As I understand it we have evidence that the small patch of universe that we can detect is expanding. Everything is moving away from everything else. I am curious then how we account for all the evidence that galaxies collide with each other including our eventual collission with another galaxy. We have hubble pictures of galaxies in the process of collision. Something is amiss

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This message has been edited by AdminJar, 02-20-2006 08:47 PM

Thread moved here from the Suggestions and Questions forum.

We like to start all new science or faith topics out in Proposed New Topics. For example, this is definitely not a Coffeehouse subject, more Cosmology or Misc Topics in Creation/Evolution.Which place seems best to you?And are you simply asking how the Universe can be expanding yet galaxies colide?

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Cosmology fits the bill.
When the statement is made: "Everything is moveing away from everything else" What exactly do they mean by that. I have read a fair amount on the web over time but if we use this to show big bang theory then all objects should expand out from a central point so yes...how is it that we account for collisions of such massive structures as galaxies?
Unless they are observing whole galaxy clusters and basing this observation on that. That would mean that Galaxy clusters have rotation or interactive movement of some independant nature to account for the collisions?

Thread moved here from the Proposed New Topics forum.

The question has a very mundane answer.
Space as a whole is expanding and carrying everything with it, but there are simply certain things which can over take the rate of expansion.
For instance the Milky Way and Andromeda are expanding away from eachother, but the expansion isn't great enough to overcome their velocities directed at each other.

I am under the assumption that with an expansion everything should move away from the source at an over all uniform rate of expansion.So what you are saying is that objects such as our galaxy and Andromeda travel on vectors independant of thier original vector which is in a direrection heading away from the point source. Or are are you saying that they are traveling at different rates along the same path?
Something must account for the interaction independant of the overall expansion.This message has been edited by 2ice_baked_taters, 02-23-2006 12:22 AMThis message has been edited by 2ice_baked_taters, 02-23-2006 12:32 AM

Imagine a long, flexible rubber strip.If you pull on the ends it will stretch uniformly. So one inch of it will turn into two and one foot into two feet. You pull it so it doubles in length each minute.Now imagine two ants that are one inch apart and that can walk at two inches per minute. Two ants that are one inch apart and walking toward each other can collide.Two ants that are one foot apart can not.The increase in distance between them is the "expansion velocity" ( think that is the term ????) and the walking they do is the "proper motion".

Yes I know....the ants are "on" the rubber band.So under the context of big bang, there is a vast amount of interaction counter to and or independent of the theory of big bang. In other words the universe is expanding as a whole but many parts of it are doing thier own little thing in addition?

The interaction isn't "counter to or independent" of the big bang theory. The big bang is the expansion ("streatching") of spacetime itself. Moving around within spacetime is separate from that expansion. The theory doesn't say that you can't move around. In fact, it's not clear to me that the increase in distance due to the expansion of space is actually "moving" since the objects (galaxies in this case) stay in the same piece of space; they don't move.This is analogous to an ant standing still on the rubber sheet It is not "moving" relative to the rubber. The rubber is the universe of course.This message has been edited by NosyNed, 02-23-2006 11:24 AMThis message has been edited by NosyNed, 02-23-2006 11:25 AM

Essentially the expansion of space is an altering of the "distance field" (or the metric to give it its correct name).Lets assume the universe has only 2 spatial dimensions.
And lets say the distance field has the form ds = dx*t + dy*t.That is, the distance between two objects is the difference in their x direction values multiplied by the time added to the difference in their y direction values multiplied by time.Lets say we have two galaxies, one at x=2, y=9 and another at x=4, y=15.
This mean dx=2 and dy=6.Now lets look at expansion.
Lets start of at one second, that is when t=1.
The distance field has the from ds = dx + dy
Since dx=2 and dy=6, ds=8. So the distance between the galaxies is 8 at one second.However lets zoom to 16 seconds.
The distance field now has the form ds = 16*dx + 16*dy.
So ds = 16*2 + 16*6 = 128.So the distance between the two galaxies has gone from 8 to 128 in 15 second even though they are still at the same points.

like the electrons creating a sphere of influence around the nucleus of atoms in my body must follow the general direction of my body when I take a walk? Yes, this hints at what I still cannot put into words.

The universe is expanding and as such everything in it is being moved
along with the expansion. For the most part "everthing is moving away from each other" simply means that the mass in the universe is fixed but the space in which it resides is getting bigger, so the distances between the mass are growing. This does not mean that mass within the universe cannot have a velocity and direction that could cause it to impact other mass. There is more discussions on this topic at Space KB, if you are interested.

Unfortunately, analogies distort the true understanding of the theory.Mathematics paint the clearest picture but obviously, most people don't grasp basic mathematics, let alone the math that is used to explain the entire universe.In any event, this archive can explain the answers to your questions much more clear than I can.- Evidence for the Big BangIf you read through the information and have questions, feel free to ask and I will do my best to answer them the best that I can.This message has been edited by complexPHILOSOPHY, 04-28-2006 02:54 PM