Finally I have found the time to read your post! It was really due, as this post is a great one (as all your posts usually are). As you may have noted it from elsewhere, last week was really intense for me and I had to decouple from the chain. However, I am back and slowly catching up with all blogs posted on STEMsocial last week.
I have a single thing to say here, more as a comment than as anything else. The topic is indeed a bit far from my zone of comfort…
In high-energy physics, energy conservation is related to the translational invariance of the laws of physics. However, in an expanding universe there is no such a translation invariance so that on a global scale there is no rule telling us that energy should be conserved. Therefore, there is no reason for energy conservation and this principle can be violated. Notice that I say "can", and not "must".
Therefore in an expanding universe care must be taken when we discuss even the mere notion of energy. For instance, it is very possible to see the energy of the CMB photons going into the expansion of the universe. This would provide a way for the energy to be a conserved quantity.
I wish you a very nice week! Cheers!
Don't worry about it. I know how busy you are, and I really have no idea how you keep up with all that you do :) I only moderate a community plus few other minor things and RL, and barely finding enough time to write and post once a week and/or read and keep up with things.
About the energy conservation:
It "can", but with current theories, Noether's theorem, and data, it "is" violated on that timescale due to no translation invariance in an expanding universe as you have mentioned.
Regarding CMB energy loss;
As far as I know, there isn't as nearly CMB to cover for it. Dark energy is increasing at a much higher rate than the CMB loses energy.
Ofcourse, we are not throwing out conservation of energy or the second law of thermodynamics (which is another topic), as violations are only on such extremes and it is unhelpful to do so.
Thanks for the always insightful comments, and wish you a wonderful week too!
Thanks for this replies, which I agree with. Let me come back to one point:
Let me be more specific: the CMB contributes to it. It does not need to take it all. I was probably a bit too sloppy in my initial comment ;)
After looking a bit on the web, I have found this very nice blog on the topic. This goes along the same lines as my comment, but in a more expanded manner. The more important item it points out is that we must be careful even with the way we define energy in an expanding universe.
Unfortunately, the disasters are back since this morning :(
OMG, it's the same article I found and read right after reading your first comment and doing some Googling about the topic. xD
Yeah, I totally agree with what you said after the initial misunderstanding got cleared up now.
Ouch! Really hope nothing too big or unmanageable. :(Ahaha nice coincidence. In fact, it is not the first time I get to this blog when browsing extra material online. This is a very good one.
Manageable, but painful emotionaly.
Sorry to hear that man :(
This is how it is, unfortunately...