R: energy is real

[Paolo Cavallo <ton0621@IPERBOLE.BOLOGNA.IT>]

----- Original Message -----
From: John Denker <jsd@MONMOUTH.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Thursday, March 16, 2000 7:01 PM
Subject: Re: energy is real

> > > 1) Energy is real.
> >
> > Would you care to defend this position or is it a pronouncement
> > *ex cathedra*?
>
> That position can be defended in multiple ways.
>
> First and foremost, usefulness:  Some people find energy to be a useful
> concept.  If it's not useful to you, that's your problem.  Please don't
> inflict your problems on other people.

As a third party, I really can't understand the aggressiveness of this message. I think
Leigh's question was quite civil! Even if I do not share his position, I don't think he's
trying to "inflict problems"!

Is energy real? Are fields real? Is curvature real? Are laws real? Is the absolute phase
of a quantum amplitude real?
I find these questions legitimate ones. They force us to think about the meaning of "real"
in a scientific contest. Is this a case of "inflicting problems"?

Usefulness is a different matter. A lot of fictional constructs are useful, like imaginary
planes in electrostatics. "Reality" is big business, and I think that your attitude is
"unusefully" harsh.

>    a) Maybe you can show that the notion is wrong, perhaps by demonstrating
> a formal contradiction or inconsistency in the theory, or by showing that
> it makes a prediction that is inconsistent with experiment.
>    b) Maybe you have a better way to do the calculations that other people
> do using the energy notion.

Let us read Feynman again: "It is important to realize that we have no knowledge of what
energy *is*. [...] it is just a strange fact that we can calculate some number and when we
finish watching nature go through her tricks and calculate the number again, it is the
same." We must say that to a certain extent energy is a human construct: are human
constructs real? I suspect that physics has not yet an ontology good enough to answer
similar questions, but we could work on that.

> In either case, the burden is on _you_ to recruit believers by
> demonstrating that you have a more useful way of doing things.  Just saying
> no no no everybody else is wrong (without offering anything better) is
> unlikely to bring many recruits.

Again: I find this passage harsh without needing. You seem to intend that number and
consensus are relevant in physics: is this you're trying to say?

> Another argument: My dictionary defines "real" mainly as the opposite of
> fictional.
>
> Ghosts are fictional; energy is real. If I write a fiction book about
> ghosts, I can say pretty much anything I please.  In contrast, if
> I write a physics book about energy, I am very highly constrained as to
> what I can say.  I am constrained by reality.

Yes, indeed. The way I talk about energy when I talk of physical phenomena contrains me.
But even when I draw a fictional plane in the space between two charges I am constrained
by reality to draw the plane appropriately. The plane is no less fictional. So, your
argument is not decisive. I can agree with you in saying that energy is real, but your
argument is not a stringent one.

> In this sense, energy and other abstractions have a more permanent reality
> than, say, hydrogen atoms do.  If I have a box that is impermeable to
> hydrogen, I can turn hydrogen atoms into something else (e.g. neutrons)
> that silently escape from the box;  the net result is that hydrogen atoms
> disappear from the interior without ever passing (as such) through the walls.

This is a trick, isn't it? By the way, how do you do that?

> You should try it some time:  try to get rid of some unwanted energy in a
> hurry.  If you think energy is fictional, if you think you can make energy
> disappear just by wishing, then your wishes are much more powerful than
> mine.  Please tell us all how you do it!

Energy is a construct we made exploring nature and trying to describe it. So, it is
obvious we are constrained by reality when we use it! "Good" and "evil" are much more
useful in communication and description of human reality than energy is. Are good and evil
"real"?
The matter is bigger than you put it, I'm afraid. Leigh's ideas are useful to deepen our
understanding of our own concept: I find no use in being aggressive.

Writing in English is hard work for me. Please forgive me if I have been improper, obscure
or (God forbid) harsh to anyone.

Best regards,

Paolo Cavallo