   Question about the Big Bang
  Ive been doing a lot of thinking about the Big Bang recently, and Im not understanding some of the ideas surrounding this theory.I do understand that the reason we believe a Big Bang occurred is because of the fact that all galaxies appear to be moving away from ours, giving the impression of an expanding universe.  I also understand that we can tell the galaxies are moving away from us due to the red-shift in the light from these galaxies.And this has always made me wonder.  If the galaxies are all expanding from a central point, the Big Bang Ground Zero in other words, then wouldnt a little calculus tell us what our distance is from said Ground Zero?  If the actual velocities are added to the relative velocities (the ones that cause the red-shift for us) then wouldnt that shift the relative velocities so that we could tell the direction that the Big Bang originated?Whats bugging me about knowing the direction of the Big Bang Ground Zero is that it is said that no matter what direction we look in, we are looking further back in time, due to the space-time continuum.  Some say that the furthest galaxies out are the first ones to form after the Big Bang occurred.  The problem is, this should hold true no matter which way in the sky we look, yet there should only be one direction toward Ground Zero.  Furthermore, wouldnt the fact that these first galaxies being 13 billion light years out mean that the universe is even older than this, considering that it simply took 13 billion light years for the light to get to us, which doesnt account for the time it took the galaxies to get that far out?Am I totally on the wrong track here?   
Quote:Original post by OmegavoltAnd this has always made me wonder.  If the galaxies are all expanding from a central point, the Big Bang Ground Zero in other words, then wouldnt a little calculus tell us what our distance is from said Ground Zero?  If the actual velocities are added to the relative velocities (the ones that cause the red-shift for us) then wouldnt that shift the relative velocities so that we could tell the direction that the Big Bang originated?The traditionaly analogy is that if you draw dots on a balloon and then inflates it, looking at its surface, each dot is moving away from every other, but there is no central point. Or if you prefer, every point is the central point of the expansion.Mathematically, if you take a plane with (x,y) coordinates and start doubling those (x,y)->(2x,2y), you will find that everything is going away from everything else. The point O (0,0) would seem to be fixed, because its coordinates do not change, but that is just an illusion: you could do a change of frame of reference to any other point and it would now appear to be going away, just like everything else. Wherever you place yourself, everything seems to be going away from you, at a speed that only depends on how far they are from you, not on their direction or "absolute" position -- if there were such a thing.Quote:Whats bugging me about knowing the direction of the Big Bang Ground Zero is that it is said that no matter what direction we look in, we are looking further back in time, due to the space-time continuum.We are seeing light that was emitted in the past. How far past is dependent on how far the light source was at that time.Quote:Some say that the furthest galaxies out are the first ones to form after the Big Bang occurred.  The problem is, this should hold true no matter which way in the sky we look, yet there should only be one direction toward Ground Zero.There is no Ground Zero.Quote:Furthermore, wouldnt the fact that these first galaxies being 13 billion light years out mean that the universe is even older than this, considering that it simply took 13 billion light years for the light to get to us, which doesnt account for the time it took the galaxies to get that far out?If you were able to instantly move to one of those galaxies, you would indeed travel more than 13 billion light years, because it is now further away. Yet, if you were to look back at Earth, you would indeed find out that it is 13 billion light years away. You would also find it considerably different from how it looked in the telescope, since you were seeing how it was 13 billion years ago. Which is why it is said that they were the first one to form - they weren't, everything happened simultaneously, but the light that was emitted during their formation is only reaching us now.Quote:Am I totally on the wrong track here?In part. Relativity involves significant mental gymnastic.   ;Quote:There is no Ground Zero.There isn't?  Isnt the Big Bang explosion itself Ground Zero?  I mean, they say the universe began as an infinitely dense golf ball-sized mass, right?  When the explosion occurred all matter in the universe expanded, not only away from itself as you stated, but away from the original location of the explosion as well.  I understand that expansion is going on right now from all points in the universe.  Thats why all the galaxies are red-shifted.  But in addition to that, they should be speeding along away from the original location of the Big Bang explosion right?  It wouldnt be much of a 'big bang' if they aren't.Quote:We are seeing light that was emitted in the past. How far past is dependent on how far the light source was at that time.Right.  So theoretically, if we look back far enough in one direction, we should see a galaxy just as its stars light up.  But then how is it possible that we can look in the exact opposite direction and see the exact same thing?  The Big Bang theory states that galaxies lit up some billion or so years after t=0, when the galaxies were still relatively close together.  Yet our observations tell us that the further back in time we look in 2 directions, the further apart the galaxies were.Looking back in time should show that universe is smaller, yet we look back in time and the universe is bigger.;Quote:Original post by OmegavoltQuote:There is no Ground Zero.There isn't?  Isnt the Big Bang explosion itself Ground Zero?  I mean, they say the universe began as an infinitely dense golf ball-sized mass, right?  When the explosion occurred all matter in the universe expanded, not only away from itself as you stated, but away from the original location of the explosion as well.It's not that all the matter in the universe is expanding outward into space, it's that space itself is expanding, "dragging" everything along with it.  Hypothetically, initially every single point in space was infinitely close to every single other point; they were all at the singularity.  Thus, they all have equal claim to being the center.   ;Quote:Original post by AgonyQuote:Original post by OmegavoltQuote:There is no Ground Zero.There isn't?  Isnt the Big Bang explosion itself Ground Zero?  I mean, they say the universe began as an infinitely dense golf ball-sized mass, right?  When the explosion occurred all matter in the universe expanded, not only away from itself as you stated, but away from the original location of the explosion as well.It's not that all the matter in the universe is expanding outward into space, it's that space itself is expanding, "dragging" everything along with it.  Hypothetically, initially every single point in space was infinitely close to every single other point; they were all at the singularity.  Thus, they all have equal claim to being the center.Yeah, I had the same misunderstanding until recently.  It doesn't help that people are reluctant to come out and say this.  The closest they come is saying things like, "The distance between two objects is increasing".  That's true, but that's also true if their momenta are in opposite directions.  Here, it's not a question of momentum.  It may be helpful to view galaxies as being stationary with space being inserted between them.The balloon example would be more helpful if it were first explained that it's representing a 2D universe.  The example tries to show objects moving apart in a 2D space which is the balloon's surface.  What people see is objects moving apart in a 3D space.  When you say "There is no central point", people think "Yeah there is, the center of the balloon".;  I wrote this back in January but never finished because I dont like finishing things. I even started writing some mathematica stuff to convert into gifs. :(  Most texts which give a lay treatment of the big bang topic fail to impart a thorough picture of what is meant by the whole topic. They tend to leave a misconception that the universe began with the big bang and the big bang was an explosion. That people would think that the big bang was an explosion is not at all suprising. It is after all, called the big bang and Im not sure I know of anything that causes bigger bangs than explosions. But this is a very wrong impression of what occured way back then. The task of this work is twofold, to force help structure a set of free floating concepts in my mind and to give a thorough accounting of the Big Bang. One which would leave little room for assumptions to enter.The first thing to realize is that the big bang does not deal with the begining of the universe, such explorations are best left to philosophers and theologans, they are not addressable by science. The big bang instead deals with the period of time shortly after what some argue was a singularity. The truth of this though is highly questionable as singularities and point.  The universe can have no begining since---I found some notes I began to make:The Universe and a set of points. A the space between the points expandedCases:Finite Size and boundedInfinite but Bounded---Shape of space time At boundaries, things curve to shapeExamples shapesInfinite and Unbounded-No edge just goes on, likely no inherent shapeno begining to timetopological descripyions likely most sensibleGroup of topological structutures that are locally euclidean[Edited by - Daerax on June 13, 2006 5:35:52 PM];Quote:Original post by AgonyIt's not that all the matter in the universe is expanding outward into space, it's that space itself is expanding, "dragging" everything along with it."Dragging" it from where?To say that all points in space in our current visible universe can all claim to be the center, then that means that the universe expands infinitely in all directions.  If we are the center, and the galaxies 13 billion LY away are also at the center, then there are galaxies 13 billion LYs further out than them, and so on, and so on.If this is not so, then the galaxies 13 billion LYs away would be considered at the 'edge' of this expanding space, right?;Quote:Original post by OmegavoltQuote:Original post by AgonyIt's not that all the matter in the universe is expanding outward into space, it's that space itself is expanding, "dragging" everything along with it."Dragging" it from where?To say that all points in space in our current visible universe can all claim to be the center, then that means that the universe expands infinitely in all directions.  If we are the center, and the galaxies 13 billion LY away are also at the center, then there are galaxies 13 billion LYs further out than them, and so on, and so on.If this is not so, then the galaxies 13 billion LYs away would be considered at the 'edge' of this expanding space, right?Nothing is being dragged, more pulled apart. Difference of vocabulary probably the cause of this confusion. Space itself is being stretched. Nothing else is moving. Take a rubber band. Make five random dots near each other on it. stretch it. thats whats going on with the unviverse. Also, did you notice how the dots near to each other behave with respect to those that are far apart?  There is No explosion (nothing moved!), no centre to expansion. As to your question of ad infinitum boundaries, that may or may not be the case. :)[Edited by - Daerax on June 13, 2006 6:04:26 PM];Quote:Original post by OmegavoltI mean, they say the universe began as an infinitely dense golf ball-sized mass, right?No. As Daerax says, we don't really have much idea what it might have been the instant before it 'exploded'. Our physical models start to break down too close to such a singularity. To clarify things, let's expand on the balloon model.The universe is a balloon, it's fabric being space-time itself. Galaxies and things like that are little dots drawn on the surface of the balloon. There is a rule that you can't move faster than a certain speed across the surface of the balloon.However, that speed limit does not effect how quickly you can inflate the balloon. You can inflate it so that the dots appear to be moving away from each other faster than the speed limit, however since the dots aren't actually moving across the surface the speed limit is never actually broken.   ;Quote:Original post by AgonyQuote:Original post by OmegavoltQuote:There is no Ground Zero.There isn't?  Isnt the Big Bang explosion itself Ground Zero?  I mean, they say the universe began as an infinitely dense golf ball-sized mass, right?  When the explosion occurred all matter in the universe expanded, not only away from itself as you stated, but away from the original location of the explosion as well.It's not that all the matter in the universe is expanding outward into space, it's that space itself is expanding, "dragging" everything along with it.  Hypothetically, initially every single point in space was infinitely close to every single other point; they were all at the singularity.  Thus, they all have equal claim to being the center.Yes, this space that is expanding is known as the fourth dimension (aka space time)   