Dark energy has no mass. Neither does vacuum energy, the one necessary to make the Big Bang theory work (inflation, more precisely).
The idea that spacetime can exist and continue in the absence of celestial objects works in a Newtonian model or a pre-Newtonian one. I don’t think today’s cosmologists can accept that 99.9(9)% of the mass in the universe can go poof without affecting the existent spacetime. “[…] in 1915, Einstein introduced his revolutionary General Theory of Relativity. In this, space and time were no longer Absolute, no longer a fixed background to events. Instead, they were dynamical quantities that were shaped by the matter and energy in the universe.” (source: Stephen Hawking, The Origin of the Universe) Thus, if spacetime were to continue to exist, it would do so only because there would be energy and potential mass left.
Both bend spacetime. That is essentially mass. That they bend spactime gravity in a negative direction is an interesting issue, but they do bend spacetime.
You can stop there. You are creating a new story, you can introduce whatever ideas you like. The known laws of the universe suggest that the universe can’t lose 99.9(9)% of its mass, so what happens after an impossible event is pure fiction. There is no physics to describe it. Like I said, my hypothesis is that when the mass vanishes, the Great Old Ones will reawaken. I like it much more. There is scope for a lot of fun, and many sequels.
You can’t start with the current understood physics of spacetime, selectively break a significant fraction of the known laws, and then expect to be able to selectively choose a few of the facts of spacetime to predict what happens. It simply makes no sense except as a bit of fictional fun.
If the rest of the universe disappeared, most of the dark matter and dark energy would traipse away along with it. The theory of dark stuff is closely tied to inconsistencies in our observations of galactic velocities, so it would no longer be a concern anyway.
However, the sun is pumping out bucketloads of neutrinos every second, which travel at near the speed of light, and photons which travel at the speed of light, so the beyond-realm would quickly fill up with an expanding flux of matter and energy.
More importantly, how big is our solar system? The theorized Oort Cloud is thought to extend out 10Pm or more. How do you decide where the last qualifying body or vapor is?
Somehow I feel this thread deserves a better conclusion.
It’s pure curiosity. Several times now I’ve decided to stop poking my nose into a subject that I know I’m so weak at. But there are several thoughts related to ideas in this thread that keep nagging me (although there are hordes of things in ‘real life’ to keep me busy). Here are some of these thoughts.
Is the question in the OP really meaningless? Is it worth wondering what would happen when everything else except the solar system disappeared? Of course, everything else except the solar system cannot just disappear – it’s like the entire universe would disappear. Since there’s nothing in the laws of physics that would allow for it, the question seems absurd and anyone producing a scenario in which he/she imagined the consequences of such an impossible event may appear to speak gibberish.
However, thought experiments often include an impossible premise with the purpose of challenging conventions or revealing a hidden reality. The ‘hidden reality’ in this thread might be the idea that spacetime is not a shell that can be filled or emptied at will. The existence of space and time is closely determined by the existence of mass and energy.
The Big Bang theory includes complex notions, such as singularity, inflation or vacuum energy. A layman like me lacks the tools to scientifically assess the validity of the theory. My choices are limited, so all I can do is stay informed and judge the information with the poor critical apparatus at hand. One thing is clear though. If singularity, inflation and vacuum describe things as they have happened, there is nothing in the laws of physics that wouldn’t allow them to happen again.
There is a great deal to be said in support of such thought experiments. Where perhaps you go off the rails is in taking them too far too quickly, and presenting not so much the ‘what if’ but the ‘this is what happens if’ as a fully developed conclusion.
The idea that empty space creates mass is something Fred Hoyle proposed as part of the “steady state” theory of the universe. (Well he proposed that mass filled the expanding void, but close.) For a time there was some credence placed upon the viability of this theory until evidence for the big bang became overwhelming. It was Fred that gave us the name “big bang” which he coined as a derisive moniker for the theory.*
Mach’s postulate was something Einstein gave a lot of credence to. Einstein wrote to Mach outlining how he thought general relativity supported the idea. (The relationship between Einstein’s work and Mach’s is quite something in its own right. )
IMHO Fred is one of the more egregious omissions from the Nobel Laureates. Sadly he went a bit off the rails in later life, which probably poisoned his chances, but his work on nuclceogenesis is pivotal to our understanding of the universe, and a brilliant bit of work that meets every criteria for a trip to Stockholm.