Understanding the Relative vs Absolute Nature of Energy Conservation

In summary, the conservation of energy holds true in any reference frame, but energy is relative and can have different values depending on the frame of reference. This is the difference between the concepts of "invariant" and "conserved". In General Relativity, the conserved quantity is called the stress-energy pseudotensor, which is globally conserved but coordinate dependent.
  • #1
Denton
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Or is it absolute? I've heard the conservation of energy on a large scale doesn't hold true. How can this be so?
 
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  • #2
Energy is relative, both in Relativity and in Newtonian mechanics. This means that different reference frames will determine different values for the energy of a given object at a given point in space and time. However, the conservation of energy holds in any reference frame. This means that, in a single reference frame the total energy (KE + PE) will be constant over time.

This is the difference between the concepts of "invariant" and "conserved". Energy is conserved, but not invariant.
 
  • #3
In General relativity, for technical reasons, the conserved quantity is called the stress-energy pseudotensor, rather than the stress-energy tensor. This is why you may have heard that energy is not globally conserved. As DaleSpam indicated, the stress-energy pseudotensor is globally conserved, but it is coordinate dependent.

Edmund Bertshinger's notes:
http://web.mit.edu/edbert/GR/gr7.pdf
 
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FAQ: Understanding the Relative vs Absolute Nature of Energy Conservation

What is the difference between relative and absolute energy conservation?

Relative energy conservation refers to the idea that energy can be transformed from one form to another, but the total amount of energy in a closed system remains constant. Absolute energy conservation, on the other hand, states that the total amount of energy in the universe is always constant and cannot be created or destroyed.

Why is understanding the relative vs absolute nature of energy conservation important?

Understanding the relative and absolute nature of energy conservation is important because it allows us to accurately predict and understand the behavior of energy in different systems. It also helps us to develop more efficient and sustainable energy sources.

Can relative energy conservation be violated?

No, relative energy conservation is a fundamental law of physics known as the law of energy conservation. It has been tested and proven to hold true in all observed systems.

How does the concept of entropy relate to relative vs absolute energy conservation?

Entropy is a measure of the disorder or randomness in a system. In relative energy conservation, entropy can increase or decrease as energy is transformed from one form to another. However, in absolute energy conservation, the total amount of energy and entropy in the universe remains constant.

Are there any exceptions to the law of energy conservation?

Currently, there are no known exceptions to the law of energy conservation. However, there are some phenomena, such as dark energy, that are not fully understood and may have an impact on our understanding of energy conservation in the future.

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