We got here because you know have enough understanding now to get to an issue. This issue causes problems for layman and crackpots because they don't take the effort to resolve an issue and that is Energy and Time. Those two things are needed to resolve the concept of nothing. Ok I will have a crack at it.
Historically when it was first realized classical physics was wrong science had to deal with sort of closing off classical physics so it was consistent as best it could be. GR itself actually gets caught up in this because of energy and time in it's definitions.
So here is a statement of fact if you are using classical physics you must assume conservation of energy of the universe as a whole. If you are using QM you must assume the universe doesn't have conservation of energy, the universe is a perpetual energy machine. So how can two completely different statements both be right?
Well it rolls on definition .. surprise!!! Classical physics has time-translation invariance, the thing Dave Proffitt was playing with. It basically says things like space and time are fixed, not changing with time (and time itself is static) and running a physical interaction backward is the same as running it forward. You saw Dave realized something that it might be important with his playing with black holes.
GR joined time and space together and suddenly you break that condition, spacetime is no longer invariant. So when you are using GR as an interface to classical physics the trick to do is put any none classic energy in the gravitational field itself to stop classic physics imploding. Is it actually valid to do that well yes so long as the problem you are looking at isn't the universe itself, it won't cause you any problems.
So there is nothing wrong with saying GR conserves energy for most of your science, and it won't cause you any dramas but you need to remember what you did.
When we cross over to QM we have to deal with this there is no density of a gravitational field to place the energy in, yeah it really was a trick. We also need to deal with the fact spacetime is evolving, space and time are both changing or can change. Spacetime will likely expand or shrink, the static condition requires an unnatural balancing act. Think of a country economy growing at exactly zero for any prolonged length of years that is the same highly unlikely situation.
What you want in classical physics is the energy to be "worth" a static and consistent amount. So when your photon takes off with a set amount of energy it arrives at a destination some billion years later with the same amount of energy or all the classical laws are going to collapse. In an expanding universe and with classic physics definitions your photon takes off and your universe expands so your energy density decreases (you have more space to fill with the same energy) and your photon appears redshifted so it really is losing energy and then it gets to the destination some billion years later and magically it has the same energy as it left. This usually causes fun trying to watch even scientists explain it and they usually end up lying.
So how does QM-GR resolve the above well you are talking about an observer and what he sees ... it's an observer they see there own reality. The photons reality is it arrives at the destination in exactly zero seconds and hence it contains the same energy as when it left.
Even when dealt with well it's problematic, lets give you an example:
http://www.fnal.gov/pub/science/inquiring/questions/red_shift1.htmlDo you spot the omission in the answer, you can't have a reference frame for the universe so he didn't really answer the question posed. What he did was restore conservation as the question was asked by someone only backgrounded in classical physics. From his answer it is clear to me he knows the full answer he is just trying to simplify it back to the OP.
This is my problem with your "nothing" I have been trying to give it back to you in a way you can deal with in your semi classical physics you are currently using. You keep using me and you references and what we see ... well we see a great many strange things because we are observers.
In essence you are doing the same trick as Dave Proffit imposing your little biased "observer view" as some proxy for the universe as a whole. My warning remains the same as to Dave be VERY CAREFUL doing this you are just a pathetic little observer you don't speak for the universe.
So lets see if you can get the concept just because you see nothing or something just makes it real to you, NOT the universe. Same problem as our little photon, you see the photons losing energy doesn't make it a universal truth. You have got your head around the frame of reference issue for time in GR, you now need to extend that to taking care with any observation you seek to make universal.
From a QM point of view and in your terms the universe can go from minus a pile of something thru zero to positive a pile of something. Is minus something okay with you in that it probably isn't what you would call something but it also isn't zero. If I can have that then I can sort of agree with your statement.
My concern isn't about your definition (you seem to think it is), it is after getting you to think relativity the first thing you have now gone and done is put a big absolute in the middle and called it "nothing". So I am seeking clarification on what observer or are you really trying to say that for everyone AKA what Dave does with time.
