Again, crash into what?
Well, and is that not the problem? A vast tract of empty spacetime, outside the solar system, would be nothingness. Homogenous, isotropic and at equilibrium. From what I understand, an equilibrium state is apex, meaning that it is inherently unstable. All that nothingness, beyond our local light cone, would have a natural tendency to exit its equilibrium state.
In other words, we might be absolutely alone for a while, but probably not forever.
Of course all the matter disappearing in the Universe leaving our system in all of our models, so if you’ve broken the model already you can say what is the point in asking what it predicts. It would be like asking someone five years ago if Donald Trump was elected president would he build a wall on the Mexican border? (NB not a political comment against or for Mr Trump just a joke!).
Of course we can still take some basic principles and ideas from our models and what we largely know is that the effect of the rest of the Universe beyond the solar system can be described as a small perturbation of the solar system considered as an isolated system. Therefore if I had to give answer I would say that small perturbation would disappear having minimal effect, but note the situation is as impossible as Leicester City winning the Premiership.
Do you really want to argue with Newton’s First Law of Motion? What force would cause it to stop?
This situation would occur only if the disappearance of the rest of the universe included spacetime as well. It is a hypothesis that participants to this thread regard as absurd. For me, the disappearance of 99.9(9)% of all matter in the universe is just as freaky, but who cares. So, I’m just saying - for those who care - if the rest of the universe including matter, energy and spacetime disappeared, the Sun would suddenly find itself like a bullet within a firing gun whose muzzle is sealed. That kind of crash.
I guess the question aims at this very aspect. Is the continuance of the solar system in the absence of everything else a viable model? It is like asking whether a particular equation can have a solution or not.
Again, the question in the OP is not clear. Okay, I understand, spacetime stays and only celestial objects disappear. But that would not include the vacuum energy and quantum fluctuations on an unimaginably vast scale. As I understand things, the existing matter comprised by celestial bodies is the expression of the universe’s current state of equilibrium. When 99.9(9)% of all the matter goes poof, there will be more intense and complicated fluctuations, possibly vacuum catastrophes and the like.
This still seems to a version of arguing about Mach’s principle.
If inertia is a result of motion relative to the universe’s background of mass, if all that mass vanished, your inertia vanishes as well, as there is no longer anything to be moving relative too. So the notion that there should be a residual proper motion, or residual energy that somehow needs to be conserved in some other form doesn’t make sense. It only existed because of the background matter. The conservation laws require this background matter in order to work. No background, no conservation. In the local solar system, it would be assumed, some local conservation laws still work. But conservation of momentum against the background of the universe stopped when that background went away.
To make an analogue. If a bank owes you $1000 (i.e. you have this in your account) and the bank vanishes from the face of the planet, you don’t suddenly find you asset transferred somewhere else. You no longer have the money. Indeed the money no longer exists. (cf fractional reserve banking.)
Given there is not a huge amount of support for Mach at the moment, and there is no known way to understand what it means for the rest of the universe to vanish, there is of course no proper answer. Most answers are more along the line of “What would you like the answer to be? Then we fit the unknown physics to match.”
If you forgive lack of rigorous knowledge of physics and bear with my persistence, I think if the bank vanishes (together with my money) there wouldn’t solely be an asset loss - there would a wide range of financial/economic, social and even political implications. Personally, the National Bank would compensate for my loss (according to the local laws here).
Mass is energy ultimately. The mass people refer to in this thread is the result of the universe’s current equilibrium. Once this mass is gone, is there a reason why the remaining energy cannot lead to the formation of additional mass? One can wipe out any remaining energy and the possibility that new mass should be created only if the spacetime outside the solar system vanished too, but apparently people here don’t want that. One can’t have one’s cake and eat it too. Either the entire mass, energy and spacetime surrounding the solar system disappears completely, or there is spacetime left with its additional energy and potential mass (whose formation would not take long due to the disequilibrium created by the very disappearance of the existing mass). I think.
As far as I can tell, he means The Edge of the Universe™.
Our current universe has no edge, and even if all but a small pocket of it disappeared, we don’t know that that pocket will have an edge. It’s possible that it would wrap around, like a video game where, when you go off the left edge of the screen, you reappear on the right.
That’s probably the best answer, but I suspect an unsatisfactory one to people posing these kinds of questions.
When considering the change of the Sun’s velocity, I considered this very idea as well. I realized that the resulting Sun’s movement may be rectilinear within the three dimensional reality but keep a circular orbit along a fourth macro dimension. I know of theories putting forth the existence of an additional seven or eight micro dimension but I’ve never heard of a cosmological model of our universe where tesseracts really existed.
With nothing else out there, there would be no heliopause
Perhaps, then it might be more interesting and useful to ask a slightly different question? Suppose that perhaps a million years ago the Sun had a close encounter with a massive object that caused it to assume a trajectory leaving the Milky Way and heading into void space and that for human history, the Milky Way has only been visible simply as a discrete object in a black sky. Would other galaxies be visible? (Or maybe it was 65M years ago and the end of the dinosaurs was a side-effect.)
This was a major plot point in Greg Egan’s early novel Quarantine – the solar system was somehow cut off from the rest of the universe for unknown reasons.
Also, about the only thing I remember about Robert Metzger’s book Picoverse is that it involved creation of solar-system-sized universes.
I’m really alluding to the time before bank regulation. Avoiding too much of a sidetrack, but fractional reserve banking creates money, and in the same way as it is created, it can vanish. Much like if the stock market crashes (and the two are not exactly distinct things.)
There is no ultimately about it. Energy isn’t a final state for mass. If you have energy, you have mass. Right there at the same time. Indeed, right now, almost the entire mass of your body is in the form of the binding energy of the quarks forming the nucleons.
What remaining energy? If the mass is gone, the energy is gone. Like you said, they are the same thing. It isn’t a matter that one is a surrogate for the other, or somehow the two are separate things that are always found together until one magically vanishes. Say you have 100 mass units, and 99 of them vanish. You have 1 left. That is it. One mass unit. You can say you have 100 equivalent energy units, and 99 of them vanish, you have one energy unit left. Same thing.
Again - what remaining energy?
Why should this happen? We can work with the physics as we know it, and break as little of the currently known laws as we can, or, given we have already wiped out a goodly part of them, I guess we can come up with whatever fable one likes.
But you are adding additional plot to the story. The OP said the external universe vanished. Now you are saying there is a new plot line to the story where there is special ‘potential’ mass inherent in empty spacetime. Sure, given we are making up the story as we go, there is no reason why not. Personally I’m waiting for the Great Old Ones to appear. That should spice things up. Given there is no known physics that can make mass/energy disappear, why we should expect there to be a ‘disequilibrium’ if it does isn’t clear. No reason why not, but exactly the same reason why. Making stuff up is fun. But once you start doing so, realise that it is fiction, and it is a stylistic choice what you go for, not anything underpinned by science.
Whether other galaxies would be visible depends on which direction the system is headed. Right now, there are only a handful of things outside our galaxy that are visible with the naked eye. Two of them are the Magellanic Clouds, and they’re small and close to our galaxy, so are unlikely to be visible at that distance.
The others are the Andromeda and Triangulum galaxies (M31 and M33), which are both in more-or-less the same direction. If the direction the sun is headed does not take us significantly further away from them, they’d be visible. Or if the direction is somewhat away from them, it could be that Andromeda is visible but M33 is not.
It’s also possible that the Sun could be near one of the many very small irregular galaxies in the Local Group. Ludmark’s Nebula, for example. We only know about 50 or so right now, but there’s expected to be hundreds of them.
End of the Universe. You know, where that restaurant is.
The sun’s orbital velocity around the galactic hub is 143 miles/sec. If we assume 100% transfer of momentum to a right angle trajectory out of the galactic plane, in one million years it would have moved 765 light years. It would still be within the galaxy – the Milky Way is on average 1,000 light years thick. The universe as a whole when viewed from earth wouldn’t look much different. The Milky Way also wouldn’t look vastly different.
If it happened 65 million years ago the solar system would be 50,000 light years away, which is 1/3 the distance to our closest satellite galaxy, the Large Magellanic Cloud. In this case the universe as a whole still wouldn’t look much different.
The Milky Way itself would look different as viewed from earth. The solar system would be about 1/2 the diameter of the Milky Way away from the galactic plane. Unlike as depicted in paintings and movies, the overall surface brightness of galaxies is quite low. The spiral arms of the Milky Way would not be blazing across the night sky, but you might be able to see them on a dark night from a rural location with your naked eye.
That restaurant is at the end of time not of space.
In order to get the sun to escape the galaxy, you’d have to give it lots more velocity. Otherwise it’ll just be in a different orbit at the same distance (going into the galactic halo is not escaping the galaxy). But your basic point is right; even if you increased it by a factor of 10, it’d still not be a long ways out of the galaxy in a million years. So I suggest that the velocity be increased by a factor of 10 and the ejection event be moved back to, oh, a half a billion years ago. Something along those lines, anyway.