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[Science]Universe Expansion and colliding galaxies

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vincent    154

I'll start off with hubble's theory of the expansion of the Universe. And maybe i'll answer my own question.

hubble's observations that the most distant galaxies are receding from us faster than the closer galaxies can be explained if the universe is expanding in a way similiar to the way a giant raisin cake rises. If you picture yourself as sitting on a raisin, all the other raisins will recede from you as the cake rises. Since there is more dough between you and the more distant raisins, the dough will expand more and the distant raisins will recede more rapidly that closer ones. Similarly, the universe is expanding. we have the same view no matter which raisin or galaxy we are on, so the fact that all raisins and galaxies seem to be receding doesn't say that we are at the center of the universe. Indeed, the universe has no end. (we would have to picture a raisin cake exteding infinitely in all directions to get a more accurate analogy).

Since the universe is uniformly now, we can ask what happened in the past. As we go back in time, the universe must have been more compressed, until it was at quite a high density 15 billion or so years ago. Most model of the origin of the universe that there then was a big bang that started the expansion. A widely accepted model --the inflationary universe --holds that the early universe grew larger rapidly for a short time before it settled down to its current rate of expansion. The big bang itself may not have occured; the firt matter coud have formed as a chance of fluctuation in the nothingness of space.

the temperatures were so high in the first microsecond of the universe that not even the chemical elements had formed. But as the universe cool, first basic atomic particles, such as protons (hydrogen nuclei), and then heavier atoms formed. Still, the universe was opaque until it cooled down to 3,000 oC. When it reaced that temperature, protons and electrons combined to make hydrogen atoms, and the universe at that time has cooled as the universe has continued to expand, and it is now detectable as a faint flow in sensitive radio telescopes. the glow gas a temperature of only 4 kelvins (3 oC above absolute zero) and is our best evidence that the early universe was hot and dense.

Astronomers ask what will happen to the universe in the future. the evidence is not all in. One possibility is that the universe is open -- it will continue to expand forever. Another possibility is that the universe will eventually stop it's expansion and begin to contract. We know that this cannot happen for at least 50 billion years -- at least threetimes longer that the current age of the universe -- becuase we can observe the rate at which the universe is now expanding. Still, if the universe does contract in the long run, then we will have a closed universe that will wind up in a big crunch. the inflationary model indicates that the universe will expand forever. Evidence from the studies of supernovae, released in 1998, seem to indicate that the universe is accelerating it's expansion rather than slowing up. The interpretation as of this writing is that the universe contains energy in a form characterized by a cosmological constant, a term in the equations of Albert Einstein used to describe the universe.

Observations from the telescopes on the ground, from the Hubble Space telescope and the Chandra X-Ray Observatory in orbit, from the Very Long Baseline Array of radio telescopes stretching over the whole of the United States, and from the instruments are expected to help us improve the accuracy  of our forecast of the future of the universe

Now if the space between galaxies is the dough in the raisin loaf, then how are galaxies colliding (galactic collision is a fact btw)? When you bake a rasin loaf, do some raisins bake together? I never baked a raisin loaf :blush:

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username    0

I thought about it too, it would seem that all galaxies should be constantly moving further apart, it is a problem some people have with the big bang theory, there are blue and red shifting stars which means they are moving in different directions, from what i remember from my astronomy class, its said to be caused by the gravitational interactions between the two or more galaxies

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vincent    154
I thought about it too, it would seem that all galaxies should be constantly moving further apart, it is a problem some people have with the big bang theory, there are blue and red shifting stars which means they are moving in different directions, from what i remember from my astronomy class, its said to be caused by the gravitational interactions between the two or more galaxies

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See thats what i'm reading as well. The only reason that comes to mind is the cluster of galaxies that are forming.... we know that our galaxy, andromeda, and some other are part of the Virgo cluster and are gravitationaly bound to each other, but this raisin cake theory disputes that, doesn't it? :blink: Am i missing something?

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username    0

man i have no clue, its over my head, i guess maybe forming black holes help bring them together... which eventually all form back together, resulting in another big bang, which repeats itself forever...

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rob.derosa    6

an easy way around this: galaxy A could be moving away from the 'focal point' of the univerese at such speed. galaxy B could be moving in the same direction away from that point at twice the speed of galaxy A. therefore in the future at some point they will collide.

or it could just be that although the universe is expanding, 'local' graitational interactions within the various superclusters cause the collisions.

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vincent    154

They can't be at the same point though? Unless the particular point is very,very,very huge

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j.nudd    0
an easy way around this: galaxy A could be moving away from the 'focal point' of the univerese at such speed. galaxy B could be moving in the same direction away from that point at twice the speed of galaxy A. therefore in the future at some point they will collide.

or it could just be that although the universe is expanding, 'local' graitational interactions within the various superclusters cause the collisions.

I don't think you mean they both start at the focal point, do you? Ripgut is right, it will be nearly impossible for them to be at the focal point.

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Fred Derf    217
I'll start off with hubble's theory of the expansion of the Universe. And maybe i'll answer my own question.

Now if the space between galaxies is the dough in the raisin loaf, then how are galaxies colliding (galactic collision is a fact btw)?  When you bake a rasin loaf, do some raisins bake together? I never baked a raisin loaf :blush:

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While the universe is expanding, all matter attracts other matter. Matter tends to cluster together and while the two galaxies are expanding outwards together, they are still attracted to each other and they eventually pull themselves together and collide.

One interesting concept is why is the expanding universe accelerating? Before the Big Bang theory, it was thought that the universe was contracting. Einstein attempted to alter his formula for gravity but inserting a fudge factor (a universal constant). He eventually crumpled that idea and threw it in the dumpster.

Since we have noticed that the universe is expanding and we have created the Big Bang theory. What is interesting is that, some scientists are turning back to Einstein's universal constant as a way of explaining why the universe is acelerating as it expands. It may be a form of negative tension, like an elastic band. At any way, I thought it interesting that scientists from today would take an old idea of Einstein out of the proverbial garbage and dust it off.

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vincent    154
While the universe is expanding, all matter attracts other matter.  Matter tends to cluster together and while the two galaxies are expanding outwards together, they are still attracted to each other and they eventually pull themselves together and collide.

One interesting concept is why is the expanding universe accelerating?  Before the Big Bang theory, it was thought that the universe was contracting. Einstein attempted to alter his formula for gravity but inserting a fudge factor (a universal constant).  He eventually crumpled that idea and threw it in the dumpster.

Since we have noticed that the universe is expanding and we have created the Big Bang theory.  What is interesting is that, some scientists are turning back to Einstein's universal constant as a way of explaining why the universe is acelerating as it expands.  It may be a form of negative tension, like an elastic band.  At any way, I thought it interesting that scientists from today would take an old idea of Einstein out of the proverbial garbage and dust it off.

586044873[/snapback]

That makes sense, since gravitational force wins the battle. thanks :)

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davemania    1

The expansion of the universive have nothing to do with galaxy colliding. Universie expansion is about stretchng the space which has nothing to do with the movement of galaxies. The galaxies themeselves have their own movement vectors.

I don't know why scientist like to give credit to Einsteins constant, Einstein used his constant to describe a static universive, although he is probably right that there is a constant but the context in which he used it was wrong.

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Argote    73

Yes, there is gallactic collision, in fact the Milky way and Andromeda are on a crash course

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