Re: refutation of the nonreality of energy

[Brian McInnes <bmcinnes@PNC.COM.AU>]

John Decker wrote

> Here's how:  take two airplanes, alike in every relevant aspect, except
> that one of them has a lot more energy.  It could have more altitude and/or
> more airspeed;  the form doesn't matter.  But you will find that trying to
> land that airplane is very different from trying to land the other.  How do
> I explain this to my students?  I tell them about energy.  It works for them.



John, why do do you have to tell them any more than the faster
airplane experiences a larger change of velocity as it stops, so a
larger force has to be applied to it?  You could go further and
discuss changes in momentum or, yes, changes in energy but you don't
have to do that in explaining why it stops.  It's the forces that are
the important quantities.


> If it doesn't work for you, well, that's your problem.  Please don't foist
> your problems onto vulnerable students who will have to go out into the
> real world where real people use local conservation of energy all the time.

It will probably "work for them" if you told them that you need angels
to stop planes and the faster plane will need more angels.  In the
middle ages it was thought that one needed angels to keep one's arrows
moving towards the enemy who, presumably didn't have enough angels to
empower their arrows.  Whether something "works" for students or
mediaeval scholars doesn't mean it's good physics. 20th century school
and undergraduate physics education is littered with misleading,
semi-true, or plain wrong explanations of the real world.

>
Later you write
> Sometimes I can detect it;  usually in order to make my point all I need to
> do is prevent it, perhaps by surrounding point A with a physical
> energy-boundary such as a Dewar flask ("Thermos bottle").  In those rare
> cases where there *appears* to be a violation of local conservation of
> energy -- by energy-flow mysteriously penetrating the boundary -- then we
> have a mystery of the highest order, the sort of paradox from which the
> great advances of physics come.  In particular, I cite
>  a) the discovery of cosmic rays, which was motivated by a
> barrier-penetration mystery of this sort, and
>  b) the discovery of neutrinos, ditto.

Surely all you are detecting is a change in a property of the system
enclosed by the Dewar flask. Some matter has entered the system (most
of it has passed through) and some interactions have occurred that
have lead to an increase in the energy of the system.  This could be
interpreted as energy flow across the boundary but there is NO need to
interpret it in this way.  In my model: matter flow, yes; energy
change, yes; energy flow, no.

Brian McInnes