• Mass and Energy

    From ram@ram@zedat.fu-berlin.de (Stefan Ram) to sci.physics.relativity,sci.physics on Thu Jan 1 16:19:52 2026
    From Newsgroup: sci.physics.relativity

    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :that mass could be converted to energy as
    :predicted by Einstein's E = mc-#.

    I can spot three mistakes here right off the bat.

    First, the phrase "mass could be converted to energy" is based on
    a misconception, since mass already /is/ a form of energy - there's no
    "conversion" happening. It's like saying, "water can be turned into a
    liquid" - no, water /is/ a liquid.

    Second, "E=mc^2" only applies to systems at rest. In general,
    it's "E^2=(mc^2)^2+(pc)^2", where "p" is the system's momentum.
    (That basically says mass is the magnitude of the four-momentum.)

    Third, mass is conserved in nuclear fission. This point is often
    explained incorrectly, even in otherwise solid textbooks like Grif-
    fiths.

    I've laid out the full argument elsewhere, but here's the (suffi-
    cient) short version:

    Take a nucleus that's at rest, so its total momentum p=0.

    After fission, because momentum is conserved, the total momentum
    of all the fragments is still zero. That means the relation "E^2=(mc^2
    )^2+(pc)^2" simplifies to "E=mc^2" both before and after the split.

    Since energy is also conserved, the total energy E of the nucleus
    and its fragments - including their kinetic energy - stays the same,
    call it E. From "E=mc^2", it immediately follows: if E stays constant,
    m does too.

    E_"before" = E_"after" - due to conservation of energy (0)

    E_"before" = m_"before" c^2 - as you said yourself (1)

    E_"after" = m_"after" c^2 - the same as (1), just later (2)

    m_"after" = m_"before" - substituting (1) and (2) into (0) (3)
    and dividing by c^2

    Only when you change what you call the "system", and treat the split
    products separately, do you get systems with nonzero momentum and
    find a mass defect and non-zero kinetic energies.


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  • From nospam@nospam@de-ster.demon.nl (J. J. Lodder) to sci.physics.relativity,sci.physics on Thu Jan 1 22:38:13 2026
    From Newsgroup: sci.physics.relativity

    Stefan Ram <ram@zedat.fu-berlin.de> wrote:

    Please do not quote mine,
    and please do not break threads,

    Jan

    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :that mass could be converted to energy as
    :predicted by Einstein's E = mc?.

    I can spot three mistakes here right off the bat.
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  • From ram@ram@zedat.fu-berlin.de (Stefan Ram) to sci.physics.relativity on Fri Jan 2 14:28:52 2026
    From Newsgroup: sci.physics.relativity

    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :1n + U-235 raA Ba-141 + Kr-92 + 3n
    . . .
    :Are you claiming that the mass 3.916659E-25 kg
    :is not converted to 2.78E-11 J kinetic energy?

    When you start in the rest system of "1n + U-235",
    its momentum is p=0. As the momentum is conserved,
    the momentum of "Ba-141 + Kr-92 + 3n" then also is
    p=0, so its kinetic Energy still is zero.

    Only when you change the definition of what your
    system is, you get kinetic energy. For example,
    when you look at only one of the "3n", it has
    kinetic energy.

    For another example: On my table, a cup is resting.
    In my room, it has the momentum of /zero/. The cup
    contains gluons. When I look at one of those gluons
    in isolation, its momentum is non-zero. This energy
    is part of the mass of the cup. So, I have converted
    mass into kinetic energy by observing a different
    system: What appears as kinetic energy of the gluon
    appears as mass of the cup.

    The point is that the fission was not discovered because
    someone thought that since E = mc-#, it must be possible
    to release energy by splitting atom.

    We see kinetic energy because we get the products,
    like "3n" is isolation. So, effectively, there is
    kinetic energy, because it is apt in this case to
    look at only one of the products in isolation.

    However, the kinetic energy depends on the definition
    of the observed system, as I explained.

    So why did you say that it is a common misconception that:
    "The atomic bomb proved in a very convincing way
    that mass could be converted to energy as predicted by
    Einstein's E = mc-#?

    (I think I already answered this in my previous post.)


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  • From x@x@x.net to sci.physics.relativity,sci.physics on Fri Jan 2 10:03:39 2026
    From Newsgroup: sci.physics.relativity

    On 1/1/26 08:19, Stefan Ram wrote:
    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :that mass could be converted to energy as
    :predicted by Einstein's E = mc-#.

    I can spot three mistakes here right off the bat.

    First, the phrase "mass could be converted to energy" is based on
    a misconception, since mass already /is/ a form of energy - there's no
    "conversion" happening. It's like saying, "water can be turned into a
    liquid" - no, water /is/ a liquid.

    The basic problem is that you think that 'science' is
    'automatically true' and all you have to do is say
    words that sound like 'science' and they are automatically
    'true' because they 'sound like science'.

    For your words to have value, you must care what is true.

    I am skeptical that you care what is true. I think that
    your words can be dismissed as relatively valueless on
    that basis.

    I do not care if you play with the words 'water' and
    'liquid'. It is reasonable to consider your words
    to be relatively meaningless because you do not care
    what is true to begin with.

    ...

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  • From x@x@x.net to sci.physics.relativity,sci.physics on Fri Jan 2 10:06:35 2026
    From Newsgroup: sci.physics.relativity

    On 1/1/26 08:19, Stefan Ram wrote:
    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :that mass could be converted to energy as
    :predicted by Einstein's E = mc-#.

    I can spot three mistakes here right off the bat.

    First, the phrase "mass could be converted to energy" is based on
    a misconception, since mass already /is/ a form of energy - there's no
    "conversion" happening. It's like saying, "water can be turned into a
    liquid" - no, water /is/ a liquid.

    The basic problem is that you think that 'science' is
    'automatically true' and all you have to do is say
    words that sound like 'science' and they are automatically
    'true' because they 'sound like science'.

    For your words to have value, you must care what is true.

    I am skeptical that you care what is true. I think that
    your words can be dismissed as relatively valueless on
    that basis.

    I do not care if you play with the words 'water' and
    'liquid'. It is reasonable to consider your words
    to be relatively meaningless because you do not care
    what is true to begin with.

    ...

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  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity,sci.physics on Fri Jan 2 21:07:29 2026
    From Newsgroup: sci.physics.relativity

    x wrote:
    On 1/1/26 08:19, Stefan Ram wrote:
    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :that mass could be converted to energy as
    :predicted by Einstein's E = mc-#.

    I can spot three mistakes here right off the bat.

    First, the phrase "mass could be converted to energy" is based on
    a misconception, since mass already /is/ a form of energy - there's no
    "conversion" happening. It's like saying, "water can be turned into a
    liquid" - no, water /is/ a liquid.

    Correct.

    The basic problem is that you think that 'science' is
    'automatically true' [...]

    No, the problem is that you have no clue what you are talking about, but you are too incompetent to realize that:

    <https://en.wikipedia.org/wiki/DunningrCoKruger_effect>

    Also, you have posted this twice.
    --
    PointedEars

    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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  • From x@x@x.net to sci.physics.relativity on Fri Jan 2 15:40:06 2026
    From Newsgroup: sci.physics.relativity

    On 1/2/26 12:07, Thomas 'PointedEars' Lahn wrote:
    x wrote:
    On 1/1/26 08:19, Stefan Ram wrote:
    > "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    > :that mass could be converted to energy as
    > :predicted by Einstein's E = mc-#.
    >
    > I can spot three mistakes here right off the bat.
    >
    > First, the phrase "mass could be converted to energy" is based on
    > a misconception, since mass already /is/ a form of energy - there's no
    > "conversion" happening. It's like saying, "water can be turned into a >> > liquid" - no, water /is/ a liquid.

    Correct.

    The basic problem is that you think that 'science' is
    'automatically true' [...]

    No, the problem is that you have no clue what you are talking about, but you are too incompetent to realize that:

    You are afraid of not being omniscient. I will make a note of that.

    <https://en.wikipedia.org/wiki/DunningrCoKruger_effect>

    Also, you have posted this twice.

    Yes, I did so by mistake. I am capable of doing that.


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  • From x@x@x.net to sci.physics.relativity on Fri Jan 2 16:05:47 2026
    From Newsgroup: sci.physics.relativity

    On 1/2/26 12:07, Thomas 'PointedEars' Lahn wrote:
    x wrote:
    On 1/1/26 08:19, Stefan Ram wrote:
    > "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    > :that mass could be converted to energy as
    > :predicted by Einstein's E = mc-#.
    >
    > I can spot three mistakes here right off the bat.
    >
    > First, the phrase "mass could be converted to energy" is based on
    > a misconception, since mass already /is/ a form of energy - there's no
    > "conversion" happening. It's like saying, "water can be turned into a >> > liquid" - no, water /is/ a liquid.

    Correct.

    The basic problem is that you think that 'science' is
    'automatically true' [...]

    No, the problem is that you have no clue what you are talking about, but you are too incompetent to realize that:

    You appear to be afraid of being omniscient, however I
    do not know if I will make any note of it on usenet.

    I do not care if you are omniscient or not. I am
    thinking that if you are an omniscient being, but
    are either lying or never explain yourself, then
    your omniscience is useless to me? I am not sure.

    <https://en.wikipedia.org/wiki/DunningrCoKruger_effect>

    Also, you have posted this twice.

    I was aware that I posted this twice earlier, and I do not
    know if there is something wrong with some part of usenet
    that makes it unable to post unless you post twice. Should
    I care? Maybe or maybe not.



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  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity on Sat Jan 3 14:30:46 2026
    From Newsgroup: sci.physics.relativity

    x wrote:
    On 1/2/26 12:07, Thomas 'PointedEars' Lahn wrote:
    x wrote:
    The basic problem is that you think that 'science' is
    'automatically true' [...]

    No, the problem is that you have no clue what you are talking
    about, but you are too incompetent to realize that:

    You appear to be afraid of being omniscient,
    [...]

    Also, you have posted this twice.

    I was aware that I posted this twice earlier, and I do not
    know if there is something wrong with some part of usenet
    that makes it unable to post unless you post twice. Should
    I care? Maybe or maybe not.

    You are insane. Get well soon.

    F'up2 poster
    --
    PointedEars

    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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  • From Paul B. Andersen@relativity@paulba.no to sci.physics.relativity on Sat Jan 3 22:39:44 2026
    From Newsgroup: sci.physics.relativity

    Den 02.01.2026 15:28, skrev Stefan Ram:
    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :1n + U-235 raA Ba-141 + Kr-92 + 3n
    . . .
    :Are you claiming that the mass 3.916659E-25 kg
    :is not converted to 2.78E-11 J kinetic energy?

    When you start in the rest system of "1n + U-235",
    its momentum is p=0. As the momentum is conserved,
    the momentum of "Ba-141 + Kr-92 + 3n" then also is
    p=0, so its kinetic Energy still is zero.

    Are you serious? :-D

    You have two nuclei side by side.
    One with 56 protons, one with 36 protons.
    What do you think will happen?
    --
    Paul

    https://paulba.no/
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  • From Thomas Heger@ttt_heg@web.de to sci.physics.relativity on Sun Jan 4 09:06:34 2026
    From Newsgroup: sci.physics.relativity

    Am Freitag000002, 02.01.2026 um 21:07 schrieb Thomas 'PointedEars' Lahn:
    x wrote:
    On 1/1/26 08:19, Stefan Ram wrote:
    > "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    > :that mass could be converted to energy as
    > :predicted by Einstein's E = mc-#.
    >
    > I can spot three mistakes here right off the bat.
    >
    > First, the phrase "mass could be converted to energy" is based on
    > a misconception, since mass already /is/ a form of energy - there's no
    > "conversion" happening. It's like saying, "water can be turned into a >> > liquid" - no, water /is/ a liquid.

    Correct.
    NO!!!

    Water is not a liquid per se.

    Instead water occurs in three different states, from which only one is
    liquid.


    Energy is also something else than mass, because the term 'energy'
    denotes a quantity in physics and this has a different meaning than 'mass'.

    Mass is actually a measure for resistance against acceleration and
    measured in kg.

    Energy is derived from the quantity work, which is defined as W=force*distance.

    The units are Newtonmeter or Joule.

    The quantity you erroneously call 'mass' is not measured in kg but in mol.

    What you actually wanted to say, that is: matter is actually immaterial
    and a form of energy.

    BUT: 'the amount of matter' is not measured in kg but in mol.

    ...

    TH
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  • From nospam@nospam@de-ster.demon.nl (J. J. Lodder) to sci.physics.relativity on Sun Jan 4 12:28:41 2026
    From Newsgroup: sci.physics.relativity

    Thomas Heger <ttt_heg@web.de> wrote:

    Am Freitag000002, 02.01.2026 um 21:07 schrieb Thomas 'PointedEars' Lahn:
    x wrote:
    On 1/1/26 08:19, Stefan Ram wrote:
    > "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    > :that mass could be converted to energy as
    > :predicted by Einstein's E = mc?.
    >
    > I can spot three mistakes here right off the bat.
    >
    > First, the phrase "mass could be converted to energy" is
    > based on a misconception, since mass already /is/ a form of
    > energy - there's no "conversion" happening. It's like saying,
    > "water can be turned into a liquid" - no, water /is/ a liquid.

    Correct.
    NO!!!

    Water is not a liquid per se.

    Instead water occurs in three different states, from which only one is liquid.


    Energy is also something else than mass, because the term 'energy'
    denotes a quantity in physics and this has a different meaning than 'mass'.

    Mass is actually a measure for resistance against acceleration and
    measured in kg.

    Energy is derived from the quantity work, which is defined as W=force*distance.

    The units are Newtonmeter or Joule.

    The quantity you erroneously call 'mass' is not measured in kg but in mol.

    What you actually wanted to say, that is: matter is actually immaterial
    and a form of energy.

    BUT: 'the amount of matter' is not measured in kg but in mol.

    You are way behind the times.
    As of the CGPM 2018 both the kilogram and the joule are defined
    as numerical multiples of the Hz. (with defined constants in between)
    So the relation between them is a numerical constant too,

    Jan


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  • From Paul.B.Andersen@relativity@paulba.no to sci.physics.relativity,sci.physics on Sun Jan 4 20:51:49 2026
    From Newsgroup: sci.physics.relativity

    Den 01.01.2026 17:19, skrev Stefan Ram:
    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :that mass could be converted to energy as
    :predicted by Einstein's E = mc-#.

    I resent very much that you:
    1. Break threads so it is impossible to see to what you are responding.
    2. Paraphrase and not quote.

    I can guess that you were responding to my statement:
    "The atom bomb proved in a very convincing way
    that mass could be converted to energy as
    predicted by Einstein's E = mc-#."

    This statement isn't very precise, but not wrong.
    So let's look at a more precise statement about
    what is happening in an atomic fission bomb:

    One possible fission process is:

    1n + U-235 raA Ba-141 + Kr-92 + 3n

    The atomic weight (mass) of these are:

    Left side:
    1n 1.008664 u
    U-235 235.0439299 u
    -------------------
    236.0525939 u = 3.919748214E-25 kg

    Right side:
    Ba-141 140.914412 u
    Kr-92 91.926156 u
    3n 3.025992 u
    ---------------------
    235.866560 u = 3.916659047E-25 kg

    Lost mass: m = 0.1860339 u = 3.089167695E-28 kg

    E = mc-# ree 2.776404839E-11 J


    I can spot three mistakes here right off the bat.

    First, the phrase "mass could be converted to energy" is based on
    a misconception, since mass already /is/ a form of energy - there's no
    "conversion" happening. It's like saying, "water can be turned into a
    liquid" - no, water /is/ a liquid.

    Note that m = 3.089167695E-28 kg is the _lost_ mass,
    it doesn't exist any more.
    So where has it gone?
    It is converted to E = mc-# ree 2.776404839E-11 J of _kinetic energy_.
    Kinetic energy is not mass. Thus "convert".


    Second, "E=mc^2" only applies to systems at rest. In general,
    it's "E^2=(mc^2)^2+(pc)^2", where "p" is the system's momentum.
    (That basically says mass is the magnitude of the four-momentum.)

    E = mc-# is the energy content, or the energy equivalent of
    the mass m. Mass is invariant, so this equation is valid for
    all speeds of the mass.

    However, the _total_ energy of a moving mass is:
    E = m+|c-# = mc-# + (+|-1)mc-#
    The first term mc-# is the invariant energy content of the mass m,
    the second term is the kinetic energy of the mass m.
    Kinetic energy is not mass!


    Third, mass is conserved in nuclear fission. This point is often
    explained incorrectly, even in otherwise solid textbooks like Grif-
    fiths.

    Could it be that you are wrong and the textbook is right? :-D

    Before the fission the mass of the U-235 nucleus + 1 neutron
    is: mreU = 3.919748214E-25 kg

    After the fission the mass of the Ba-141 and Kr-92 nuclei + 3 neutrons
    is: mree = 3.916659047E-25 kg.

    So the mass isn't conserved, m = mreU-mree= 3.089167695E-28 kg has
    disappeared because it is converted to kinetic energy which is not mass.

    The energy is conserved, though.

    Energy before fission:
    Energy content of mass mreU = mreUc-# = 3.522894007E-8 J
    Total energy before fission EreU = 3.522894007E-8 J

    Energy after fission:
    Energy content of mass mree E = mreec-# = 3.520117602E-8 J
    Kinetic energy from lost mass K = (mreU-mree)c-# = 2.776404839E-11 J
    Total energy after fission Eree = E + K = 3.522894007E-8

    EreU = Eree energy conserved
    --
    Paul

    https://paulba.no/
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  • From nospam@nospam@de-ster.demon.nl (J. J. Lodder) to sci.physics.relativity on Mon Jan 5 13:17:11 2026
    From Newsgroup: sci.physics.relativity

    Stefan Ram <ram@zedat.fu-berlin.de> wrote:

    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :1n + U-235 ? Ba-141 + Kr-92 + 3n
    . . .
    :Are you claiming that the mass 3.916659E-25 kg
    :is not converted to 2.78E-11 J kinetic energy?

    When you start in the rest system of "1n + U-235",
    its momentum is p=0. As the momentum is conserved,
    the momentum of "Ba-141 + Kr-92 + 3n" then also is
    p=0, so its kinetic Energy still is zero.

    You can't be serious.
    As a matter of fact, fission was confirmed
    on the level of individual nuclei (so not in bulk, chemically)
    from cloud chamber photographs in which the fission products
    move off in opposite directions with a high kinetic energy. [1]
    For example: <https://www.sciencephoto.com/media/1206/view/single-fission-of-uranium-nucleus>

    [snip more nonsense]

    Jan

    [1] Almost all of the fission energy appears as kinetic energy of the
    fission fragments, with relatively little going into the neutrons.
    Can you understand why that is?
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  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity on Tue Jan 6 02:49:51 2026
    From Newsgroup: sci.physics.relativity

    [Fixed quotations]

    Stefan Ram wrote:
    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    1n + U-235 raA Ba-141 + Kr-92 + 3n
    [...]
    Are you claiming that the mass 3.916659E-25 kg
    is not converted to 2.78E-11 J kinetic energy?

    The _rest energy_ corresponding to this mass is converted _partially_ to kinetic energy. As always, one form of energy is, or several forms of
    energy are, converted to one or more other forms of energy.

    That is the/my main problem with the popular-scientific statement "mass is converted to energy".

    When you start in the rest system of "1n + U-235",

    The English term is "rest _frame_" instead.

    its momentum is p=0.

    Its _total_ linear momentum which is a *vector*.

    As the momentum is conserved, the momentum of "Ba-141 + Kr-92 + 3n"
    then also is p=0, so its kinetic Energy still is zero.

    [Your utter misuse of punctuation aside: ]

    You are making the blunder there of calculating the total kinetic energy of
    a system based on the vector sum of the linear momenta of its components,
    not the sum of their separate kinetic energies.

    The former approach is incorrect because the kinetic energy is supposed to
    be a measure of motion. In the center-of-momentum (COM) frame, previously there was no motion, but now there is; so the kinetic energy of the system *must* change. (Another way to see this is relativistically: A system with moving parts must have a larger total energy than one with parts at relative rest; but the mass of the parts has not changed because it is Lorentz-invariant, and we cannot presume any forces between the parts, so
    the kinetic energy of the system must have changed.)

    Therefore, the correct formula is (approximately)

    T = T_1 + T_2 = 1/2 m_1 {V_1}^2 + 1/2 m_2 {V_2}^2
    = {P_1}^2/(2 m_1) + {P_2}^2/(2 m_2)

    or (exact)

    T = T_1 + T_2 = m_1 c^2 [gamma(V_1) - 1] + m_2 c^2 [gamma(V_2) - 1],

    where the V's are the velocities, and the P's are the linear momenta; NOT

    T = P^2/[2 (m_1 + m_2)] = (P_1 + P_2)^2/[2 (m_1 + m_2)],

    or something like that.

    [This is a consequence of the energy--momentum relation
    E^2 = m^2 c^4 + p^2 c^2: For m != we have p = gamma m v,
    and thus E = gamma m c^2.]

    Therefore, even though the total linear momentum is conserved, and equal to
    the zero vector in the COM frame by definition, the total kinetic energy is
    NOT (unless the process is an ideal elastic collision, but that is not what
    we are discussing here).

    This can also be proven: Approximately,

    dT/dt = m_1 V_1 A_1 + m_2 v_2 A_2 = P_1 A_1 + P_2 A_2

    or (exact)

    dT/dt = m_1 gamma^3(V_1) V_1 A_1 + m_2 gamma^3(V_2) V_2 A_2
    = gamma^2(V_1) P_1 A_1 + gamma^2(V_2) P_2 A_2

    where the A's are the (3-)accelerations. That is, the total kinetic energy
    is only conserved as long as there is no acceleration, which is what one
    should expect. (Notice that this is a scalar product.)

    But there has to be an acceleration for the linear momenta P_1 and P_2 to change from zero to non-zero; so the total kinetic energy is NOT conserved
    from before to after that happens.
    --
    PointedEars

    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity,sci.physics on Tue Jan 6 03:04:28 2026
    From Newsgroup: sci.physics.relativity

    Paul.B.Andersen wrote:
    Note that m = 3.089167695E-28 kg is the _lost_ mass,
    it doesn't exist any more.
    So where has it gone?
    It is converted to E = mc-# ree 2.776404839E-11 J of _kinetic energy_. Kinetic energy is not mass. Thus "convert".

    /Non sequitur./

    Second, "E=mc^2" only applies to systems at rest. In general,
    it's "E^2=(mc^2)^2+(pc)^2", where "p" is the system's momentum.
    (That basically says mass is the magnitude of the four-momentum.)

    E = mc-# is the energy content, or the energy equivalent of
    the mass m.

    The first wording is simply wrong. E (better: EreC) is the *rest* energy of _an object_ whose mass is m. One can also call that the energy content _of that object_ at relative rest (as Einstein did, but this wording is
    obsolete), but NOT "of the mass". Mass is a quantity, not a object; a
    quantity has no content.

    Mass is invariant, so this equation is valid for all speeds of the mass.

    Again, mass is a quantity, NOT an object. It does not make sense to say "speeds of the mass". That makes as much sense as e.g. "mass of the charge".

    However, the _total_ energy of a moving mass is:
    E = m+|c-# = mc-# + (+|-1)mc-#
    The first term mc-# is the invariant energy content of the mass m,

    No, the first term is the rest energy equivalent to the mass m.

    Mass does not have an energy content, _objects_ have.

    the second term is the kinetic energy of the mass m.

    No, it is the kinetic energy of an _object_ with mass m and relative speed
    v, hidden in +| = +|(v).

    Kinetic energy is not mass!

    And mass is NOT energy or "has energy". You would be well to realize that.

    Third, mass is conserved in nuclear fission. This point is often
    explained incorrectly, even in otherwise solid textbooks like Grif-
    fiths.

    Could it be that you are wrong and the textbook is right? :-D

    He is wrong, obviously. But you are also wrong in multiple respects:

    Before the fission the mass of the U-235 nucleus + 1 neutron
    is: mreU = 3.919748214E-25 kg

    After the fission the mass of the Ba-141 and Kr-92 nuclei + 3 neutrons
    is: mree = 3.916659047E-25 kg.

    So the mass isn't conserved,

    Correct.

    m = mreU-mree= 3.089167695E-28 kg has disappeared because it is converted to kinetic energy which is not mass.

    Again: NOT the mass is partially converted to kinetic energy, but the rest energy E_0 = m c^2 *equivalent to* the mass m.
    --
    PointedEars

    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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  • From Thomas Heger@ttt_heg@web.de to sci.physics.relativity on Tue Jan 6 09:03:27 2026
    From Newsgroup: sci.physics.relativity

    Am Sonntag000004, 04.01.2026 um 12:28 schrieb J. J. Lodder:
    ...

    Energy is also something else than mass, because the term 'energy'
    denotes a quantity in physics and this has a different meaning than 'mass'. >>
    Mass is actually a measure for resistance against acceleration and
    measured in kg.

    Energy is derived from the quantity work, which is defined as
    W=force*distance.

    The units are Newtonmeter or Joule.

    The quantity you erroneously call 'mass' is not measured in kg but in mol. >>
    What you actually wanted to say, that is: matter is actually immaterial
    and a form of energy.

    BUT: 'the amount of matter' is not measured in kg but in mol.

    You are way behind the times.
    As of the CGPM 2018 both the kilogram and the joule are defined
    as numerical multiples of the Hz. (with defined constants in between)
    So the relation between them is a numerical constant too,

    Well, actually I can read and I found this on the CGPM website:

    "In the 14th CGPM, the SI was completed by adding mole as a base unit
    for amount of substance, making the total number of base units seven."


    TH

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  • From Thomas Heger@ttt_heg@web.de to sci.physics.relativity,sci.physics on Tue Jan 6 09:15:55 2026
    From Newsgroup: sci.physics.relativity

    Am Sonntag000004, 04.01.2026 um 20:51 schrieb Paul.B.Andersen:
    Den 01.01.2026 17:19, skrev Stefan Ram:
    "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:
    :that mass could be converted to energy as
    :predicted by Einstein's E = mc-#.

    I resent very much that you:
    1. Break threads so it is impossible to see to what you are responding.
    2. Paraphrase and not quote.

    I can guess that you were responding to my statement:
    -a"The atom bomb proved in a very convincing way
    -a that mass could be converted to energy as
    -a predicted by Einstein's E = mc-#."

    This statement isn't very precise, but not wrong.
    So let's look at a more precise statement about
    what is happening in an atomic fission bomb:

    One possible fission process is:

    1n + U-235 raA Ba-141 + Kr-92 + 3n

    The atomic weight (mass) of these are:

    Left side:
    1n-a-a-a-a-a 1.008664-a u
    U-235 235.0439299 u
    -------------------
    -a-a-a-a-a 236.0525939 u = 3.919748214E-25 kg

    Right side:
    Ba-141-a-a 140.914412 u
    Kr-92-a-a-a-a 91.926156 u
    3n-a-a-a-a-a-a-a-a 3.025992 u
    ---------------------
    -a-a-a-a-a-a-a-a 235.866560 u = 3.916659047E-25 kg

    Lost mass: m = 0.1860339 u = 3.089167695E-28 kg

    E = mc-# ree 2.776404839E-11 J


    -a-a I can spot three mistakes here right off the bat.

    -a-a-a-a-a-a-a First, the phrase "mass could be converted to energy" is based on
    -a-a a misconception, since mass already /is/ a form of energy - there's no >> -a-a "conversion" happening. It's like saying, "water can be turned into a >> -a-a liquid" - no, water /is/ a liquid.

    Note that m = 3.089167695E-28 kg is the _lost_ mass,
    it doesn't exist any more.
    So where has it gone?
    It is converted to E = mc-# ree 2.776404839E-11 J of _kinetic energy_. Kinetic energy is not mass. Thus "convert".


    -a-a-a-a-a-a-a Second, "E=mc^2" only applies to systems at rest. In general, >> -a-a it's "E^2=(mc^2)^2+(pc)^2", where "p" is the system's momentum.
    -a-a (That basically says mass is the magnitude of the four-momentum.)

    E = mc-# is the energy content, or the energy equivalent of
    the mass m. Mass is invariant, so this equation is valid for
    all speeds of the mass.

    You contradicted yourself!!

    Here your claim is, that mass is invariant, while a little below you
    claim, that energy is conserved, while mass has vanished from a
    radioactive sample.

    But you can't keep both claims, because they contradict each other.

    So let's keep energy and regard matter as some strange form of energy.

    I actually had this idea long ago and wrote kind of book about it:

    https://docs.google.com/presentation/d/1Ur3_giuk2l439fxUa8QHX4wTDxBEaM6lOlgVUa0cFU4/edit?usp=sharing

    (As proof of concept I had 'Growing Earth' in mind.)


    TH

    ...
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  • From nospam@nospam@de-ster.demon.nl (J. J. Lodder) to sci.physics.relativity on Tue Jan 6 10:56:35 2026
    From Newsgroup: sci.physics.relativity

    Thomas Heger <ttt_heg@web.de> wrote:

    Am Sonntag000004, 04.01.2026 um 12:28 schrieb J. J. Lodder:
    ...

    Energy is also something else than mass, because the term 'energy'
    denotes a quantity in physics and this has a different meaning than 'mass'.

    Mass is actually a measure for resistance against acceleration and
    measured in kg.

    Energy is derived from the quantity work, which is defined as
    W=force*distance.

    The units are Newtonmeter or Joule.

    The quantity you erroneously call 'mass' is not measured in kg but in mol. >>
    What you actually wanted to say, that is: matter is actually immaterial
    and a form of energy.

    BUT: 'the amount of matter' is not measured in kg but in mol.

    You are way behind the times.
    As of the CGPM 2018 both the kilogram and the joule are defined
    as numerical multiples of the Hz. (with defined constants in between)
    So the relation between them is a numerical constant too,

    Well, actually I can read and I found this on the CGPM website:

    "In the 14th CGPM, the SI was completed by adding mole as a base unit
    for amount of substance, making the total number of base units seven."

    You really are way behind the times, that was more than 50 years ago.

    The mole is just another defined number, these days,
    (and it does not have any fundamental significance)

    Jan
    --
    "One mole is an aggregate of exactly 6.02214076?1023 elementary
    entities" (SI as it is nowadays)
    ('entities' may be electrons, atoms, molecules, whatever)


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  • From Ross Finlayson@ross.a.finlayson@gmail.com to sci.physics.relativity on Tue Jan 6 06:52:04 2026
    From Newsgroup: sci.physics.relativity

    On 01/06/2026 01:56 AM, J. J. Lodder wrote:
    Thomas Heger <ttt_heg@web.de> wrote:

    Am Sonntag000004, 04.01.2026 um 12:28 schrieb J. J. Lodder:
    ...

    Energy is also something else than mass, because the term 'energy'
    denotes a quantity in physics and this has a different meaning than 'mass'.

    Mass is actually a measure for resistance against acceleration and
    measured in kg.

    Energy is derived from the quantity work, which is defined as
    W=force*distance.

    The units are Newtonmeter or Joule.

    The quantity you erroneously call 'mass' is not measured in kg but in mol. >>>>
    What you actually wanted to say, that is: matter is actually immaterial >>>> and a form of energy.

    BUT: 'the amount of matter' is not measured in kg but in mol.

    You are way behind the times.
    As of the CGPM 2018 both the kilogram and the joule are defined
    as numerical multiples of the Hz. (with defined constants in between)
    So the relation between them is a numerical constant too,

    Well, actually I can read and I found this on the CGPM website:

    "In the 14th CGPM, the SI was completed by adding mole as a base unit
    for amount of substance, making the total number of base units seven."

    You really are way behind the times, that was more than 50 years ago.

    The mole is just another defined number, these days,
    (and it does not have any fundamental significance)

    Jan



    What, you never heard of "running constants"?

    People keep forgetting what makes the old they've
    wrapped as new then wondering why it won't sit straight.


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  • From nospam@nospam@de-ster.demon.nl (J. J. Lodder) to sci.physics.relativity on Tue Jan 6 16:12:10 2026
    From Newsgroup: sci.physics.relativity

    Ross Finlayson <ross.a.finlayson@gmail.com> wrote:

    On 01/06/2026 01:56 AM, J. J. Lodder wrote:
    Thomas Heger <ttt_heg@web.de> wrote:

    Am Sonntag000004, 04.01.2026 um 12:28 schrieb J. J. Lodder:
    ...

    Energy is also something else than mass, because the term 'energy'
    denotes a quantity in physics and this has a different meaning than
    'mass'.

    Mass is actually a measure for resistance against acceleration and
    measured in kg.

    Energy is derived from the quantity work, which is defined as
    W=force*distance.

    The units are Newtonmeter or Joule.

    The quantity you erroneously call 'mass' is not measured in kg but in >>>>mol.

    What you actually wanted to say, that is: matter is actually
    immaterial and a form of energy.

    BUT: 'the amount of matter' is not measured in kg but in mol.

    You are way behind the times.
    As of the CGPM 2018 both the kilogram and the joule are defined
    as numerical multiples of the Hz. (with defined constants in between)
    So the relation between them is a numerical constant too,

    Well, actually I can read and I found this on the CGPM website:

    "In the 14th CGPM, the SI was completed by adding mole as a base unit
    for amount of substance, making the total number of base units seven."

    You really are way behind the times, that was more than 50 years ago.

    The mole is just another defined number, these days,
    (and it does not have any fundamental significance)

    Jan



    What, you never heard of "running constants"?

    People keep forgetting what makes the old they've
    wrapped as new then wondering why it won't sit straight.

    What part of '(exactly)' don't you understand?

    Jan

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  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity on Tue Jan 6 21:31:14 2026
    From Newsgroup: sci.physics.relativity

    Thomas 'PointedEars' Lahn wrote:
    Therefore, the correct formula is [...] (exact)

    T = T_1 + T_2 = m_1 c^2 [gamma(V_1) - 1] + m_2 c^2 [gamma(V_2) - 1],

    where the V's are the velocities, and the P's are the linear momenta;
    [...]

    [This is a consequence of the energy--momentum relation
    E^2 = m^2 c^4 + p^2 c^2: For m != we have p = gamma m v,
    and thus E = gamma m c^2.]

    I meant: m != 0 ("m not equal to zero").
    --
    PointedEars

    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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  • From Paul.B.Andersen@relativity@paulba.no to sci.physics.relativity on Tue Jan 6 22:12:41 2026
    From Newsgroup: sci.physics.relativity

    Den 06.01.2026 03:04, skrev Thomas 'PointedEars' Lahn:
    E = mc-# is the energy content, or the energy equivalent of
    the mass m.

    The first wording is simply wrong. E (better: EreC) is the *rest* energy of _an object_ whose mass is m. One can also call that the energy content _of that object_ at relative rest (as Einstein did, but this wording is obsolete), but NOT "of the mass". Mass is a quantity, not a object; a quantity has no content.

    You are nit-picking again!
    Of course "mass" is the mass of an object.
    and E = mc-# is the energy content of the mass of an object.

    It is quite common to write things like:
    "Let the speed of the mass m be v".
    Everybody will understand that m is the mass of an object.
    And so do you. So why the nit-picking ?
    This is a post in a Usenet group, not a scientific paper.

    Back to the subject:

    The mass of an objects is invariant, and so is the energy
    content of the object.
    The E in the equation E = mc-# is invariant, which means
    that it is independent of the speed of the object.

    It makes no sense to call E = mc-# "the *rest* energy of
    _an object_ whose mass is m."

    The energy of a moving object with mass m is:
    E = +|mc-# = mc-# + (+|-1)mc-#
    The term mc-# is the invariant energy content of the object with mass m,
    the term (+|-1)mc-# is the kinetic energy of the object with mass m.

    The energy content E = mc-# of the object with mass m
    is a property of the object with mass m.

    But a frame dependent entity like kinetic energy or relative speed
    is not a property of the moving object.
    They are properties of the relationship between the object
    and a frame of reference.

    The kinetic energy which can have any value depending on
    the arbitrary choice of frame of reference, is not part
    of the energy content of the object.

    (Note however that in the fission where the two
    nuclei and 3 neutrons are moving away from each other
    in such a way that momentum is conserved, the _sum_
    of their kinetic energies is invariant.)

    -------

    m = mreU-mree= 3.089167695E-28 kg has disappeared because it is converted to >> kinetic energy which is not mass.
    Quote out of context:

    Before the fission the mass of the U-235 nucleus + 1 neutron
    is: mreU = 3.919748214E-25 kg

    After the fission the mass of the Ba-141 and Kr-92 nuclei +
    3 neutrons is: mree = 3.916659047E-25 kg.

    So the mass isn't conserved, +om = mreU-mree= 3.089167695E-28 kg


    Again: NOT the mass is partially converted to kinetic energy, but the rest energy E_0 = m c^2 *equivalent to* the mass m.

    Energy before fission:
    Energy content of mass mreU: E = mreUc-# = 3.522894007E-8 J

    Energy after fission:
    Energy content of mass mree: E = mreUc-#= 3.520117602E-8 J

    The difference is +oE = mreUc-# - mreUc-# = +omriac-# = 3.089167695E-28 J

    The binding energy holding the nucleons together is
    part of the energy content of the mass of the U-235 nucleus.
    When the nucleus is split, the binding energy in the Ba-141
    and Kr-92 nuclei will be +oE less. The sum of the kinetic energy
    of the two nuclei and 3 neutrons will be +oE = 3.089167695E-28 J

    I say that the mass +om lost from the U-235 nucleus is converted
    to kinetic energy of the two nuclei and 3 neutrons.

    You are free to choose your wording.
    --
    Paul

    https://paulba.no/
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  • From Paul.B.Andersen@relativity@paulba.no to sci.physics.relativity on Tue Jan 6 22:27:15 2026
    From Newsgroup: sci.physics.relativity

    Den 06.01.2026 22:12, skrev Paul.B.Andersen:
    Energy before fission:
    Energy content of mass mreU: E = mreUc-# = 3.522894007E-8 J

    Energy after fission:
    Energy content of mass mree: E-a = mreUc-#= 3.520117602E-8 J

    The difference is +oE = mreUc-# - mreUc-# = +omriac-# = 3.089167695E-28 J

    Typo. +oE = 2.776404839E-11 J
    --
    Paul

    https://paulba.no/
    --- Synchronet 3.21a-Linux NewsLink 1.2
  • From Ross Finlayson@ross.a.finlayson@gmail.com to sci.physics.relativity on Tue Jan 6 13:43:16 2026
    From Newsgroup: sci.physics.relativity

    On 01/06/2026 01:12 PM, Paul.B.Andersen wrote:
    Den 06.01.2026 03:04, skrev Thomas 'PointedEars' Lahn:
    E = mc-# is the energy content, or the energy equivalent of
    the mass m.

    The first wording is simply wrong. E (better: EreC) is the *rest*
    energy of
    _an object_ whose mass is m. One can also call that the energy
    content _of
    that object_ at relative rest (as Einstein did, but this wording is
    obsolete), but NOT "of the mass". Mass is a quantity, not a object; a
    quantity has no content.

    You are nit-picking again!
    Of course "mass" is the mass of an object.
    and E = mc-# is the energy content of the mass of an object.

    It is quite common to write things like:
    "Let the speed of the mass m be v".
    Everybody will understand that m is the mass of an object.
    And so do you. So why the nit-picking ?
    This is a post in a Usenet group, not a scientific paper.

    Back to the subject:

    The mass of an objects is invariant, and so is the energy
    content of the object.
    The E in the equation E = mc-# is invariant, which means
    that it is independent of the speed of the object.

    It makes no sense to call E = mc-# "the *rest* energy of
    _an object_ whose mass is m."

    The energy of a moving object with mass m is:
    E = +|mc-# = mc-# + (+|-1)mc-#
    The term mc-# is the invariant energy content of the object with mass m,
    the term (+|-1)mc-# is the kinetic energy of the object with mass m.

    The energy content E = mc-# of the object with mass m
    is a property of the object with mass m.

    But a frame dependent entity like kinetic energy or relative speed
    is not a property of the moving object.
    They are properties of the relationship between the object
    and a frame of reference.

    The kinetic energy which can have any value depending on
    the arbitrary choice of frame of reference, is not part
    of the energy content of the object.

    (Note however that in the fission where the two
    nuclei and 3 neutrons are moving away from each other
    in such a way that momentum is conserved, the _sum_
    of their kinetic energies is invariant.)

    -------

    m = mreU-mree= 3.089167695E-28 kg has disappeared because it is converted to
    kinetic energy which is not mass.
    Quote out of context:

    Before the fission the mass of the U-235 nucleus + 1 neutron
    is: mreU = 3.919748214E-25 kg

    After the fission the mass of the Ba-141 and Kr-92 nuclei +
    3 neutrons is: mree = 3.916659047E-25 kg.

    So the mass isn't conserved, +om = mreU-mree= 3.089167695E-28 kg


    Again: NOT the mass is partially converted to kinetic energy, but the
    rest
    energy E_0 = m c^2 *equivalent to* the mass m.

    Energy before fission:
    Energy content of mass mreU: E = mreUc-# = 3.522894007E-8 J

    Energy after fission:
    Energy content of mass mree: E = mreUc-#= 3.520117602E-8 J

    The difference is +oE = mreUc-# - mreUc-# = +omriac-# = 3.089167695E-28 J

    The binding energy holding the nucleons together is
    part of the energy content of the mass of the U-235 nucleus.
    When the nucleus is split, the binding energy in the Ba-141
    and Kr-92 nuclei will be +oE less. The sum of the kinetic energy
    of the two nuclei and 3 neutrons will be +oE = 3.089167695E-28 J

    I say that the mass +om lost from the U-235 nucleus is converted
    to kinetic energy of the two nuclei and 3 neutrons.

    You are free to choose your wording.


    In Einstein's original formula,
    the E of the mass is of the K.E.,
    the kinetic energy, and the mc^2 is
    only the first term of the Taylor series
    expansion, all the rest not only having
    different units in the dimensional analysis
    yet being higher-order terms usually considered
    negligeable, yet, as a numerical method an
    approximation, of course there's a non-zero error term,
    which would be considered the content and meaning
    of the higher-order terms.


    K.E. = mc^2 + error_term()


    If you think that's fun, consider the notion
    that any actual change in velocity at all
    has nominally infinitely-many nominally non-zero
    higher-order terms of acceleration -
    almost all of them infinitesimal.


    Things like this like Hooke's law and
    Clausius/Arrhenius are very common in
    physics, Einstein's mass/energy equivalency
    formula, a truncation of an expression.


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  • From Python@python@cccp.invalid to sci.physics.relativity on Tue Jan 6 21:46:11 2026
    From Newsgroup: sci.physics.relativity

    Le 06/01/2026 |a 22:43, Ross Finlayson a |-crit :
    [snip non sense] Einstein's mass/energy equivalency
    formula, a truncation of an expression.

    You are the result of the truncation of sanity, Ross.


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  • From Paul.B.Andersen@relativity@paulba.no to sci.physics.relativity,sci.physics on Tue Jan 6 22:57:53 2026
    From Newsgroup: sci.physics.relativity

    Den 06.01.2026 09:15, skrev Thomas Heger:
    Am Sonntag000004, 04.01.2026 um 20:51 schrieb Paul.B.Andersen:

    E = mc-# is the energy content, or the energy equivalent of
    the mass m. Mass is invariant, so this equation is valid for
    all speeds of the mass.

    You contradicted yourself!!

    Here your claim is, that mass is invariant, while a little below you
    claim, that energy is conserved, while mass has vanished from a
    radioactive sample.

    But you can't keep both claims, because they contradict each other.


    Invariant means "the same in all frames of reference"
    or "independent of speed".

    It does _not_ mean "constant".

    Mass is invariant.
    The mass of an object is the same in all frames of reference.
    The mass of an object does not depend on the speed of the object.

    But mass can change. Heat the object, and its mass will increase,

    I have told you before, but I know you will not learn.
    You never do.
    --
    Paul

    https://paulba.no/
    --- Synchronet 3.21a-Linux NewsLink 1.2
  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity on Tue Jan 6 23:27:10 2026
    From Newsgroup: sci.physics.relativity

    Paul.B.Andersen wrote:
    ^^^^^^^^^^^^^^^
    I just noticed that since 2025-12-14, when the "Organization" header field
    of your postings changed, you also do not have a space in there anymore.
    Not including a space there may exclude your postings from being read,
    through real-name filters.

    Den 06.01.2026 03:04, skrev Thomas 'PointedEars' Lahn:
    E = mc-# is the energy content, or the energy equivalent of
    the mass m.

    The first wording is simply wrong. E (better: EreC) is the *rest* energy of >> _an object_ whose mass is m. One can also call that the energy content _of >> that object_ at relative rest (as Einstein did, but this wording is
    obsolete), but NOT "of the mass". Mass is a quantity, not a object; a
    quantity has no content.

    You are nit-picking again!

    No, to distinguish between the concepts here is vital for a proper understanding.

    Of course "mass" is the mass of an object.
    and E = mc-# is the energy content of the mass of an object.

    NOT E = m c-#, but EreC = m c-#, is the _energy_ of an object with mass m at relative rest, its *rest energy*.

    It is quite common to write things like:
    "Let the speed of the mass m be v".

    Maybe in colloquial or popular-scientific (con)texts; but this is a
    scientific newsgroup, and it is not only good form but required to be
    precise here and in this regard.

    Everybody will understand that m is the mass of an object.

    Irrelevant. The problem is that *you* do not understand it correctly
    despite the many explanations and references that I gave (you) already.

    And so do you. So why the nit-picking ?

    It is not nitpicking, but requiring a clarity of expression to arrive at a proper understanding of a subject.

    This is a post in a Usenet group, not a scientific paper.

    This is a _scientific_ newsgroup.

    The mass of an objects is invariant,

    It is _Lorentz_-invariant, NOT invariant /per se/.

    and so is the energy content of the object.

    No.

    The E in the equation E = mc-# is invariant,

    This pop-cultural equation is *wrong*, as I have pointed out /ad nauseam/.

    which means that it is independent of the speed of the object.

    /Ex falso quodlibet./

    It makes no sense to call E = mc-# "the *rest* energy of
    _an object_ whose mass is m."

    It *does*. That is what it *is*. "Rest energy" is the agreed physical/scientific term for that form of energy.

    If there is confusion: "rest" here is not meant as in "and all the rest",
    but as in "at rest", i.e. "not moving".

    See also: <https://en.wikipedia.org/wiki/Invariant_mass#Rest_energy>

    The energy of a moving object with mass m is:
    E = +|mc-# = mc-# + (+|-1)mc-#

    That is the *total energy* of *any* object with mass m, including one that
    is moving in the chosen rest frame (then we have +| > 1).

    [The total energy also includes the potential energy, but coordinates can be chosen such that the latter is zero.]

    The term mc-# is the invariant energy content of the object with mass m,

    One can say that; but as I already pointed out, that wording is both
    obsolete and imprecise.

    the term (+|-1)mc-# is the kinetic energy of the object with mass m.

    If the potential energy is zero.

    The energy content E = mc-# of the object with mass m
    is a property of the object with mass m.

    *No, it is the other way around*: The mass m of an object is a measure of
    its rest energy or, as Einstein wrote in "Does the Inertia of a Body Depend Upon Its Energy Content?" its "energy content" -- by which he meant "its
    energy content _at relative rest_":

    ,-<https://web.archive.org/web/20240708111817/https://einsteinpapers.press.princeton.edu/vol2-trans/188>
    |
    | [...], we are led to the more general conclusion: The mass of a body is a
    | measure of its energy content; if the energy changes by L, the mass
    | changes in the same sense by L/9 * 10^20, if the energy is measured in
    | ergs and the mass in grams.

    [Unfortunately, since the commercialization of the Digital Einstein Papers
    we are required to refer to archived versions or unofficial
    translations/copies :-(]

    But a frame dependent entity

    _quantity_, not entity

    like kinetic energy or relative speed is not a property of the moving object.

    Self-contradictory.

    They are properties of the relationship between the object
    and a frame of reference.

    /Non sequitur./

    The kinetic energy which can have any value depending on
    the arbitrary choice of frame of reference, is not part
    of the energy content of the object.

    That depends on how one defines that. "Energy content" is an obsolete term
    to begin with.

    However, if one simply substitutes "total energy" for "energy content", then the total energy of an object depends on the choice of rest frame; and the "energy content" that Einstein means is just that of an object/body (with non-zero mass) *at relative rest* -- in modern terminology, the
    object's/body's *rest* energy.

    So the mass isn't conserved, [...]

    There is no and has never been a disagreement among the two of us about that.

    Again: NOT the mass is partially converted to kinetic energy, but the rest >> energy E_0 = m c^2 *equivalent to* the mass m.

    Energy before fission:
    Energy content of mass mreU: E = mreUc-# = 3.522894007E-8 J

    Energy after fission:
    Energy content of mass mree: E = mreUc-#= 3.520117602E-8 J

    The difference is +oE = mreUc-# - mreUc-# = +omriac-# = 3.089167695E-28 J

    The binding energy holding the nucleons together is
    part of the energy content of the mass of the U-235 nucleus.
    When the nucleus is split, the binding energy in the Ba-141
    and Kr-92 nuclei will be +oE less. The sum of the kinetic energy
    of the two nuclei and 3 neutrons will be +oE = 3.089167695E-28 J

    You keep missing the point.

    I say that the mass +om lost from the U-235 nucleus is converted
    to kinetic energy of the two nuclei and 3 neutrons.

    Which is simply the wrong idea.

    You are free to choose your wording.

    No, one is NOT free to choose one's wording if one wants to participate in a fruitful scientific discussion. That is a fundamental misconception. Scientific terms have meaning, and the meaning of certain terms has been
    agreed upon, like total energy, rest energy, mass, kinetic energy, and potential energy.

    What actually happens here is that rest energy is (partially) converted to other forms of energy. This is equivalent to a reduction in mass; precisely what Einstein wrote in his paper, and in a sense precisely what he suggested
    in that paper as an experimental test:

    | Perhaps it will prove possible to test this theory using bodies whose
    | energy content is variable to a high degree (e.g., salts of radium).
    --
    PointedEars

    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity,sci.physics on Tue Jan 6 23:51:57 2026
    From Newsgroup: sci.physics.relativity

    Paul.B.Andersen wrote:
    Den 06.01.2026 09:15, skrev Thomas Heger:
    Am Sonntag000004, 04.01.2026 um 20:51 schrieb Paul.B.Andersen:
    E = mc-# is the energy content, or the energy equivalent of
    the mass m. Mass is invariant, so this equation is valid for
    all speeds of the mass.

    You contradicted yourself!!

    Here your claim is, that mass is invariant, while a little below you
    claim, that energy is conserved, while mass has vanished from a
    radioactive sample.

    But you can't keep both claims, because they contradict each other.

    Invariant means "the same in all frames of reference"
    or "independent of speed".

    That is what *you* mean by it *here*, NOT what it *generally* means.

    What *you* mean *here* is more precisely called "_Lorentz_-invariant".


    F'up2 sci.physics.relativity
    --
    PointedEars

    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity on Wed Jan 7 05:12:19 2026
    From Newsgroup: sci.physics.relativity

    Thomas 'PointedEars' Lahn wrote:
    Paul.B.Andersen wrote:
    Invariant means "the same in all frames of reference"
    or "independent of speed".

    That is what *you* mean by it *here*, NOT what it *generally* means.

    What *you* mean *here* is more precisely called "_Lorentz_-invariant".
    It turns out, though, that the mass of a massive particle (sic) is
    *generally* frame-invariant (not just under a Lorentz boost) as it is proportional to the norm of the 4-momentum:
    With the general spacetime metric
    ds-# = c-#d-a-# = g_++++ dx^++ dx^++ = dx_++ dx^++,
    where -a is proper time, and [g]_++++ is the metric tensor, we have
    d-a = dt reU[(1/c-#) x|c_++ x|c^++],
    where t is coordinate time, and x|c^++ := dx^++/dt.
    The *4-velocity* is defined as
    [u]^++ := d[x]^++/d-a = dt/d-a [x|c]^++.
    For timelike worldlines, its norm squared is always
    u_++ u^++ = (dt/d-a)-# x|c_++ x|c^++ = 1/[(1/c-#) x|c_+# x|c^+#] x|c_++ x|c^++ = c-#.
    The *4-momentum* is
    [p]^++ = m [u]^++,
    where m is mass, so its norm squared is
    p_++ p^++ = m-# u_++ u^++ = m-#c-#,
    and the mass of a massive particle is the *scalar*, thus frame-invariant, m = 1/c reU(p_++ p^++). reA
    LaTeX: <https://www.HostMath.com/Show.aspx?Code=%5Cbegin%7Balign*%7D%0A%5Cnewcommand%7B%5Ccoloneqq%7D%7B%5Cmathrel%7B%3A%3D%7D%7D%0A%5Cnewcommand%7B%5Cfourvec%7D%5B1%5D%7B%7B%5Cmathbf%7B%231%7D%7D%7D%0A%5Cnewcommand%7B%5Cd%7D%7B%7B%5Cmathrm%7Bd%7D%7D%7D%0A%7B%5Cd%20s%7D%5E2%20%3D%20c%5E2%7B%5Cd%5Ctau%7D%5E2%20%26%3D%20g_%7B%5Cmu%5Cnu%7D%20%5C%2C%20%5Cd%20x%5E%5Cmu%20%5C%2C%20%5Cd%20x%5E%5Cnu%20%3D%20%5Cd%20x_%5Cnu%20%5C%2C%20%5Cd%20x%5E%5Cnu%20%5C%5C%0A%5CLeftrightarrow%20%7B%5Cd%5Ctau%7D%20%26%3D%20%5Cd%20t%20%5C%2C%20%5Csqrt%7B%5Cfrac%7B1%7D%7Bc%5E2%7D%20%5C%2C%20%5Cdot%20x_%5Cnu%20%5C%2C%20%5Cdot%20x%5E%5Cnu%7D.%20%5C%5C%0A%5Cfourvec%20u%5E%5Cmu%20%5C%20%26%5Ccoloneqq%20%5Cfrac%7B%5Cd%5Cfourvec%20x%5E%5Cmu%7D%7B%5Cd%5Ctau%7D%20%3D%20%5Cfrac%7B%5Cd%20t%7D%7B%5Cd%5Ctau%7D%20%5C%2C%20%5Cdot%7B%20%5Cfourvec%20x%7D%5E%5Cmu%20%5C%5C%0A%5Cimplies%20u_%5Cnu%20%5C%2C%20u%5E%5Cnu%20%26%3D%20%7B%5Cleft(%5Cfrac%7B%5Cd%20t%7D%7B%5Cd%5Ctau%7D%5Cright)%7D%5E2%20%5C%2C%20%5Cdot%20x_%5Cnu%20%5C%2C%20%5Cdot%20x%5E%5Cnu%20%3D%20%5Cfrac%7B1%7D%7B%5Cdfrac%7B1%7D%7Bc%5E2%7D%20%5C%2C%20%5Cdot%20x_%5Calpha%20%5C%2C%20%5Cdot%20x%5E%5Calpha%7D%20%5C%2C%20%5Cdot%20x_%5Cnu%20%5C%2C%20%5Cdot%20x%5E%5Cnu%20%3D%20c%5E2.%20%5C%5C%0A%5Cfourvec%20p%5E%5Cmu%20%26%3D%20m%20%5C%2C%20%5Cfourvec%20u%5E%5Cmu%20%5C%5C%0A%5Cimplies%20p_%5Cnu%20%5C%2C%20p%5E%5Cnu%20%26%3D%20m%5E2%20%5C%20u_%5Cnu%20%5C%2C%20u%5E%5Cnu%20%3D%20m%5E2%20c%5E2%20%5C%5C%0A%5Cimplies%20m%20%26%3D%20%5Cfrac1c%20%5C%2C%20%5Csqrt%7Bp_%5Cnu%20%5C%2C%20p%5E%5Cnu%7D.%0A%5Cend%7Balign*%7D>
    --
    PointedEars
    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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  • From =?UTF-8?Q?Maciej_Wo=C5=BAniak?=@mlwozniak@wp.pl to sci.physics.relativity on Wed Jan 7 08:16:34 2026
    From Newsgroup: sci.physics.relativity

    On 1/7/2026 5:12 AM, Thomas 'PointedEars' Lahn wrote:
    Thomas 'PointedEars' Lahn wrote:
    Paul.B.Andersen wrote:
    Invariant means "the same in all frames of reference"
    or "independent of speed".

    That is what *you* mean by it *here*, NOT what it *generally* means.

    What *you* mean *here* is more precisely called "_Lorentz_-invariant".

    It turns out, though, that the mass of a massive particle (sic) is *generally* frame-invariant

    It just turns out that you're talking this
    way together with tour fellow idiots,
    nothing more. Feynman, for instance, was
    talking a different way.

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  • From Ross Finlayson@ross.a.finlayson@gmail.com to sci.physics.relativity on Wed Jan 7 04:14:49 2026
    From Newsgroup: sci.physics.relativity

    On 01/06/2026 02:27 PM, Thomas 'PointedEars' Lahn wrote:
    Paul.B.Andersen wrote:
    ^^^^^^^^^^^^^^^
    I just noticed that since 2025-12-14, when the "Organization" header field
    of your postings changed, you also do not have a space in there anymore.
    Not including a space there may exclude your postings from being read, through real-name filters.

    Den 06.01.2026 03:04, skrev Thomas 'PointedEars' Lahn:
    E = mc-# is the energy content, or the energy equivalent of
    the mass m.

    The first wording is simply wrong. E (better: EreC) is the *rest* energy of
    _an object_ whose mass is m. One can also call that the energy content _of >>> that object_ at relative rest (as Einstein did, but this wording is
    obsolete), but NOT "of the mass". Mass is a quantity, not a object; a
    quantity has no content.

    You are nit-picking again!

    No, to distinguish between the concepts here is vital for a proper understanding.

    Of course "mass" is the mass of an object.
    and E = mc-# is the energy content of the mass of an object.

    NOT E = m c-#, but EreC = m c-#, is the _energy_ of an object with mass m at relative rest, its *rest energy*.

    It is quite common to write things like:
    "Let the speed of the mass m be v".

    Maybe in colloquial or popular-scientific (con)texts; but this is a scientific newsgroup, and it is not only good form but required to be
    precise here and in this regard.

    Everybody will understand that m is the mass of an object.

    Irrelevant. The problem is that *you* do not understand it correctly
    despite the many explanations and references that I gave (you) already.

    And so do you. So why the nit-picking ?

    It is not nitpicking, but requiring a clarity of expression to arrive at a proper understanding of a subject.

    This is a post in a Usenet group, not a scientific paper.

    This is a _scientific_ newsgroup.

    The mass of an objects is invariant,

    It is _Lorentz_-invariant, NOT invariant /per se/.

    and so is the energy content of the object.

    No.

    The E in the equation E = mc-# is invariant,

    This pop-cultural equation is *wrong*, as I have pointed out /ad nauseam/.

    which means that it is independent of the speed of the object.

    /Ex falso quodlibet./

    It makes no sense to call E = mc-# "the *rest* energy of
    _an object_ whose mass is m."

    It *does*. That is what it *is*. "Rest energy" is the agreed physical/scientific term for that form of energy.

    If there is confusion: "rest" here is not meant as in "and all the rest",
    but as in "at rest", i.e. "not moving".

    See also: <https://en.wikipedia.org/wiki/Invariant_mass#Rest_energy>

    The energy of a moving object with mass m is:
    E = +|mc-# = mc-# + (+|-1)mc-#

    That is the *total energy* of *any* object with mass m, including one that
    is moving in the chosen rest frame (then we have +| > 1).

    [The total energy also includes the potential energy, but coordinates can be chosen such that the latter is zero.]

    The term mc-# is the invariant energy content of the object with mass m,

    One can say that; but as I already pointed out, that wording is both
    obsolete and imprecise.

    the term (+|-1)mc-# is the kinetic energy of the object with mass m.

    If the potential energy is zero.

    The energy content E = mc-# of the object with mass m
    is a property of the object with mass m.

    *No, it is the other way around*: The mass m of an object is a measure of
    its rest energy or, as Einstein wrote in "Does the Inertia of a Body Depend Upon Its Energy Content?" its "energy content" -- by which he meant "its energy content _at relative rest_":

    ,-<https://web.archive.org/web/20240708111817/https://einsteinpapers.press.princeton.edu/vol2-trans/188>
    |
    | [...], we are led to the more general conclusion: The mass of a body is a
    | measure of its energy content; if the energy changes by L, the mass
    | changes in the same sense by L/9 * 10^20, if the energy is measured in
    | ergs and the mass in grams.

    [Unfortunately, since the commercialization of the Digital Einstein Papers
    we are required to refer to archived versions or unofficial translations/copies :-(]

    But a frame dependent entity

    _quantity_, not entity

    like kinetic energy or relative speed is not a property of the moving object.

    Self-contradictory.

    They are properties of the relationship between the object
    and a frame of reference.

    /Non sequitur./

    The kinetic energy which can have any value depending on
    the arbitrary choice of frame of reference, is not part
    of the energy content of the object.

    That depends on how one defines that. "Energy content" is an obsolete term to begin with.

    However, if one simply substitutes "total energy" for "energy content", then the total energy of an object depends on the choice of rest frame; and the "energy content" that Einstein means is just that of an object/body (with non-zero mass) *at relative rest* -- in modern terminology, the object's/body's *rest* energy.

    So the mass isn't conserved, [...]

    There is no and has never been a disagreement among the two of us about that.

    Again: NOT the mass is partially converted to kinetic energy, but the rest >>> energy E_0 = m c^2 *equivalent to* the mass m.

    Energy before fission:
    Energy content of mass mreU: E = mreUc-# = 3.522894007E-8 J

    Energy after fission:
    Energy content of mass mree: E = mreUc-#= 3.520117602E-8 J

    The difference is +oE = mreUc-# - mreUc-# = +omriac-# = 3.089167695E-28 J

    The binding energy holding the nucleons together is
    part of the energy content of the mass of the U-235 nucleus.
    When the nucleus is split, the binding energy in the Ba-141
    and Kr-92 nuclei will be +oE less. The sum of the kinetic energy
    of the two nuclei and 3 neutrons will be +oE = 3.089167695E-28 J

    You keep missing the point.

    I say that the mass +om lost from the U-235 nucleus is converted
    to kinetic energy of the two nuclei and 3 neutrons.

    Which is simply the wrong idea.

    You are free to choose your wording.

    No, one is NOT free to choose one's wording if one wants to participate in a fruitful scientific discussion. That is a fundamental misconception. Scientific terms have meaning, and the meaning of certain terms has been agreed upon, like total energy, rest energy, mass, kinetic energy, and potential energy.

    What actually happens here is that rest energy is (partially) converted to other forms of energy. This is equivalent to a reduction in mass; precisely what Einstein wrote in his paper, and in a sense precisely what he suggested in that paper as an experimental test:

    | Perhaps it will prove possible to test this theory using bodies whose
    | energy content is variable to a high degree (e.g., salts of radium).


    "Ex falso quodlibet" is a lesson, not a fact.

    Truths is discovered /
    lies are invented /
    when a lie's discovered /
    that's a truth.


    Ex falso nihilum.


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  • From Ross Finlayson@ross.a.finlayson@gmail.com to sci.physics.relativity on Wed Jan 7 04:32:05 2026
    From Newsgroup: sci.physics.relativity

    On 01/06/2026 01:46 PM, Python wrote:
    Le 06/01/2026 |a 22:43, Ross Finlayson a |-crit :
    [snip non sense] Einstein's mass/energy equivalency
    formula, a truncation of an expression.

    You are the result of the truncation of sanity, Ross.



    Honi soit qui mal y pense?


    Before Einstein, like two or three decades before,
    already mass/energy equivalency in a form about the
    same as Einstein's first example, which is a truncation
    of a Taylor series, it was Karl somebody, Neumann I
    think it was,

    https://en.wikipedia.org/wiki/Carl_Neumann

    where I'm not exactly sure about that, yet the
    idea of mass/energy equivalency was already around.


    So, the "severe abstraction" of the "mechanical reduction",
    or as after Lagrange what arrived at Kelvin and these days
    is most usually about thermo 2'nd law the statistical ensemble,
    is an example of, "restriction of comprehension", which is a
    term from logic, opposite "expansion of comprehension".


    Anyway ideas about mass/energy equivalency like "impetus"
    and "vis viva" have been around a long time.

    Then, space-contraction-linear and space-contraction-rotational
    have also been around a long time, for example about the
    gyroscopic effects. (Here "heft".)


    The most usual ideas of the laws of motion as
    rest/rest motion/motion and equal/opposite are
    ideals, as they are, with classical mathematical setups,
    yet, practically never so. Thinkers like DesCartes
    and Kelvin attribute more to mechanics than that.


    Wow, Einstein's haircut is a lot like that Carl Neumann's.


    --- Synchronet 3.21a-Linux NewsLink 1.2
  • From Paul B. Andersen@relativity@paulba.no to sci.physics.relativity on Wed Jan 7 22:18:03 2026
    From Newsgroup: sci.physics.relativity

    Den 06.01.2026 23:27, skrev Thomas 'PointedEars' Lahn:
    Paul.B.Andersen wrote:

    The mass of an objects is invariant,

    It is _Lorentz_-invariant, NOT invariant /per se/.

    and so is the energy content of the object.

    No.

    The E in the equation E = mc-# is invariant,

    This pop-cultural equation is *wrong*, as I have pointed out /ad nauseam/.>
    which means that it is independent of the speed of the object.

    /Ex falso quodlibet./

    It makes no sense to call E = mc-# "the *rest* energy of
    _an object_ whose mass is m."

    It *does*. That is what it *is*. "Rest energy" is the agreed physical/scientific term for that form of energy.

    You are right, EreC = mc-# is called the "Rest energy" of
    a body with mass m.
    It is also called "the invariant energy" of a body with mass m.

    Because the energy EreC = mc-# is invariant, the same in all
    frames of reference, independent of the speed of the object.

    That's why find the name "rest energy" rather misleading.


    Above I was quoted to have said:
    "The E in the equation E = mc-# is invariant, which means
    that it is independent of the speed of the object."

    Your response was:
    "This pop-cultural equation is *wrong*, as I have pointed out
    /ad nauseam/.

    Can you explain your response?

    -----------------------------------
    To give the context of discussion below:

    One possible fission process is:

    1n + U-235 raA Ba-141 + Kr-92 + 3n

    The atomic weight of these are:

    Left side:
    1n 1.008664 u
    U-235 235.0439299 u
    -------------------
    236.0525939 u = 3.919748214E-25 kg

    Right side:
    Ba-141 140.914412 u
    Kr-92 91.926156 u
    3n 3.025992 u
    ---------------------
    235.866560 u = 3.916659047E-25 kg

    Lost mass: m = 0.1860339 u = 3.089167695E-28 kg

    E = mc-# ree 2.776404839E-11 J ree 174 MeV


    Energy before fission:
    Energy content of mass mreU: E = mreUc-# = 3.522894007E-8 J

    Energy after fission:
    Energy content of mass mree: E = mreUc-#= 3.520117602E-8 J

    The difference is +oE = mreUc-# - mreUc-# = +omriac-# = 2.776404839E-11 J

    The binding energy holding the nucleons together is
    part of the energy content of the mass of the U-235 nucleus.
    When the nucleus is split, the binding energy in the Ba-141
    and Kr-92 nuclei will be +oE less. The sum of the kinetic energy
    of the two nuclei and 3 neutrons will be +oE = 2.776404839E-11 J

    You keep missing the point.

    Which point am I missing?

    I say that the mass +om lost from the U-235 nucleus is converted
    to kinetic energy of the two nuclei and 3 neutrons.

    Which is simply the wrong idea.

    What actually happens here is that rest energy is (partially) converted to other forms of energy. This is equivalent to a reduction in mass;

    How is this different from what I said?

    The "rest energy" of the U-238 nucleus is
    E = mreUc-# = 3.522894007E-8 J

    The part of this energy +oE = 3.089167695E-28 J
    is converted to kinetic energy.

    This is equivalent to a reduction in mass +om = 3.089167695E-28 kg

    The energy equivalent of the reduction of the mass
    is +omriac-# = 2.776404839E-11 J
    This energy is converted to kinetic energy.
    --
    Paul

    https://paulba.no/
    --- Synchronet 3.21a-Linux NewsLink 1.2
  • From Chris M. Thomasson@chris.m.thomasson.1@gmail.com to sci.physics.relativity,sci.physics on Wed Jan 7 13:20:50 2026
    From Newsgroup: sci.physics.relativity

    On 1/6/2026 1:57 PM, Paul.B.Andersen wrote:
    Den 06.01.2026 09:15, skrev Thomas Heger:
    Am Sonntag000004, 04.01.2026 um 20:51 schrieb Paul.B.Andersen:

    E = mc-# is the energy content, or the energy equivalent of
    the mass m. Mass is invariant, so this equation is valid for
    all speeds of the mass.

    You contradicted yourself!!

    Here your claim is, that mass is invariant, while a little below you
    claim, that energy is conserved, while mass has vanished from a
    radioactive sample.

    But you can't keep both claims, because they contradict each other.


    Invariant means "the same in all frames of reference"
    or "independent of speed".

    It does _not_ mean "constant".

    Mass is invariant.
    The mass of an object is the same in all frames of reference.
    The mass of an object does not depend on the speed of the object.

    But mass can change. Heat the object, and its mass will increase,

    I have told you before, but I know you will not learn.
    You never do.



    Its odd to think of a cup of water as the water evaporates. The cup is
    an object with its own mass. But, now its holding water. So, the cup
    "weighs" more in a sense... But, as the water evaporates, that weight
    will go back to the weight of the original cup...

    Think of two equal mass cups on a scale. They balance. Add water to one,
    its not balanced. However, the water will evaporate and the scale shall
    go back to balanced over time?
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  • From Chris M. Thomasson@chris.m.thomasson.1@gmail.com to sci.physics.relativity,sci.physics on Wed Jan 7 13:29:32 2026
    From Newsgroup: sci.physics.relativity

    On 1/7/2026 1:20 PM, Chris M. Thomasson wrote:
    On 1/6/2026 1:57 PM, Paul.B.Andersen wrote:
    Den 06.01.2026 09:15, skrev Thomas Heger:
    Am Sonntag000004, 04.01.2026 um 20:51 schrieb Paul.B.Andersen:

    E = mc-# is the energy content, or the energy equivalent of
    the mass m. Mass is invariant, so this equation is valid for
    all speeds of the mass.

    You contradicted yourself!!

    Here your claim is, that mass is invariant, while a little below you
    claim, that energy is conserved, while mass has vanished from a
    radioactive sample.

    But you can't keep both claims, because they contradict each other.


    Invariant means "the same in all frames of reference"
    or "independent of speed".

    It does _not_ mean "constant".

    Mass is invariant.
    The mass of an object is the same in all frames of reference.
    The mass of an object does not depend on the speed of the object.

    But mass can change. Heat the object, and its mass will increase,

    I have told you before, but I know you will not learn.
    You never do.



    Its odd to think of a cup of water as the water evaporates. The cup is
    an object with its own mass. But, now its holding water. So, the cup "weighs" more in a sense... But, as the water evaporates, that weight
    will go back to the weight of the original cup...

    Think of two equal mass cups on a scale. They balance. Add water to one,
    its not balanced. However, the water will evaporate and the scale shall
    go back to balanced over time?

    LOL! Think if the cups were made of paper. The water itself might break
    down the cup and parts of the cup would wash away...
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  • From Thomas 'PointedEars' Lahn@PointedEars@web.de to sci.physics.relativity,sci.physics on Wed Jan 7 22:53:44 2026
    From Newsgroup: sci.physics.relativity

    Chris M. Thomasson wrote to sci.physics.relativity and sci.physics:
    Its odd to think of a cup of water as the water evaporates. The cup is
    an object with its own mass. But, now its holding water. So, the cup "weighs" more in a sense...

    The mass of the cup only has increased because when we say "cup" now we mean the substance of the cup *and* the water.

    But, as the water evaporates, that weight will go back to the weight of
    the original cup...

    That is only true if the water actually leaves the cup. Put a lid on the
    cup so that the water cannot escape, and the mass of the water-filled cup
    will not decrease.

    But, more relevant to this discussion, by increasing the rest energy of the water(-filled cup) by increasing the kinetic energy of the water molecules
    (and to some extent the substance of the cup, too) by heating the
    water(-filled cup), the mass of the water(-filled cup) increases slightly (probably unmeasurably, given m = E_0/c^2).

    See also the videos that I referred to in <mid:10j721n$1i2q$1@gwaiyur.mb-net.net>.

    Think of two equal mass cups on a scale. They balance. Add water to one,
    its not balanced. However, the water will evaporate and the scale shall
    go back to balanced over time?

    If the water *leaves* the cup, yes.

    Notice also that what you are measuring there is weight, not mass. That is, this is only an indirect determination of mass that depends on gravitation, therefore the assumption of a uniform gravitational field (which we know is
    not so, but just a relatively good approximation near the surface).

    F'up2 sci.physics.relativity
    --
    PointedEars

    Twitter: @PointedEars2
    Please do not cc me. / Bitte keine Kopien per E-Mail.
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