# Question about the universe



## AlexanderSen (Dec 8, 2014)

I have seen some artists impressions of the universe as the universe being circular and flat. If so then what is on top and below? (O_O)


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## Foxbat (Dec 8, 2014)

Not a scientist, not an expert but here goes -
The same question could be made about the Big Bang (what is it expanding into?) and the way I understand it - nothing. There is the universe and there is the void.


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## Harpo (Dec 8, 2014)

Any image of the universe, in whatever shape or form, implies - simply by the image having an edge or a border or an outline - that there's another place for something else beyond and outside the universe.  If the universe is everywhere, then there can't be anything elsewhere, except in the multiverse sense of other everywheres overlapping, just like a recording studio's mixing desk.  (If you only listen to the recording of the cowbell, you might wonder how there's room for anything else in the entire song)


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## Brian G Turner (Dec 8, 2014)

The actual shape of the universe has been an interesting debate within cosmology - it's shape defines it's fate. Saddle-shaped is another alternative.


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## Ray McCarthy (Dec 8, 2014)

Foxbat said:


> There is the universe and there is the void


Vacuum has space and Time. The Void is nothing, has nothing and probably no laws of physics?


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## HareBrain (Dec 8, 2014)

Excuse my ignorance, but I thought the universe expanded out from the Big Bang at the speed of light, and has done ever since. If that's so, how is it anything but spherical? And if not, what causes the variation in speed of expansion?


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## Mirannan (Dec 8, 2014)

HareBrain said:


> Excuse my ignorance, but I thought the universe expanded out from the Big Bang at the speed of light, and has done ever since. If that's so, how is it anything but spherical? And if not, what causes the variation in speed of expansion?



The confusion is caused in part because the universe has not three dimensions but four. Alternatives discussed so far for the large-scale structure of the universe include basically flat (or a 4D analogue, I'll assume that henceforth), hyperbolic (the saddle shape mentioned above) or spherical. The alternatives could be distinguished by probing the geometry. A hyperbolic universe would have more objects at large distances than expected, a spherical one would have fewer. Complicated, of course, by the fact that the distances involved mean that one is looking a long way back in history as well so that has to be taken into account.

Yup, it makes my brain hurt as well.


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## Foxbat (Dec 8, 2014)

HareBrain said:


> Excuse my ignorance, but I thought the universe expanded out from the Big Bang at the speed of light, and has done ever since. If that's so, how is it anything but spherical? And if not, what causes the variation in speed of expansion?


 Gravitational distortion caused by the presence other universes?


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## Mirannan (Dec 8, 2014)

Foxbat said:


> Gravitational distortion caused by the presence other universes?



More likely random fluctuations in density in the very early eras of the Universe. And I mean VERY early - not too large a multiple of the Planck time.


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## Ray McCarthy (Dec 8, 2014)

Foxbat said:


> Gravitational distortion caused by the presence other universes?


no, because that only applies to Galaxies.
There would be nothing for gravity to act on outside a universe. By definition if you can interact with something, even only by gravity it's IN our Universe.


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## Michael Colton (Dec 8, 2014)

It is fairly accepted now that that the universe is flat. The topology is more debated than the geometry at this point.

Nifty link.


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## chrispenycate (Dec 9, 2014)

That simplification is, I believe, a mapping of a five dimensional space onto a three dimensional surface. If the universe were flat in three dimensions, we'd know it, and it isn't. But the universe they gave me in LonCon is almost spherical, but not quite, and inflatable. But people always get confused when I try to explain that any given point is the centre of the universe, where ever you are you can't be on the frontier, there will always be as much each side of you, before and behind.


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## Harpo (Dec 9, 2014)

Yep, wherever I go in a flat seascape, the horizon remains equally far away.  This is why I advocate horizon worship to rank alongside sun & moon worship


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## Nick B (Dec 9, 2014)

'The observable universe' is the term to remember. Simply because that is all we can see, does not mean that is all that there is.
The flat shape you see is just a flattened version since you can't print off a 3d version. Just like a star map in a book.

Ray, gravity could potentialy affect our observable universe if for instance it exists within a larger fabric of spacetime where multiple big bang events have occured. There could be billions out there that we can not detect simply because they may be so far away that the light from them has not reached us. For instance if another cluster of galaxies existed a hundred trillion light years away from us, the light would not reach us for another 99.986 trillion years. At which point it will likely not be seen with human eyes.

Had this conversation on the astronomy board i am a member of, a while ago.

Just because we can not see, measure and quantify a thing, doesn't mean it doesnt exist.


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## Ray McCarthy (Dec 9, 2014)

Quellist said:


> Ray, gravity could potentialy affect our observable universe if for instance it exists within a larger fabric of spacetime where multiple big bang events have occured.


That would be items outside what we can observe, but by definition, NOT separate Universes, but far distant clusters of galaxies in the Universe.

Our Universe IS the "larger fabric of spacetime", any other universes are by definition, separate spacetime fabrics and thus undetectable.


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## Nick B (Dec 9, 2014)

I was taking what was termed 'universe' to mean observable universe.
Also, i would disagree with the statement that other universes are seperate to our spacetime. They 'may' be seperate to our spacetime, or they may possibly be connected at some fundamental level if for instance. Imagine universes are like floors in a tower block, with elevators as wormholes, black holes or whatever you want to imagine. Are the floors seperate, or part of a greater whole?

The problem is we currently do not know how to find out. We cant say for sure either way, or if any of these other possible universes ( or unobservable parts of our universe) exist at all.


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## BAYLOR (Dec 9, 2014)

The universe could be spherical or sausage shaped like the in  T*he Third Policeman*.


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## Aquilonian (Dec 12, 2014)

@ the OP: I recommend you read "The Goldilocks Enigma" by Paul Davies which explains this a lot better than I could, ie how can the Universe have a "shape" if it's not defined by the shape of it's surroundings, as it has no surroundings.

TGE also has a lot to say about other things- I've read it three times and understand a bit more each time.


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## JoanDrake (Dec 13, 2014)

It's turtles all the way down.

The most frightening prospect to me is that the entire Universe, and us and everything in it, is just the projection of holograms on the Universe's edges. I don't know why that scares me, but it does.


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## Nick B (Dec 13, 2014)

Read The Holographic Universe (if you havn't already), it may go some way to explaining how that just might be. It goes way deeper than just that though.


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## Foxbat (Dec 14, 2014)

Quellist said:


> I was taking what was termed 'universe' to mean observable universe.
> Also, i would disagree with the statement that other universes are seperate to our spacetime. They 'may' be seperate to our spacetime, or they may possibly be connected at some fundamental level if for instance. Imagine universes are like floors in a tower block, with elevators as wormholes, black holes or whatever you want to imagine. Are the floors seperate, or part of a greater whole?
> 
> The problem is we currently do not know how to find out. We cant say for sure either way, or if any of these other possible universes ( or unobservable parts of our universe) exist at all.


I've always wondered if universes are more likely to be connected at a quantum level. Particles have a habit of appearing a disappearing. Perhaps when they 'disappear' they are actually moving through different universes? If this were so and we were somehow able to track a particle beyond what we can do right now, we might be able to detect the presence of other universes? Perhaps the reason why the amount of mass has never added up is because it is constantly shifting between these universes?........just my mad musings.....


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## Nick B (Dec 14, 2014)

Nothing wrong at all with musings no matter how outrageous, especially for the sff crowd 

I actually have some unconventional thoughts about the nature of reality. Take dark matter for instance, and the fact that it accounts for the vast majority of the mass of the universe. Strange stuff, you can't see it or measure it, the only way to even tell it is there is by the lensing effect of it's gravity. But what if 'dark matter' wasn't in fact dark at all, what if it merely existed outside our normal physical space, maybe in some form of subspace or hyperspace, but a space that was so linked to our own physical universe that it could still exert it's gravitational force? It could exist in all it's non-invisible glory, elsewhere, yet still exert the gravitational effect of its mass right here. I havn't heard any scientists debate any such theory, probably for fear of being called mad. But is that any more mad than having invisible matter?


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## Ursa major (Dec 14, 2014)

I seem to recall suggestions that one reason gravity is so weak (comparatively) is that it is leaking into other "dimensions", so the idea that it might also leak into ours doesn't sound that far-fetched.


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## Venusian Broon (Dec 14, 2014)

Quellist said:


> Take dark matter for instance, and the fact that it accounts for the vast majority of the mass of the universe. Strange stuff, you can't see it or measure it, the only way to even tell it is there is by the lensing effect of it's gravity.



You can definitely measure 'it', whatever it is. Galaxies spin too fast for the matter that we can see involved and hence one of the explanations invoked is that each galaxy has a big dark matter component that only interacts with the gravitational forces. So actually pretty common and garden observations. The mass of the universe being made up of mostly dark matter, is another issue, as that comes down to considerations about the big bang and the universe's expansion (or contracting or not doing anything at all depending on what is the consensus at the moment, always seems to change every decade...) and therefore the dark matter component will change to fit whatever is deemed to be this years best guess at a universe. Therefore IMO not as strong as supporting evidence. 

Of course you don't need to invoke matter at all. Just use Modified Gravity (originally when it came out it was Modified Newtonian dynamics or MOND) which alters gravity's attractiveness over different length scales. (But you can't then use General Relativity, so it has it's problems I admit. And if you can't invoke GR then building a cosmological model of the universe is very daunting - the standard one with GR has performed ok with the data and observations we've made and no one has built a convincing non-GR cosmological model of the universe that explains as well as or more things that the standard one.)



Quellist said:


> But what if 'dark matter' wasn't in fact dark at all, what if it merely existed outside our normal physical space, maybe in some form of subspace or hyperspace, but a space that was so linked to our own physical universe that it could still exert it's gravitational force? It could exist in all it's non-invisible glory, elsewhere, yet still exert the gravitational effect of its mass right here. I havn't heard any scientists debate any such theory, probably for fear of being called mad. But is that any more mad than having invisible matter?



Why not indeed! It is important to always think differently about problems and to be frank I've heard much madder stuff being proposed, this seems reasonably tame... 

...but, putting my scientists hat on for a further second though I'd say that you are invoking two 'dark' elements with no observable data: The matter itself and whatever this sub- or hyper space is. Thus in comparing things that have not _really_ been directly observed, dark matter has one mad thing, your theory has two. Invoking Occam's razor, I'm afraid dark matter wins it for me to be the leading testable theory at the moment if I were given the choice!


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## Ray McCarthy (Dec 14, 2014)

I wonder what the real explanations are. Dark matter and Dark energy seem like temporary fudges.


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## Nick B (Dec 14, 2014)

I agree on that Broon, one unknown thing is better than two unknowns. What I find irritating at the moment is that there is no-one offering any explanation for what dark matter _is, _or even might be, other than that it is invisible matter. That sits very badly with me I'm afraid as it just looks too much like a convenient fudge (as Ray said). It gets bandied about by every scientist as though it is fact, yet there isn't actually any fact to back it up, barely any reasonable theory even.
I watched a documentary ages ago that had a fairly large section about dark matter and at no point did the guy actually try and say what it _was_, only that he could prove it was there because of the lensing effect it had on light. I am much more interested in peoples ideas as to what it may be. We know something is there, or at least there is some effect in play. And we know that galaxies dont have anywhere near enough visible mass to hold together. So we know, again, that something is happening. What we don't hear much of is any ideas (no matter how strange) as to what dark matter (and dark energy, and in fact dark flow) actually _is_.
I am somewhat concerned that a great many scientific minds are too afraid of being ridiculed to offer up some radical thinking on the subject.


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## Venusian Broon (Dec 14, 2014)

There was a Horizon programme a while back that did in fact have some candid working astrophysicists and cosmologists (I can't remember exactly which one it was, they all blur into a few tropes in my mind) who basically said what Ray said. That all the 'dark' hypothesises are in fact fudges invoked to 'explain' some 'orrible observations. (and implicitly, I suppose, an attempt try and save the standard models of cosmology.) 

It is indeed my starting position on them really. If I were being generous to them (and inflation - another bug bear of mine) then they are really just hypothesises advanced to 'start a framework of discussion' about what the f*** is happening out there. 

So galaxies spin too fast for their weight then the simplest solution is to add some mass, but we clearly can't see or detect the stuff at the moment and therefore have no idea what it is. But at least that gives us something to look for that might be plausible. Thus we suggest dark matter. (That they have found lensing effects after all this is progress of sorts I have to admit.) All that hoo-ha about the Large Hadron Collider was not only to find the Higgs but perhaps peek at some new physics, and perhaps present new candidates for the role of 'dark matter particle'. Unfortunately as far as I am aware nothing much new has popped up. 
Universe expanding faster than we thought. Needs some sort of energy to do so. Let's call it dark energy as we have no idea why it's there or what it is. 
Strange pattern in the velocities of galaxy clusters. Might be non-random. If so, we have no idea why this is the case. Call it dark flow. 
The Universe, if we believe the big bang hypothesis, must have quickly expanded at a massive accelerated rate then calmed down - or Inflation in other words! (I'd try and fit dark into this from now on - 'dark random burst of speed' anyone ) Why? We don't know. Mind you, hasn't stopped people constructed whole multiverses out of that simple idea!
I think to answer your final point Quellist, is that these are all tinkering about the big standard models of physics, which so far have all had some staggering successes in explaining things. To be radical with new explanations is likely to throw all that out, hence the caution exhibited. What probably needs to be overhauled are these models - to be made 'better': General Relativity, Quantum mechanics and the standard model of particle physics etc...


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## Ray McCarthy (Dec 14, 2014)

And were did the Big Bang Antimatter go?

I wish I could do the maths, come up with a better theory, which is then partially verified by a building a Jump Engine, which sadly will take ages to get to really deep space (1 to 20 light days) before it can be tested. They don't award posthumous Nobel Prizes.

This is an SF&F site, not the excellent Physics one, so we can dream


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## BAYLOR (Dec 14, 2014)

Ray McCarthy said:


> And were did the Big Bang Antimatter go?





Presumably cancelled out in the Big Bang?


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## Michael F (Dec 14, 2014)

AlexanderSen said:


> I have seen some artists impressions of the universe as the universe being circular and flat. If so then what is on top and below? (O_O)


 I think that that philiosphy is as close as quantum in it's proposal that the universe(s) is mind shaped.


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## Ursa major (Dec 14, 2014)

And if the reverse were true, presumably we wouldn't be able to go out of our minds....


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## Foxbat (Dec 15, 2014)

Ray McCarthy said:


> And were did the Big Bang Antimatter go?



The way I understand it, matter and antimatter produces 100% annihilation when they come into contact with each other (with a resultant characteristic gamma emission). 

If this holds true for the rest of the Cosmos then I would guess that there is more matter than antimatter. 

This also means that they can't change the matter/antimatter ratio from 1:1 in the Enterprise Warp Core and get any different results


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## goldhawk (Dec 16, 2014)

There seems to be a lot of confusion here.

The universe is flat, or almost flat. Internal measurements of our universe are consistent with a flat universe. And, of course, the amount of possible error in the measurements means it could be very slightly curved.

The observable universe is limited by the distance where its expansion is equal to the speed of light. We can't see anything beyond that because any light from it would never reach us. The observable universe is estimated at 46 B-ly in diameter.

*A brief history of the universe*

The universe started when gravity precipitated out of the other forces creating time, space, mass, and energy. Before that, nobody knows what existed since there is no evidence from there. It could be an empty void, or it could be an infinitely dense energy field. Nobody knows.

At about 10⁻³⁰ seconds after the Big Bang, the other forces, that is, the Strong Nuclear force, the Weak Nuclear force, and the electromagnetic force precipitated out from each other. This cause to universe to hyper-expand, increasing its size by a factor or 10⁷⁸ in 10⁻⁵⁰ of a second. The resulting size is estimated to be several thousand light-years in diameter.

Between that time and the CMB (cosmic microwave background), the universe was full of electrons, protons, and photons. There were other quanta presents but they were a very tiny fraction of the whole. The universe continued to expand during this time.

The CMB happened when the expanding universe got cool enough for the electrons to drop into orbitals of the protons, creating hydrogen atoms and allowing the left-over photons to freely travel space. Its these photons that we measure as the CMB.

From then on, the universe continued to expand and gravity pulled the hydrogen together, eventually forming stars, galaxies, planets, and everything else we see today.


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## Ray McCarthy (Dec 16, 2014)

goldhawk said:


> The universe started when


I love creation myths. 


goldhawk said:


> and gravity pulled the hydrogen together, eventually forming stars, galaxies, planets, and everything else we see today.


This bit seems fairly definite.


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## Michael Colton (Dec 16, 2014)

Reading threads like this always makes me feel like an odd science fiction fan. Are there many others out there that simply have no interest in these sorts of questions?


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## Foxbat (Dec 16, 2014)

Whilst I roughly grasp time, space , mass etc. being created at the beginning of the universe....what I don't get is what happened before - I mean - how can there be a before  if there was no time and how can there be any matter without time and - therefore - how can there be a beginning without time or matter?


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## Nick B (Dec 16, 2014)

Goldhawk, that is theory. It may be the best theory we have, but it's still theory. Our best measurements may say the universe is ( or is nearly) flat, but that doesnt stop gravity from bending it all over the place. There is no explanation as to why the universe 'appears' flat and yet we accept that gravity bends space all over the place.
There is no definitive answer, because we don't have all the facts. All we have is the best guess based on current understanding.


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## goldhawk (Dec 16, 2014)

Quellist said:


> Goldhawk, that is theory. It may be the best theory we have, but it's still theory. Our best measurements may say the universe is ( or is nearly) flat, but that doesnt stop gravity from bending it all over the place. There is no explanation as to why the universe 'appears' flat and yet we accept that gravity bends space all over the place.
> There is no definitive answer, because we don't have all the facts. All we have is the best guess based on current understanding.



Of course, it's all speculation. After all, nobody was there at the time to record it.


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