How long before we perceive any effects on Earth? (apart from the obvious changes to the night sky…) I’m guessing even the combined gravitational pull of every star in the universe other than Sol is negligible, due to inverse square, perhaps not even measurable. Would it be 1000s of years, 100s of 1000s, before anything serious happens? Never?
I guess we can be sure it would be at least 4.2 years, since the nearest star is 4.2 light years away.
The largest effect would be from the mass of astronomers on the unemployment line.
That’s about the size of it. Very little in the way of heat and light reach us from all the other stars. The night sky would be somewhat darkler, but I suspect nocturnal animals could cope with the loss. Gravitational effects are insignificant. What else is there?
Something tells me that a lot of ships/planes would crash/ground due to the lack of celestial navigation.
And before you say that we have GPS, keep in mind that we rely on a celstial body (the constellation of Aries) during the spring equinox to keep us true.
Tripler
That’s just one of the damned things I learned and kept from college - the Aries equinox thing.
It would have more of an effect on amateur astronomers than professional astronomers. Aside from the fact that the astrophysicists would be the ones asked why it happened, and aside from the fact that within a few thousand years we’ll be able to observe stars in other galaxies with ease, you still have the fact that astronomers in planetary, ISM, galactic, and cosmology would still be working for some millions of years, plenty of time for the stellar astronomers to switch fields.
Physical information travels at the speed of light (about 300,000 km/sec), which would include both the stars’ luminosity as well as their gravitational fields — or sudden lack thereof as is the case here. Since the stars vary widely in their distance from us, they would seem to vanish from our sky in a progression lasting many centuries. For example, Sirius is one of the closer stars, at a “mere” 8 light-years away, whereas Polaris is about 430 light-years away. And, I think there are some naked-eye stars that are over a thousand light-years distant. Give it about 2,000 years or so for the night sky to be entirely devoid of stars.
But not devoid of light quite yet. The Magellenic clouds are a few hundred thousand ly away, and so would take correspondingly longer to disappear. The Andromeda galaxy, now nice and easy to spot with all those distracting stars gone, is over 2 million ly away and so will be around considerably past the point you and I will stop caring. So will many other galaxies.
It’s more like all those stars are evenly distributed around us, approximately, and so their gravitational fields cancel out, approximately. However, the sudden vanishing of all other stars would mean that the solar system would no longer orbit the center of the Milky Way galaxy.
Unh…might be kinda hard to see the non-existent ones:
Right, but the point is, galaxies are at least several 10s of thousands of light-years away, and more typically millions of light-years away. If the stars in another galaxy go out, we’ll still be able to observe them for millions of years thereafter.
There’s thousands of years of back-information coming from the distant ones. If they winked out today, it’d be thousands of years before we realised it.
I don’t know of any galaxies closer than about 2 MY, do you?
Large Magellanic Cloud
In light 
of what others in this thread are assuming, I would like to retract my previous post for fear I may appear impossibly ignorant.
I am well aware that, if distant galaxies ceased to exist, but their light was already on the way to earth, that it would take a very long time for the light, and the subsequent absence of light, to reach us, so they would appear to wink out gradually.
But I assumed the OP meant, “what would happen if the night sky suddenly, instantly displayed no stars?” – so go easy on me.
Hell’s bells! And all this time I thought it was only a little closer to us than Andromeda.
I think that’s a reasonable interpretation too, and I would have gone along with it if it weren’t for the last sentence in the OP. Maybe DarrenS can clarify what was meant?
The above is correct, but as to there being no major results that is a different story. Also if you take that fact into account then the idea that the stars would disappear is false, since we will see the light long after the star is gone.
The only way that stars cease to exist is for them to explode (and then they actually still exist, but are not visible). However here we are dealing with all the stars exploding at once and that type of event just has to have eventual consequences. I don’t think Alpha Centuri would have serious consequences, but Sirius which is only 8.6 light years away may be another story. If that happens then there are some others with 13 light years away, that are large enough to finish off what Sirius started.
If that doesn’t do it there has to be an even larger effect from all the stars in our galaxy exploding at once. Without googling I believe the center of our galaxy is about 15,000 light years away. That means that earth would probably be gone in the next 15,000 years. If you think that isn’t serious, just remember that our star is good for about another 5 billion years.
Oh, and as to gravity, it wouldn’t change since as I said in the beginning even because a star explodes doesn’t mean it ceases to exist.
I reread the OP and it said “ceased to exist”. I wouldn’t even begin to deal with it under those terms, since even in the bible it took God a full seven days. :rolleyes:
If you’re talking about removing all the “stuff” out there beyond us, including the background radiation presumably from the big bang, the temperature of space would conceivably drop by about 3 Kelvin (i.e. 3 degrees celsius colder). I’m not sure what effect that would have on the global weather patterns, but theoretically it could have a significant effect.
But I think there’s more to this question than what meets the eye (literally). Sidetracking from the issue of EM radiation - what effect would their disappearance have on the curvature of space-time itself? Removing all that space-time bending mass would have to have some effect, but I’m having difficulty picturing exactly what. Would it dramatically contract back like a rubber-band? Or would the removal of all that mass just make it so that the unverse would keep on expanding forever with more or less the same shape it has now?
Some great answers here.
Just to clarify what I was thinking - I was indeed considering the case where the stars cease to exist suddenly, in concert. I was curious if any stars outside our solar system (including the Oort cloud etc.) have any effect on us at all, except for the few photons that reach us. I find it interesting that the universe is so “disperse” that everything outside our solar system could vanish, and all it would do is make the night sky less interesting.
Taking th OP’s “cease to exist” literally, which is the point of this thread, wouldn’t all the other planets and non-star stuff turn and head toward the only massive gravity source left (The Sun)?
Peace,
mangeorge
I think that’s about it.
Sol is orbiting the centre of the Milky Way just like the rest of the stars in the galaxy. But none of those stars ever come close enough that their gravitational influence could disrupt our solar system, for example. At those distances they’re not doing anything to keep our solar system ‘in line’ or anything; they hardly affect us. We orbit the Sun, and that’s about it.
If the whole galaxy disappeared, especially the stars in the central bulge (and the black hole at the very middle), Sol wouldn’t have anything to orbit. So, like anything else whose central attracting force has been cut off (like a ball on a string being swung in circles), Sol would just keep going in whatever direction its velocity happened to be at that instant. It would travel away from where the Milky Way used to be. But Sol’s influence on its planets is strong enough that the planets wouldn’t notice.
It’s a big universe.