Universe expands, galaxies collied ???

Question

This article
http://news.yahoo.com/s/nm/20070515/sc_nm/space_matter_dc
brought me to this question. How come that while universe is expanding and everything is getting away from each other, this article shows evidence of collision between galaxies ?
This would suggest that at some point those galaxies has not been moving away from each other. As far as i understand this codtrudicts some theories...

Answer 1

it does seem odd that galaxies would collide when they are supposed to be getting farther apart.

however you must realize that galaxies colliding is only one small part of the universe. even a huge galaxy cluster is small compared to the rest of the universe. so right now we are moving towards the andromeda galaxy, our little local group is moving towards the virgo supercluster of galaxies, but if you look elsewhere you will see that galaxies are moving away from us due to the expansion of the universe.

so galaxies colliding does not contradict the universe expanding, you just have to open your vision up more. one part of space might be collapsing but overall space is expanding.

Answer 2

Hmmmm....That's very interesting. I'd read of dark matter and dark energy before and how their existence has been proposed as an explanation of the apparently anomalous movements of some distant galaxies.

This assumption is partly founded on the precepts of the "big bang" theory. This theory, which seems to have taken pretty firm hold, basically states that the whole universe originated from a "primordial explosion" at a single point in (ahem) empty space. (Or non-space, if you like.)

So...just a thought: what if the "big bang" theory is not quite correct? Why is it essential to work from the assumption of a single explosion from a single point? Is it completely unfeasible that there may have been multiple points, and even that the explosions did not occur simultaneously? (Yes, I know time concepts such as simultaneity are problematic here but I have to use some kind of terminology to make any sort of sense of what I'm trying to say.)

I'll put it this way...If the theory of a singular primordial explosion is not correct, then the only alternative is that there was some other non-singular (or unique event) process that resulted in our known, physical universe. In that case, if there were multiple "creation points" (to use the term but in a non-religious sense), then sooner or later it seems reasonable that collisions of galaxies would occur. Or have already occurred, actually, seeing as the light from them has taken an awfully long time to reach us.

Okay, I know that many physicists will jump up and down (or oscillate about a mean position in some other way) and protest that the "big bang" theory explains things so perfectly that it must be correct. That doesn't mean, however, that it's the only possible explanation. It is, after all, only a theory. :)

It's also interesting that some of the observed distant galaxies are not only moving away from us, but they are actually accelerating...It was this observation that rang so many bells for scientists and led to the proposition of "dark energy", far as I know from what I've read....

Anyway, there's my two cents' worth :)

Answer 3

Your suspicions are not unreasonable. In order to explain the collapses, they had to invent "dark matter". Dark matter would supply all the missing gravity to support the big bang theory. The big bang is just an unproven theory. As we learn more about the universe, it seems to contradict the big bang. There are guys that still want to believe it so they invent more abstract ways to explain it. The universe could be electrically connected and stars could be merely inductively coupled plasma emmisions. That would require a much much smaller universe and would explain why the pictures of supposedly far away galaxies are so clear. If the big bang were true, there should be more distortion the further away you look. However, now matter how far we look, the pictures are crystal clear.

The picture you are looking at can be just a common wave function diffraction pattern. They even say it looks like a ripple in a pond, a classic wave pattern.

Answer 4

I personally do not think that galaxies can collide.
I have seen pictures and computer simulations of colliding galaxies but I do not believe it is an accurate illustration of reality.
Galaxies do move away from each other the expansion is not accelerating.
A galaxy is an end stage in the evolution of a universe,and activity at the galactic center would prevent any sort of collision.
The same activity produces a red shift that is interpreted as an accelerated recession.

Answer 5

The expansion of the universe is such that it is undetectable at small distances. 'Small' here means distances less than the distance between galaxies. But even at the distances between close galaxies, the 'peculiar motion' of the galaxies, due to gravity, etc, can be enough to overwhelm the overall expansion. This was actually one of the biggest difficulties in getting accurate measurements of the overall expansion: the nearby galaxies don't move away fast enough to outpace their peculiar motions and the distant galaxies were difficult to determine their distances accurately.

In general, the gravity inside of a cluster of galaxies is enough to overwhelm the expansion effects. Once you get to larger structures, you do see the expansion.

Answer 6

well, suppose there are three galaxies....
as the universe is expanding with an fixed speed.
now, the distances in galaxies are 1-2=1 million ly ; 2-3=2 million ly.....
now after so many years, if we calculate the distances, they will be 1-2=2 million ly ; 2-3=4 million ly....

if you draw a diagram, it will be in ur mind quickly... all galaxies were at a distance early.... and they are moving away from each other at the speed of expansion of universe and they are going away from the centre of universe, then how will they collide???
except from very nearby galaxies which have gravity of other on them.. for ex. milky way and andromeda..

Answer 7

the enlargement is an effortless tendency that's more beneficial because the area between galaxies receives larger. for extremely close galaxies, the speed of enlargement is reasonably small and is beaten by utilising the gravity of the galaxies themselves. The Andromeda galaxy is amazingly interior of attain galactic criteria, so the gravity betwen our Milky way and it actual makes them advance closer at the same time. an same interest applies for the galaxies themselves. to truly see the enlargement outcomes, you ought to have distances on the order of tens to thousands of tens of millions of light years. Galaxies are 'purely' some hundred thousand lightyears throughout. via this, the gravity contained in the galaxies is superior than the enlargement.

Answer 8

my guess is the universe is incomprehensible at the moment, so the death and birth of known universe's we can see and you call it collision in you question. Galaxy's, solar system's, are just grain's of sand along an endless beach, and some rub each other, some are twice or ten time's bigger than other's, so the bigger one's have "collision's" with smaller one's, and the result is what we call black hole's, and other thing's, that we just found out been happening for eternity, and us tiny human's, are just a beginning entity is what appear's to be endlessness beginlessness our mind's can't comprehend

Answer 9

It's simple. Galaxies that are close to each other have mutual gravitational attractions that overcomes exansion.