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two Expanding Universe Questions



 
 
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  #1  
Old July 20th 09, 11:21 AM posted to sci.astro
Roedy Green
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Posts: 7
Default two Expanding Universe Questions

How would you tell the difference between an expanding universe and
light slowing down over time? I would think since light is your
yardstick, they would look the same.

Second question, is there any evidence on a local scale of an
expanding universe, or does it all come from the Doppler shift of
distant galaxies? Is there any way to notice the meter bar in Paris
has grown a tad, or anything comparable?
--
Roedy Green Canadian Mind Products
http://mindprod.com

"The industrial civilisation is based on the consumption of energy resources that are inherently limited in quantity, and that are about to become scarce. When they do, competition for what remains will trigger dramatic economic and geopolitical events; in the end, it may be impossible for even a single nation to sustain industrialism as we have know it in the twentieth century."
~ Richard Heinberg, The Party’s Over: Oil, War, and the Fate of Industrial Societies
  #2  
Old July 20th 09, 03:15 PM posted to sci.astro
Androcles[_8_]
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Posts: 1,135
Default two Expanding Universe Questions


"Roedy Green" wrote in message
...
How would you tell the difference between an expanding universe and
light slowing down over time? I would think since light is your
yardstick, they would look the same.


It's not quite that simple, but you are on the right track.
http://www.androcles01.pwp.blueyonder.co.uk/Doolin'sStar.GIF
As each star in a galaxy moves toward us, the light it emits travels
faster than when it was moving away. Faster light passes the slower
light emitted earlier if the galaxy is far enough away. However, for
MOST of the period we only see the slow light, as you can see by
the spacing along the top of the graph.
The light isn't slowing as it travels, it was already slow when it left,
so all the lines are straight. But they are not parallel as they would
be if all the light had the same speed.



Second question, is there any evidence on a local scale of an
expanding universe, or does it all come from the Doppler shift of
distant galaxies?


It only comes from a mistaken belief that the speed of light is
tied to the ectoplasm or aether or whatever it is called instead
of the emitting body.

Match the caption with the gif:

--
A) http://tinyurl.com/lv2fl7
B) http://tinyurl.com/njgouh
C) http://tinyurl.com/klkfc9
D) http://tinyurl.com/l6lt4g
1) applies to light (in vacuum) and sound (in air)
2) applies to light but not sound
3) applies to sound but not light
4) applies to neither light nor sound

(If you think A) and 1) match, write down "A1".)


Is there any way to notice the meter bar in Paris
has grown a tad, or anything comparable?


Not a snowball's chance in hell.



  #3  
Old July 20th 09, 03:41 PM posted to sci.astro
dlzc
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Posts: 1,426
Default two Expanding Universe Questions

Dear Roedy Green:

On Jul 20, 3:21*am, Roedy Green
wrote:
How would you tell the difference between
an expanding universe and light slowing
down over time?


Light slowing down would *compress* the Universe. Bound systems...

*I would think since light is your yardstick,
they would look the same.


Additionally, it would have serious consequences for atomic orbitals,
molecular bonding, and other fundamental relations. I believe the
fine structure constant has been observed to have changed by 1 part in
10^8 in the last 13 billion years, so c cannot have changed too much
in relation to the other important "constants".

Now what "universal expansion" could also be simulated by is
decreasing the length of the second, as compared over aeons. A bound
system will shrink, making the Universe appear larger...

Second question, is there any evidence on
a local scale of an expanding universe, or
does it all come from the Doppler shift of
distant galaxies?


Any sort of bound system will automatically exclude (so far) any
detection of expansion. Expansion is only detectable outside the
Virgo supercluster (in which we are located).

*Is there any way to notice the meter bar in
Paris has grown a tad, or anything
comparable?


The meter bar was "stretching" by 1 part in 10^8 each *year*, which is
why it was abandoned as a standard. Steel decreases in length by 1
part in 10^8 each year. But this has nothing to do with an expanding
Universe.
http://nvl.nist.gov/pub/nistpubs/jre...tml/j43bee.htm

Here is some more answers for you:
http://www.astro.ucla.edu/~wright/cosmology_faq.html#MX
http://www.astro.ucla.edu/~wright/cosmology_faq.html#SS
http://www.astro.ucla.edu/~wright/cosmology_faq.html#UN
http://www.astro.ucla.edu/~wright/cosmo_01.htm

David A. Smith
  #4  
Old July 20th 09, 05:08 PM posted to sci.astro
Roedy Green
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Posts: 7
Default two Expanding Universe Questions

On Mon, 20 Jul 2009 15:15:58 +0100, "Androcles"
wrote, quoted or indirectly quoted
someone who said :

Is there any way to notice the meter bar in Paris
has grown a tad, or anything comparable?


Not a snowball's chance in hell.



I want to get some idea how fast the universe is expanding. What
units would you measure it in? What does the function for the size of
the universe given time T look like? Is there a sort of compound
interest going on, or is the growth approximately linear?
--
Roedy Green Canadian Mind Products
http://mindprod.com

"The industrial civilisation is based on the consumption of energy resources that are inherently limited in quantity, and that are about to become scarce. When they do, competition for what remains will trigger dramatic economic and geopolitical events; in the end, it may be impossible for even a single nation to sustain industrialism as we have know it in the twentieth century."
~ Richard Heinberg, The Party’s Over: Oil, War, and the Fate of Industrial Societies
  #5  
Old July 20th 09, 05:18 PM posted to sci.astro
Androcles[_8_]
external usenet poster
 
Posts: 1,135
Default two Expanding Universe Questions


"Roedy Green" wrote in message
...
On Mon, 20 Jul 2009 15:15:58 +0100, "Androcles"
wrote, quoted or indirectly quoted
someone who said :

Is there any way to notice the meter bar in Paris
has grown a tad, or anything comparable?


Not a snowball's chance in hell.



I want to get some idea how fast the universe is expanding.



It isn't, but being a ****wit you'd make a stupid statement like that
and snip the reply I gave you earlier because you didn't read it.
**** off.
*plonk*

Do not reply to this generic message, it was automatically generated;
you have been kill-filed, either for being boringly stupid, repetitive,
unfunny, ineducable, repeatedly posting politics, religion or off-topic
subjects to a sci. newsgroup, attempting cheapskate free advertising
for profit, because you are a troll, simply insane or any combination
or permutation of the aforementioned reasons; any reply will go unread.

Boringly stupid is the most common cause of kill-filing, but because
this message is generic the other reasons have been included. You are
left to decide which is most applicable to you.

There is no appeal, I have despotic power over whom I will electronically
admit into my home and you do not qualify as a reasonable person I would
wish to converse with or even poke fun at. Some weirdoes are not kill-
filed, they amuse me and I retain them for their entertainment value
as I would any chicken with two heads, either one of which enables the
dumb bird to scratch dirt, step back, look down, step forward to the
same spot and repeat the process eternally.

This should not trouble you, many of those plonked find it a blessing
that they are not required to think and can persist in their bigotry
or crackpot theories without challenge.

You have the right to free speech, I have the right not to listen. The
kill-file will be cleared annually with spring cleaning or whenever I
purchase a new computer or hard drive.

I hope you find this explanation is satisfactory but even if you don't,
damnly my frank, I don't give a dear. Have a nice day.








  #6  
Old July 20th 09, 08:25 PM posted to sci.astro
dlzc
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Posts: 1,426
Default two Expanding Universe Questions

Dear Roedy Green:

On Jul 20, 9:08*am, Roedy Green
wrote:
....
I want to get some idea how fast the universe
is expanding. *What units would you measure
it in?


The usual way is "km/sec / kparsec", also known a "Hubble's constant".

*What does the function for the size of the
universe given time T look like?


Fairly complex, with wide errorbars. For the first few hundred
thousand years, it was *very* high, then drops to a very small value,
then within the last few billion years, increases to its current value
("acceleration of expnasion").

*Is there a sort of compound interest going on,
or is the growth approximately linear?


Approximately linear over short time periods. I'd suggest you review
the links I provided for what current observation supports on this
topic.

David A. Smith
  #7  
Old July 20th 09, 09:14 PM posted to sci.astro
Yousuf Khan
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Posts: 594
Default two Expanding Universe Questions

Roedy Green wrote:
How would you tell the difference between an expanding universe and
light slowing down over time? I would think since light is your
yardstick, they would look the same.


This is called the "Tired Light" hypothesis.

Tired light - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Tired_light

Second question, is there any evidence on a local scale of an
expanding universe, or does it all come from the Doppler shift of
distant galaxies? Is there any way to notice the meter bar in Paris
has grown a tad, or anything comparable?


Actually on a local scale, i.e. within our own Local Group of Galaxies
cluster, and within our Virgo supercluster of galaxies, things look
mostly like they're moving together. So they are blueshifted.

Yousuf Khan
  #8  
Old July 21st 09, 02:57 AM posted to sci.astro
John Polasek
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Posts: 95
Default two Expanding Universe Questions

On Mon, 20 Jul 2009 03:21:23 -0700, Roedy Green
wrote:

How would you tell the difference between an expanding universe and
light slowing down over time? I would think since light is your
yardstick, they would look the same.

It there were no expansion and the light reaching us slowed down as it
went, then you would see a blue shift, because the frequency would
stay the same and L = c/F so L would become shorter along with c,
causing a blue shift. But we only see a red shift.
Second question, is there any evidence on a local scale of an
expanding universe, or does it all come from the Doppler shift of
distant galaxies? Is there any way to notice the meter bar in Paris
has grown a tad, or anything comparable?

Only from the Doppler shift of distant galaxies.
John Polasek
  #9  
Old July 21st 09, 10:18 AM posted to sci.astro
Mike Dworetsky
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Posts: 715
Default two Expanding Universe Questions

"Roedy Green" wrote in message
...
How would you tell the difference between an expanding universe and
light slowing down over time? I would think since light is your
yardstick, they would look the same.


If the speed of light was changing over time (by enough to create the
appearance of an expanding universe) then the fine structure constant
"alpha" would be changing. If that happened all of atomic and nuclear
physics would have been radically different in the past. However,
observations of distant quasars and of the Oklo natural nuclear reactor of
about 2 billion years ago imply that alpha has not varied by very much if at
all, over cosmological time scales.


Second question, is there any evidence on a local scale of an
expanding universe, or does it all come from the Doppler shift of
distant galaxies? Is there any way to notice the meter bar in Paris
has grown a tad, or anything comparable?


No, you can't observe cosmological expansion effects locally on the Earth or
within our own galaxy. Space is expanding, not the objects within it. And
the metre bar in Paris is now a historical artifact, because the metre is
defined using light itself (as is the second).

--
Roedy Green Canadian Mind Products
http://mindprod.com

"The industrial civilisation is based on the consumption of energy
resources that are inherently limited in quantity, and that are about to
become scarce. When they do, competition for what remains will trigger
dramatic economic and geopolitical events; in the end, it may be
impossible for even a single nation to sustain industrialism as we have
know it in the twentieth century."
~ Richard Heinberg, The Party's Over: Oil, War, and the Fate of
Industrial Societies



--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #10  
Old July 21st 09, 03:17 PM posted to sci.astro
Androcles[_8_]
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Posts: 1,135
Default two Expanding Universe Questions


"Mike Dworetsky" wrote in message
...
"Roedy Green" wrote in message
...
How would you tell the difference between an expanding universe and
light slowing down over time? I would think since light is your
yardstick, they would look the same.


If the speed of light was changing over time (by enough to create the
appearance of an expanding universe) then the fine structure constant
"alpha" would be changing.



Bwhahahahahaha!
If your mind operated any faster you'd graduate to idiot.
Take this simple test.


A) http://tinyurl.com/lv2fl7
B) http://tinyurl.com/njgouh
C) http://tinyurl.com/klkfc9
D) http://tinyurl.com/l6lt4g
1) applies to light (in vacuum) and sound (in air)
2) applies to light but not sound
3) applies to sound but not light
4) applies to neither light nor sound








 




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