How does expansion fit in with colliding galaxies?

EndofMysteries

I've seen it described and taught many times that from the big bang, space is expanding and all parts expand equally. Almost like a balloon if you put marks on it, they will move outward equally and never touch each other.

But then I hear about colliding galaxies such as, "the Andromeda galaxy is racing toward the Milky Way at a speed of 250,000 mph â fast enough to circle the world in just six minutes. And it's scheduled to collide, head-on, with the Milky Way in approximately 3.75 billion years."

How does expansion fit it to that? Based on the rubber band, balloon, etc explanations for expansion, it should be impossible that two galaxies collide no?

sir82

Sigh.

Google is your friend.

Village Idiot

I believe, if I'm not mistaken, that expansion is only progressing slowly in our era but is due to speed up in the billions of years to come. It is said that many billions of years from now expansion will get to the point where we won't be able to see anything outside of our galaxy.

OneEyedJoe

It's all about scale. Space is expanding, but that doesn't mean that we're getting noticeably further from the sun. The same works for Andromeda. On a cosmic scale, it's quite close to us and heading towards us. Space between us and Andromeda is expanding, but at a rate that makes the expansion nearly negligible compared to the relative velocities involved.

The Andromeda galaxy is another member of the "local group" (those astrophysicists are just so creative with their names, aren't they?) of galaxies. Their gravitational interaction keeps them in a cluster together for now, and can even cause collisions like the one we're destined for. While the universe is expanding, the immense gravity created by the galaxies grouped relatively closely overwhelms the expansion at a local level.

Marvin Shilmer

How does expansion fit it to that?

How? The same force that draws asteroids to collide with other planetary objects also draws galaxies to collision, when proximity is sufficiently close. Gravity.

Viviane

Googles and maths, how does it work?

disposable hero of hypocrisy

Thanks for asking this, it's something I hadn't even wondered about and even if I had I'd prolly be afraid to look ignorant if I asked. Good question.

Village Idiot

Just as a side comment, this universe manifests both order and disorder but not intelligent design. Jehovah is not a good designer. He should have taken architect classes before creating it.

EndofMysteries

I haven't found any really good answer.

If gravity can overcome the expansion, could there be a scenario where instead of infinite expansion and one day no galaxies seeing anything outside of their galaxy instead be that galaxies collide, creating larger ones with more mass and stronger gravity, and eventually they all eat up one another? (like when droplets of water touch they become one larger one)

Viviane

Then you've not looked very hard.

How does expansion fit in with colliding galaxies?

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