What Actually Is Energy?

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Energy is defined as the potential of a physical system to perform work and can be transformed between different forms according to physical laws. The discussion highlights that while energy can be related to mass and the speed of light through Einstein's equation, its fundamental nature is often defined rather than explained in terms of its "true" essence. Understanding energy involves exploring its relationships with other physical quantities, such as momentum, which are unified in conservation laws. The conversation emphasizes that seeking a deeper explanation may not yield a definitive answer, as definitions often suffice in scientific discourse. Overall, energy is a conserved quantity that reflects the stability of physical laws over time.
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Hello guys, newbie here.

Just a question about 'energy' which may or may not have an easy answer.

As we all know 'energy' is the potential of a physical system to do 'work'. And 'energy' can be converted from one form to another as per the relevant laws.

But what actually is 'energy'?
Or what actually is this 'potential to do work' stuff made of?

As we also all know, 'energy' is mass x speed of light squared.

So is it right to assume that 'energy' has a direct connection to light speed? And if so is 'energy' constrained by the value of light speed in any way? (In that light speed is a single value in a vacuum and a single value in other mediums etc.).

Am I getting mixed up in various meanings or are these valid questions?

Thanks for any help on this.
 
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"energy" is that quantity which is conserved by virtue of the laws of physics not changing over time.
 
Hi AJ_2010, welcome to PF

AJ_2010 said:
As we all know 'energy' is the potential of a physical system to do 'work'. And 'energy' can be converted from one form to another as per the relevant laws.

But what actually is 'energy'?
Or what actually is this 'potential to do work' stuff made of?
In physics we often define some quantity. Once you have defined a quantity that definition is what it is. There is rarely any scientific answer to questions about what something "actually" or "really" is independent of the definition.

However, what is often interesting and useful for gaining a deeper understanding of something is to learn its relationships with other quantities. For instance, as JDlugosz mentioned, energy is related to the symmetry of a system, specifically the fact that energy is conserved implies that the laws of physics don't change over time.

Another interesting relationship is the relationship between energy and momentum in relativity. They have the same relationship to each other as time and space have, so the conservation of energy and the conservation of momentum can be combined into one unified conservation law.
 
Thanks for the replies.
Seems I was trying to find an explanation of something that doesn't have the type of explanation I was looking for.
 
So I know that electrons are fundamental, there's no 'material' that makes them up, it's like talking about a colour itself rather than a car or a flower. Now protons and neutrons and quarks and whatever other stuff is there fundamentally, I want someone to kind of teach me these, I have a lot of questions that books might not give the answer in the way I understand. Thanks
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