[Klaustrophobia]

Well, unless our understanding of physics is totally wrong, I have no reason to question our understanding of physics.

it's not a question of our understanding of physics, it's the complexity that would be required to actually model something like a galactic collision.  and after that it's a question of processing power.  i understand what you are saying about a probabilistic approach, but personally i still call that a guess.  one thing i've learned from my time in uni is that whenever scientists start throwing around the word "probability," it frequently means "we don't have a ****ing clue."  it's mind-numbing how many "probablitites" are COMPLETELY made up, because there is no way to actually determine them.

[peterv]

i seriously doubt a simulation that could predict what will happen to our sun to a degree of accuracy that could be considered more than a wild guess will be possible for MANY years to come.

Also, our knowledge about the chart of the Milky - way and Andromeda is (very) incomplete. As watsisname said we can only deal with probabilities, based on very pour databases.

[Pred the Penguin]

No one with a human life-span would ever be able to notice the changes happening in any case.

[Kolgena]

Well, unless our understanding of physics is totally wrong, I have no reason to question our understanding of physics.

it's not a question of our understanding of physics, it's the complexity that would be required to actually model something like a galactic collision.  and after that it's a question of processing power.  i understand what you are saying about a probabilistic approach, but personally i still call that a guess.  one thing i've learned from my time in uni is that whenever scientists start throwing around the word "probability," it frequently means "we don't have a ****ing clue."  it's mind-numbing how many "probablitites" are COMPLETELY made up, because there is no way to actually determine them.

Just use nVidia PhysX 

I kid I actually have a friend who models systems of stars, and he says that it's all about getting reasonable performance while maintaining goodish (not so goodish?) accuracy.

[el_magnifico]

Moreover, there is a small chance
that the Sun will be more tightly bound to Andromeda at
some point during the merger. In such a case, Andromeda
will capture the Sun and future astronomers in the solar system
might see the Milky Way as an external galaxy in the
night sky.

So, if we're still around and colonizing other star systems, that means our presence will eventually expand to cover at least two galaxies?
I'm not sure if that is good or bad for the universe...

[watsisname]

it's not a question of our understanding of physics, it's the complexity that would be required to actually model something like a galactic collision.  and after that it's a question of processing power.  i understand what you are saying about a probabilistic approach, but personally i still call that a guess.  one thing i've learned from my time in uni is that whenever scientists start throwing around the word "probability," it frequently means "we don't have a ****ing clue."  it's mind-numbing how many "probablitites" are COMPLETELY made up, because there is no way to actually determine them.

Please reread what I have presented you.  The reason we don't know for sure where the sun will end up is because we don't know where the sun will be in its orbit when the merger happens.  That's because we don't know exactly when the merger will happen.  If we did, we'd have a much better idea of what the result would be.  So in the meantime, we examine all possible outcomes for stars that can represent the sun in the merger.  Nothing is simply "made up".

And as it stands, our ability to model mergers is extraordinarily accurate.  They reproduce what we actually observe to a striking degree, including the formation of ellipticals, ring galaxies, and tidal streams.  We can even tell which features will be created from what types of mergers.

In short, saying "we don't have a a ****ing clue" is utterly wrong and I'd appreciate it if you didn't knock the science without reading more into it first.

[Rodo]

And then the red shivans from our galaxy meet the green shivans from Andromeda, and all hell breaks loose.

[redsniper]

Christmas Shivans!

[Shivan Hunter]

omg JAD4 ideas

[Bob-san]

it's not a question of our understanding of physics, it's the complexity that would be required to actually model something like a galactic collision.  and after that it's a question of processing power.  i understand what you are saying about a probabilistic approach, but personally i still call that a guess.  one thing i've learned from my time in uni is that whenever scientists start throwing around the word "probability," it frequently means "we don't have a ****ing clue."  it's mind-numbing how many "probablitites" are COMPLETELY made up, because there is no way to actually determine them.

Please reread what I have presented you.  The reason we don't know for sure where the sun will end up is because we don't know where the sun will be in its orbit when the merger happens.  That's because we don't know exactly when the merger will happen.  If we did, we'd have a much better idea of what the result would be.  So in the meantime, we examine all possible outcomes for stars that can represent the sun in the merger.  Nothing is simply "made up".

And as it stands, our ability to model mergers is extraordinarily accurate.  They reproduce what we actually observe to a striking degree, including the formation of ellipticals, ring galaxies, and tidal streams.  We can even tell which features will be created from what types of mergers.

In short, saying "we don't have a a ****ing clue" is utterly wrong and I'd appreciate it if you didn't knock the science without reading more into it first.

I'm going to make a rash assumption and say that projects like Milkyway@home have been helping up the accuracy of our simulated galaxy. Anyways, I'm actually more curious about the actual effects of the merger on systems. Will there be intense radiation? More eccentric orbits? Influx of debris? Major bodily collisions? Et cetera. And if a system is thrown out of the galaxy (or galaxies), what issues will it have?

Basically all of this is purely theoretical stuff; if humanity even exists in hundreds of millions of years, they'll either know it or be ignorant to it (because what are the odds of them being at this point of the information age?).

[watsisname]

Giant post incoming!

If a civilization finds their sun thrown out of the galaxy, then I think it's kind of a bittersweet outcome.  Obviously on the one hand they're much more isolated from other star systems, so unless they have some really nice FTL or long-term bio-stasis technology then they're kind of stuck there... but on the other hand that means they don't have to worry about the chance of getting wiped out by a nearby supernova or something of that sort.  I'd think it's a better fate than plunging through the dense galactic center, honestly.

I can't say much for the question of radiation, because IIRC there's much about the galactic magnetic field that we don't know about yet.  I can say that it's pretty much inevitable that the merger would send material towards the supermassive black holes at the center of the galaxies, thus causing a lot of accretion and giving off a great deal of radiation.  Most of that radiation ends up being spewed out in polar jets though, so it might not be too big of an issue as that'd be directed away from us.  But if we were sent through the galactic center, ehhhh... that might not be so healthy, but I wouldn't know.  At the very least it'd make the night sky a lot more full of stars.

The effects on planetary systems is minimal at best.  The distance between objects is great enough such that the chances of there being collisions between stars or planets is virtually nonexistent (though not strictly impossible).  It actually shouldn't happen much more frequently than it does at any other time, since stars are orbiting the center of the galaxy somewhat haphazardly to begin with.  Stars belonging to the halo and bulge especially, as their orbits are highly inclined relative to the disk.

For a more convincing argument of this, just look at globular clusters.  The stars have chaotic spherical orbits and the star density is much higher than you'd find in most areas of two merging galaxies.  Since we don't see signs of stars smashing each other in globulars, it's pretty safe to say that collisions must be extremely rare.

So with all the stuff that doesn't happen during a merger, what does happen?

Well, although stars don't really hit one another, molecular clouds most certainly do, and this should trigger a burst of star formation.  We see this happening pretty often actually, where a galaxy interacting with another one undergoes a fit of star formation.  We call these starburst galaxies, and the Antennae Galaxies are a great example.

Also, with the Milky Way and M31 being both large and comparable in size, we also expect that they will eventually form a single large elliptical galaxy, though this is a slower process.  Eventually the tidal streams are essentially "smoothed out", leaving a big (probably spherical) agglomeration of stars.  The burst of star formation will also end once most of the available gas has been either consumed or dispersed, and as the elliptical ages it will become yellower in color as the bluer, more massive stars die out.


tl;dr, mergers don't do much on the local scale.  Stars don't really hit each other and planetary orbits are mostly undisturbed.  The significant effects are generally on the galactic scale.