What Actually Is Energy?

  • Context: Undergrad 
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Discussion Overview

The discussion revolves around the concept of 'energy', exploring its definition, nature, and relationships with other physical quantities. Participants examine the implications of energy being defined as the potential to do work and its connection to fundamental principles in physics, such as conservation laws and relativity.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the fundamental nature of energy, asking what it is made of and how it relates to the potential to do work.
  • Another participant asserts that energy is a conserved quantity due to the laws of physics remaining unchanged over time.
  • A different participant emphasizes that definitions in physics are crucial, suggesting that understanding energy's relationships with other quantities, such as momentum, can provide deeper insights.
  • There is a mention of the relationship between energy and momentum in relativity, indicating that they are interconnected in a way similar to time and space.
  • One participant expresses a sense of frustration in seeking an explanation that may not exist, indicating the complexity of the topic.

Areas of Agreement / Disagreement

Participants express differing views on the nature of energy and its definition, with some focusing on its relationships and conservation while others seek a more fundamental understanding. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

The discussion highlights the limitations of seeking a definitive answer about the nature of energy, as it is heavily dependent on definitions and relationships within physics. There are unresolved aspects regarding the implications of energy being related to light speed and its constraints.

AJ_2010
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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.
 

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