blike Posted July 19, 2002 Posted July 19, 2002 The linear relationship in hubbles law implies that the universe is uniformly expanding. Knowing this, can astronomers/physicists study the motions of other galaxys and come up with a center point from which everything started? In essence, the center of the universe? Wouldn't this also give us an idea of the approximate age of the universe?
Guest Unregistered Posted July 19, 2002 Posted July 19, 2002 right, I'm not 100% sure on this, so correct me if I'm wrong, but say all space is expanding uniformly, that would give everything at a given distance from us that lies on a sphere with us at the centre, the same red shift, so no, you couldn't tell where the centre of the universe is. if such a thing would make sense. on the other hand, when we consider the cosmic microwave background, technically this is supposed to be uniform (disregarding the fluctuations and so on that supposedly gave rise to our galaxies and such) in all directions. Now it is known that light will red or blue shift, depending on what direction we are travelling with respective to the motion of the light - so - if we look at the CMB for red shift in one direction and blue shift in the other, could that give us an absolute velocity with respect to the CBB, which we can then extrapolate backwards a few billion years to find where we came from? I don't know... there may be some flaw in my reasoning for either or both of these arguments, but it would be nice to see how they are pulled apart/approved. If my suggested experiment brings anything up, remember to quote me
Radical Edward Posted July 19, 2002 Posted July 19, 2002 oops, unregistered is me by the way.. I forgot to log in.
aman Posted July 19, 2002 Posted July 19, 2002 If we someday break the barrier of C+ travel by whatever method, warping space-time, wormholes, or other innovations, then we should be able to reach the edge barrier of the universe. If we travelled far enough out away where we saw the universe as a ball in the distance we could calculate where the center was, but we still wouldn't know if the whole universe had moved in a direction and actually left the vicinity of where the big bang initially happened. I guess I didn't help much but wasn't it fun to go so far from the universe with your mind. Fast trip too and made it back safe. Just for thought Just aman
blike Posted July 19, 2002 Author Posted July 19, 2002 Radical Edward: say all space is expanding uniformly, that would give everything at a given distance from us that lies on a sphere with us at the centre, the same red shift, so no, you couldn't tell where the centre of the universe is. Never thought of that.
Radical Edward Posted July 19, 2002 Posted July 19, 2002 Originally posted by blike Never thought of that. indeed, but what about my counter example. tonight my friends and I were trying to work out what the red/blue shift of the CMB would be actually relative to, and we couldn't figure it out. oh well......
Radical Edward Posted July 19, 2002 Posted July 19, 2002 Originally posted by aman If we travelled far enough out away where we saw the universe as a ball in the distance there is a difference between seeing 'stuff' in the distance, and the universe itself, since the universe includes space-time, not merely matter and electromagnetic radiation (aka light/radio/gamma waves) you could never travel away from space-time to such an extent as to see it as a ball in the distance, since in order to do so, you would need to be in space-time (and be within the light cone of any existing matter)
aman Posted July 20, 2002 Posted July 20, 2002 I guess instead of actually sending a body outside the the universe I should have said picture it in your mind. Just as quantum physicists can't actually send there bodies to observe quantum phenomena I should have emphasized sending your imagination there. That is where we see phenomena we can't actually experience but we still see. Thanks for the correction. All of this is built on seeing it in your head first and then finding valid arguments for or against and going after it if it is logical. Trying to be logical. Just aman
Memry Posted July 20, 2002 Posted July 20, 2002 I've heard it said that Enlightenment can start with a headache *lol*.
Radical Edward Posted July 20, 2002 Posted July 20, 2002 I was discussing this with some colleagues in the pub last night (the pub and the coffee room are the places where all big thoughts occur, not the lab - this is a common misconception!) Quite an interesting discussion really, and it brought back the baloon analogy, which explains it fairly well. imagine space-time as the surface of this balloon, say it's a spherical balloon. there is no center, no origin of which to speak, and when we talk about the universe expanding, then the surface area of this balloon is getting bigger, in that all points on the balloon get further away from all the other points, while not moving away from any specified point. In short, the old school church was actually right, we are at the centre of the universe. but then so is everything else. we still couldn't figure out what red/blue shifting of the CMB would give you motion relative to, other than that particular point in space at the time the universe left thermal equilibrium. Still it sounds alot like absolute motion to me.. :/
aman Posted July 20, 2002 Posted July 20, 2002 Just for thought. If the big bang is relative to an exploding super black hole then why couldn't it still be a black hole and we are just holograms collapsing at different relative speeds towards its center? No proof, I guess I'm confusing things but this way we would definitely have a center. Center is the question. Just aman
chris Posted July 28, 2002 Posted July 28, 2002 woah... interesting theory aman. But, i like living in the box. and making sure im not a halogram..
Radical Edward Posted July 28, 2002 Posted July 28, 2002 hologram? that would be the reproduction of a wave front....
Radical Edward Posted July 28, 2002 Posted July 28, 2002 I was just defining holograms as I know them... I wasn't sure what aman was on about that's all
chris Posted July 28, 2002 Posted July 28, 2002 isnt a hologram kinda like a mirage. something we think is real but isnt?
John Posted August 18, 2002 Posted August 18, 2002 If the universe is the result of an explosion in an empty vacuum, then wouldn't it follow that the universe is roughly spherical in shape? If so, then go back to the balloon. The balloon is spherical, and it represents (without the curves around massive objects) the physical dimensions of our universe. The balloon is expanding. We reside on one side of the balloon. In order to find the center of the universe, wouldn't we just need to determine which object has the greatest redshift? That object would be moving in a direction directly opposite of ours, so (assuming the universe's expansion is roughly uniform, as it would be in this balloon scenario anyway) that would give us a direct line across the center of the universe. Perhaps that's what blike originally meant anyway. I don't know about Hubble's Law. In that case, just disregard my post here. Otherwise...?
Radical Edward Posted August 18, 2002 Posted August 18, 2002 no, it's not quite like that... there was no vacuum in the first place, no space or time, these only came into being at the big bang. when we say space is expanding, that means space itself, not just stuff flying out into a big (sort of) empty space. In the balloon analogy, all space is the surface of the balloon, nothing occupies the 'volume' of the balloon.
aman Posted February 24, 2003 Posted February 24, 2003 Then with that analogy the new pictures from the edge of our observable universe would actually by bent around from behind so they seem to come from somewhere they really aren't. It sure seems like we can look 14 billion years away in just about every direction. Just aman
fafalone Posted February 24, 2003 Posted February 24, 2003 This universe is relatively flat. Key word there is relatively. Compared to its 13+ billion light year width, the height could be only a couple billion light years; and we'd never know without some fancy equipment.
NSX Posted February 24, 2003 Posted February 24, 2003 Originally posted by fafalone This universe is relatively flat. Key word there is relatively. Compared to its 13+ billion light year width, the height could be only a couple billion light years; and we'd never know without some fancy equipment. What if it turns out to be like how the people of the past thought the Earth was flat? lol
aman Posted February 24, 2003 Posted February 24, 2003 You mean it's kinda shaped like a fat persons fart in a plastic chair at a nudist colony. Now it makes sense. Thanks :banme: Just aman
NSX Posted February 24, 2003 Posted February 24, 2003 Originally posted by aman You mean it's kinda shaped like a fat persons fart in a plastic chair at a nudist colony. Now it makes sense. Thanks :banme: Just aman eww...I think that's enough SF for me today...
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