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wolram
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How do you imagine a finite universe ? i find it very difficult.
wolram said:How do you imagine a finite universe ? i find it very difficult.
marcus said:remember we are just talking SPATIAL finite
timewise it can still go on forever
what is the problem imagining a spatially finite universe?
it is the old "surface of a balloon" thing except the surface of a balloon is only 2D and you have to think of what would be the 3D analog of that.
Silverbackman said:Then again I know more than a being from a dot, circle, and twosphere world. Is it possible for a foursphere, fivesphere, ect. ect. till infinite?
But doesn't the known curvature of the universe suggest that we live in a flat universe and not a saddle or sphere universe? If so then how can we be living in a threespere?
SpaceTiger said:I don't understand the question...
wolram said:I have an idea to call my image the, ( frustrated boomerang), curved space
with expasion.
I think he wondered how many dimensions that can possibly exist. If there may be "infinitely many" dimensions... (1D,2D,3D,4D,...,?D).
Silverbackman said:Yea, I wonder what a eightsphere universe would look like. Or how about a 1,678,489,986sphere?
VikingF said:Yeah... Me too! :tongue:
According to String theory, there exist 10 dimensions, and M-theory says that there exist 11.
There is an anthroopic argument as to why we are living in a 3D + time universe.Silverbackman said:Why an omnipotent God or even randomness of Nature would pick 4, 7, or 11 as the "official" number of one of the most important aspects of our universe is beyond me.:uhh:
Silverbackman said:Yea but they say those dimensions may just exist. It doesn't have anything to do with the universe being a tensphere or elevensphere I think. Or does it? Actually it probably does because I assume 10 or 11 dimensions cannot exist unless is within some sort of nsphere (or something like an nsphere).
Garth said:There is an anthroopic argument as to why we are living in a 3D + time universe.
Time is necessary for process, we exist and evolution of complex beings requires process, therefore time.
In a 1D or 2D spatial universe there is not enough topological freedom for complex organic molecules to operate, the 3D geometry is important for proteins etc. to 'do their stuff'. Hence we cannot exist in a spatial 1D or 2D universe.
Keplerian orbits are unstable in a spatially 4D or higher universe. The Newtonian law of gravity becomes [itex]F = GMm/r^3[/itex] in a 4D universe for example and the Earth would spiral into or away from the Sun. Hence we cannot exist in a spatial 4D or higher universe.
We exist: therefore our universe has 3 space D + time.
Garth
No, if I have not misunderstood it completely, String theory says that our universe is one of infinitely many three dimensional (or four with time) universes in an infinite ten- or eleven dimensional multiverse.
It's like the drawing on the piece of paper in front of me is two dimensional in a four dimensional universe.
Balence said:Any shape still has space out side of it, therefore the universe is still infinite.
marcus said:and anyway, Wolram, there are SEVERAL kinds of finite 3D spaces possible------the threesphere is not the only one. there are a whole bunch, just like in the 2D situation you can have donut shapes with more than one hole. But this does not matter. It is enough to just imagine one possible spatially finite 3D thing----and the threesphere is good enough.
marcus said:remember we are just talking SPATIAL finite
timewise it can still go on forever
what is the problem imagining a spatially finite universe?
it is the old "surface of a balloon" thing except the surface of a balloon is only 2D and you have to think of what would be the 3D analog of that.
setAI said:I conjecture that it is possible for a finite AND flat universe without the topology of a torus or similar form- in fact it can have ANY arbitrary topology as long as it is closed-
...one could construct such a lattice of quantum logic gates on the surface of a sphere- or any other closed shape- yet the topology of the emergent spacetime metric could compute a FLAT spacetime that wraps around-
consider a classical computational analog: the game Asteroids- where the ship flies straight but wraps around when it hits the edge of the screen- the virtual space of the ship is flat- but the edges are connected in the software- so the virtual space is finite yet unbounded
string querry said:the surface of the balloon is 2D, yes, but why do the theorist always use the surface of the ballon. Why not the volume of the ballon, such as a balloon fuill of gel...
It is only a model to help people conceptualize the idea of spherical space.string querry said:the surface of the balloon is 2D, yes, but why do the theorist always use the surface of the ballon.
Garth said:It is only a model to help people conceptualize the idea of spherical space.
3D space is a 'space-like' slice or 'foliation' of 4D space-time.
We cannot visualize 4 dimensions - at least I cannot - and therefore in order to get the idea across, and for students to 'see' what we are talking about, it is helpful to reduce the number of dimensions and suppress one of the space dimensions...
A triangle's interior angles sum to 1800. In a spherical space a triangle's interior angles sum to > 1800, and in a hyperbolic space they sum to < 1800, for example.
I hope this helps.
Garth
If the universe was finite then for any given point there must exist another point within a finite distance at which motion in any direction will not increase the distance between the two.wolram said:How do you imagine a finite universe ? i find it very difficult.