what is energy and what is mass

[Roland]

Just like religion, modern physical analysis creates the basic
concepts, which we do not understand, and nevertheless, must accept on
faith and use to derive all derivative natural laws. It would be a pity
if it turns out that present human intelligence is inadequate to grasp
the mathematics that defines these basic concepts. Fortunately, not
all people think they have a unique grasp of what energy and mas are;
otherwise the world of physics would be as screwed up as the rest of
the non-scientific world.

[Amir]

I just had an interresting discussion with my physics teacher on this
one and here is what I learned: mass can be described (for now) as 5
things
1) quantity of matter=density*volume
2)wheighting mass as in |F|=g*m1*m2/r^2 where m1 is "pulling" m2
3)inertial mass as in F=ma that becomes a=F/m, here mass is "resiting"
the force F
4)Mass as energy m=E/c^2, much like particle are wieghted in eV, KeV,
MeV, etc
5)Mass is the inertia of a eletrical charge(check
http://en.wikipedia.org/wiki/Kilograms#Fundamental-constant_approaches)
for this one but quickly stated it goes like this :
The kilogram is the mass which would be accelerated at precisely
2=D710-7 m/s=B2 if subjected to the per metre force between two straight
parallel conductors of infinite length, of negligible circular cross
section, placed 1 metre apart in vacuum, through which flow a constant
current of exactly 6.241 509 629 152 65=D71018 elementary charges per
second.
It goes hand in hand with the definition of an ampere, so might want to
check it out too.
As for energy, it can be described as the potential for causing a
change. but that's just as unclear so we just gonna have to have faith
on this one

[Cl.Massé]

"Roland" <rolandorg519@yahoo.com> a écrit dans le message de news:
1147438007.167997.65580@y43g2000cwc.googlegroups.c om

> Just like religion, modern physical analysis creates the basic
> concepts, which we do not understand, and nevertheless, must accept on
> faith and use to derive all derivative natural laws. It would be a pity
> if it turns out that present human intelligence is inadequate to grasp
> the mathematics that defines these basic concepts.

Another "physicists don't understand what they are doing" topic? As you
say, there are "natural laws", that is, they are natural, and it is all what
it is. That they are fully explainable by a mathematical theory is quite
another topic, a speculative one, since there is no mathematical proof of
it, or have you one?

> Fortunately, not
> all people think they have a unique grasp of what energy and mas are;
> otherwise the world of physics would be as screwed up as the rest of
> the non-scientific world.

Mass is the parameter m in the formula F = m gamma, or
{i gamma_mu D^mu + m} psi = 0. Why? Because it works that way. Energy is
the parameter E in the formula E = m c^2 or D^t psi = -i E psi. Doesn't
really work that way? Try again. God doesn't play dice, but we don't know
whether He is a good mathematician. And if His proofs were false?

--
~~~~ clmasse on free F-country
Liberty, Equality, Profitability.

[rloldershaw@amherst.edu]

I'm not sure if this is going to clarify anything, but here goes.

Sometime in the 19th century physicists and chemists worked out the
laws of thermodynamics and came up with the equation PV = nRT.

The equation worked very nicely in explaining the relationships among
pressure, temperature and volume for ideal gases.

But suppose some impertinent natural philosopher came along and said:
"What is this mysterious 'P' in your equation? I want a better
explanation, or better yet a conceptual picture, of what pressure is."

The physicist of the time says: "Well, P is pressure and it is equal to
nRT/V, and that's all there is to it. There is no deeper explanation,
and no "pictures" are needed, or even possible."

But, of course, in the 20th century we learned that the 19th century
paradigm was incomplete. We learned about atoms and statistical
mechanics. A deeper explanation was possible, and useful conceptual
models and pictures were also possible.

What Roland, and some others who have raised the same point in various
ways, is saying, I think, is perhaps there is a far deeper explanation
of E than the word "energy" or the relation "equals mc^2", in analogy
to the situation with P.

That seems like a very good point to me. It should not be summarily
dismissed. It should be given serious consideration.

Rob

"Why be a slave on the dark side, when the freedom of enlightenment is
so readily available"

[Dirk Bruere]

Roland wrote:
> Just like religion, modern physical analysis creates the basic
> concepts, which we do not understand, and nevertheless, must accept on
> faith and use to derive all derivative natural laws. It would be a pity
> if it turns out that present human intelligence is inadequate to grasp
> the mathematics that defines these basic concepts. Fortunately, not
> all people think they have a unique grasp of what energy and mas are;
> otherwise the world of physics would be as screwed up as the rest of
> the non-scientific world.
>
Energy is Nature's book keeping.
It plays the same part as money does in a modern economy - it keeps
track of who owes what etc. You can have actual energy delivered to you,
for example in the form of heat, which corresponds to 'cash'. Or you can
have potential energy which is a kind of IOU, redeemable for cash under
the right circumstances. You can borrow energy just like money, but
there are strict rules on repayment times (see quantum mechanics,
uncertainty principle). There is no interest in general to be paid,
although the longer the energy/money circulates the less useful it
becomes (thermodynamics, entropy) which corrsponds to monetary
inflation. As for real energy inflation, see 'inflation, big bang etc'.

Anyone care to work mass into the metaphor?

Dirk

[Cl.Massé]

<rloldershaw@amherst.edu> a écrit dans le message de news:
1147914176.355161.119690@38g2000cwa.googlegroups.c om

> I'm not sure if this is going to clarify anything, but here goes.
>
> Sometime in the 19th century physicists and chemists worked out the
> laws of thermodynamics and came up with the equation PV = nRT.
>
> The equation worked very nicely in explaining the relationships among
> pressure, temperature and volume for ideal gases.
>
> But suppose some impertinent natural philosopher came along and said:
> "What is this mysterious 'P' in your equation? I want a better
> explanation, or better yet a conceptual picture, of what pressure is."
>
> The physicist of the time says: "Well, P is pressure and it is equal to
> nRT/V, and that's all there is to it. There is no deeper explanation,
> and no "pictures" are needed, or even possible."
>
> But, of course, in the 20th century we learned that the 19th century
> paradigm was incomplete. We learned about atoms and statistical
> mechanics. A deeper explanation was possible, and useful conceptual
> models and pictures were also possible.

Less than an explanation, it is a hypothetical model, it is *one possible*
explanation. The atomic model enables to predict other laws, but there is
no qualitative change, it is still *one possible* explanation of a larger
set of natural law. And above all, if an experimental data were to
contradict the model, only the model will be rejected, and not the known
natural laws. If we go a step further, and say that all model are bound to
be disproved, we are left with the natural laws, and that's all there is to
it. That doesn't imply we can't put some order in them.

Besides, the definition of pressure isn't the ideal gas state equation,
since it isn't universal. The definition of pressure is force over surface,
and it is all what it is. A physical quantity is only defined by its
comparison with a standard, and every physical dimension so far is a
combination of 4 fundamental dimensions.

> What Roland, and some others who have raised the same point in various
> ways, is saying, I think, is perhaps there is a far deeper explanation
> of E than the word "energy" or the relation "equals mc^2", in analogy
> to the situation with P.

Perhaps, but the phrase "the mathematics that defines these basic concepts"
let me think he is from the conviction that every physical law must be
demonstrated mathematically from nothing. Some mathematician has claimed to
have rigorously "proven" the law of inertia. That's necessarily false
since inertia is an experimental fact. All we can do is look for basic
physical assumptions that, through mathematics, yield the law. Those
assumptions aren't even faith, since no serious scientist can take them at
face value, there are very fruitful hypothesis, and nothing more.

Now, in this example, what has to be explained isn't E, but the relation
E = m c^2. But we aren't at all in the situation of P. The Einstein
equation is universal, and similar to the one saying that one meter is the
distance run by light in a certain number of periods of a certain atomic
transition. It gives the relation between the dimensions of mass and
energy.

--
~~~~ clmasse on free F-country
Liberty, Equality, Profitability.

[rloldershaw@amherst.edu]

These are all very good points. I would only caution that "natural
laws" can evolve, be found incomplete, or be proven incorrect, just
like models.

I hope you will indulge me and consider the following argument, which I
do not claim as complete or even useful. The possibility described
below just interests me, and perhaps others will find it stimulating.

Consider electron-positron annihilation. The two massive particles
interact and annihilate into pure energy, in the form of two oppositely
directed gamma rays. Now consider short gamma ray bursts. Here it is
thought that two ultracompact stellar objects merge and eject jets of
particles and gamma rays.

In the atomic scale case, the physics is treated as "pristine", while
in the stellar scale case the physics is thought to be more messy. The
unusual idea I would like people to consider is that if we could
observe the atomic scale event with arbitrarily fine resolution, might
not the physics be just as "messy" as in the stellar case? This is a
fairly unusual way to think about how nature works, I readily admit,
but possibly a valid one. I don't think we have any empirical
justification for ruling out a subquantum scale with dimensions as
small compared to atomic particles as atomic particles are to stellar
"particles". And if it were true, then the understanding of the energy
emitted in the atomic case might be considerably transformed, even if E
= mc^2 as a general law is retained.

Rob

[lazycai]

The fact that energy and mass are interchangable (under some specific conditions, just like all tranformations of energy between different forms) always makes me believe that mass is just a special type of energy. Of course, then my definition of energy could already have been different from the common definition of energy, which I do not really know what it is.

Based on the tiny bit of physics I have learnt, there are just three fundamental types of energy:
1. photon energy
2. kinetic energy, which is based on the state of motion of a mass in a certain frame of reference chosen
3. potential energy, which is based on the forces acting on the mass in some force fields (after all, all forces exists in the form of fields)

Probably there are still more, but I can only think of these three based on what I know.
I am just wondering why mass is not considered as a form of energy?

Thanks for reading.