What is energy?
What is power?           What is work?
How do we design the most efficient automobile?
How do we heat (or cool) our house with the least energy use?
How do we most effectively reduce our need for energy?
Learn, understand, use: The science of the 19th century.
Fans of Keith Devlin, "The Math Guy" of NPR, might find this fable, following Devlin's pursuit of "The Math Gene," revealing in its ancient ancestor view of energy.
Those concepts are ancient.

Human understanding of the concepts comes from the science of only the past century and a half. 

Energy, power, and work are powerful concepts in the hands of those who understand the science.  But even though the concepts are simple, they are subtle. Very subtle.  What, at first glance, they seem to be, they are not.  We need to take a lot of second glances before these concepts become our tools.


 
some
First Glances 

Work is what tires us.
Energy is what we run out of when we get tired or when the car’s gas gauge is on empty. Power is the ability to get things done.

We need some second glances
because there are problems with these concepts:

“Energy is the capacity to do work.”  Perhaps half of all physics textbooks define energy with this statement.  But those same textbooks will define free energy as “total energy minus that energy which is unavailable for doing work.”  Together, these two definitions amount to a logical fallacy.  Resolution demands a second look. 

Science happens when someone recognizes a fallacy and then figures out how to resolve it.

This fallacy is fatal, but surprisingly few see it—even textbook authors who have had the fallacy pointed out to them sometimes fail to see it.  They must look deeper.

“According to the laws of physics—they’re known as the first and second laws of thermodynamics, and there are no known exceptions to them—you can’t use energy more than once.”

This statement was made in a newspaper by an Oregon governor’s energy advisor.  When it was quoted to a group of physicists it brought a great round of laughter.  When quoted to groups of non-physicists it always gets a lot of knowing nods of approval.

What do the physicists see that the non-physicists do not?

“Society must conserve energy: remember in science there’s a ‘law of conservation of energy’.”

This one, too, is a good joke to a physicist, but a serious warning to many others. 

Why the difference?

“This refrigerator’s efficiency is 300%.”  “This auto engine’s efficiency can be no greater than 37.4%.”

For decades, engineering students were taught to calculate efficiencies of machines.  They learned that “heat engines” (most engines that burn fuel are heat engines) can have efficiencies no greater that about 37% or so, but that many machines can have efficiencies more than 100%.  Surely “efficiency” should be something that runs the gamut from 0 to 100 percent.  Why doesn’t it?  How should we define efficiency so that it does?


 
Some great leaps in scientific understanding accrued from about Newton’s time (1680 or so) to the last half of the 19th century (the era of thermodynamics).  The needed resolutions to those "needs for second glances" lie in those leaps.

But those second glances are seldom seen by those who only learn what they are.  Not seen, that science remains mysterious.  It remains abstract—“ivory towered and quite out of touch with the real world.”  It remains knowledge that is unusable.

Learning is one thing; seeing is something else.

Here are a couple of clues—in perhaps unexpected places—toward resolutions of the discrepancies

Clue #1:
it's in
The Feynman Lectures on Physics,  p 4-1,  Addison Wesley, 1963.

Feynman gives his answer to the question, "What is Energy."

His answer is as far from the troubling definition,  “Energy is the capacity to do work,” as it could be.  (And it's explained on the next page of this Web site.)  Or you can click on the picture of 'The Feynman Lectures' below.

Clue #2: 
it's in
What Is Life?, by Erwin Schrödinger

Erwin Schrödinger, too, put his finger on some critical “unseen” things when he answered the question “How does the living organism avoid decay?” in his essay “What is Life?” Read it

Return via your "Back" button.

Start to resolve the descrepancies by looking at some definitions.



 

Feynman: What is energy?