| Topic: |
Science > Physics |
| User: |
"Nick" |
| Date: |
10 Aug 2005 12:50:46 AM |
| Object: |
Galaxies expanding with space? The Space Stretch |
Either the galaxies are moving through space
or space is stretching out inbetween them.
What does the space stretch do to the
space's geometry?
Space stretch geometry?
-- Light Falls --
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| User: "T Wake" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
10 Aug 2005 02:11:02 PM |
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"Nick" <macromitch@yahoo.com> wrote in message
news:1123653046.070484.291670@o13g2000cwo.googlegroups.com...
Either the galaxies are moving through space
or space is stretching out inbetween them.
Didnt you like the answers you had last time.
What does the space stretch do to the
space's geometry?
Ask a new question.
Space stretch geometry?
Why do you think this is wrong?
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| User: "Nick" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
10 Aug 2005 04:50:43 PM |
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what is the geometry of stretching space?
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| User: "T Wake" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
10 Aug 2005 05:34:35 PM |
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"Nick" <macromitch@yahoo.com> wrote in message
news:1123710643.092342.275390@g49g2000cwa.googlegroups.com...
what is the geometry of stretching space?
What do you mean by "stretching space?"
IIRC the expansion of space was not a stretch, more an increase in the
distance between large scale structures.
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| User: "Spoonfed" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
13 Aug 2005 10:40:41 AM |
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T Wake wrote:
"Nick" <macromitch@yahoo.com> wrote in message
news:1123710643.092342.275390@g49g2000cwa.googlegroups.com...
what is the geometry of stretching space?
What do you mean by "stretching space?"
IIRC the expansion of space was not a stretch, more an increase in the
distance between large scale structures.
Depending on who you talk to. If you talk to me, that's what I would
tell you. I would also tell you that "space stretching" is a misnomer,
but a lot of people don't know that. They use dots on a polka-dot
balloon to show that the center of an expanding two dimensional surface
is not necessarily on the surface, then go on to say that it is the
same with our universe.
The analogy is very vague, and it must break down at some point. Does
the universe wrap around on itself like the surface of the balloon?
Does the center of the universe lie on a vector perpendicular to all
spatial directions? Do the dots on the surface of the balloon expand,
or do they shrink relative to the surface of the balloon, being held
together by gravity and molecular forces? If the dots on the surface
expand, then of course, it would not seem like the universe were
expanding at all, since our meter sticks would expand at the same rate.
Finally there is no cause and effect related to this balloon model. We
don't see some evidence pointing to the balloon and only the balloon.
All we see is that objects in the universe are moving away from us. We
also see that there is a dim all-pervasive black-body radiation called
the CMB. The CMB has been carefully mapped, and resembles an acoustic
signature of a roughly spherical object (for instance, a balloon)... As
long as you don't look to close. An acoustic signature would, of
course, involve molecules bouncing off each other and exchanging energy
across the surface of the sphere, whereas the surface of this sphere
has a radius of at least 13 billion light years.
However, to a number-cruncher, an acoustic signature is an acoustic
signature, and currently the money (whatever tiny amount there is), and
the interest (also pretty small, I think), is in looking at the
anomolies in the acoustic signature, and trying to find local causes
for the lowest frequency elements of the acoustical signature to be
missing.
The issue of these missing frequencies, according to the August issue
of Scientific American "could send us back to the drawing board about
the early universe." I've not been able to understand what is on the
current drawing board, but I do know one thing that is missing: A
proper appreciation for the relativistic effects due to the momentum of
the receding objects.
Why are people ignoring these effects? I gather that people believe
"The galaxies aren't really receding. The space is expanding between
the galaxies making them appear to recede." Which returns us to Nick's
question. What is the geometry of stretching space?
The clearest answer is what T Wake has given. Space is not stretching.
The objects within it are moving apart. However, this is in direct
conflict with the belief that the galaxies are not really receding.
Finally, another issue obfuscates this further. There is more than one
way to define simultaneity in cosmology.
The first way is what I would think is most obvious, to simply take a
photograph, and anything on a surface equidistant from the lens that
shows up in the photo should be considered simultaneous, making some
minor corrections for differences in gravitational potential of the
source image. *totally obvious, right? actually it sounds a lot more
complicated than I thought.*
The second way to define simultaneity is by measurement of any
particular object's proper age, that is the time it would measure
itself aging since, for instance the big bang. It is in this model,
where if you plot positions versus time, you actually get a universe
which is infinite in extent, completely homogeneous, and expanding over
time. This seems to me to be an odd way of defining simultaneity, but
it does make some of the other often repeated statements about
cosmology make more sense.
So there are a lot of arguments caused because there is more than one
context in which to describe the phenomena, analogies are useful in one
context and not in another, and the mathematics are sometimes suggested
without reference to specific problems. The answers are vague, and the
questions are even more vague, and the more people know about the
topic, the less they want to say, because they are more aware of what
they don't know.
This is just the way it seems to me this morning.
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| User: "Nick" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
13 Aug 2005 11:39:06 PM |
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Space stretching can be represented by a closed
universe where there is no boundary expanding at
the speed of light. Instead the space inbetween
the galaxies is stretching.
To answer my question, the space stretch can be
represented in Riemanian geometry as the expanding
surface of a hypersphere. Curvature would go down
inbetween the galaxies as more distance is created.
Gravity will only get weaker inbetween galaxies.
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| User: "T Wake" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
14 Aug 2005 03:19:45 PM |
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"Nick" <macromitch@yahoo.com> wrote in message
news:1123994346.746049.92320@g43g2000cwa.googlegroups.com...
Space stretching can be represented by a closed
universe where there is no boundary expanding at
the speed of light. Instead the space inbetween
the galaxies is stretching.
You are wrong, and space stretching is your interpretation not mine.
To answer my question, the space stretch can be
represented in Riemanian geometry as the expanding
surface of a hypersphere. Curvature would go down
inbetween the galaxies as more distance is created.
Gravity will only get weaker inbetween galaxies.
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| User: "Nick" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
14 Aug 2005 11:38:11 PM |
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T Wake wrote:
"Nick" <macromitch@yahoo.com> wrote in message
news:1123994346.746049.92320@g43g2000cwa.googlegroups.com...
Space stretching can be represented by a closed
universe where there is no boundary expanding at
the speed of light. Instead the space inbetween
the galaxies is stretching.
You are wrong, and space stretching is your interpretation not mine.
To answer my question, the space stretch can be
represented in Riemanian geometry as the expanding
surface of a hypersphere. Curvature would go down
inbetween the galaxies as more distance is created.
Gravity will only get weaker inbetween galaxies.
Did you originate this thread?
Did I mention your interpretation?
I say the surface of a hypersphere.
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| User: "T Wake" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
15 Aug 2005 02:52:31 AM |
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"Nick" <macromitch@yahoo.com> wrote in message
news:1124080691.808366.8140@z14g2000cwz.googlegroups.com...
T Wake wrote:
"Nick" <macromitch@yahoo.com> wrote in message
news:1123994346.746049.92320@g43g2000cwa.googlegroups.com...
Space stretching can be represented by a closed
universe where there is no boundary expanding at
the speed of light. Instead the space inbetween
the galaxies is stretching.
You are wrong, and space stretching is your interpretation not mine.
To answer my question, the space stretch can be
represented in Riemanian geometry as the expanding
surface of a hypersphere. Curvature would go down
inbetween the galaxies as more distance is created.
Gravity will only get weaker inbetween galaxies.
Did you originate this thread?
Did I mention your interpretation?
However it is not possible to get others to explain or justify confusion
generated by "your" (lack of) understanding.
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| User: "" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
15 Aug 2005 02:55:30 AM |
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And you've been brainwashed
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| User: "T Wake" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
15 Aug 2005 03:04:54 AM |
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<macromitch@internetCDS.com> wrote in message
news:1124092530.933281.213640@g14g2000cwa.googlegroups.com...
And you've been brainwashed
No where near as much as you have.
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| User: "" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
15 Aug 2005 03:07:47 AM |
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But I haven't went to school
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| User: "T Wake" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
15 Aug 2005 03:12:47 AM |
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<macromitch@internetCDS.com> wrote in message
news:1124093267.451529.200210@g43g2000cwa.googlegroups.com...
But I haven't went to school
Well that is fairly obvious.
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| User: "Jim Black" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
17 Aug 2005 08:31:30 PM |
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Nick wrote:
I say the surface of a hypersphere.
It'll work for this problem, as long as you bear in mind that it only
represents one of the three possibilities, the others being an infinite
flat universe and an infinite saddle-shaped universe. If you want to
get an idea of what each looks like, you can build a model. You can
approximate a sphere nicely with pentagons and hexagons in the pattern
of a soccer ball. Substitute hexagons for the pentagons, and you get
flat space. Substitute seven-sided heptagons, and you get the
saddle-shaped possibility.
The next step in what it seems you are trying to do is to introduce
time. Special relativity treats time as a dimension, just like length,
width, and height. The main difference between time and space is that
for a right triangle where the legs are distances, the hypotenuse has a
length of sqrt(x^2 + y^2), but if one of the legs is a time, the
hypotenuse's length is sqrt(x^2 - c^2 t^2).
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| User: "" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
17 Aug 2005 11:28:07 PM |
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Only one possibility as I see it
Closed universe obeying No boundary proposal
That universe is the surface of a hypersphere.
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| User: "Jim Black" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
18 Aug 2005 09:32:24 PM |
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wrote:
Only one possibility as I see it
Closed universe obeying No boundary proposal
That universe is the surface of a hypersphere.
The others don't have boundaries either, because they're infinite.
If you make your hypersphere big enough, it gets closer and closer to
an infinite flat universe. If you accept a closed universe as a
possibility, you should be okay with the flat case, unless you have
some objection to an infinite universe.
What objection could that be?
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| User: "" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
19 Aug 2005 12:04:07 AM |
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Infinite universe Jim?
It had a beining and is expanding at a finite rate.
You can't get infinity out of that.
The only infinity is the future.
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| User: "T Wake" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
19 Aug 2005 03:55:47 AM |
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<macromitch@internetCDS.com> wrote in message
news:1124427847.043301.49910@f14g2000cwb.googlegroups.com...
Infinite universe Jim?
It had a beining and is expanding at a finite rate.
You can't get infinity out of that.
The only infinity is the future.
Do you understand what gibberish this is.
If you had a piece of string, of infinite length, it would have a start
point and as you followed it, its length would expand at a finite rate.
If the universe is finite - where is the boundary?
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| User: "" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
19 Aug 2005 09:13:58 PM |
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Let me take the oportunity to use this post for which
it was orignally intended twake:
If a closed universe is expanding there is no edge.
Instead the space inbetween the galaxies is stretching.
What is interesting is that in cosmology the light
transversing this space is also stretched. It gets
longer and less energetic. This redshift is how we
determine their distances.
If there is no boundary the universe can be seen to
be the surface of a hypersphere.
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| User: "T Wake" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
19 Aug 2005 09:25:52 PM |
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<macromitch@internetCDS.com> wrote in message
news:1124504038.043625.43460@g44g2000cwa.googlegroups.com...
Let me take the oportunity to use this post for which
it was orignally intended twake:
Ok, a novel approach for you.....
If a closed universe is expanding there is no edge.
Well, it depends how you use closed. The general cosmological use for a
"Closed Universe" is one which has a finite amount of expansion possible. It
is still infinite in size.
If the universe is anything but infinite in size, it has an edge.
Instead the space inbetween the galaxies is stretching.
No. Stretching is a bad analogy as it implies things which aren't so.
The balloon model is not the real thing. It is an analogy to help people
understand some of the concepts.
What is interesting is that in cosmology the light
transversing this space is also stretched. It gets
longer and less energetic. This redshift is how we
determine their distances.
Where does the energy go?
If there is no boundary the universe can be seen to
be the surface of a hypersphere.
Nope.
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| User: "John Sefton" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
20 Aug 2005 12:17:38 AM |
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wrote:
Space stretches and this is the cause of the light stretch.
What is your explanation?
Uniform stretch everywhere doesn't work.
This is why shells grow in spirals.
Take 3 towns,; A, B, and C.
B is 10 km north of A. C is 10 km
north of c.
Now double all the distances
in one unit time.
B is now 20 km north of A.
C is now 20 km north of B.
So what?
Well, B moved 10 klicks.
How far did C move? (Hint: B is now
where C used to be.)
Well, B moved 10 klicks. How far
did C move in equal time? What about
D, E, F.....all originally at 10 klick
intervals? Get the picture?
John
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| User: "Spoonfed" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
22 Aug 2005 09:05:20 PM |
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John Sefton wrote:
macromitch@internetCDS.com wrote:
Space stretches and this is the cause of the light stretch.
What is your explanation?
Uniform stretch everywhere doesn't work.
This is why shells grow in spirals.
Take 3 towns,; A, B, and C.
B is 10 km north of A. C is 10 km
north of c.
Now double all the distances
in one unit time.
B is now 20 km north of A.
C is now 20 km north of B.
So what?
Well, B moved 10 klicks.
How far did C move? (Hint: B is now
where C used to be.)
Well, B moved 10 klicks. How far
did C move in equal time? What about
D, E, F.....all originally at 10 klick
intervals? Get the picture?
John
So it would seem, B moved 10, C moved 30, D moved 50, E 70, F 90, to
infinity, so of course it looks like somewhere along the way something
must be moving at faster than the speed of light.
However, if you know your Special Relativity, you know that F is both
time dilated and length contracted. G is more so, H is more still, I,
more still, etc. Until you get out to Y which is moving 99.999% of the
speed of light, has experienced, for all intents and purposes, no time
at all, and is still adjacent to Z.
Yes, one second has passed for you, but one second has not passed for
"the universe"
The universe looks like this:
http://www.spoonfedrelativity.com/files/rel-big-bang.gif
Not like this
http://www.spoonfedrelativity.com/files/galileanreal.gif
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| User: "Jim Black" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
20 Aug 2005 09:21:24 AM |
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John Sefton wrote:
macromitch@internetCDS.com wrote:
Space stretches and this is the cause of the light stretch.
What is your explanation?
Uniform stretch everywhere doesn't work.
This is why shells grow in spirals.
Take 3 towns,; A, B, and C.
B is 10 km north of A. C is 10 km
north of c.
Now double all the distances
in one unit time.
B is now 20 km north of A.
C is now 20 km north of B.
So what?
Well, B moved 10 klicks.
How far did C move? (Hint: B is now
where C used to be.)
Well, B moved 10 klicks. How far
did C move in equal time? What about
D, E, F.....all originally at 10 klick
intervals? Get the picture?
John
That's why the velocity of galaxies away from us is proportional to
their distance (until relativistic effects kick in, and their relative
velocity compared to us becomes ambiguous).
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| User: "Spoonfed" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
22 Aug 2005 09:34:36 PM |
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Jim Black wrote:
That's why the velocity of galaxies away from us is proportional to
their distance (until relativistic effects kick in, and their relative
velocity compared to us becomes ambiguous).
Relative velocity does not become ambiguous when relativistic effects
kick in. There might be a bit of extra work involved in establishing
precisely when and where the relative velocity happened or how long it
lasted, it is all very definable and not ambiguous at all.
Events can be described in space and time very precisely according to
an agreed upon reference frame, just as we on earth all describe time
on earth according to GMT.
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| User: "Nick" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
22 Aug 2005 09:56:30 PM |
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Cosmology of space expansion in closed universe
only works if the space stretch inbetween the galaxies
is equivalent to them moving away *through* space.
Space stretch stretches light just like velocity does.
Mitch -- Light Falls --
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| User: "Spoonfed" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
22 Aug 2005 11:27:01 PM |
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Nick wrote:
Cosmology of space expansion in closed universe
only works if the space stretch inbetween the galaxies
is equivalent to them moving away *through* space.
Space stretch stretches light just like velocity does.
Mitch -- Light Falls --
I believe you may be confused.
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| User: "Ben Rudiak-Gould" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
24 Aug 2005 08:29:32 AM |
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Spoonfed wrote:
Jim Black wrote:
That's why the velocity of galaxies away from us is proportional to
their distance (until relativistic effects kick in, and their relative
velocity compared to us becomes ambiguous).
Relative velocity does not become ambiguous when relativistic effects
kick in.
I think the crux of the disagreement is that he's talking about general
relativistic effects, while you're talking about special relativistic effects.
He is correct. You would be correct if the universe were accurately
described by special relativity at cosmological scales, but it's not.
-- Ben
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| User: "Jim Black" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
23 Aug 2005 03:29:08 PM |
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Spoonfed wrote:
Jim Black wrote:
That's why the velocity of galaxies away from us is proportional to
their distance (until relativistic effects kick in, and their relative
velocity compared to us becomes ambiguous).
Relative velocity does not become ambiguous when relativistic effects
kick in. There might be a bit of extra work involved in establishing
precisely when and where the relative velocity happened or how long it
lasted, it is all very definable and not ambiguous at all.
Events can be described in space and time very precisely according to
an agreed upon reference frame, just as we on earth all describe time
on earth according to GMT.
If we want to make a meaningful statement about the relative velocity
between us and very distant galaxies, we must specify the path one
taken in going from one object to the other, and how much time is spent
on each part of the path. Otherwise, the statement is ambiguous, not
because of special relativity, but because of general relativity. The
idea that one gets different answers for different ways of getting from
one object to the other is at the very core of general relativity.
Consider the situation in which we want to compare the velocity of the
center of the earth (A) at a certain time t1 with the velocity of an
object (B) falling towards the earth at some later time t2. Suppose
that if we compare the velocity of A and B at time t1, that we find
that they are at rest with respect to each other. If we then wait at
object B until time t2, we will detect no velocity change, since the
object is freely falling. We would conclude that the relative velocity
between A at time t1 and B at time t2 was zero. If on the other hand,
we begin by waiting at point A until time t2, and then make the
comparison with object B, we will detect a velocity difference.
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| User: "John Sefton" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
21 Aug 2005 12:21:39 AM |
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Jim Black wrote:
John Sefton wrote:
macromitch@internetCDS.com wrote:
Space stretches and this is the cause of the light stretch.
What is your explanation?
Uniform stretch everywhere doesn't work.
This is why shells grow in spirals.
Take 3 towns,; A, B, and C.
B is 10 km north of A. C is 10 km
north of c.
Now double all the distances
in one unit time.
B is now 20 km north of A.
C is now 20 km north of B.
So what?
Well, B moved 10 klicks.
How far did C move? (Hint: B is now
where C used to be.)
Well, B moved 10 klicks. How far
did C move in equal time? What about
D, E, F.....all originally at 10 klick
intervals? Get the picture?
John
That's why the velocity of galaxies away from us is proportional to
their distance (until relativistic effects kick in, and their relative
velocity compared to us becomes ambiguous).
Which is fine if we are the center.
John
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| User: "Jim Black" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
21 Aug 2005 07:19:22 AM |
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John Sefton wrote:
Jim Black wrote:
John Sefton wrote:
macromitch@internetCDS.com wrote:
Space stretches and this is the cause of the light stretch.
What is your explanation?
Uniform stretch everywhere doesn't work.
This is why shells grow in spirals.
Take 3 towns,; A, B, and C.
B is 10 km north of A. C is 10 km
north of c.
Now double all the distances
in one unit time.
B is now 20 km north of A.
C is now 20 km north of B.
So what?
Well, B moved 10 klicks.
How far did C move? (Hint: B is now
where C used to be.)
Well, B moved 10 klicks. How far
did C move in equal time? What about
D, E, F.....all originally at 10 klick
intervals? Get the picture?
John
That's why the velocity of galaxies away from us is proportional to
their distance (until relativistic effects kick in, and their relative
velocity compared to us becomes ambiguous).
Which is fine if we are the center.
John
Watch what happens if we simply change reference frames:
time
^
| * * * *
| * * * *
| * * * *
| * * * *
+------------------------> position
time
^
| * * * *
| * * * *
| * * * *
| * * * *
+------------------------> position
time
^
| * * * *
| * * * *
| * * * *
| * * * *
+------------------------> position
time
^
| * * * *
| * * * *
| * * * *
| * * * *
+------------------------> position
Every galaxy sees the other galaxies moving away from it at a rate
proportional to their distances.
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| User: "Spoonfed" |
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| Title: Re: Galaxies expanding with space? The Space Stretch |
22 Aug 2005 08:53:18 PM |
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Watch what happens if we simply change reference frames:
time
^
| * * * *
| * * * *
| * * * *
| * * * *
+------------------------> position
time
^
| * * * *
| * * * *
| * * * *
| * * * *
+------------------------> position
time
^
| * * * *
| * * * *
| * * * *
| * * * *
+------------------------> position
time
^
| * * * *
| * * * *
| * * * *
| * * * *
+------------------------> position
Every galaxy sees the other galaxies moving away from it at a rate
proportional to their distances.
True. In fact, Hubble's law is nothing more than Distance = Rate *
Time: You can verify this by checking the units.
Hubble's Constant * Distance = Velocity
50 km/second per MegaParsec is equal to somewhere around 1/13 billion
years.
The diagrams you have drawn show a Galilean Transformation, showing a
fairly small change in speed, less than ten percent of the speed of
light. This would cover the area within a billion light years of
Earth; within 10% of the radius of the universe.
When we get outside that range, if Hubble's Law still holds true, we
need to use a Lorentz Transformation, as the Galilean transformation is
only an approximation.
But the d=r*t law remains true not only in the Galilean transformations
you have shown, but is also true with Lorentz Transformations. Observe
the following animation, showing a Lorentz Transformation, similar to
the Galilean Transformation you have shown.
http://casa.colorado.edu/~ajsh/sr/wheel.html#spacetime_wheel
Notice, when the lines are nearly vertical, they are fairly similar to
those you've drawn with ASCII above. The lines at the edges, on the
other hand, are squeesed in extremely tightly.
Though the lines get squeezed in together, they do not change their
linear quality. They are straight lines, indicating a linear
relationship, preserving Distance=Rate*Time.
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