Does Hubble's Expansion voilate conservation of energy by redshifting EM waves?

In summary, the conversation discusses the concept of energy conservation in General Relativity and how it relates to the expansion of the universe and the frequency and energy of radiation. The participants also mention a link to a website and a paper discussing this topic. They express their thoughts and doubts about the topic and its current understanding in scientific literature. Overall, the conversation highlights the complexity and ongoing research surrounding this topic.
  • #1
SubTachyon
19
0
I am assuming the answer to my question is no, but what am I missing?
My reasoning is very basic: E=hf, therefore as the universe expands the wavelength of all the far traveling radiation is increased and due to constant velocity c their frequency must decrease which translates into them losing energy.
I would appreciate if somebody could shed some light on this for me, please.
(bad puns are bad... :P)
 
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  • #2
Similary, some galaxies are now receding apart @ velocities > c (in stark contadiction to Einstein's posit).

To answer your question;- both red-shift and corresponding velocitiy are due to spatial expansion ... it's not that the galaxies are shifting, merely the space inbetween is.

There's no law regarding the speed limit of space itself, is there?
 
  • #3
I don't believe you read my question properly. It has nothing to do with velocity; I'm concerned with the energy of the waves.

If a photon is created with the frequency of 100 Hz and after traveling between two distant galaxies due to the expansion of the universe it's frequency drops to 10 Hz it should have lost 90% of it's energy.
 
  • #4
The easy answer is that conservation of energy does NOT apply in General Relativity. Energy is not a well defined quantity in GR either. (Or so I've been told)
 
  • #6
salvestrom said:
http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

this might appeal to you.

Ah, a nice read. I love the opening lines.
Is Energy Conserved in General Relativity?

In special cases, yes. In general — it depends on what you mean by "energy", and what you mean by "conserved".

Pretty much what I've been told.
 
  • #7
Thank you, that was a useful link.

''Those who harbor no qualms about pseudo-tensors will say that radiant energy becomes gravitational energy.''
That's what I thought about as well, though I am not entirely satisfied with it as an answer and I guess that until I cover GR in more depth I probably won't be satisfied anyway.
Although it would seem that even the people who concern themselves with GR still struggle to come up with a coherent and verifiable answer to this problem.

Edit: I found similar topic in the archive - https://www.physicsforums.com/archive/index.php/t-156255.htmlEDIT2: I found this paper online on this same exact topic: http://arxiv.org/ftp/arxiv/papers/1111/1111.2331.pdf
Could anyone comment on it's credibility? The author is implying a static universe which I know to be a very unorthodox idea in today's cosmology so I holding to my skepticism for now but if someone with more experience in scientific process and literature could comment on this I would greatly appreciate it.
 
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FAQ: Does Hubble's Expansion voilate conservation of energy by redshifting EM waves?

1. How does Hubble's expansion relate to the conservation of energy?

Hubble's expansion is a process in which the universe is constantly expanding, causing the distance between galaxies to increase. This expansion does not violate the conservation of energy, as energy is still conserved in the universe. However, the expansion does affect the wavelength of electromagnetic waves, causing them to appear redshifted.

2. What is redshifting of electromagnetic waves?

Redshifting is a phenomenon in which the wavelength of electromagnetic waves is stretched, causing them to appear redder. This is due to the expansion of the universe, which causes the waves to travel through more space, leading to a longer wavelength.

3. Does the redshifting of electromagnetic waves violate the conservation of energy?

No, the redshifting of electromagnetic waves does not violate the conservation of energy. While the energy of the waves may appear to decrease, the total energy in the universe remains constant. This is because the energy is simply being spread out over a larger distance, resulting in a decrease in the energy density.

4. How does Hubble's expansion affect the energy density of the universe?

Hubble's expansion causes the energy density of the universe to decrease over time. This is because the energy is being spread out over a larger volume as the universe continues to expand. This decrease in energy density is not a violation of conservation of energy, as the total energy in the universe remains constant.

5. Are there any other factors that may affect the redshifting of electromagnetic waves?

While Hubble's expansion is a major factor in the redshifting of electromagnetic waves, there are other factors that may also play a role. These include the relative motion between the source of the waves and the observer, as well as the effects of gravity on the waves as they travel through space.

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