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Is The Universe Hollow?
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If we accept that the big bang happened and everything is still travelling outward from its origin, should we expect that there would be a region of space completely empty of matter, and for this void to be getting bigger all the time? If not, then the only explanation I can think of is that I am being a bit naïve in expecting the big bang to have happened 'somewhere', but it's all my poor brain can manage.
Thanks,
CS
Thanks,
CS
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Depends on what you mean by completely empty. The vacuum of space is thought to be seething with virtual particles coming into and out of existence. So nothing is really empty, at least not for long or far.
Things are not really travelling outward from an origin. Space is being created between everything giving it all the appearance of travelled outwards. Our understanding is that everywhere is the origin, just spread apart.
There is no edge as far as we know. As otherwise, what is this solid thing one postulates that we are a hollow part of ? It is the reason that I think space has to be curves and return back on itself. How else do we avoid believing in an edge we can not explain ?
Things are not really travelling outward from an origin. Space is being created between everything giving it all the appearance of travelled outwards. Our understanding is that everywhere is the origin, just spread apart.
There is no edge as far as we know. As otherwise, what is this solid thing one postulates that we are a hollow part of ? It is the reason that I think space has to be curves and return back on itself. How else do we avoid believing in an edge we can not explain ?
Thanks Mr Geezer (may I call you 'Old'?). I accept what you say to a degree but I understand that space and time are now thought to be all the same thing. If we can extrapolate back to the point in time *when* the big bang banged (14.7bn years ago?), doesn't the same apply to a point in space *where* it happened? I agree about the particles but really meant the massive bodies such as galaxies. I appreciate there is probably no edge, and so no 'shell' composed of these bodies but I needed a title for this question! Finally how is the space between massive bodied being created? Thanks, CS
I'm not a quantum physicist so I have no clear cut answer as to how space is created/expanding/whatever you wish to call it; but I'd suspect it had something to do with "uncertainty" ensuring that as space has no reason not expand, it inevitably does. But were I you I'd await an expert rather than a popular science enthusiast to give a more detailed explanation of that one.
Massive areas of matter tend to clump together, but with large "empty" space between. The universe is possibly (probably ?) much the same throughout on a larger scale, it's just as we zoom in we see galaxies and the like as separate.
I'm unsure I understand your question re the point *where* it all happened. Everywhere you see is that point now. No single point in today's universe is the point where matter used to be created and has now left. It is everywhere we look and consists of places where galaxies are, and spaces between galaxies, both.
Massive areas of matter tend to clump together, but with large "empty" space between. The universe is possibly (probably ?) much the same throughout on a larger scale, it's just as we zoom in we see galaxies and the like as separate.
I'm unsure I understand your question re the point *where* it all happened. Everywhere you see is that point now. No single point in today's universe is the point where matter used to be created and has now left. It is everywhere we look and consists of places where galaxies are, and spaces between galaxies, both.
I strongly suspect our universe (and any others) unfolded and resides within a black hole. Just as light cannot escape from the gravitational confines of a black hole, forced to curve back within its boundry, we cannot see beyond the boundry of our own universe out to the larger universe in which our own resides.
It is a pity the noted intellectual Jim 360 isnt here to help out
I always thought the universe expanded in something ( like a balloon being blown up ) It isnt. The space itself is expanding. So there isnt a hole where the space was and now isnt
Space has to be isotropic - that is it has to look the same from every point. So there is never a point where you see everything whizzing past you
I wish Jim was here - he knows about it
I always thought the universe expanded in something ( like a balloon being blown up ) It isnt. The space itself is expanding. So there isnt a hole where the space was and now isnt
Space has to be isotropic - that is it has to look the same from every point. So there is never a point where you see everything whizzing past you
I wish Jim was here - he knows about it
The balloon analogy while flawed is nevertheless quite a nice one. The point there is that you have to imagine the surface of the balloon as being the Universe. Then when you blow the balloon up and space expands, the "centre of expansion" is somewhere in the middle of the balloon -- and, crucially, not anywhere on the surface. Hence it is possible for the centre of expansion to be not a part of the thing that is expanding.
Where it falls down is that you can see the balloon as expanding into something. Unfortunately this is (probably) not what is actually happening. Instead, the Universe creates its own space as it expands. I suppose it would also imply the "hole" that you are thinking of. Again, the balloon analogy can help if fully understood -- people living on the surface of the balloon can only perceive what is going on on the surface of the balloon and cannot see what is not directly on or part of the surface. Hence they would never be aware of the void in the middle (although a clever balloon physicist might be able to imagine its existence).
I say probably, because firstly in a "multiverse" picture it sort of follows that there has to be a meta-universe in which all the various Universes are sitting; and even without other Universes there is nothing to stop you just inventing a further dimension that extends beyond the confines of the Universe in which we live and can provide a real sort of "space" beyond it. These are very tricky concepts although the mathematics is not too difficult once you get your head around the notation. The key concept to read up on is that of a manifold (google it).
As Old geezer has said already, there is no "centre" of expansion, then, in the sense of a point in space you could visit and say "here is where it began". Because the entire universe was created at the Big Bang, everywhere you stand was once at the very same point and so you are at the centre of the universe. And so am I. And then neither of us are, in a sense, as well, as the "real" centre isn't a part of the Universe, just as for the expanding balloon.
Thanks PP for singing my praises although it should be stressed that while I am a professional physicist, I spend most of my time working on the physics of tiny particles and don't normally get that involved in Cosmology, which is at entirely the other end of the scale of physics. Still, hopefully my experience elsewhere counts for something.
Where it falls down is that you can see the balloon as expanding into something. Unfortunately this is (probably) not what is actually happening. Instead, the Universe creates its own space as it expands. I suppose it would also imply the "hole" that you are thinking of. Again, the balloon analogy can help if fully understood -- people living on the surface of the balloon can only perceive what is going on on the surface of the balloon and cannot see what is not directly on or part of the surface. Hence they would never be aware of the void in the middle (although a clever balloon physicist might be able to imagine its existence).
I say probably, because firstly in a "multiverse" picture it sort of follows that there has to be a meta-universe in which all the various Universes are sitting; and even without other Universes there is nothing to stop you just inventing a further dimension that extends beyond the confines of the Universe in which we live and can provide a real sort of "space" beyond it. These are very tricky concepts although the mathematics is not too difficult once you get your head around the notation. The key concept to read up on is that of a manifold (google it).
As Old geezer has said already, there is no "centre" of expansion, then, in the sense of a point in space you could visit and say "here is where it began". Because the entire universe was created at the Big Bang, everywhere you stand was once at the very same point and so you are at the centre of the universe. And so am I. And then neither of us are, in a sense, as well, as the "real" centre isn't a part of the Universe, just as for the expanding balloon.
Thanks PP for singing my praises although it should be stressed that while I am a professional physicist, I spend most of my time working on the physics of tiny particles and don't normally get that involved in Cosmology, which is at entirely the other end of the scale of physics. Still, hopefully my experience elsewhere counts for something.
On a personal note, I'm really glad that PP values my opinion so much but it's not at all nice to walk into a thread that I might be interested in and find that I'm the topic of discussion myself, especially when the conversation here's gone the way it has. Might be better in future to wait until I show up, at least.
NASA predicts confidently (at least as late as 2013) that, since mass density determines the "shape" of the universe, measurements taken by WMAP (Wilkinson Microwave Anisotropy Probe) of the cosmic microwave background (CMB) radiation fluctuations indicated the universe was known to be flat with only a 0.4 percent margin of error...
FAO Naomi,
For me it's little more than a hunch based on my attempts to wrap my head around the possible cosmogony and global geometry of the universe. If you find the following interesting you might want to follow the link to Black-hole cosmology. If I come across a related video I'll share that as well if anyone's interested.
http://
For me it's little more than a hunch based on my attempts to wrap my head around the possible cosmogony and global geometry of the universe. If you find the following interesting you might want to follow the link to Black-hole cosmology. If I come across a related video I'll share that as well if anyone's interested.
http://
Well Naomi I was not at all pleased to read your "no, I don't [want to listen to jim]" and I wish you had put it less bluntly. On the other hand Peter was going a little overboard in telling you who you want to listen to when really that's up to you.
It's really a difficult position to be in. I don't want to criticise someone for being nice to me. Peter was overselling it and trying to force a decision on you and while I am disappointed by your reaction, he started the conversation.
I just hope in future not to ealk into another AB thread where I'm being simultaneously oversold and dismissed before having even got involved.
It's really a difficult position to be in. I don't want to criticise someone for being nice to me. Peter was overselling it and trying to force a decision on you and while I am disappointed by your reaction, he started the conversation.
I just hope in future not to ealk into another AB thread where I'm being simultaneously oversold and dismissed before having even got involved.
Jim, I was responding to mibs whom I consider to be just about the most knowledgeable person on this site in the area under discussion (not that he makes a big deal of it which is probably why you aren’t aware of it) – and that’s who I wanted to hear from. The science section doesn’t revolve around you and no one is stopping you adding your two-pennyworth if you want to. Now do please stop being so precious.
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