Definition of 'energy'

[phildonnia]

I think we can all agree that 'energy' is a word with a precise meaning in physics, and a much different meaning in common use. Perhaps we can also agree that the identification of these two meanings leads directly to many of the misconceptions of woo^2 physics.

How can 'energy' in the physics sense be explained to the non-physicist? The definition in physics is

1) The capacity of a physical system to do work. (dictionary.com)

And the usual meaning:

2) The capacity for work or vigorous activity; vigor (dictionary.com)

Here's the difference: a cup of coffee, when ingested, imparts very little energy-1 to the animal body. Yet it gives you lots of energy-2, and enables you to get out of bed and get to work. On the other hand, a cup of lard, when ingested, will give a tremendous amount of energy-1, but will suck the energy-2 out so fast that you'll be lying down moaning and clutching your stomach. A light breakfast of Cheerios, of course, gives you both kinds.

It seems to me that many of the spurious reasonings concerning 'energy' could be identified by avoiding this confusion.

Around here, when we say 'energy', we mean... what? How can you define 'energy' (in the physics sense) in a way that a non-physicist will get an approximate idea of the concept? Or does 'energy' belong in the same category as "quark flavor", inaccessable to someone not familiar with the physical theory?

And what is the guy in the street supposed to make of all the different forms of energy? It seems that scientists occasionally find energy "missing", in some experiment, and assuming that this is impossible, they go on to postulate a new unexplored area of physics in which the energy is "found" again.

For example, if you connect a battery to a piece of wire, you find that the heating of the wire doesn't quite account for the energy lost from the battery. So you go on to study magnetic fields, and find your missing energy there. Many other examples of this exist. I realize that there's more to it than that, but to the non-physicist, it looks like energy is just some made-up thing that they keep re-defining to fit a theory.

 

[Orangutan]

Hope this isn't to offtopic.

I remember reading about how a british energy conservation campagn changed it's wording. It used to talk about how to insulate your home to keep the heat in which is scentifically more descriptive, but research showed that 'Joe Bloke' identified more with the concept of keeping cold out.

So to the man on the street there is also negative energy too it's what cold things have, and its what depresses your mood.

O.

 

[toddjh]

How can you define 'energy' (in the physics sense) in a way that a non-physicist will get an approximate idea of the concept? Or does 'energy' belong in the same category as "quark flavor", inaccessable to someone not familiar with the physical theory?

I think it all depends on whether the average joe is comfortable with the concept of potential energy. Personally, I vote yes. Your lard/cheerio example is a good one: most people are intuitively familiar with potential energy in the form of food calories.

After you get past that hurdle, I think it's good enough to define energy as the ability to create heat or cause motion. That works for nearly all everyday purposes.

Jeremy

 

[Ziggurat]

For example, if you connect a battery to a piece of wire, you find that the heating of the wire doesn't quite account for the energy lost from the battery. So you go on to study magnetic fields, and find your missing energy there. Many other examples of this exist. I realize that there's more to it than that, but to the non-physicist, it looks like energy is just some made-up thing that they keep re-defining to fit a theory.

One way of thinking about it is in terms of how energy is transfered, instead of in terms of how it is stored. Energy is transfered by applying a force over some distance (meaning that what you're applying the force to moves as you apply the force, not necessarily that you're applying the force at a distance from the source). And the amount of energy transfered is the force times that distance it is applied over.

In macroscopic mechanical situations, this is often fairly easy to visualize: lifting an object requires applying a force upwards over the distance it is lifted, and you're transfering energy to that object which will then have more potential energy. In some cases, it's less obvious, but it's still there: resistive heating in a circuit is also caused by pushing on the electrons in the system (with an applied voltage), which in turn push on the nuclei of the material (which start moving around randomly - hence heat).

 

[Iamme]

So. Helium came from hydrogen, right? Where did all that hydrogen come from? "Energy"?

 

[CurtC]

So. Helium came from hydrogen, right? Where did all that hydrogen come from? "Energy"?

It came from the soup of subatomic particles that condensed after the singularity. When the soup cooled enough, electrons and protons were able to bind together to form hydrogen without constantly being torn apart by energtic photons. Does this answer your question?

As to the OP, one thing that might have been better would have been to call this quantity of "ability to do work" some coined word instead of co-opting an existing one. On the other hand, woos always mis-use the term "frequency" although the seem to have no clear idea of what the everyday term means. To a woo, IMO, "frequency" and "energy" are the same thing (and no, they don't understand Heisenberg's relation of them).

 

[jan]

I think in the woo dictionary, we have

energy = frequency = force = vibration = field = information = aura = soma = chakra = ...

Basically, it's all just the same. Or it just doesn't matter.

 

[rastamonte]

I used to get in huge amounts of trouble with my wife (a chiropractor, meditator, spiritual seeker) for assuming she was using the same definitions for her words that I was. I finally figured out that her definitions and mine were so completely different that we were, in effect, speaking entirely different languages. I actually started the annoying habit of putting my fingers up to indicate quotes whenever I was talking to her and using her definitions with words like "energy" and "vibrations".