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wolram
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This may be a silly question, but how do we give a shape to the universe if it is The same from every point we look?
We don't give a shape.wolram said:This may be a silly question, but how do we give a shape to the universe if it is The same from every point we look?
wolram said:This may be a silly question, but how do we give a shape to the universe if it is The same from every point we look?
wolram said:I get the analogy of the Earth, but as regards to the universe what does flat mean, surly due to gravity and dark matter the universe must be globular, but how can that be flat?
wolram said:surly due to gravity and dark matter the universe must be globular, but how can that be flat?
wolram said:but as regards to the universe what does flat mean
But if the universe were a sphere, that would clearly imply a preferred direction and there is zero evidence of such a thing.Arman777 said:The universe can have a spherical geomtery or it can be just flat as ours, but If its sphere the R (radius of the sphere) must be so huge that, we observe, the observable universe as flat.
wolram said:as regards to the universe what does flat mean
phinds said:if the universe were a sphere, that would clearly imply a preferred direction
That's not very exciting since the OU is just a sphere centered on you.wolram said:Thank you for your replies, I can see now that when we talk about the universe having shape we only mean the observable universe
You are misunderstanding the analogy. I recommend the link in my signature.Valentin Kanev said:Using the balloon analogy, what's inside the balloon skin? Is it the Universe from a moment ago?
Valentin Kanev said:Using the balloon analogy, what's inside the balloon skin? Is it the Universe from a moment ago?
I find a universe centred on !e particularly exciting :)phinds said:That's not very exciting since the OU is just a sphere centered on you.
_PJ_ said:I find a universe centred on !e particularly exciting :)
- a joke only.
Tom Mcfarland said:Do you see any problem with its logic?
Tom Mcfarland said:Is it not true that the big bang thesis posits a point-like start to our universe
Tom Mcfarland said:Here is another neat topological way to convince yourself that the universe must have the topology of S³.
Tom Mcfarland said:First, consider the universe starting with us now, extending out (and backward in time) to the surface S of last scattering (at which CMB was produced). We see this surface isotropically in all directions in microwave light. This is a 3-ball (the interior of a big 2-sphere plus boundary S).
Tom Mcfarland said:when we view the CMB, we are looking at a very narrow interval on the time axis, so I have treated this surface of last scattering (S) as a purely space-like surface, albeit at a particular time.
Tom Mcfarland said:Has this claim actually been verified
Tom Mcfarland said:We have a 4-ball bounded by a space-like S containing the (invisible) early universe. and another 4-ball containing the visible universe, also bounded by S.
Tom Mcfarland said:As before, we merge these two objects by identifying their common boundaries S. We now have a universe with one time dimension (t = 0 to now)
Tom Mcfarland said:and whose spatial context is S³ (positive curvature, not flat).
Tom Mcfarland said:I had assumed that the surface of last scattering (S) was a 2-sphere, not a 3-sphere, like the colorful maps of the CMB we have seen.
Tom Mcfarland said:I had intended to glue the two 3-balls exactly as you did.
Tom Mcfarland said:I don't think I understand your use of the terms "time-like" and "space-like"
Tom Mcfarland said:I do not know how to use this feature.
Tom Mcfarland said:I had treated the surface of last scattering as identical to the particular "slice" of our 4-D space-time universe from which the currently visible CMB originated, which you acknowledge is a 2-sphere.
Tom Mcfarland said:I appreciate your prodding me to account for the passage of time, and hope to re-think the above spatial idea to justify positive curvature.
Tom Mcfarland said:at this link, right?
PeterDonis said:It won't.
Tom Mcfarland said:Your hypothetical example seems to violate conservation of energy. That is, a single flash contains a finite amount of energy E
Tom Mcfarland said:I appreciate the parallel with the CMB, but I had assumed that the 2-sphere slice (S) of the surface of last scattering which we see today is not the same slice which we see tomorrow.
Tom Mcfarland said:If and when these slices are receding from us at speed c, we will no longer see them ??
Tom Mcfarland said:I am not sure which side of the slice S you are calling "interior" and which the "exterior". That is, which side are "we" on?
Tom Mcfarland said:Looking around, we seem to be on the interior of some spherical slice S??
Tom Mcfarland said:So you are claiming that the side of S containing the early
universe has unknown topology?
The shape of the universe is a topic that has been debated by scientists for centuries. Currently, the most widely accepted theory is that the universe is flat, meaning that it has an infinite extent in all directions.
According to the theory of cosmic inflation, the shape of the universe is the same from every point. This means that no matter where you are in the universe, you would see the same overall structure and distribution of matter.
Scientists have been able to determine the shape of the universe through various methods, including studying the cosmic microwave background radiation, measuring the geometry of distant galaxies, and observing the distribution of matter and energy in the universe.
While the shape of the universe is currently believed to be flat, it is possible that it could change over time. Some theories suggest that the universe could eventually collapse in on itself, resulting in a different shape.
The shape of the universe plays a crucial role in our understanding of the cosmos. It helps us to understand the overall structure and evolution of the universe, as well as the distribution of matter and energy within it. It also has implications for theories such as the Big Bang and the expansion of the universe.