Naked Science Forum
On the Lighter Side => New Theories => Topic started by: bcs4 on 14/04/2014 19:43:40
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If an object were located in the very center of all mass in the universe (or perhaps multiverse) would time on that object stop (based on general relativity)?
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If an object were located in the very center of all mass in the universe (or perhaps multiverse) would time on that object stop (based on general relativity)?
Assuming that there is a centre it wouldn't stop time. The density of the entire mass would have to be contained within what is known as its Schwarzschild radius which describes the event horizon of a black hole. We would all be living in that black hole and therefore the universe would be collapsing instead of expanding. The only alternative to that scenario is for us to be in a hypothetical white hole. These have never been observed and are thought to be unstable if possible at all.
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On that basis I would think that gravity anywhere would be evidence that the universe should be contracting, even though it appears to be expanding.
However, I was just thinking that in the customary fabric representation of spacetime that the center of mass would be in close proximity to the deepest depression in the fabric. If a black hole tears the fabric, then a deep depression would not be equal to a tear, but if a black hole doesn't tear the fabric, then the center of of mass would likely be as deep as most black holes, if not all.
It would also seem that it would be near the point of the big bang.
I hate to go on because my example could already be ridiculous, but the event horizon surrounding such a depression would be of such size that the sides of the depression might be a relatively gradual slope.
If that might be true, could matter (or whatever it might be) simply slide out of the horizon with the momentum that might be the result of a relatively small "bump" in comparison to the massive event that would be necessary if the fabric were very steep?
Sorry to be long winded, but I'm looking for a comfortable way to stop thinking about this, and this seems to be the right place..
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It would also seem that it would be near the point of the big bang.
Imagine a two dimensional universe which is found on the surface of a 3D bubble. Before the bubble was blown up to its current size, it was a single point. That point is where the big bang for that 2D universe took place, but now that the bubble's been inflated, the point where the big bang took place is no longer inside the 2D universe. Well, it's in it in one sense as it's contained by it, but you can't get to that point within the 2D fabric of the 2D universe because you're trapped in the surface layer of the bubble and the empty interior is inaccessible. Now imagine a three dimensional universe built into the surface layer of a 3D bubble - you'll need to be able to think in four space dimensions to do this, so it's hard. That's what our universe is like, and the location of the big bang is not in the surface layer, so you won't be able to reach that point no matter where you go in the universe. Alternatively, all points in the universe have equal claim to be the point of the big bang as they can be regarded as an expanded version of that point.
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I understand what you're saying, but wouldn't matter be left in the center of the ball or did all matter/energy expand away from the center without exception at the same rate of speed? I've been imagining it more as an explosion in the normal sense, where everything would radiate away from the center at differing speeds, but with more stuff (that's the best word I can come up with) closer to the center, lessening at the edge, with accretion taking place throughout. No matter what, it all seems to go against an increasing rate of expansion (unless I imagine it as a drop of oil on the surface of water, and the expansion only takes place in certain areas until it levels).
Considering the amount of work you've done answering my questions, thank you for helping put some of the circular thoughts of this 19th century gentleman(?) scientist to rest.
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I understand what you're saying, but wouldn't matter be left in the center of the ball or did all matter/energy expand away from the center without exception at the same rate of speed? I've been imagining it more as an explosion in the normal sense, where everything would radiate away from the center at differing speeds, but with more stuff (that's the best word I can come up with) closer to the center, lessening at the edge, with accretion taking place throughout. No matter what, it all seems to go against an increasing rate of expansion (unless I imagine it as a drop of oil on the surface of water, and the expansion only takes place in certain areas until it levels).
Considering the amount of work you've done answering my questions, thank you for helping put some of the circular thoughts of this 19th century gentleman(?) scientist to rest.
I don't think anyone will ever be able to determine the point source for the big bang. Mass may well still be present at the source but the density would be so low that it may as well be zero. Imagine a normal explosion with a shock wave, except that in the case of the big bang there was no medium for the shock wave to move through except the expanding mass. The shock wave was likely dragging out the mass from the centre until the force died down below a certain level. This is what is known as inflation. It may not have happened exactly as I described so don't take that as fact but something caused an acceleration. This eventually slowed. The result would have been most of the material being condensed in close proximity to this spherical shock front.
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One other point worth noting. As light cannot escape a black hole then maybe gravity can't escape either. If gravity waves are trapped around the singularity then when the big bang happens it may well be a gravitational shock wave that draws out the mass. Initially this will be a strong force but die off with distance due to its inverse square nature until its action is almost but never quite negated.
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I understand what you're saying, but wouldn't matter be left in the center of the ball or did all matter/energy expand away from the center without exception at the same rate of speed?
Nothing would be left at the centre, but I should point out that the idea of the expanding bubble is not necessarily correct - it's just the easiest model to understand and is particularly useful as a way of explaining why the centre can't be identified in the universe as it is now. An alternative way of looking at things eliminates the bubble with mathematical tricks which mean that if you go in a straight line in one direction you will eventually come back to where you started but without going round in a circle, so there is no single model that can be pointed to as the correct one. It's easiest to stick with the bubble though, and it may represent how reality actually is. The 3D fabric of the universe which we can move around in is all contained in the surface layer of the bubble, and because the centre of the universe is not in the surface of the bubble, we cannot go there any more - everything that started at that point has been kept inside the surface layer and been dragged out and away from that central point by the expansion of the surface, dragged away in all directions from the hidden centre, and at an accelerating pace.
I've been imagining it more as an explosion in the normal sense, where everything would radiate away from the center at differing speeds, but with more stuff (that's the best word I can come up with) closer to the center, lessening at the edge, with accretion taking place throughout.
That is something you have to get away from because that describes an explosion inside an existing space, but with the big bang it's radically different because the space (the surface of the bubble) is being created by the explosion along with the content, and all the matter is then dragged along by this expanding space. Galaxies were not exploded apart from each other, but are sitting more or less still within an expanding space as the bubble gets bigger. This is why you will often see it shown in TV documentaries by using a balloon which has pictures of galaxies drawn on it and which is then blown up to show how they move further apart as it's inflated. That doesn't explain why the galaxies themselves aren't expanded by this process (maybe they are a bit - I don't know), but it does show why this is quite different from a little explosion within a universe where space is already there for stuff to move through and things can be made to expand through that space by setting off bombs.
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Once again, thanks very much for your help. Your ability to focus on the question and explain in a logical progression is rare..