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Thread: Is there really an accelerating expansion of the Universe?

  1. #1 Is there really an accelerating expansion of the Universe? 
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    I am a little confused as to how cosmologists think the Universe is expanding and that this expansion is accelerating.....

    My reason for this confusion is this. If we peer into deep space then in effect we are looking back in time so the deeper you peer into space the further back in time you go. Cosmologists say the deeper they look into space the faster the galaxies are moving so they use this as a statement that the Universe is expanding but they are looking back into the past so surely that must mean the galaxies were moving faster in the past then they are today.

    Please help me to get this clear in my mind and explain this conundrum?

    Tony


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  3. #2  
    Forum Ph.D. Nevyn's Avatar
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    The theory is that the universe is expanding and that rate is increasing. The origin of the universe is widely debated but let's go with the Big Bang theory. The universe is said to have started with an explosion with all the matter in the universe being cast out from a central point, let's say we are looking at the universe 2 hours after the BB. The speed of the univere will be greater at the edge than that near the centre. As the universe has not stopped expanding and is still accelerating, then as we look further into space, we should see what you are saying

    I think...


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  4. #3  
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    Quote Originally Posted by Nevyn
    The theory is that the universe is expanding and that rate is increasing. The origin of the universe is widely debated but let's go with the Big Bang theory. The universe is said to have started with an explosion with all the matter in the universe being cast out from a central point, let's say we are looking at the universe 2 hours after the BB. The speed of the univere will be greater at the edge than that near the centre. As the universe has not stopped expanding and is still accelerating, then as we look further into space, we should see what you are saying

    I think...
    There appear to be two errors, at least, in your statements.
    1. The Big Bang was not an explosion. That is an unfortunate analogy for it suggests, as you have stated, that matter was cast out from the centre. That sounds as if there is something for it to be cast out into. Such is not the case. The expansion of the Universe is the expansion of space itself.
    2. There is no centre, or alternatively we are all at the centre, everywhere in the Universe.
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  5. #4  
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    Quote Originally Posted by Ophiolite
    2. There is no centre, or alternatively we are all at the centre, everywhere in the Universe.
    Somehow that doesn't seem realistic. As far as i know the accepted theory is that the universe is NOT infinite, so how are we all at the centre? Wouldn't the centre be the point in the universe where the big bang started?
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    If you assume there is a centre then you are implying an edge or end also, which means there would be something outside, this simply cannot be as the universe IS everything. The current model(s) of the universe sugget there is no edge no centre, that whatever your position it will you appear you are the centre of your universe...
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  7. #6  
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    But wouldn't that be implying that the universe is infinite?
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  8. #7  
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    The earth doesn't have an edge but has a center.
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  9. #8  
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    think of the universe as an inflating balloon. The centre everything started is now inside the balloon, so not on the surface and every point on the surface is equally legitimate to each other.
    where are we? what are we?
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  10. #9  
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    Yeah i kind of realised that with my earth analogy. Damn.
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  11. #10  
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    I am sorry guys but you still have not answered my original question.
    When we look back into deep space we are in fact looking back in time and the further back in time we look the faster we see galaxies moving so surely this means that in the early Universe galaxies were moving faster than they are today, yes or no?

    Tony
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  12. #11  
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    Quote Originally Posted by Uclock
    I am sorry guys but you still have not answered my original question.
    When we look back into deep space we are in fact looking back in time and the further back in time we look the faster we see galaxies moving so surely this means that in the early Universe galaxies were moving faster than they are today, yes or no?

    Tony
    Tony,

    The reccessional velocity (how fast they appear to be moving away from us) is referenced to our own position. As I undrestand it, it is thought to be us that is moving at incredible speed away from 'them' all galaxies are supposed to be moving apart at higher rates with time.

    So if the galaxy you are looking at 12BLY ago is stationary your would still see the redshift as we move further [and hence faster] from it. OK?
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  13. #12  
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    The universe, (As I like to vision it) is finite with no edge or boundaries. I believe that matter warps space time onto itself and the fact that we appear to have more matter then anti matter, I think is the reason why our universe is expanding at all.



    I don't really think it matters whether we take into account when we're looking back in time up at the stars, because if you know the entire universe at any one moment, you'll know it's whole history.

    All you need is to take the direction, velocity and distance away to figure out where it oughtta be today if we wanted to visit it.
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  14. #13  
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    Quote Originally Posted by Uclock
    I am sorry guys but you still have not answered my original question.
    When we look back into deep space we are in fact looking back in time and the further back in time we look the faster we see galaxies moving so surely this means that in the early Universe galaxies were moving faster than they are today, yes or no?

    Tony
    yes you are looking back in time. what was then is all you can see as whats happening now has no means to tell you. the energy emitted and only that which we can see, travel at 186,200 MP second. the sunlight as it reflects off the atmosphere was sent a little over eight minutes before and the light in distant objects picked up by the land telescopes or the Hubble, was sent up to 14.2 billion years ago. in fact that image is from a period 9 billion years plus, before our sun was forming. those places as well are long gone or moved from where we observed. if you like the big bang idea maybe now there 27 or so billion years out there.

    according to many those distant objects are moving faster. even the premise of Red Blue shifts in observance is based on how far away the objects are. for many reasons not everyone feels this is the case. in my case its all the near by activity of obvious movements, include colliding galaxy, galaxy heading for another and even in our case a couple dwarf galaxy (small irregular) will absorb into our Milky Way and if you need something to worry about many millions of years from now Andromeda, our nearest spiral galaxy is said to be on course to collide with us...

    in your thinking, remember we as a solar system move along with our galaxy at a fairly high speed, forget the estimate speed, but we as a solar system travel about 700,000 mp hour around the galaxy core...or every 250 million years.
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