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Looking into the past with a telescope



 
 
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  #21  
Old January 28th 07, 05:26 PM posted to sci.astro.amateur
Brian Tung[_1_]
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Default Looking into the past with a telescope

Chris L Peterson wrote:
Is radial symmetry a condition of having a center? I would think the
Universe must have a center in some higher dimension, regardless of its
shape and topology (even if that center isn't a simple point).


I suppose it depends on what you mean by "center." If you just mean
something like "center of mass," then you're probably right. I was
thinking more of a geometric center, obviously.

--
Brian Tung
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  #22  
Old January 28th 07, 05:30 PM posted to sci.astro.amateur
Starboard
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Default Looking into the past with a telescope



Does it have a center in some higher dimension?


It might, but not necessarily. The universe need not exhibit radial
symmetry.


Tell me this: Did the entire universe that we know today expand from a
point? What is it exactly that is expanding? I visualize it as light
from the early universe radiating out, pushing the frontier in all
directions, creating new space, as we speak?

Errol

  #23  
Old January 28th 07, 05:44 PM posted to sci.astro.amateur
Chris L Peterson
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Default Looking into the past with a telescope

On 28 Jan 2007 09:30:40 -0800, "Starboard" wrote:

Tell me this: Did the entire universe that we know today expand from a
point? What is it exactly that is expanding? I visualize it as light
from the early universe radiating out, pushing the frontier in all
directions, creating new space, as we speak?


If by "point" you mean a 3-dimensional location, then the answer is no.
The expansion of the Universe isn't the spreading out of matter and
energy (which seems to be the way you imagine it), but the spreading out
of the "stuff" the Universe itself is made of. The expansion is
occurring in a higher dimension, so there is no 3D point that can be
identified with the center. Others have already pointed out a useful
analogy, if you can get your mind wrapped around it: when you blow up a
balloon, the 2D surface of the balloon is getting larger. It is
expanding about a 3D point at the center of the balloon, but that point
doesn't exist in the 2D world of the balloon's surface. In the same way,
our perceived 3D universe can be getting larger even though we have no
way of localizing the center of that expansion, which is a 4D (or
higher) point.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #24  
Old January 28th 07, 06:06 PM posted to sci.astro.amateur
Steve Paul
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Default Looking into the past with a telescope

"Starboard" wrote in message
ups.com...


Does it have a center in some higher dimension?


It might, but not necessarily. The universe need not exhibit radial
symmetry.


Tell me this: Did the entire universe that we know today expand from a
point? What is it exactly that is expanding? I visualize it as light
from the early universe radiating out, pushing the frontier in all
directions, creating new space, as we speak?

Errol


Not that this answers your question, but I'd like to interject my
"perspectives", since you are "visualizing".

1) We can only measure so far. Therefore at some point we reach that limit
in all directions, and that defines a sphere.

2) #1 doesn't necessarily define the shape, origin, or expansion of the
universe.

#1 is a simple concept that just about anyone can understand. I give this
model to others who are not normally astronomy minded, because, well,
because they generally don't ever give the universe much thought. I myself
do not grasp much, if any of #2 in detail, so I'm silent on the subject,
other than to say what I just said above.

I can live the rest of my life perfectly happily accepting the simple model
of #1 and being a star-gazer, appreciating the "simple" elegance and beauty
of large scale, or Newtonian physics, stars, and the universe as I
understand it day to day. I think most "non-astronomers", and non-physicists
appreciate having a simple view of a spherical universe to start with, and
then if they wish, to pursue the matter of considering what lies beyond that
sphere, what consitutes the sphere, and how the universe itself is a living
thing (in that it possibly has a life cycle of its own) in which that sphere
exists.


  #25  
Old January 28th 07, 06:25 PM posted to sci.astro.amateur
Steve Paul
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Default Looking into the past with a telescope

"Chris L Peterson" wrote in message
...
On 28 Jan 2007 09:30:40 -0800, "Starboard" wrote:

Tell me this: Did the entire universe that we know today expand from a
point? What is it exactly that is expanding? I visualize it as light
from the early universe radiating out, pushing the frontier in all
directions, creating new space, as we speak?


If by "point" you mean a 3-dimensional location, then the answer is no.
The expansion of the Universe isn't the spreading out of matter and
energy (which seems to be the way you imagine it), but the spreading out
of the "stuff" the Universe itself is made of.


Uh oh... I'm getting in way over my head here..

What is "stuff", if not matter and energy?

The expansion is
occurring in a higher dimension, so there is no 3D point that can be
identified with the center. Others have already pointed out a useful
analogy, if you can get your mind wrapped around it: when you blow up a
balloon, the 2D surface of the balloon is getting larger. It is
expanding about a 3D point at the center of the balloon, but that point
doesn't exist in the 2D world of the balloon's surface. In the same way,
our perceived 3D universe can be getting larger even though we have no
way of localizing the center of that expansion, which is a 4D (or
higher) point.


I think my "sphere", is embedded in the surface of the balloon. I'm okay
with that. Possibly the issue is one of scale. The immensity of the universe
is not something that I'm ready to deal with, being finite minded. My sphere
is a finite object defined by how far we can measure backward in time when
we hit the "beginning". If we look through a measuring device and we see all
the way to the background radiation, then we can see no further. If that is
defined as 13 billion years, then our sphere is 13 billion light years in
radius.

But that doesn't define the shape, or size of the actual universe at all. I
can accept that quite easily, given that for someone who happens to be 13
billion light years away, the sphere (if I may) of the measurable universe
for them is also 13 billion light years in radius, as defined by the "age"
of the universe, as measured from here, given that we can only see 13
billion light years distant.


  #26  
Old January 28th 07, 07:04 PM posted to sci.astro.amateur
Brian Tung[_1_]
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Default Looking into the past with a telescope

Steve Paul wrote:
Uh oh... I'm getting in way over my head here..

What is "stuff", if not matter and energy?


Space-time.

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
  #27  
Old January 28th 07, 07:38 PM posted to sci.astro.amateur
Starboard
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Posts: 126
Default Looking into the past with a telescope


Tell me this: Did the entire universe that we know today expand from a
point? What is it exactly that is expanding? I visualize it as light
from the early universe radiating out, pushing the frontier in all
directions, creating new space, as we speak?


Errol Not that this answers your question, but I'd like to interject my
"perspectives", since you are "visualizing".
1) We can only measure so far. Therefore at some point we reach that limit
in all directions, and that defines a sphere.
2) #1 doesn't necessarily define the shape, origin, or expansion of the
universe.


Steve,

I might as well explain in a little more detail what it is I do
visualize. And please, try not to laugh....

First I'd like to state that what I am going to describe will be
described from a perspective that did not exist. I state the obvious
only because earlier, Greg shot me down for my metaphor about a guy
watching the big bang expand. He quickly stated that such a condition
was impossible. Of course I knew that I was only trying to conduct
a little thought experiment. Much the same, the analogy of the
balloon. After all, people cannot exist as 2D creatures right? That's
the equivalent of starting a metaphor with, "assume a cow is
spherical."

I visualize some event taking place and the first particle coming
into existence . Perhaps it be the very first quark only moments after
quark confinement. At this point, space does not exist. The way I see
it, space will come into play after the second particle forms. At
this point, one could say that there is space between the two
particles. Or, one is here and the other is there. Again, I know there
are no eyes to see it. Heck, there are probably no photons....

At this point, time does not exist yet. Time will become noticeable
once the third event takes place because at that point, an observer
could say that the time between the first two events create the first
unit of time passage. The observer now has a reference.

After the dark period (got that from an October 06 Time Magazine
issue), I visualize radiation spewing in three dimensions. By
radiation, I mean light of every imaginable frequency, and other crap
that I wouldn't dare try to pronounce. I imagine that it is not
homogenous. I imagine that mass is not evenly distributed, therefore,
gravity will limit expansion accordingly. I imagine the wave front
encompassing my observer in my though experiment. He is now in the
suddenly in the universe. Now he feels like he is being tugged on by
gravity, light is shining in his face, he is in the universe as we
know it.

Bottom line is that in my mind's model, there is no other stuff.

I'm going to stop here so that you can all take a break. Give your jaw
and stomach a rest.

Errol

  #28  
Old January 28th 07, 08:28 PM posted to sci.astro.amateur
Davoud[_1_]
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Default Looking into the past with a telescope

Chris L Peterson:
Is radial symmetry a condition of having a center? I would think the
Universe must have a center in some higher dimension, regardless of its
shape and topology (even if that center isn't a simple point).


Brian Tung:
I suppose it depends on what you mean by "center." If you just mean
something like "center of mass," then you're probably right. I was
thinking more of a geometric center, obviously.


I can think of no reason why the Universe can't have a central region
in three-dimensional space if the Big Bang theory is correct. If the
Universe exhibits perfect radial symmetry, then the center is a simple
point in three-dimensional space; if, due to quantum fluctuations, the
Universe has minor bumps at its edge, like the surface of a rocky
planet, then the center in three-dimensional space would need to be
spread out; a central /region/ rather than a point. I have trouble
seeing the Universe having taken the shape of a banana or

The problem is the edge. I can at least grasp the /concept/ of a
center. In my version of the balloon analogy the balloon is perfectly
spherical (or very nearly so, considering the above-mentioned quantum
fluctuations it doesn't need a stem because it is self-inflating.
Every point is moving away from a common center, which is where those
points started out (wrapped in a single dimension?) when the balloon
was infinitely small. But the /edge/ of the Universe? From inside the
balloon I can move to the edge and encounter a material substance that
I cannot penetrate. My balloon is transparent, and I can see what is
outside that object. But I can't get my mind around an immaterial edge
beyond which is nothing whatsoever, not even empty space. One
cosmologist, half joking, said "It could be a brick wall, for all we
know."

Physicists used to say that, ultimately, the Universe could and would
be explained by a few simple laws that everyone could understand at
least in a rudimentary way. I think that all hope for such an
explanation has been abandoned. String theory, Inflation, the notion
that gravity is so weak because it is Not of This World, but is just
leaking in from another dimension; the Universe may be a hologram; the
Universe may not exist at all except in our minds; the physicists
themselves don't agree on or understand this stuff. That doesn't bode
well for me understanding it.

Here is my one prediction, however: There will not be a Theory of
Everything that unifies gravity with the other forces. Gravity, it will
be decided, is distinct, and must be understood on its own terms.

Davoud

--
usenet *at* davidillig dawt com
  #29  
Old January 28th 07, 08:37 PM posted to sci.astro.amateur
Greg Crinklaw
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Default Looking into the past with a telescope

Starboard wrote:
First I'd like to state that what I am going to describe will be
described from a perspective that did not exist. I state the obvious
only because earlier, Greg shot me down for my metaphor about a guy
watching the big bang expand. He quickly stated that such a condition
was impossible. Of course I knew that I was only trying to conduct
a little thought experiment. Much the same, the analogy of the
balloon. After all, people cannot exist as 2D creatures right? That's
the equivalent of starting a metaphor with, "assume a cow is
spherical."


I think you need to stop being so stuck on your own view and instead try
to understand the one people are presenting you with. Please try to let
go of your preconceptions. A good popular book on cosmology might help
a lot. As you read it, come back here and ask questions to clarify things.

To answer your question above, the 2D world is an analogy. Don't
confuse this with a model of the universe--it isn't. It's just an
analogy meant to explain a concept. It is *not* the same as your cow
assumption!

As a 3D being you understand the world in 3 dimensions. But what if
there are more dimensions than you can perceive? What would that look
like? The answer is that you'd observe some odd things about the
universe--things that don't easily fit into your 3D view, like a
universe that expands away from any point within it, and has no center.

The 2D analogy is there merely as a means of investigating how more
dimensions than can be sensed can produce a universe with some of these
odd characteristics. You have to imagine a 2D being who knows nothing
beyond the surface of the balloon. The entire universe is the surface
only. So when the balloon is blown up, where is the center? The answer
is twofold: for the 2D being it has no center. But for you as a 3D
being you can see that the center lies in a dimension beyond that of the
surface of the balloon. What is obvious to the 3D being is not apparent
at all to the 2D being. Her only hope is to note some odd things about
her universe and postulate more dimensions to explain them.

Try to imagine this analogy from the point of view of the 2D being.
Think about questions like, what would they observe if someone from
outside blew up the balloon? If they started out in one direction and
traveled far enough, they would come back to where they started. That
would seem like magic. So how would they explain that scientifically?
But please keep in mind that the universe is NOT the surface of a
balloon. Again, it is the concept of what more dimensions than can be
perceived might look like that is important. Once that concept is
understood, then understand that in our own universe there are some
weird things that can't easily be explained in 3D. But postulating more
dimensions explains them neatly.

Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
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To reply take out your eye
  #30  
Old January 28th 07, 08:44 PM posted to sci.astro.amateur
Greg Neill
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Default Looking into the past with a telescope

"Davoud" wrote in message ...

I can think of no reason why the Universe can't have a central region
in three-dimensional space if the Big Bang theory is correct.


If the BB is correct, then every place in the 3D universe was
once co-located with the center. So there is no unique place
that one can call The Center, since every place equally
fulfills the role.


 




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