What Is the True Nature of Energy?

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SUMMARY

The forum discussion centers on the complex nature of energy, exploring its definitions and implications in physics. Key equations such as E=mc², E=hf, and E=mgh illustrate the various forms of energy, including kinetic and potential energy. Participants emphasize that while energy is crucial for performing work and is often perceived as a precursor to force, its fundamental essence remains elusive. Richard Feynman's insights highlight that energy is an abstract concept, defined as the source of gravitational fields, yet its true nature is still not fully understood.

PREREQUISITES
  • Understanding of basic physics concepts, including force and work
  • Familiarity with key equations related to energy, such as E=mc² and E=mgh
  • Knowledge of gravitational fields and their relationship to energy
  • Basic grasp of quantum mechanics principles, including the Heisenberg Uncertainty Principle
NEXT STEPS
  • Study Richard Feynman's "Lectures on Physics" for deeper insights into energy and its implications
  • Explore the concept of the stress-energy tensor in general relativity
  • Research the relationship between energy and force in classical mechanics
  • Investigate the philosophical implications of energy as discussed in quantum mechanics
USEFUL FOR

Students of physics, educators, and anyone interested in the foundational concepts of energy and its role in the universe will benefit from this discussion.

  • #91
Dale Spam, sorry for misstyping your identify.

Drakkith,

I think I understand. Energy is the sum total of force times distance. I propose only that we leave it at that. I may be mistaken, perhaps you know what energy is beyond this definition?

James
 
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  • #92
James A. Putnam said:
Dale Spam, sorry for misstyping your identify.

Drakkith,

I think I understand. Energy is the sum total of force times distance. I propose only that we leave it at that. I may be mistaken, perhaps you know what energy is beyond this definition?

James

I've already given my views multiple times above.
 
  • #93
James A. Putnam said:
What is energy?
How many times do I have to repeat this: energy is the capacity to do work. And work, in turn, is clearly defined in terms of experimentally measurable values. Crystal clear and unambiguous.
 
  • #94
I haven't seen any answers above that explained what energy is.

James
 
  • #95
James A. Putnam said:
I haven't seen any answers above that explained what energy is.
If you haven't seen it then perhaps the font was too small

Energy is the capacity to do work.

Hopefully you could see it that time. :rolleyes:
 
  • #96
Dale Spam,

"How many times do I have to repeat this: energy is the capacity to do work. And work, in turn, is clearly defined in terms of experimentally measurable values. Crystal clear and unambiguous."

You do not have to repeat it. What is capacity if it is not cause? Experimentally measurable values tell us about effects. Your crystal clear is no answer to: What is energy? Unless you are saying that it is a given?

James
 
  • #97
I ask for an answer and you respond with gigantic fonts. How about a crystal clear answer?

James
 
  • #98
James A. Putnam said:
I haven't seen any answers above that explained what energy is.

James

Yes you have. You just don't agree with them.

I ask for an answer and you respond with gigantic fonts. How about a crystal clear answer?

We've given you one. You are trying to get a philosophical answer which we cannot give you.
 
  • #99
I do agree with 'energy is force times distance'. What else is it that I should agree with?

James
 
  • #100
James A. Putnam said:
I do agree with 'energy is force times distance'. What else is it that I should agree with?

James

I don't think that is correct. I believe you are describing work, not energy.
 
  • #101
No I am describing energy.

James
 
  • #102
James A. Putnam said:
No I am describing energy.

James

From wikipedia:

Since work is defined as a force acting through a distance (a length of space), energy is always equivalent to the ability to exert pulls or pushes against the basic forces of nature, along a path of a certain length.

Work is force x distance, energy is not.
 
  • #103
Work is force times distance that results in useful something or other. Energy is force times distance whether or not it is useful to us.

James
 
  • #104
James A. Putnam said:
Work is force times distance that results in useful something or other. Energy is force times distance whether or not it is useful to us.

James

I don't think that's true. Got a reference?
 
  • #105
You don't think that is true? Do yo
 
  • #106
Drakkith,

Sorry, don't know what interrupted my reponse. Energy is defined as force times distance. That effect can occur in internal or external circumstances. For instance, a collection of gas molecules in thermal equilibrium all have energy. If those molecules are allowed to do that which they do when they are freed, they will push against a piston and perform work which is the product of their force times the distance the piston moves. I know you know this. Energy is not the cause in either circumstance. Force is the cause. The fundamental question is: What is force?

No I don't have a reference. Have you ever seen an introductory physics text that does not distinguish between internal energy that does nothing more than exist and internal energy that is put into circumstances where it might result in pushing something so that we may differentiate between energy that has produced work and energy that just exists?

James
 
  • #107
James A. Putnam said:
Your crystal clear is no answer to: What is energy?
When someone asks "What is X" then the answer is the definition of the word "X". Energy is defined as the capacity to do work, so when someone asks "What is energy" the answer is the capacity to do work.
 
  • #108
James A. Putnam said:
Energy is defined as force times distance.
No, it is not. For example, consider kinetic energy. An object of mass m moving at a constant velocity v has 0 force, so force times distance is also 0, but it has a kinetic energy of 1/2 mv², which is non-zero. Therefore energy is not force times distance. Work is force times distance, energy is the capacity to do work. The moving object may collide with some other object and exert a force over a distance, so the moving object has the capacity to do work even if it is not currently doing work.
 
  • #109
If you ask my crazy ex-girlfriend, she'll tell you it's the feeling you get when you have Jesus in your soul!
 
  • #110
Dale Spam,

"An object of mass m moving at a constant velocity v has 0 force, so force times distance is also 0, but it has a kinetic energy of 1/2 mv², which is non-zero. Therefore energy is not force times distance."

No that is not correct. It is true that an object moving at a constant velocity has something theorists call kinetic energy. However, that energy attrributed to it is the result of a calculation of force times distance. The sum total is called energy even though it is no longer experiencing force times distance. However, the loose use of the word energy does not relieve it of its definition. There is no other definition of energy other than force times distance. There are circumstances where the word energy is applied as if it is potential, that condition is a theoretical decision. The empirical circumstance is that energy is force times distance. The question remains: What is force? I don't see answers for that question. Force is skipped over.

Energy is a name applied to results of force times distance. The use of the name energy for any object that is not undergoing acceleration is a substitute for the long answer. The long answer has to do with the amount of force times distance that that object can exert later if it is allowed to do so.

James
 
  • #111
Force:

In physics, a force is any influence that causes a free body to undergo a change in speed, a change in direction, or a change in shape.
 
  • #112
James A. Putnam said:
There is no other definition of energy other than force times distance.
No, all of these define energy the way I have suggested:
http://www.bios.niu.edu/meserve/bios106/Outline.Lect5.Bios106.pdf
http://flightline.highline.edu/wmoses/EnvScience/LectureNotes/PDF/Energy.pdf
http://www.physchem.co.za/OB12-mec/energy.htm
http://en.wikipedia.org/wiki/Energy
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
http://books.google.com/books?id=QB...esnum=6&ved=0CEUQ6AEwBTgK#v=onepage&q&f=false

Can you provide any credible reference for your definition?
 
Last edited by a moderator:
  • #113
But I think kinetic energy is also a potential to do work. Although energy follows from integral of forces, technically they are not pushing a force and act on a displacement, they just have potential to do work. Though the dot product is constant, the force and displacement are yet to be determine, if you aren't sure of any of the quantity how can you
define it using the two quantities?
 
  • #114
"n physics, a force is any influence that causes a free body to undergo a change in speed, a change in direction, or a change in shape."

So I ask: What is force? In other words: What is cause? If the answers are givens that is fine so long as they are admitted to be unexplained givens.

James
 
  • #115
James A. Putnam said:
"n physics, a force is any influence that causes a free body to undergo a change in speed, a change in direction, or a change in shape."

So I ask: What is force? In other words: What is cause? If the answers are givens that is fine so long as they are admitted to be unexplained givens.

James

Again, you are looking for philosophical answers. Nothing we can give you will satisfy you because science cannot give a philosophical answer.
 
  • #116
IMO, if you want an answer that cannot be directly expressed mathematically you are asking for something that cannot be given by physics.
 
  • #117
WannabeNewton said:
IMO, if you want an answer that cannot be directly expressed mathematically you are asking for something that cannot be given by physics.

But there got to be something that cannot be described by another mathematical quantity. Ifyou use one thing to describe another, what about that thing? If no quantity is given to describe the object, how can we use mathematics?
 
  • #118
No, all of these define energy the way I have suggested:

These are not definitions. These are descriptions of what effects might be expected. I am asking about cause. Energy is not a cause.

"Can you provide any credible reference for your definition?"

Ok. From College Physics by Sears and Zemansky : "Work is done only when a force is exerted on a body while the body at the same time moves in such a way that the force has a component along the line of motion of its point of application."

What work is performed by an assemblage of gas molecules bouncing around that object?
 
  • #119
"IMO, if you want an answer that cannot be directly expressed mathematically you are asking for something that cannot be given by physics."

Energy is expressed mathematically as fxd.
 
  • #120
Yes energy can be expressed mathematically. My point is that you are asking for a definition of energy that is mainly philosophical and cannot be backed up by math.
 

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