If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
Are you trying to be logical? On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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-- Siegfried
Steve, the mistake you're making is imagining the Big Bang as happening in a larger space. The Big Bang created the entire universe and it expanded very quickly. The entire universe was and is expanding. Imagine dots all over the surface of a balloon, and inflate the balloon. All of the dots move away from each other as the balloon expands. The balloon surface is analagous to the fabric of three-dimenstional space. On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
Does the baloon have a center? On Jan 16, 2015 12:08 PM, "Chuck Hards" <chuck.hards@gmail.com> wrote:
Steve, the mistake you're making is imagining the Big Bang as happening in a larger space. The Big Bang created the entire universe and it expanded very quickly. The entire universe was and is expanding.
Imagine dots all over the surface of a balloon, and inflate the balloon. All of the dots move away from each other as the balloon expands. The balloon surface is analagous to the fabric of three-dimenstional space.
On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
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No. The universe is the skin of the balloon only. It's a finite 2-dimensional universe, projected in 3 dimensions. On Friday, January 16, 2015, Siegfried Jachmann <siegfried@jachmann.org> wrote:
Does the baloon have a center? On Jan 16, 2015 12:08 PM, "Chuck Hards" <chuck.hards@gmail.com <javascript:;>> wrote:
Steve, the mistake you're making is imagining the Big Bang as happening in a larger space. The Big Bang created the entire universe and it expanded very quickly. The entire universe was and is expanding.
Imagine dots all over the surface of a balloon, and inflate the balloon. All of the dots move away from each other as the balloon expands. The balloon surface is analagous to the fabric of three-dimenstional space.
On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com <javascript:;>> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
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The Big Bang was a density singularity, not a space-time singularity. Space-time did not exist before the Big Bang, therefore, there was no point "in space" to expand out from. The Big Bang was not like an explosion in our three-dimensional space...something one could trace back to a center. Hopefully, the following won't be too obscure. I've had a long day. Physical surfaces have two types of geometry, intrinsic and extrinsic. Intrinsic geometric properties refer to measurements made entirely on the surface itself. All other geometric properties are extrinsic. No one knows the shape of our universe, that's an extrinsic property of the space-time geometry and no one has been outside our universe and looked back at the surface and observed its shape. We can only make measurements within space-time, therefore, any data we obtain about our space-time's geometry are, by definition, intrinsic. It is hopeless for us to try to envision the geometry of our three-dimensional space-time as being, somehow, bent through a fourth dimension. What would that look like? For this reason, physical space has no known extrinsic geometry. We make measurements within space-time and infer (because of distance distortion) the "curvature" and geometry of space-time. Curvature of space-time, according to the map of general relativity, is a mathematic property and refers to the use of distorted models for explaining the geometry of space-time. For an analogy of this concept, think of our own planet. Earth is a sphere, but we can measure its curvature from two-dimensional measurements taken entirely on its surface. To do this, one can make an atlas of maps of Earth's surface. How does one derive the curvature of Earth from this atlas of maps? Through the distance distortion made apparent from flattening out the sphere to generate the maps. We can reconstruct the full three-dimensional geometry of Earth from a system of flat maps taken of its surface (an intrinsic measurement) by looking at the two-dimensional distance distortions in these maps. This was Mercator's great insight when he produced his nautical maps. One sees the distance distortion he needed to provide in his maps so that a heading of constant curvature on the spherical Earth appeared as a straight line on his maps. This is why Greenland appears so large on a Mercator projection...it's the consequence of a two-dimensional projection of a spherical surface with the curvature of the spherical surface manifesting itself as distance distortion. As one does not need the third dimension to ascertain the curvature of Earth, similarly, one does not need to observe a fourth dimension to investigate the "curvature" of our three-dimensional space. Additionally, our universe appears to have no preferred center and on large scales appears isotropic and homogeneous. Why? It is the curvature of space-time that makes this so. Again, another analogy with Earth. Suppose we take a bunch of Eiffel Tower models (imagine big ones) and spread them out in a network across Earth's surface. We would notice that we could place these Eiffel Tower models on our two-dimensional surface in such a way as to have a homogeneous and isotropic structure in our placement and it would appear to anyone on the surface of Earth that the network has no edge, no boundary or any preferred center. I threw this in because it's not the balloon analogy. There Sig, no balloons. Finally, the curvature of our universe (on large distance scales) provides a similar metric to matter within it....no edge, no boundary and no preferred center. Hopefully, this wasn't too obscure? Dave
On Jan 16, 2015, at 11:07, Joe Bauman via Utah-Astronomy <utah-astronomy@mailman.xmission.com> wrote:
You are on that point as is everything else.
------------------------------
On Fri, Jan 16, 2015 6:50 AM MST Stephen Peterson wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 12:07, Chuck Hards <chuck.hards@gmail.com> wrote:
Steve, the mistake you're making is imagining the Big Bang as happening in a larger space. The Big Bang created the entire universe and it expanded very quickly. The entire universe was and is expanding.
Imagine dots all over the surface of a balloon, and inflate the balloon. All of the dots move away from each other as the balloon expands. The balloon surface is analagous to the fabric of three-dimenstional space.
On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
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With high Eifel Towers wouldn't you be able to measure a difference in angles, i.e., that they are not parallel? If they are not parallel, then they point to a center. On Jan 16, 2015 11:57 PM, "Dave Gary" <davegary@me.com> wrote:
The Big Bang was a density singularity, not a space-time singularity. Space-time did not exist before the Big Bang, therefore, there was no point "in space" to expand out from. The Big Bang was not like an explosion in our three-dimensional space...something one could trace back to a center. Hopefully, the following won't be too obscure. I've had a long day.
Physical surfaces have two types of geometry, intrinsic and extrinsic. Intrinsic geometric properties refer to measurements made entirely on the surface itself. All other geometric properties are extrinsic. No one knows the shape of our universe, that's an extrinsic property of the space-time geometry and no one has been outside our universe and looked back at the surface and observed its shape. We can only make measurements within space-time, therefore, any data we obtain about our space-time's geometry are, by definition, intrinsic. It is hopeless for us to try to envision the geometry of our three-dimensional space-time as being, somehow, bent through a fourth dimension. What would that look like? For this reason, physical space has no known extrinsic geometry. We make measurements within space-time and infer (because of distance distortion) the "curvature" and geometry of space-time. Curvature of space-time, according to the map of general relativity, is a mathematic property and refers to the use of distorted models for explaining the geometry of space-time. For an analogy of this concept, think of our own planet.
Earth is a sphere, but we can measure its curvature from two-dimensional measurements taken entirely on its surface. To do this, one can make an atlas of maps of Earth's surface. How does one derive the curvature of Earth from this atlas of maps? Through the distance distortion made apparent from flattening out the sphere to generate the maps. We can reconstruct the full three-dimensional geometry of Earth from a system of flat maps taken of its surface (an intrinsic measurement) by looking at the two-dimensional distance distortions in these maps. This was Mercator's great insight when he produced his nautical maps. One sees the distance distortion he needed to provide in his maps so that a heading of constant curvature on the spherical Earth appeared as a straight line on his maps. This is why Greenland appears so large on a Mercator projection...it's the consequence of a two-dimensional projection of a spherical surface with the curvature of the spherical surface manifesting itself as distance distortion. As one does not need the third dimension to ascertain the curvature of Earth, similarly, one does not need to observe a fourth dimension to investigate the "curvature" of our three-dimensional space.
Additionally, our universe appears to have no preferred center and on large scales appears isotropic and homogeneous. Why? It is the curvature of space-time that makes this so. Again, another analogy with Earth. Suppose we take a bunch of Eiffel Tower models (imagine big ones) and spread them out in a network across Earth's surface. We would notice that we could place these Eiffel Tower models on our two-dimensional surface in such a way as to have a homogeneous and isotropic structure in our placement and it would appear to anyone on the surface of Earth that the network has no edge, no boundary or any preferred center. I threw this in because it's not the balloon analogy. There Sig, no balloons. Finally, the curvature of our universe (on large distance scales) provides a similar metric to matter within it....no edge, no boundary and no preferred center.
Hopefully, this wasn't too obscure?
Dave
On Jan 16, 2015, at 11:07, Joe Bauman via Utah-Astronomy < utah-astronomy@mailman.xmission.com> wrote:
You are on that point as is everything else.
------------------------------
On Fri, Jan 16, 2015 6:50 AM MST Stephen Peterson wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 12:07, Chuck Hards <chuck.hards@gmail.com> wrote:
Steve, the mistake you're making is imagining the Big Bang as happening in a larger space. The Big Bang created the entire universe and it expanded very quickly. The entire universe was and is expanding.
Imagine dots all over the surface of a balloon, and inflate the balloon. All of the dots move away from each other as the balloon expands. The balloon surface is analagous to the fabric of three-dimenstional space.
On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
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Dave's point is that while a balloon has a center, the two dimensional surface of the balloon does not. The balloon surface is a model that we can easily visualize. It's an analogy for the centerless space that we cannot easily visualize, but which the data firmly dictates. If there were an edge, or a center, we would have found it. We have looked long and hard for it to the point that now we can rule out their existence. People new to the problem just assume that we haven't looked hard enough. They are wrong. You need to realize that there is structure beyond our common sense perceptions. We can infer this structure but no directly see it or easily imagine it. DT From: Siegfried Jachmann <siegfried@jachmann.org> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Saturday, January 17, 2015 6:18 PM Subject: Re: [Utah-astronomy] Center of the universeCenter of the universe With high Eifel Towers wouldn't you be able to measure a difference in angles, i.e., that they are not parallel? If they are not parallel, then they point to a center. On Jan 16, 2015 11:57 PM, "Dave Gary" <davegary@me.com> wrote:
The Big Bang was a density singularity, not a space-time singularity. Space-time did not exist before the Big Bang, therefore, there was no point "in space" to expand out from. The Big Bang was not like an explosion in our three-dimensional space...something one could trace back to a center. Hopefully, the following won't be too obscure. I've had a long day.
Physical surfaces have two types of geometry, intrinsic and extrinsic. Intrinsic geometric properties refer to measurements made entirely on the surface itself. All other geometric properties are extrinsic. No one knows the shape of our universe, that's an extrinsic property of the space-time geometry and no one has been outside our universe and looked back at the surface and observed its shape. We can only make measurements within space-time, therefore, any data we obtain about our space-time's geometry are, by definition, intrinsic. It is hopeless for us to try to envision the geometry of our three-dimensional space-time as being, somehow, bent through a fourth dimension. What would that look like? For this reason, physical space has no known extrinsic geometry. We make measurements within space-time and infer (because of distance distortion) the "curvature" and geometry of space-time. Curvature of space-time, according to the map of general relativity, is a mathematic property and refers to the use of distorted models for explaining the geometry of space-time. For an analogy of this concept, think of our own planet.
Earth is a sphere, but we can measure its curvature from two-dimensional measurements taken entirely on its surface. To do this, one can make an atlas of maps of Earth's surface. How does one derive the curvature of Earth from this atlas of maps? Through the distance distortion made apparent from flattening out the sphere to generate the maps. We can reconstruct the full three-dimensional geometry of Earth from a system of flat maps taken of its surface (an intrinsic measurement) by looking at the two-dimensional distance distortions in these maps. This was Mercator's great insight when he produced his nautical maps. One sees the distance distortion he needed to provide in his maps so that a heading of constant curvature on the spherical Earth appeared as a straight line on his maps. This is why Greenland appears so large on a Mercator projection...it's the consequence of a two-dimensional projection of a spherical surface with the curvature of the spherical surface manifesting itself as distance distortion. As one does not need the third dimension to ascertain the curvature of Earth, similarly, one does not need to observe a fourth dimension to investigate the "curvature" of our three-dimensional space.
Additionally, our universe appears to have no preferred center and on large scales appears isotropic and homogeneous. Why? It is the curvature of space-time that makes this so. Again, another analogy with Earth. Suppose we take a bunch of Eiffel Tower models (imagine big ones) and spread them out in a network across Earth's surface. We would notice that we could place these Eiffel Tower models on our two-dimensional surface in such a way as to have a homogeneous and isotropic structure in our placement and it would appear to anyone on the surface of Earth that the network has no edge, no boundary or any preferred center. I threw this in because it's not the balloon analogy. There Sig, no balloons. Finally, the curvature of our universe (on large distance scales) provides a similar metric to matter within it....no edge, no boundary and no preferred center.
Hopefully, this wasn't too obscure?
Dave
On Jan 16, 2015, at 11:07, Joe Bauman via Utah-Astronomy < utah-astronomy@mailman.xmission.com> wrote:
You are on that point as is everything else.
------------------------------
On Fri, Jan 16, 2015 6:50 AM MST Stephen Peterson wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 12:07, Chuck Hards <chuck.hards@gmail.com> wrote:
Steve, the mistake you're making is imagining the Big Bang as happening in a larger space. The Big Bang created the entire universe and it expanded very quickly. The entire universe was and is expanding.
Imagine dots all over the surface of a balloon, and inflate the balloon. All of the dots move away from each other as the balloon expands. The balloon surface is analagous to the fabric of three-dimenstional space.
On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com>
wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
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If one were measuring to the center of Earth, but we are restricting ourselves entirely to the surface. This is why I mentioned Mercator. Before his time, if one plotted a straight-line course (say from Cuba to England) and one stayed on that particular course (let’s just say 41 degrees) and one did not account for the curvature of Earth, then maintaining that course would result in one not hitting the objective. Ships, because of this very thing, were missing their destinations by miles on long voyages. It was very expensive and sometimes very hazardous. I believe (one should check this to make sure) that the distance difference in latitude (when converting from a spherical surface to a flat projection) is a function of the integral of the secant. In other words, it is not a strictly linear conversion. In Mercator’s time, most ships did not carry an accurate globe of Earth’s surface on board the ship. The captain of a vessel (and his navigator) had access to an atlas of maps. Plotting a straight-line course on those maps and not taking the curvature of Earth into account (which is all they had before Mercator’s projective maps) was oftentimes disastrous. The point was that one can infer three-dimensional geometry from two-dimensional data if one fudges-in the distance distortion. Time to go to work. Thanks for the discussion. You guys make me think. Wait a minute….thinking? Dave On Jan 17, 2015, at 18:18, Siegfried Jachmann <siegfried@jachmann.org> wrote:
With high Eifel Towers wouldn't you be able to measure a difference in angles, i.e., that they are not parallel? If they are not parallel, then they point to a center. On Jan 16, 2015 11:57 PM, "Dave Gary" <davegary@me.com> wrote:
The Big Bang was a density singularity, not a space-time singularity. Space-time did not exist before the Big Bang, therefore, there was no point "in space" to expand out from. The Big Bang was not like an explosion in our three-dimensional space...something one could trace back to a center. Hopefully, the following won't be too obscure. I've had a long day.
Physical surfaces have two types of geometry, intrinsic and extrinsic. Intrinsic geometric properties refer to measurements made entirely on the surface itself. All other geometric properties are extrinsic. No one knows the shape of our universe, that's an extrinsic property of the space-time geometry and no one has been outside our universe and looked back at the surface and observed its shape. We can only make measurements within space-time, therefore, any data we obtain about our space-time's geometry are, by definition, intrinsic. It is hopeless for us to try to envision the geometry of our three-dimensional space-time as being, somehow, bent through a fourth dimension. What would that look like? For this reason, physical space has no known extrinsic geometry. We make measurements within space-time and infer (because of distance distortion) the "curvature" and geometry of space-time. Curvature of space-time, according to the map of general relativity, is a mathematic property and refers to the use of distorted models for explaining the geometry of space-time. For an analogy of this concept, think of our own planet.
Earth is a sphere, but we can measure its curvature from two-dimensional measurements taken entirely on its surface. To do this, one can make an atlas of maps of Earth's surface. How does one derive the curvature of Earth from this atlas of maps? Through the distance distortion made apparent from flattening out the sphere to generate the maps. We can reconstruct the full three-dimensional geometry of Earth from a system of flat maps taken of its surface (an intrinsic measurement) by looking at the two-dimensional distance distortions in these maps. This was Mercator's great insight when he produced his nautical maps. One sees the distance distortion he needed to provide in his maps so that a heading of constant curvature on the spherical Earth appeared as a straight line on his maps. This is why Greenland appears so large on a Mercator projection...it's the consequence of a two-dimensional projection of a spherical surface with the curvature of the spherical surface manifesting itself as distance distortion. As one does not need the third dimension to ascertain the curvature of Earth, similarly, one does not need to observe a fourth dimension to investigate the "curvature" of our three-dimensional space.
Additionally, our universe appears to have no preferred center and on large scales appears isotropic and homogeneous. Why? It is the curvature of space-time that makes this so. Again, another analogy with Earth. Suppose we take a bunch of Eiffel Tower models (imagine big ones) and spread them out in a network across Earth's surface. We would notice that we could place these Eiffel Tower models on our two-dimensional surface in such a way as to have a homogeneous and isotropic structure in our placement and it would appear to anyone on the surface of Earth that the network has no edge, no boundary or any preferred center. I threw this in because it's not the balloon analogy. There Sig, no balloons. Finally, the curvature of our universe (on large distance scales) provides a similar metric to matter within it....no edge, no boundary and no preferred center.
Hopefully, this wasn't too obscure?
Dave
On Jan 16, 2015, at 11:07, Joe Bauman via Utah-Astronomy < utah-astronomy@mailman.xmission.com> wrote:
You are on that point as is everything else.
------------------------------
On Fri, Jan 16, 2015 6:50 AM MST Stephen Peterson wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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Sent from my iPad
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On Jan 16, 2015, at 12:07, Chuck Hards <chuck.hards@gmail.com> wrote:
Steve, the mistake you're making is imagining the Big Bang as happening in a larger space. The Big Bang created the entire universe and it expanded very quickly. The entire universe was and is expanding.
Imagine dots all over the surface of a balloon, and inflate the balloon. All of the dots move away from each other as the balloon expands. The balloon surface is analagous to the fabric of three-dimenstional space.
On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
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Erudite. 73 Sent from my iPad
On Jan 16, 2015, at 11:55 PM, Dave Gary <davegary@me.com> wrote:
The Big Bang was a density singularity, not a space-time singularity. Space-time did not exist before the Big Bang, therefore, there was no point "in space" to expand out from. The Big Bang was not like an explosion in our three-dimensional space...something one could trace back to a center. Hopefully, the following won't be too obscure. I've had a long day.
Physical surfaces have two types of geometry, intrinsic and extrinsic. Intrinsic geometric properties refer to measurements made entirely on the surface itself. All other geometric properties are extrinsic. No one knows the shape of our universe, that's an extrinsic property of the space-time geometry and no one has been outside our universe and looked back at the surface and observed its shape. We can only make measurements within space-time, therefore, any data we obtain about our space-time's geometry are, by definition, intrinsic. It is hopeless for us to try to envision the geometry of our three-dimensional space-time as being, somehow, bent through a fourth dimension. What would that look like? For this reason, physical space has no known extrinsic geometry. We make measurements within space-time and infer (because of distance distortion) the "curvature" and geometry of space-time. Curvature of space-time, according to the map of general relativity, is a mathematic property and refers to the use of distorted models for explaining the geometry of space-time. For an analogy of this concept, think of our own planet.
Earth is a sphere, but we can measure its curvature from two-dimensional measurements taken entirely on its surface. To do this, one can make an atlas of maps of Earth's surface. How does one derive the curvature of Earth from this atlas of maps? Through the distance distortion made apparent from flattening out the sphere to generate the maps. We can reconstruct the full three-dimensional geometry of Earth from a system of flat maps taken of its surface (an intrinsic measurement) by looking at the two-dimensional distance distortions in these maps. This was Mercator's great insight when he produced his nautical maps. One sees the distance distortion he needed to provide in his maps so that a heading of constant curvature on the spherical Earth appeared as a straight line on his maps. This is why Greenland appears so large on a Mercator projection...it's the consequence of a two-dimensional projection of a spherical surface with the curvature of the spherical surface manifesting itself as distance distortion. As one does not need the third dimension to ascertain the curvature of Earth, similarly, one does not need to observe a fourth dimension to investigate the "curvature" of our three-dimensional space.
Additionally, our universe appears to have no preferred center and on large scales appears isotropic and homogeneous. Why? It is the curvature of space-time that makes this so. Again, another analogy with Earth. Suppose we take a bunch of Eiffel Tower models (imagine big ones) and spread them out in a network across Earth's surface. We would notice that we could place these Eiffel Tower models on our two-dimensional surface in such a way as to have a homogeneous and isotropic structure in our placement and it would appear to anyone on the surface of Earth that the network has no edge, no boundary or any preferred center. I threw this in because it's not the balloon analogy. There Sig, no balloons. Finally, the curvature of our universe (on large distance scales) provides a similar metric to matter within it....no edge, no boundary and no preferred center.
Hopefully, this wasn't too obscure?
Dave
On Jan 16, 2015, at 11:07, Joe Bauman via Utah-Astronomy <utah-astronomy@mailman.xmission.com> wrote:
You are on that point as is everything else.
------------------------------
On Fri, Jan 16, 2015 6:50 AM MST Stephen Peterson wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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Sent from my iPad
On Jan 16, 2015, at 06:50, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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Sent from my iPad
Sent from my iPad
On Jan 16, 2015, at 12:07, Chuck Hards <chuck.hards@gmail.com> wrote:
Steve, the mistake you're making is imagining the Big Bang as happening in a larger space. The Big Bang created the entire universe and it expanded very quickly. The entire universe was and is expanding.
Imagine dots all over the surface of a balloon, and inflate the balloon. All of the dots move away from each other as the balloon expands. The balloon surface is analagous to the fabric of three-dimenstional space.
On Fri, Jan 16, 2015 at 6:50 AM, Stephen Peterson <scpki7l@gmail.com> wrote:
If the universe originated in the 'Big Bang', that is, expanding more or less uniformly from a single point wouldn't that point be the center? Steve Peterson, Hurricane
Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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participants (6)
-
Chuck Hards -
daniel turner -
Dave Gary -
Larry Holmes -
Siegfried Jachmann -
Stephen Peterson