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

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The expansion of the universe causes the stretching of electromagnetic wave wavelengths, raising questions about the fate of energy since energy cannot be destroyed. The discussion clarifies that the conservation of energy law applies locally rather than to the universe as a whole, meaning it is valid in small regions where spacetime curvature is negligible. Participants express confusion about the technical definition of "locally" and seek further clarification. A link is provided for additional information on the relationship between energy and general relativity. Understanding these concepts is crucial for grasping the implications of cosmic expansion on energy.
Daniel Petka
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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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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.
 
1.)Lol that's what I meant sorry
2.)What exactly do you mean by saying locally?
 
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
 
Thanks that helped
 
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