Re: Mass; E=m

[Jim Green <JMGreen@SISNA.COM>]

At 09:56 26 10 2004 , the following was  received:
> At 1:19 PM -0600 10/21/04, Jim Green wrote:
> >Suppose I weigh an ice cube and then allow it to melt and then weigh the
> >resultant water.
> >
> >Are the two weights the same?
>
> Is this question about mass?  Relativistic mass?  Looks like it could be an
> important question.
>
> Larry

Well, Larry, here I am back after a trip to outer space for a few
days.  When I left I felt that the mass thread had pretty well spent its
energy, but here we are still at it.  What a tenacious group.  I will have
a few thoughts re the past few days in a bit but you mention the issue
which bothers me the most presently.

There seem to be two groups re relativistic mass: The Pros and The Cons.

Most of the discussion has been about speed but how about other causes of
energy increase?  In this case heating.

The Pros might say that as the ice melts, its energy level increases
because the warm ambient has heated it  ie done work on the ice.  (The
_only_ way to increase the energy level of a system is to do work on
it.)  And because the energy level has increased the mass has increased --
not by enough to measure it with a balance however. So we turn to a very
large ice berg North of Greenland and we encase it in sturdy plastic and
weigh it and then tow it to NY harbor to let is melt.  If we re calibrate
for the gravity and weigh it again we find that it weighs more.  Hence we
conclude that the mass has increased as E=m ie E up so m up ie it is more
than E=m  E _is_ m

The Cons would say that indeed the total m is increased but the mass of
individual particles -- (They might say the atoms or maybe the electrons
and nucleus things) -- has not.  It has never been clear to me what the
rationale is.  I take it that they would claim that the electrons, protons,
and neutrons don't increase in energy individually.  I can't bring myself
to embrace this however,  Perhaps someone could tutor me here.  How can the
particles not increase in energy level but the ice berg does?   They say
that the particles are vibrating faster therefore the total energy has
increased....   Maybe I just don't understand the Cons.

Its good to be back

Jim

Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen