if space is expanding and all the galaxies are flying away from each other, how do galaxies collide?

Question

I know Edwin Hubble did not get it wrong, and I understand that it is space which expands, not matter, and light is stretched i.e redshift etc, but I can't visualise these galactic superclusters if everything is supposed to be receding and so fast too. Help!

Answer 1

It all goes back to the big bang. When the big bang "banged" all the matter did not go out in a straight line. i presume you know about momentum (in a newtonian framework momentum is mass*velocity). there is this thing called angular momentum--you get it from rotational motion (where regular momentum you
get from linear motion). the big bang banged and there was angular momentum carried away by the matter and now things are still spinning around each other. Basically, it is what everyone else has said in that the gravity of all the matter affected all the matter around it, which is still taking place now. does that make sense?

Answer 2

You are right up to a point, but you are failing to take into account "localised" gravitational effects. As you know, when matter formed after the Big Bang, it did not spread itself out in an homogeneous fashion. It split into clusters, which later condensed into galaxies. Again, these proto-galaxies were not homogeneous in distribution. Groups of galaxies are known as superclusters.

Within these superclusters galaxies can and do gravitate towards each other. For instance, the Milky Way is part of the Virgo supercluster, and we are actually be drawn towards some of our galactic neighbours.

Answer 3

There are a couple of issues here.

Firstly space is getting bigger - yes the metre is getting longer! This is one of the effects of an expanding universe.

Secondly tthe expansion is on a large scale so local movement - like galaxies in the local group can move towards each other - whilst on a large scale (super clusters) the clusters are moving apart.

Answer 4

the upward push is an average tendency that's bigger because of the fact the area between galaxies gets bigger. for extremely close galaxies, the fee of advance is particularly small and is crushed by the gravity of the galaxies themselves. The Andromeda galaxy is extremely interior of attain galactic standards, so the gravity betwen our Milky way and it certainly makes them improve closer jointly. an analogous attention applies for the galaxies themselves. to truly see the upward push outcomes, you may have distances on the order of tens to hundreds of thousands and thousands of sunshine years. Galaxies are 'in basic terms' some hundred thousand lightyears in the time of. by way of this, the gravity interior the galaxies is extra advantageous than the upward push.

Answer 5

Space is expanding but it doesn't mean the matter within it is receding from the point of origin in a perfect line or even at the same angles. You then have forces, such as gravity, within the universe affecting the direction of movement of matter (galaxies).

Answer 6

The gravity inside clusters can be enough to outweight the overall expansion. Remember that the velocity of expansion depends on how far away two galaxies are from each other. In essence, the galaxies orbit inside the clusters as the clusters move away from each other. Collisions occur in these clusters.

Answer 7

Gravity is the great attractor

Galaxies are massive objects and as such have massive gravity, once and a while they get close enough to be effect by each others gravity and are attracted to one another (even over the massive distances of intergalactic space) and some times they collide

Answer 8

We are going to collide with the andromida galaxy is a few billion years!!

Answer 9

Makes one wonder how many big bangs actually took place, doesn't it?

Answer 10

you have way to much time on your hands buddy