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  #1  
Old July 2nd 03, 07:33 PM
Steve Willner
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Default FW: Simple Question

[[Mod. note -- ... [snip] ...

If the universe is not expanding (point 2), then the CMBR temperature
should have been the same in the past. -- jt]]


In article ,
Richard S. Sternberg writes:
I hope I won't lose in accuracy what I gain in easy comprehension for lay
consumption, but isn't this more easily stated as Ober's Paradox, also
called the Bright Sky Paradox:

[[Mod. note -- It's _Olber_'s Paradox.


Olbers', please. Or I suppose Olbers's if you are a hypermodernist.

[[Mod. note -- ((cringing)) Oops, mea culpa! -- jt]]

However, I don't see Olbers' paradox being the same as the
Moderator's initial point. Seeing the CMBR temperature higher in the
past says the Universe is evolving, but it isn't the same observation
as noting the night sky is dark. We can imagine a dark night sky in
an unevolving Universe (one finite either in age or in space) or a
bright night sky in an evolving Universe (one densely packed with
stars).

As it happens, the explanations for the two observations are closely
related. We appear to live in a Universe of finite age (explaining
the dark night sky) that is expanding (explaining the hotter
microwave background in the past).

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)
  #2  
Old July 2nd 03, 07:33 PM
Steve Willner
external usenet poster
 
Posts: n/a
Default FW: Simple Question

[[Mod. note -- ... [snip] ...

If the universe is not expanding (point 2), then the CMBR temperature
should have been the same in the past. -- jt]]


In article ,
Richard S. Sternberg writes:
I hope I won't lose in accuracy what I gain in easy comprehension for lay
consumption, but isn't this more easily stated as Ober's Paradox, also
called the Bright Sky Paradox:

[[Mod. note -- It's _Olber_'s Paradox.


Olbers', please. Or I suppose Olbers's if you are a hypermodernist.

[[Mod. note -- ((cringing)) Oops, mea culpa! -- jt]]

However, I don't see Olbers' paradox being the same as the
Moderator's initial point. Seeing the CMBR temperature higher in the
past says the Universe is evolving, but it isn't the same observation
as noting the night sky is dark. We can imagine a dark night sky in
an unevolving Universe (one finite either in age or in space) or a
bright night sky in an evolving Universe (one densely packed with
stars).

As it happens, the explanations for the two observations are closely
related. We appear to live in a Universe of finite age (explaining
the dark night sky) that is expanding (explaining the hotter
microwave background in the past).

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)
  #3  
Old July 4th 03, 07:46 PM
Ray Tomes
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Posts: n/a
Default FW: Simple Question

Richard S. Sternberg wrote:

If the Universe is infinite and uniform (Condition #1) and not expanding
(Condition #2, which is somewhat duplicative of Condition #1), then the sky
should be infinitely bright at night. No matter how small of a percentage of
the sky is generating the light, if it has been generating that light for an
infinite time from infinite points in space, then the resulting light must
be infinite. Since the sky is dark at night, the Universe cannot be infinite
and uniform unless the proponent offers a different solution to the Paradox.


OTOH, if an infinite non-expanding universe had a roughly uniform finite
energy density at one point in time, it would be rather surprising if it
came to have an infinite energy density at some future time. Therefore
Olbers Paradox tells us next to nothing about the real universe except
that somewhere in it someone did the sums wrong. :-)

If such a universe existed over vast eons of time then clearly there would
need to be a balance between dust and other absorption and stellar
processes emissions and a means to recycle energy between these. The fact
that we don't know about any physics for such processes might have more to
do with the fact that they are inherently less likely to be observed (and
therefore lead to them becoming known physics) than with them not existing.

Ray Tomes
  #4  
Old July 4th 03, 07:46 PM
Ray Tomes
external usenet poster
 
Posts: n/a
Default FW: Simple Question

Richard S. Sternberg wrote:

If the Universe is infinite and uniform (Condition #1) and not expanding
(Condition #2, which is somewhat duplicative of Condition #1), then the sky
should be infinitely bright at night. No matter how small of a percentage of
the sky is generating the light, if it has been generating that light for an
infinite time from infinite points in space, then the resulting light must
be infinite. Since the sky is dark at night, the Universe cannot be infinite
and uniform unless the proponent offers a different solution to the Paradox.


OTOH, if an infinite non-expanding universe had a roughly uniform finite
energy density at one point in time, it would be rather surprising if it
came to have an infinite energy density at some future time. Therefore
Olbers Paradox tells us next to nothing about the real universe except
that somewhere in it someone did the sums wrong. :-)

If such a universe existed over vast eons of time then clearly there would
need to be a balance between dust and other absorption and stellar
processes emissions and a means to recycle energy between these. The fact
that we don't know about any physics for such processes might have more to
do with the fact that they are inherently less likely to be observed (and
therefore lead to them becoming known physics) than with them not existing.

Ray Tomes
  #5  
Old July 7th 03, 06:07 PM
Jonathan Silverlight
external usenet poster
 
Posts: n/a
Default FW: Simple Question

In message , Ray Tomes
writes
Richard S. Sternberg wrote:

If the Universe is infinite and uniform (Condition #1) and not expanding
(Condition #2, which is somewhat duplicative of Condition #1), then the sky
should be infinitely bright at night. No matter how small of a percentage of
the sky is generating the light, if it has been generating that light for an
infinite time from infinite points in space, then the resulting light must
be infinite. Since the sky is dark at night, the Universe cannot be infinite
and uniform unless the proponent offers a different solution to the Paradox.


OTOH, if an infinite non-expanding universe had a roughly uniform finite
energy density at one point in time, it would be rather surprising if it
came to have an infinite energy density at some future time. Therefore
Olbers Paradox tells us next to nothing about the real universe except
that somewhere in it someone did the sums wrong. :-)


Talking about infinities is a sure way to lead to mistakes, and I'm
probably going to make one, but why should the light be infinite? Won't
it be the same as the surface of a star over the whole sky?
BTW, Charlier's cosmology apparently leads to an infinite static
universe which does not suffer Olber's paradox.
--
"Roads in space for rockets to travel....four-dimensional roads, curving with
relativity"
Mail to jsilverlight AT merseia.fsnet.co.uk is welcome.
Or visit Jonathan's Space Site http://www.merseia.fsnet.co.uk
  #6  
Old July 7th 03, 06:07 PM
Jonathan Silverlight
external usenet poster
 
Posts: n/a
Default FW: Simple Question

In message , Ray Tomes
writes
Richard S. Sternberg wrote:

If the Universe is infinite and uniform (Condition #1) and not expanding
(Condition #2, which is somewhat duplicative of Condition #1), then the sky
should be infinitely bright at night. No matter how small of a percentage of
the sky is generating the light, if it has been generating that light for an
infinite time from infinite points in space, then the resulting light must
be infinite. Since the sky is dark at night, the Universe cannot be infinite
and uniform unless the proponent offers a different solution to the Paradox.


OTOH, if an infinite non-expanding universe had a roughly uniform finite
energy density at one point in time, it would be rather surprising if it
came to have an infinite energy density at some future time. Therefore
Olbers Paradox tells us next to nothing about the real universe except
that somewhere in it someone did the sums wrong. :-)


Talking about infinities is a sure way to lead to mistakes, and I'm
probably going to make one, but why should the light be infinite? Won't
it be the same as the surface of a star over the whole sky?
BTW, Charlier's cosmology apparently leads to an infinite static
universe which does not suffer Olber's paradox.
--
"Roads in space for rockets to travel....four-dimensional roads, curving with
relativity"
Mail to jsilverlight AT merseia.fsnet.co.uk is welcome.
Or visit Jonathan's Space Site http://www.merseia.fsnet.co.uk
  #7  
Old July 8th 03, 02:54 PM
Phillip Helbig---remove CLOTHES to reply
external usenet poster
 
Posts: n/a
Default FW: Simple Question

In article , Jonathan
Silverlight writes:

Talking about infinities is a sure way to lead to mistakes, and I'm
probably going to make one, but why should the light be infinite? Won't
it be the same as the surface of a star over the whole sky?


BTW, Charlier's cosmology apparently leads to an infinite static
universe which does not suffer Olber's paradox.


I REALLY recommend the corresponding chapter in Edward Harrison's
COSMOLOGY textbook to all interested in Olbers's paradox.

@BOOK {EHarrison81a,
AUTHOR = "E. R. Harrison",
TITLE = "Cosmology, the science of the universe",
PUBLISHER = "Cambridge University Press",
YEAR = "1981",
ADDRESS = "Cambridge"
}
  #8  
Old July 8th 03, 02:54 PM
Phillip Helbig---remove CLOTHES to reply
external usenet poster
 
Posts: n/a
Default FW: Simple Question

In article , Jonathan
Silverlight writes:

Talking about infinities is a sure way to lead to mistakes, and I'm
probably going to make one, but why should the light be infinite? Won't
it be the same as the surface of a star over the whole sky?


BTW, Charlier's cosmology apparently leads to an infinite static
universe which does not suffer Olber's paradox.


I REALLY recommend the corresponding chapter in Edward Harrison's
COSMOLOGY textbook to all interested in Olbers's paradox.

@BOOK {EHarrison81a,
AUTHOR = "E. R. Harrison",
TITLE = "Cosmology, the science of the universe",
PUBLISHER = "Cambridge University Press",
YEAR = "1981",
ADDRESS = "Cambridge"
}
  #9  
Old July 9th 03, 10:18 PM
Phillip Helbig---remove CLOTHES to reply
external usenet poster
 
Posts: n/a
Default FW: Simple Question

In article , "Richard S.
Sternberg" writes:

BTW, Charlier's cosmology apparently leads to an infinite static universe
which does not suffer Olber's paradox.


I haven't heard of that, and I'm quite interested. Could you either provide
a brief synopsis of Charlier's cosmology or provide a current hyperlink.
Thx.


Basically, this is a hierarchical model. Galaxies are grouped into
supergalaxies which in turn are grouped into hypergalaxies etc. This
occurs in such a way that the average density decreases the larger the
volume. It's not viable as a realistic cosmological model, but is an
interesting test case for testing assumptions etc, the exception that
proves the rule.

I believe Harrison discusses it in the book I mentioned previously in
this thread.

(Note: The word "prove" in this old adage means "test", as in the German
"pruefen" (to test) "Pruefung" (test, examination) etc and in the English
"proving ground" (e.g. for testing rockets). I never cease to be amazed
to what extent this is mis-interpreted; some people really think that
exceptions PROVE rules in the more usual sense of the term. There isn't
a German adage "Die Ausnahme prueft die Regel", but there IS "Die
Ausnahme bestaetigt die Regel", which is obviously a translation of the
mis-interpretation of the English adage.

[Mod. note: accented characters, mangled in transmission, turned into
7-bit ASCII digraphs. In general, please try to post in plain ASCII --
Usenet and e-mail are often not 8-bit clean.]

[Mod. note #2: An alternative, and in my view correct, point of view
about this expression is that it means that the fact that an exception
is documented proves *that the rule exists*; for example, in legal
contexts. The German version of the expression seems consistent with
this. See also http://alt-usage-english.org/excerpts/fxtheexc.html.
But we wander away from astrophysics -- mjh]
  #10  
Old July 9th 03, 10:18 PM
Phillip Helbig---remove CLOTHES to reply
external usenet poster
 
Posts: n/a
Default FW: Simple Question

In article , "Richard S.
Sternberg" writes:

BTW, Charlier's cosmology apparently leads to an infinite static universe
which does not suffer Olber's paradox.


I haven't heard of that, and I'm quite interested. Could you either provide
a brief synopsis of Charlier's cosmology or provide a current hyperlink.
Thx.


Basically, this is a hierarchical model. Galaxies are grouped into
supergalaxies which in turn are grouped into hypergalaxies etc. This
occurs in such a way that the average density decreases the larger the
volume. It's not viable as a realistic cosmological model, but is an
interesting test case for testing assumptions etc, the exception that
proves the rule.

I believe Harrison discusses it in the book I mentioned previously in
this thread.

(Note: The word "prove" in this old adage means "test", as in the German
"pruefen" (to test) "Pruefung" (test, examination) etc and in the English
"proving ground" (e.g. for testing rockets). I never cease to be amazed
to what extent this is mis-interpreted; some people really think that
exceptions PROVE rules in the more usual sense of the term. There isn't
a German adage "Die Ausnahme prueft die Regel", but there IS "Die
Ausnahme bestaetigt die Regel", which is obviously a translation of the
mis-interpretation of the English adage.

[Mod. note: accented characters, mangled in transmission, turned into
7-bit ASCII digraphs. In general, please try to post in plain ASCII --
Usenet and e-mail are often not 8-bit clean.]

[Mod. note #2: An alternative, and in my view correct, point of view
about this expression is that it means that the fact that an exception
is documented proves *that the rule exists*; for example, in legal
contexts. The German version of the expression seems consistent with
this. See also http://alt-usage-english.org/excerpts/fxtheexc.html.
But we wander away from astrophysics -- mjh]
 




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