collisions between galaxies

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Mardav, Nov 19, 1999.

  1. Mardav Registered Member

    Red shift data indicates that galaxies are moving apart. Information on the formation of galaxies states that the varying shapes of some galaxies are due to collisions.I know that galaxies are grouped in local clusters and superclusters.

    How can collisions occur if galaxies are moving apart?
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  3. Oxygen One Hissy Kitty Registered Senior Member

    They are 'moving apart' only in relation to the assumed center of the universe. They can still run into each other on their way 'out' due to various factors such as individual speed and direction.
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  5. Rock Registered Member

    I just wanted to insert a caviat here (about the center of the universe) for Mardav, Oxygen, I'm not trying to counter your statement. Basically I'm just expanding on it.

    Oxygen's statement about the galaxies moving away from the theoetical center of the univese is in reference to a center which is not part of what you see as the universe.... it's rather like living as part of the surface of a balloon.

    Here you are, a two dimensional being in a two dimensional world (the balloon) but it's expanding, this is shown by your astronomers using the redshift of your balloon's stars, galaxies, etc.. The direction in which it is expanding is perpendicular to the two directions which you are familiar with in your daily life. In fact, it's in a dircetion completely unfamiliar to you in any of your experiences (except by analogy to when you blow up a loop of string which you call a "circloon" in your world).

    The center of your balloon world is equidistant from ALL points in your spacetime, that is, no point on your balloon world has ever been closer to or farther from the center than any other point at any given time. (Discounting the time dilation effects of relativity, we're keeping it simple here and assuming that Newtonian absolute spacetime works well enough to describe the spatial relationships of different points on your balloon.)

    Although the surface of the balloon world is expanding, the objects on it can, in fact, must move around. Those which are fairly distant from each other will likely never interact beyond electromagnetic and gravitational means. Those which are fairly close together, however, will feel each other's influences pretty strongly. They will fall together at a rate determined by their masses and inversely proportional to their separation.

    While all this is happening, the Hubble constant shows the effects of expansion on the fabric of your balloon world, as well as upon waves travelling along its surface (they get stretched out, redshifted). Points in space close together move apart only very slowly and this is easily countered by low speeds; points far apart move apart more quickly, being the sum of expansion of a much longer distance, and this means that two objects must travel towards each other much more rapidly just to stay in one place.
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  7. steadystate Registered Member

    The following theory would easily allow for the collision of galaxies. I just read about such a collision in "Science News", an excellent weekly mag for us laymen.

    What would a universe look like with the following assumptions/characteristics:
    1.Time had no beginning, so is infinite;
    2.The universe has no physical distance limits, so one could go an infinite distance in any one direction, and not return to the starting point;
    3.The universe has no limit on the quantity of mass and energy;
    4.Multiple Big Bangs are occurring at an infinite number of places;
    5.At an infinite number of places in the universe, galaxies are converging on an already huge "black hole", soon to reach Big Bang mass;
    6.After a Big Bang in one area, galaxies and other mass/energy are still converging on
    the area, imparting rotational energy to the expanding mass/energy;
    7.Some Big Bangs would have the mass/energy to collapse again;
    8.Big Bangs with low mass/energy expand until individual mass/energy elements
    are captured by a nearby "Big Bang convergence area" (destined to be a Big Bang)?

    I would call this a "New Steady State" theory.

  8. Rock Registered Member

    Your first three axioms describe the Plasma Cosmology; I know only a little about it. It doesn't seem to be discredited, but it hasn't gained much acceptance either. The fourth axiom assumes that a Big Bang requires source mass in order to create the universe. I'm not sure that it's needed, but if it can be used, then the results would likely end up as a new universe whose dimensions are orthogonal to the infinite parent's dimensions (and likely to its siblings' dimensions). 5: is there a Big Bang critical mass? Inflationary theorists have considered masses ranging from 10 pounds down to microgram scale. 6: could the infalling galaxies interact with the bubbles' membranes?

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