often confused with matter and radiation.
The former are simply properties of the latter.
The property of mass for leptons ( quarks/electrons )only 'emerged' after the Electroweak symmetry break.

( one wonders if energy is the 'fundamental' form of mass ? )

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?

2 hours ago, beecee said:

I'm pretty sure that in actual fact no mass disappears, rather it is simply the release of "binding energy" that holds the protons and neutrons together. The mass residue from nuclear fission is Barium and Krypton. I'm willing to be corrected on that score though.

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.

On 3/22/2019 at 7:34 AM, MigL said:

Mass and energy are often confused with matter and radiation.
The former are simply properties of the latter.
The property of mass for leptons ( quarks/electrons )only 'emerged' after the Electroweak symmetry break.

( one wonders if energy is the 'fundamental' form of mass ? )

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?

On 3/23/2019 at 9:56 PM, The Photon said:

Really? So spacetime is then here to stay? I am hoping so, because replacing spacetime with something else just makes the rabbit hole go deeper.

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?