The Great Beyond?
11 Apr 2017 3:15:48 UTC
Topic 206789
(moderation:
This is as naive as it is involved, but it has to do with the size of the Universe, and maybe what is meant by the universe. I have read descriptions about the universe that include concepts such as it being a kind of Klein bottle that has no boundary, or some abstract thing that simultaneously expands, but does not expand into anything - that there is no out there beyond the Universe, and that everything that exists and even that doesn't exist is here. So while the distant galaxies speed away from us at near the speed of light, and that there is no point of origin for this expansion, the expanding universe is a finite thing. Getting bigger because space itself appears between us and everything else as it expands.
So OK, more space is being added to the universe, not that the universe is expanding into empty space, but ever since LIGO boggled my brain, I have wondered what the answer to this hypothesis is. The expansion of the universe is into unoccupied space. One might answer that by saying if the universe were an infinite place, then when we look into the night sky, it would be completely lit up, with no darkness, because an infinite number of stars would occupy every linear point from our eyesight as an inevitable result of the infinite universe. But then are black holes. So what if the native form of the universe, what we can see and the great beyond, were black holes. A big bang is the exception in this infinite place, but that obviously happens. Even if there were other expanding universes out there, the light from them would run into space dense with black holes and all light would be trapped before it got to us.. The distances would be much larger than our universe. And how often Big Bangs occur would also be a factor. We can't see light beyond our surroundings because big bangs are uncommon in time and space.
t just seems logical to me that these things are bouncing around in our visible universe, sucking up everything and not letting anything out. it is logically inevitable that they will eventually suck everything into themselves, like cosmic vacuum cleaners that are never emptied. Then the only thing that could happen would be if something happened to cause another big bang, otherwise just darkness and gravity. rule an infinite universe. Black holes of various sizes colliding would be the only event. Such a model could also explain why the most distant objects are expanding so quickly - the galaxies at the boundaries are being pulled by black holes exterior to our big bang more strongly than the interior galaxies. I understand the balloon analogy, and the expectation of greater speed at farther distance, but if the speed were greater than expected at the most distant regions of the universe, it could reflect attraction rather than simple inertia.
I suppose the difference between this and a collapsing or oscillating universe model is that there need be no point of origin into which all material must gather to reform the universe as it was. Why should it reform exactly as it was, which is at least the way you can think of it if what we see - our universe - is all that there is. Something got blown apart, and the fragments evolve, depending on mass, into greater and greater collections as multiple points. Some of it may come back together and the rest get swallowed by black holes that exist outside the boundary of our visible universe. In this way, our big bang is part of a larger system, a much more satisfying explanation in my mind. What makes me nervous about calling the universe unique is just that. When is that ever true? Never, that is when. To think that this universe is a singular thing seems too centric for me. We are more likely to be one big bang in a much bigger system that goes kaboom, whenever and whenever it can. And our perspective imposes centrism - like dropping an Alka Seltzer into the Pacific ocean. Are we surprised we can only see our bubbles if water is invisible to us? We can be sure it is not the only Alka Selzer that ever got dropped into the ocean, even if we never detected it. All the energy and mass from the fizzing pill would be completely absorbed before it reached us.
Anyway I'm sure the answer to this has been around for eons, but I would appreciate some kind of cosmological beat down or pointer to the big book of bad ideas. And who better to ask than the Black Hole people? Thanks. Don
I stopped reading after your
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I stopped reading after your first paragraph because thinking about this always makes me a little gaga and I have to make an effort to think about something else instead.
David
Miserable old git
Patiently waiting for the asteroid with my name on it.
Firstly : welcome ! An
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Firstly : welcome ! An excellent first post ! :-))
Secondly : in such matters you are fundamentally no more or less informed than the best of us ! So another welcome, to the Cosmic Ponderers Club perhaps. :-)
Thirdly : I will attack your outstanding queries in parts. Chewing a paragraph at a time seems reasonable. Here goes ....
The typical view upon this : there are likely more dimensions than we can poke ourselves in the eye with here. In complete truth the field is quite open to very many possibilities. This does not mean that anything goes. Not all hypotheses are equal. What we require scientifically, when we use a given scheme of thought, is that we get sufficiently accurate correspondence with what we have measured to date.
Now on account of having trouble visualising dimensions above three, one often relies upon an analogy in a lower number of dimensions. Having done so we then revert back to the original case and say : "Aha, it is like that !" We thus avoid the discomfort of having to pretend to look 'down' upon whatever-number-of-dimensions-are-relevant from some suitable hyper-super-dooper-whopper-spatial viewpoint.
A reasonable go at it is then as follows : consider a circle. We are in three dimensions and it is in two. We define that geometric object as the locus/curve which combines all points equidistant from some single point. That single point is the circle's centre. Implicitly there must be a number that indicates the distance in 'equidistant'. Call that the radius. The centre is not part of the circle object. It is part of the definition of the object. If there is some hypothetical sentient being on the circle ( Robert to be exact ) and always confined to be so, then for Bob the circle is actually one dimensional. Bob can only go forward or back along the circumference. Assuming Bob may place a marker then the possibility exists that Bob could go right around the circumference and come back to the marker, while only ever travelling in a single direction. If so, Bob could well ponder that maybe sumthin' funny is going on. He might form the concept of circularity without ever seeing a circle ! Maybe his name for this observed phenomenon could be 'recurrency' or the like, to get around emotional/psychological/intellectual issue of grasping the full horror of the circumstance. Circumstance ? Yes, I cracked a punny. Furthermore, if Bob had a metric ( a distance standard or ruler ) he might have counted how many of those it took to return to that marker.
Now let us screw around with Bob's head. Let the radius gently increase in time. He just be going around counting his steps with respect to his fixed metric. Each time he passes that marker he finds he has gone more of those steps than before. If we had reduced the radius then each marker passing would occur in fewer steps of Bob's ruler. In any event : from within the object Bob can only use that step count b/w marker traversals as the size of his Universe.
You will now cue a reversion. Think about a Donald living on the surface of a sphere. Again we have a centre which is unreachable for Don, plus a radius likewise not directly measurable for him. Though Don has more freedom than the circle case. From a given point on the sphere he could go in an infinite number of specific directions away. Nonetheless he might mark and then traverse around the sphere using a metric device, and finally return to the marker. However he would also require some sort of directional sense so that he doesn't wander aimlessly.
Again we could stuff about with Don's expectations via changing the radius. After some thought Don would similarly invent a hypothesis to explain that. Expansion or contraction or stasis could be a good claims to make depending upon the outcome of his travels.
Here's a thought : does Don need to go right around his space to know (a) whether there is any recurrency happening and/or (b) what's happening over time with the size of his Universe ? No he doesn't ! To avoid a longer-winded aside I'll just state that triangles ( easily constructed by Don ) will vary in some important properties ( measurable by Don ) depending on their overall dimensions with respect to that radius Don can't actually measure. There will be a scale dependency to his observations and sound deductions can be made as to either recurrency and/or Universal size.
OK. Shall we revert to our three spatial dimensions ? What can we say ? You sense it already. We can, in effect, place and examine markers. We have a metric, several choices in fact. We can't traverse ( much ) but we can use the history of light travel paths to do that for us. There is no centre of the Universe that we can measure. Just like Bob and Don it will never be accessible. However much there is a 'radius' concept we may still only ( at best ! ) deal with the analogies of circumferences of circles and spherical surface areas.
More later ... :-)
Cheers, Mike.
( edit ) Thus the visualisation that you need is more or less :
- for this demonstration stop time in the Universe ie. don't let it expand/evolve while we are doing this.
- your initial marker may as well be Earth.
- pick a direction. Any direction.
- launch forth in a straight line ( I leave out the annoying details of what that really means ).
- wait.
- some more wait ( only your personal time now, and you are very patient ).
- Earth eventually appears ahead of you.
- wave to everyone as you go past. Nothing rude please.
- do this as many times as you like, plus/minus a trailing line of string with notches every lightyear. :-)
( edit ) If that was too big to grasp then try :
- just you in the entire Universe. Plus a rock.
- face in some direction and throw the rock.
- wait.
- get hit in the back of the head with the same rock.
- do that as many times as you like .....
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Thanks Mike. Really. I am
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Thanks Mike. Really. I am clinging hard to my Cartesian world but fighting to let go. Flatlander Bob can only follow his exterior line, and Spherelander Don can roll around on a surface. What they can measure depends on markers that will change dimensions if their worlds inflate or deflate. If Bobs world, as viewed from Don, has a center and a radius, Bob isn't aware of it or could not find it, because all he can see is a long flat line. Don can't see his center because all he sees is like the sea, two dimensions going off in all directions. If he puts a motorboat with a straight tiller and waits forever, he will see it coming up behind him, after eternity -1 days. And so if Three-D Bright tells her BF goodbye and gets on Elons space ship and blasts off for the great beyond, after eternity - 1 Bright will return to her BF, waiting patiently with flowers. There would, by analogy with Bob and Don, be no center. That is something iike the Klein bottle anyway.
I must muse on this, if it is a reasonable understanding of what you wrote. Otherwise I will confuse on it. I need to grasp the essential thing here, and not want to say Bob and Don actually live in two and three dimensional worlds that do have centers, and that they can infer exist. And I also must think of a finite rather than an infinite universe. Because if Bright went jetting off expecting to see her beau again, and never did, but I guess we could never do such an experiment with a certain outcome. Every day, he would say, "well, tomorrow then, I'm sure she'll be back tomorrow." MMM - that is interesting. Infinity is an unpredictable outcome. OK, but as you say, it is a very open field. If we had the biggest humungous telescope in the universe, we might be able to see Earth by looking in any direction. And what's more, a 3D space would be entirely lit up, wouldn't it. since light would go bouncing and whizzing round and round? Except when it hit black holes of course. Actually, I don't think an externally bounded visible universe is incompatible with your centerless description of a finite universe, because it just means the universe is bigger than what we can see. Whether infinite or not. I don't mean to argue anything here. I am clueless. Really. A cosmology hobbyist. But perspective is always something I have had trouble with. For example, if Joe gets onto a space ship and blasts away from Fred at the speed of light, Fred gets older quicker than Joe, even though he is moving backwards away from Joe at the speed of light. Relative to one another, they are separating at the speed of light. Which God gave Joe the gift of youth? Thanks again Mike
I've only just seen this
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I've only just seen this thread. my own views on the universe are very much simpler but it involves some spatial thinking.
I believe the MAIN universe has been there forever and will be there forever and that it is infinite in size.
Now those two factors are extremely difficult for any human being to comprehend, simply because we live in a finite world. Things begin to live then they die, you can see all three dimensions of a book, length, width, thickness, and all 6 sides. The notion of infinity is totally alien to us.
What I believe we are seeing is the expansion of our own lOCAL universe into the MAIN universe. Where did our LOCAL universe com from? Likely from a super massive blackhole that devoured so much matter that it couldn't contain it any more and simply exploded some 13.82 billion years ago. What we are seeing and living in is the remnants of that explosion. In time the matter ejected i.e. stars, will be devoured by another super massive black hole somewhere else and there will be another LOCAL universe somewhere else in the MAIN universe.
Quite a simplistic theory really, once you accept the concept of infinity. But of course the philosophers amongst us will still ask, OK that explains the physics of what we are seeing now, but where did the main universe come from? They would have trouble accepting that it didn't come from anywhere, it was always here simply because it was. Infinity again you see.
But I find there is a problem. The furthermost stars that we can detect (in the visible universe) are 45 billion light years away, moving away from us at the speed of light. So what we are seeing has taken 45 billion years to get here, so they may not even exist today in our time frame.
So question. If they have travelled 45 billion light years distance in 13.82 billion years, mustn't they have been tavelling at over 3 times the speed of light? Yet apparently not it seems.
We have this theory of warped space/time. To me space is space and time is time. If I have a cardboard box and open it there is a space of a certain volume inside. Time is the measured elapse between one occurrence and another i.e. from when I opened the box until when I closed it.
(At this point we will ignore all this quantum stuff (and someone's cat) that says I will have altered the space in the box just by looking at it)
We are told that time passes differently for the observed and the observer. e.g. a spaceship going to a star and back at near light speed will find the people left behind older than they are upon their return. So you can warp time it seems.
We know that gravitational lensing warps light, but can you warp space which consists of nothing, but maybe cosmic dust?
Warping
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now