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Chemist@
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How certainly is the universe flat? Is is absolutely approved or not?
If yes, what will cause the big crunch?
If yes, what will cause the big crunch?
Chemist@ said:How certainly is the universe flat? Is is absolutely approved or not?
If yes, what will cause the big crunch?
Chemist@ said:T
1. When was the shape of the universe approved with the 0.4% uncertainty?
Yeah, but I wouldn't put any stock in that. Not yet, anyway. That's just not significant enough to say anything.marcus said:As I recall a very recent report, from South Pole Telescope, said that with 95% certainty the curvature was not zero but just a wee bit on the positive side of zero!
Chemist@ said:Okay, thanks. I need answers to 2 and 3. What is the most approved shape, open or closed?
We haven't yet definitively detected any deviation from zero. Could be 10^-3, 10^-4, 10^-10, 10^-100.Chemist@ said:Someone knows the latest info? How much is the cosmological curvature parameter?
Chemist@ said:...
Someone knows the latest info? How much is the cosmological curvature parameter?
A cylinder is geometrically flat (you can bend a piece of paper into a cylinder without tearing).Chemist@ said:if this deviation is high enough, then the universe would be cylinder shaped.
Chalnoth said:...
If there is a slight positive curvature, then it's like our observable universe is a small piece of a very large sphere. ...
Chemist@ said:I am a little confused now.
The biggest probability is that the universe as a whole is a sphere or the coat of a sphere?
Chemist@ said:You mean time by the 4th dimension?
The coat would have a very short dimension. What would happen if someone reaches the end of it?
Chemist@ said:You mean time by the 4th dimension?
The coat would have a very short dimension. What would happen if someone reaches the end of it?
Chemist@ said:I am a little confused now.
The biggest probability is that the universe as a whole is a sphere or the coat of a sphere?
marcus said:As I understand it, what you call the "coat" of a ball is what I would call a sphere.
in our 3d world, the ball is the solid thing and the sphere is the hollow thing. It has zero thickness. It is a pure 2D surface.
A dimension is a direction you could point, or move in.
Or, in the case of a 2D world, it is the direction a 2D animal living in a zero-thickness purely 2D surface could point, or move in.
As I understand it there is no "very short dimension" because you and I cannot point our fingers in any direction which is the 'thickness" of our 3d space. There is no direction that we can move that we would "reach the end of."
Chemist@ said:What is then a 3D sphere?
Well, the problem is that it can't be visualized. But it perhaps helps to think of the definition of a two-dimensional spherical surface, the 2-sphere. The 2-sphere is, in three-dimensional space, a set of points that are all equidistant from some center. One could similarly construct a 3-sphere in four-dimensional space (note: four spatial dimensions here, we're not even considering time just now), where each point within the 3-dimensional volume would be equidistant from the center of the 3-sphere.Chemist@ said:What is then a 3D sphere?
I think you missed, "That stretch across the visible universe." :)marcus said:Now in 2013 we are measuring triangles,
I don't know what you mean. In flat space, no matter their orientation, triangles always have angles that add to 180 degrees. You have to be in curved space for that to change.Chemist@ said:Okay thanks.
These triangles you are talking about aren't in one plane, so their angles don't have to add to 180 degrees.