Re: .Re: Why all the fascination with E = mc^2 ??

From: David McAnally (D.McAnally_at_i'm_a_gnu.uq.net.au)
Date: 06/11/04 

Date: 11 Jun 2004 16:22:15 GMT

leoppard@MailAndNews.com (Leonard Pardin) writes:

>D.McAnally@i'm_a_gnu.uq.net.au (David McAnally) wrote in message news:<caaq84$se3$1@bunyip.cc.uq.edu.au>...
>> leoppard@MailAndNews.com (Leonard Pardin) writes:
>>
>> >Bjoern Feuerbacher <feuerbac@thphys.uni-heidelberg.de> wrote in message news:<ca6hgm$44u$1@news.urz.uni-heidelberg.de>...
>>
>> <snip>
>>
>> >> Einstein showed that radiation leads to a decrease in kinetic energy,
>> >> and since the velocity stays the same, it follows that there
>> >> is a decrease in mass.
>> >>
>> >> Got it now?
>>
>> > Who says there was a decrease in kinetic energy? The body emitted
>> >radiation, the velocity remained constant, the mass remained constant,
>> >the total energy of the system (body and radiation) remained constant.
>> >The momentum remained constant. So who is to say there was a change
>> >in kinetic energy?
>>
>> That's what you need the understanding of classical mechanics and
>> mathematics for. Without the classical mechanics, you can't work out how
>> to calculate the change in the kinetic energy. And without mathematics,
>> you can't work out if the kinetic energy changes, and if so, by how much.
>>
>> You have denied yourself the mathematical background to be able to
>> calculate what happens to the kinetic energy. We need mathematics to
>> explain how to calculate the change in kinetic energy, and you have not
>> made the effort to make yourself mathematically competent to understand
>> what happens.
>>
>> > It's just as easy to say the body contained radiation energy
>> >separate from its mass.
>>
>> You would have to give us a physical mechanism for the body to contain
>> radiation energy at all.
>>

> It's not hard to imagine a body containing radiation energy.
>Consider a cannonball of mass m heated white hot located in empty
>space. Since the cannonball is in a vacuum, no heat will be
>dissipated.

Why do you think that no heat will be dissipated. What physical reason
can you give for making such a bizarre assumption?

And what would be heating the cannonball? Obviously the system consists
of more than just the cannonball. This means that there is another mass
and another source of energy.

> But the heat energy causes the iron atoms to vibrate wildly causing
>light waves to emanate into space. The only thing that could be
>measured in a reference frame moving at a constant velocity relative
>to the cannonball would be the light.

And the velocity of the cannonball and the other apparatus.

>We might adjust the measurement
>using the Lorentz transformation, but it would still be only one
>measurement of the light energy emanating from the cannonball.

The transformation law for the radiation energy is known from Einstein's
first paper.

> If everything were perfect, i.e., the perfect vacuum and no heat
>loss,

Why would there be no heat loss if you have a vacuum? Please justify
this claim.

>the only change would be the loss of energy from the emanated
>light. Nevertheless, the only difference would be the reduced
>vibrations of the heat-agitated atoms, not the mass of the cannonball.

And the nett mass of the cannonball would decrease as a consequence of the
fact that the invariant quantity E^2-c^2p^2 (which in the square of the
mass) decreases.

Also, you are beginning to move into the realm of quantum mechanics, and
you are even more unfamiliar with quantum mechanics than you are with
classical mechanics.

>The cannonball would lose energy, not mass.

Actually, it would lose mass. You don't know what happens to the
contribution to the mass of the individual atoms, even without moving into
quantum mechanics.

>No calculations could be
>made about the mass of the cannonball unless we assume a priori that
>mass is converted into energy,

Idiot. Nobody assumed it a priori. But you are too pig-headed to learn
the basic facts.

>and that's called "begging the
>question."

Only by those like you who are too stupid to learn anything. Look at the
total disaster that you made with your false claims that a heated
cannonball does not radiate heat in a vacuum. If you recognized that,
then maybe that would be a start.

David

        "But I'm always true to you, darlin', in my fashion,
         Yes, I'm always true to you, darlin', in my way."
                -- Lois Lane

-----

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