- #1
- 35,204
- 13,431
DaleSpam submitted a new PF Insights post
What is Energy?
Continue reading the Original PF Insights Post.
What is Energy?
Continue reading the Original PF Insights Post.
I wasn't trying to list forms of energy. I was trying to list definitions of energy. For instance, using the mechanics definition you can define KE, elastic potential energy, and gravitational potential energy all as different forms of energy using the same definition.anorlunda said:I do think that the sentence, "There are other definitions of energy which are used in thermodynamics, Lagrangian mechanics, and quantum mechanics. " could have been broader to specifically mention, chemical, nuclear, EM and other forms of energy that are not thermodynamic, nor mechanics. (Wikipedia lists 16 forms of energy, I'll bet there are still more.)
We can define energy the way we do because we can define any word anyway we want. By definition.Unified28 said:Energy does have it's definition. However there is a reason why we can define energy the way we do which is unknown to physicists today.
I agree, and in my experience on this forum such questions are answered clearly and directly. And then the discussion goes downhill from there.Unified28 said:it would be a scientifically correct mindset otherwise to not be afraid to answer questions about the nature of energy.
Unified28 said:Energy does have it's definition. However there is a reason why we can define energy the way we do which is unknown to physicists today.
anorlunda said:(sorry, I don't know how to do Latex in PF4.)
Islam Hassan said:If we ignore the different classical classifications of energy (heat energy, sound energy, etc) and take a fundamental view, can we say that all energy at the fundamental level is ultimately one of these four categories:
- Kinetic;
- Static, ie deriving from an object/particle's position in a physical force field;
- Energy incarnated in mass; and
- Dark energy, which we know little about.
IH
In a word, energy is "Potential"DaleSpam said:DaleSpam submitted a new PF Insights post
What is Energy?
Continue reading the Original PF Insights Post.
Just a historical correction!bhobba said:In fact that's why Einstein asked Emmy Noether to look into it because of the issues in GR.
Shyan said:Just a historical correction! Hilbert asked her to look into it, not Einstein. Einstein only received the results in a letter and was amazed.
That also happens to be my favorite definition. As I said in the commentary, I don't think that conversations about energy degenerate due to the definition (whichever one you choose), they degenerate for more human reasons.bhobba said:I have read the replys, and still I can't see why the definition Noether sorted out isn't the correct one:
http://www.physics.ucla.edu/~cwp/articles/noether.asg/noether.html
Not only does it define precisely what it is, it explains why its conserved, and even why the concept of energy becomes problematical in GR.
In fact that's why Einstein asked Emmy Noether to look into it because of the issues in GR.
Thanks
Bill
DaleSpam said:That also happens to be my favorite definition.
DaleSpam said:No, I think several other definitions are valid also. Also if you are doing a non Lagrangian theory then you need something else anyway.
And how does Noether define energy ? I couldn't figure it out reading those links.bhobba said:I have read the replys, and still I can't see why the definition Noether sorted out isn't the correct one:
http://www.physics.ucla.edu/~cwp/articles/noether.asg/noether.html
Not only does it define precisely what it is, it explains why its conserved, and even why the concept of energy becomes problematical in GR.
In fact that's why Einstein asked Emmy Noether to look into it because of the issues in GR.
Added later:
Whoops - as Shyan pointed out it was Hilbert.
Thanks
Bill
DirkMan said:And how does Noether define energy ? I couldn't figure it out reading those links.
So I have read that blog, and also the comments. If I understand it at the simple most basic level, energy is conserved because of time, that is if we have X energy in a system at time t0 , and we have energy increasing towards Y at time t1 , we can have that conserved because we can imagine rewinding back the time evolution of the energy in the system as decreasing from Y to X , and if we add up the increase and decrease we get the same X. Is it nonsense what I'm thinking ?bhobba said:Thanks
Bill
DirkMan said:Is it nonsense what I'm thinking ?
Energy is the ability to do work or cause change. It exists in many forms, such as light, heat, sound, and motion.
Energy is measured in joules (J) or sometimes in calories (cal). One joule is equal to the amount of energy needed to push with a force of one newton for a distance of one meter.
There are several types of energy, including kinetic energy (energy of motion), potential energy (stored energy), thermal energy (heat), chemical energy (stored in bonds between atoms), and electromagnetic energy (energy carried by light and other forms of radiation).
Energy can be converted from one form to another through various processes. For example, a light bulb converts electrical energy into light and heat energy. Energy can also be transferred from one object to another through collisions or interactions.
The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. This means that the total amount of energy in a closed system remains constant over time.