Steven Vincent Johnson wrote:
There has been lively debate in regards to whether E=mc^2 is an accurate
mathematical equation to describe whether energy is actually being converted
back and forth between mass and energy. No doubt many are likely to consider
it outrageous to challenge considering who came up with the equation in the
first place.
The following questions I want to ask are not only addressed to Stephen
Lawrence, but to Dave Thompson and anyone else who would care to add their
two cents worth:
I presume no one disputes the fact that individual masses belonging to
neutrons and protons contained within atomic nuclei become less as these sub
atomic particles are "fused" – that is, up to the element of Fe, iron. It is
my understanding that Fe is considered to reside at the bottom of the
so-called "energy well." As such, collectively speaking, protons and
neutrons within Fe are presumably considered to be their lightest "mass" as
measured individually. They can never exhibit less "mass" individually when
measured within other non-Fe elements. I also presume no one cares to
dispute the fact that individual protons and neutrons pertaining to nuclei
greater than Fe suddenly reverse that trend. They begin to systematically
increase in individual mass as elements gradually climb up the atomic number
scale.
I've never felt a desire to challenge these assumptions, and still don't.
However, something *is* beginning to twitch in the back of my mind.
First, the setup:
When a highly unstable radioactive element such as U235 is suddenly created,
such as when a single stray neutron invades the nucleus, we all know that
the atom shatters violently creating a random collection of smaller nuclei,
that along with a deadly collection of independent neutrons, thus the "chain
reaction" is born.
And here's my conundrum:
When these smaller atomic nuclei are created wouldn't that also mean that
the individual protons and neutrons within these lighter elements have to
suddenly regain lost mass if their atomic number is less that Fe? WHAT KINDS
OR WHAT RATIO OF LIGHTER ELEMENTS TEND TO BE GENERATED?
One could google "uranium fission products". I just did that, and it
appears that, as one might have guessed, aside from the free neutrons
which are spat out, the products are all heavier than iron.
See, for instance,
http://www.uic.com.au/uicphys.htm
Note particularly the graph "Distribution of fission products of
Uranium-235":
http://www.uic.com.au/graphics/fissU235.gif
While a large spread of nuclei are produced, the smallest atomic weight
typically produced is about 75. Iron's atomic weight is 56.
Of course, it's also true that for the process to be exothermic, all
that's needed is that the sum of the rest masses of the fission products
be less than the rest mass of the original nucleus. That's likely to be
true even if some of the products are lighter than iron (which is
certainly the case, if only because two of the "fission products" are
free neutrons!).
On average which
side of the Fe "energy well" are these lighter elements created on? I assume
it's a very messy/random affair where all sorts of lighter elements are
created, where many created elements are indeed less than the atomic number
of Fe, but that's speculation on my part. I could be wrong. If, however,
this *is* the case, where more elements lighter than Fe do tend to be
created on average, it does beg a nagging question as to where the extra
"mass" suddenly comes from in order to replenish the lost "mass" when these
smaller elements are created from the demise of a U235 atom. On top of that,
shouldn't all of the independently created neutrons ejected from the
destroyed U235 atom also suddenly possess a much higher atomic mass,
specifically that of an individual neutron? If memory serves me correctly
the mass of an independent neutron is one of the heaviest (per individual
neutron mass) in the table of elements. Where does all this "mass" come
from, particularly since so much destructive radioactive energy is being
released as U235 destroys itself.
What am I missing here?
Again, the sum of the masses of the decay products is less than the mass
of the original nucleus. Some of the pieces are above iron in the
table, some are below, but on balance, the aggregate of the fallout is
"closer to" iron than uranium was.
When nitroglycerin explodes it does so in an extremely messy reaction
which may leave behind some reactive molecules. The fact that those
bits and pieces are still reactive, however, doesn't affect the overall
picture, which is that there was a lot more energy tied up in the
original molecule than there is in the "fragments" after it breaks.
When gasoline burns in an internal combustion engine one byproduct,
IIRC, can be ozone. Yet ozone is "more energetic" than oxygen. But,
again, there's no contradiction, because overall, the reaction went
"down hill": the original molecules contained more energy than the final
aggregate of pieces.
Finally, uranium itself may seem to be a puzzle: Where did it come
from? What reaction formed it? The universe started with hydrogen; how
did atoms like uranium "climb the energy hill"? The answer, as I
understand it, is supernova explosions: There is so much energy
released in the explosion, that some amount of it may get "soaked up"
again in the core of the exploding star by _endothermic_ fusion
reactions which do not normally take place. Supernovas would burn even
hotter than they do if they weren't using up some energy creating
superheavy nuclei. (Interesting conclusion: A lot of the Earth was
formed from the ash of supernova explosions, presumably of stars which
vanished long before the solar system was formed.)
Regards,
Steven Vincent Johnson
www.OrionWorks.com
