Where Did the Energy Go in Light Waves When the Universe Expanded?

In summary, the expansion of the universe causes the wavelengths of electromagnetic waves to stretch, but the conservation of energy law does not apply to the universe as a whole. It only applies locally, meaning in small regions of space where the effects of spacetime curvature are negligible. For more information, refer to the link provided.
  • #1
Daniel Petka
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https://www.physicsforums.com/attachments/198775

The expansion of the universe stretches the wavelength of EM-waves. Though the energy equivalence says energy can't be destroyed... so where did the energy go?
 
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  • #2
Daniel Petka said:
Though the energy equivalence says energy can't be destroyed...

That's not energy equivalence, it's the conservation of energy law. Conservation of energy doesn't apply to the universe as a whole, it only applies locally.
 
  • #3
1.)Lol that's what I meant sorry
2.)What exactly do you mean by saying locally?
 
  • #4
I'm not sure about the technical definition of local, but I believe the idea is that it's a small region of space where things like the curvature of spacetime is negligible and the laws of special relativity can be used.

For more info on this topic, see this link: http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html
 
  • #5
Thanks that helped
 

Related to Where Did the Energy Go in Light Waves When the Universe Expanded?

What is the energy equivalence issue?

The energy equivalence issue is a concept in physics that states that mass and energy are two forms of the same thing. This means that mass can be converted into energy and vice versa, according to Einstein's famous equation E=mc^2.

Why is the energy equivalence issue important?

The energy equivalence issue is important because it helps us understand the fundamental relationship between mass and energy. It also plays a crucial role in fields such as nuclear physics, where mass is converted into energy in processes like nuclear fission and fusion.

How was the energy equivalence issue discovered?

The energy equivalence issue was first proposed by Albert Einstein in 1905 in his theory of special relativity. He realized that the speed of light is constant and that energy and mass are interchangeable, leading to the famous equation E=mc^2.

What are some practical applications of the energy equivalence issue?

One of the most well-known applications of the energy equivalence issue is in nuclear power. By converting a small amount of mass into energy, nuclear reactions can produce a tremendous amount of energy. This also has potential applications in space travel, where the conversion of mass into energy could power spacecraft.

Are there any limitations to the energy equivalence issue?

While the energy equivalence issue has been proven to be true in many experiments, it is still a theoretical concept and there are some limitations to its applicability. It does not apply to everyday objects and is only relevant in situations where there is a significant amount of energy involved, such as nuclear reactions or the movement of particles at high speeds.

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