I Is a "collision" of galaxies noticeable on a planetary scale

[maxjon77]

If, as suspected, the Andromeda galaxy "colides" with our own sometime in the far future, would the gravitational forces from passing stars have effect on our solar system?

In accelerated models the interaction looks quite violent, but how would it be in our "uncharted backwaters of the unfashionable end of the western spiral arm of the galaxy"?

 

[EmileJ]

No, it is extremely unlikely this would be noticable inside the solar system.

There is a decent chance our solar system would be moved. There is a extremely small chance of destruction by the supermassive black holes then. If the Sun gets moved, it is most likely it will get moved much further from the center. There is also a small chance the Sun would get tossed out of the galaxies completely and become part of a star stream.

So the constellations would look different. While the speeds of this collision are very high, distances are huge too. Constellations would not change very fast.

Source:
Galactic merger to 'evict' Sun and Earth

 

[kimbyd]

If, as suspected, the Andromeda galaxy "colides" with our own sometime in the far future, would the gravitational forces from passing stars have effect on our solar system?

In accelerated models the interaction looks quite violent, but how would it be in our "uncharted backwaters of the unfashionable end of the western spiral arm of the galaxy"?

Probably not, but it's unclear. Certainly a collision would make for a beautiful light show, and disruption of the solar system is highly unlikely. But it is conceivable that our solar system could be moved close to a more violent location (i.e., close to the galactic core, or near a star-forming nebula)*. Then a planet like the Earth could potentially be sterilized by a supernova or other violent astrophysical events. I'm not sure what the probabilities are, but I think this is still unlikely to occur. Most likely it will just be a change in the night sky.

The Earth won't be sterilized like that, though. It will have already been sterilized by our own Sun as its energy output slowly rises due to the buildup of helium in its core: in about a billion years the Earth will get warm enough that there will be a runaway greenhouse effect which will cause the oceans to boil. So no life on Earth will be around to experience such consequences.

* The reason why I say it could be moved closer to the center, opposed to EmileJ's comment, is that these dynamics are really complex. I totally believe that most of the stars this far from the center will move away, but it's hard to predict these things. It's going to be an incredibly complex interaction when Andromeda collides with the Milky Way. Many stars will be expelled from the newly-merged galaxy entirely. Many will move further out but not be expelled. Many will be closer-in.

And, once the dust is settled, the resulting galaxy will have much less star formation. Which means less and less risk of violent events over time, once that initial period has passed.

 

[Vanadium 50]

And, once the dust is settled

I saw what you did there!