Re: internal energy contributing to mass

Dear Jean Paul:

"Jean Paul" <jcorriveau@xxxxxxx> wrote in message
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On Nov 16, 9:05 pm, "N:dlzc D:aol T:com \(dlzc\)"
<dl...@xxxxxxx>
wrote:
Dear Jean Paul:

"Jean Paul" <jcorriv...@xxxxxxx> wrote in message

news:3e17bf7f-d4e3-4db8-86da-530ff284e420@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Hello.

I wish to react to some of the explanations provided in
my post 'What E = mc^2 means really?'

One explained:
'And how the individual particles are "bound",
determines how much energy there is. '

I have no trouble with this one because the binding
of atoms or molecules determines the 'toughness' of
an object. For instance a gold ball is tougher than a
rubber ball. But as long as the matter is bound, it is
matter hence mass. This is the intuitive aspect of
mass.

Let me add a little depth to that. All assemblies have
less mass than the sum of the individual particles
themselves. The more the "mass deficit", the more
stable the assembly. As you add mor and more
internal energy, the assembly starts to "come apart
at the seams".

I have trouble with this concept of mass deficit. See
more on that below.

Think of it as taking out a loan on a house. The "mass deficit"
is how much you owe to the bank.

Another explained:
' Electrons *don't* circle the nucleus of the atom.
They enter orbitals, states of reduced energy, and
"binding energy" is released. '

Suppose I can cut an apple in half without any
atoms or electrons and whatever particle being
lost in the cut. Because the cut is only possible
if molecules become unbound, does it imply that
the resulting two halves weigh less now than the
whole apple we started with (because some
energy was lost as the result of the unbounding)?

No, the mass will be very slightly higher. You
have also (by separating the halves) lost both
hydogen bonding (expressed as water affinity for
exposed apple surfaces) and van der Waals
bonding as well.

I have a feeling that 'mass deficit' has something
to do with this. More on that below.

....
For instance, suppose a hydrogen atom being
released from the sun. So are you saying that
the faster the speed of the atom, the heavier it
weighs? Hum!

No. Absolutely not.
mass = rest mass = inertial mass = gravitational
mass

Ok. So in E_0 = mc^2, 'm' is rest mass, and if
we use instead the equation E = mc^2, 'm' is the
relativist mass.

I cannot tell you how much grief you are setting yourself up for,
by even considering the whore that relativistic mass is. I
refuse to do more than dissuade someone from using it.

... you throw motion into the equation, and you
then need to consider a more useful, less
specific, equation:
E^2 = (pc)^2 + (mc^2)^2
... with p a vector, representing momentum (of
either the system as a whole, or the individual
"bits")

To follow from my reply just above, in this
equation above, 'm' is the rest mass, right?

m is always rest mass. Some outdated texts still make reference
to the whore relativistic mass, a whore that is part vector and
part scalar. I do not.

'p' is the quantity of motion of particles inside
the body.

No, it is is a descriptor of momentum... it says nothing about
the number of particles.

So rest mass and kinetic energy contribute
to the overall mass. That is what this equation
say, right?

No, the equation says that total energy of the system described
by "m" (proportional to rest energy) and "p" (proportional to
energy of motion) is the total E.

That makes sense because the more bound
energy is, the tighter the atoms are bound hence
the denser the body,

Backwards.

So a less dense body has more energy. Must be
because of that kinetic energy. A denser body has
a higher 'mass deficit', right?

"Density" is a word with much baggage. Plutonium-239 is very
dense, but is not stable. It is not as stable as iron.
Plutonium-239 has a per nucleon mass deficit, but iron's is
higher.

At the opposite, the looser the body, the less
bound the atoms are hence the lighter the body
(for instance gas).

But the closer a gas is to the mass of the sum
of the individual gas molecules.

Is this because of the mass deficit you mentioned
in your message earlier? Sorry, but this give me
a hard time. So if a rock has say 'x' billion of
atoms of each mass of 'y', then the overall mass
of the rock is less than 'x * y'. If the body is gas,
then that deficit is much less. I don't understand
this 'mass deficit', but sounds fascinating.

Consider the rotational equivalent, moment of inertia. A skater
can alter their rate of rotation, their ability to store energy
in rotation, and the amount of torque it takes to angularly
accelerate them... just by extending or pulling in their arms.
Likewise "assemblies" can have less mass depending on their
"arrangement" (when "arrangement" includes letting light out of
the assembly.)

Just a minute. I think that this starting to make
sense. If two atoms are bound, they have less
energy (hence mass) than if they were loose.

Very tiny difference, but yes.

Bound atoms have less mass because they tend
to have less kinetic energy than unbound atoms.

No constraint on what kinetic energy they can have, other than
"finite".

But then the two bound atoms need to spend
some energy all the time to stick together.

No "spending energy all the time". It is a one time outlay, and
they are "wed" until the same amount of energy (or more) comes
along and separates them.

That glue would be from electric energy.

Or strong/weak interaction, in the case of nucleii.

I recall from high school chemistry that electrons
have something to do with this.

The nucleus too.

It is this glue that adds to the 'mass deficit'.

*I* think the glue is the mass deficit.

I admit still having a very hard time understanding
what mass is.

Welcome to the cutting edge of physics. We would all like to
know how you can shield mass in such as way as it would appear
you had little (mass deficit) or none. Then we could have the
stars for the price of a bottle of diet cola and a package of
Mentos.

Do you know of a web site 'for dummies' that explain
this stuff to me? I really what to understand this. So
far the web sites I have seen are full of equations that
blow me away.

The price of entry is learning the language, and that language is
mathematics. And you will find that the fun is in the learning,
not in the knowing.

There are a number of philosophical treatises on the source of
the propery "mass". Likely if you can find something by Ernst
Mach on the subject, it will get you closer.

Google provides only 84 hits on this subject, with this search
term:
"where does mass come from" site:.edu

David A. Smith


.

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