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Is the universe a closed system?
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Aguirre
Jul 31, 2011, 11:54:40 AM7/31/11
to
It is well known and proofed that our universe expands.
Now my question to you is in what a structure? I say it can only be
into a no space- time structure. Something where is no structure at
all. Another question is where does the energy to expand comes from?
dushya
Aug 8, 2011, 6:23:25 AM8/8/11
to
I think the statement "universe is expanding" roughly means following
--
If you measure "absolute distance" between two points P1 and P2 in
space at some instant of time t1, and then at some later instant of
time t2 (>t1), then you will find that absolute distance measured at
time t2 is more than that measured at time t1.
One's first guess would be that its consuming its own energy for
expansion (assuming there is nothing "outside" it).
Regards
dushya
micro...@hotmail.com
Aug 9, 2011, 3:09:35 PM8/9/11
to
No energy required.
The closed universe is in the round boundary(of the 4th diemension)
where the 4th dimension is nowhere.
Einstein said the universe closed by the 4th dimension.
Mitchell Raemsch
[Moderator's note: The issue is subtle and/or not well defined and
probably too detailed to discuss meaningfully in a newsgroup. Readers
might want to check out this article:
http://www.scientificamerican.com/article.cfm?id=is-the-universe-leaking-energy
as well as some or all of the following (especially the first one)
http://www.scientificamerican.com/article.cfm?id=misconceptions-about-the-2005-03
http://arxiv.org/abs/astro-ph/0402278
http://arxiv.org/abs/astro-ph/0310808
http://arxiv.org/abs/astro-ph/0104349
http://arxiv.org/abs/astro-ph/0011070
-P.H.]
Frisbieinstein
Aug 12, 2011, 12:53:22 PM8/12/11
to
On Jul 31, 11:54 pm, Aguirre <sigbangschm...@gmail.com> wrote:
> It is well known and proofed that our universe expands.
>
> Now my question to you is in what a structure? I say it can only be
> into a no space- time structure. Something where is no structure at
> all.
> It is well known and proofed that our universe expands.
>
> Now my question to you is in what a structure? I say it can only be
> into a no space- time structure. Something where is no structure at
> all.
I say that it could be anything, or nothing at all. The universe is
by definition a closed system and anything outside is completely
unknown.
> Another question is where does the energy to expand comes from?
There is no reason to think that it requires any energy at all. I say
that no one has much of a clue as to what is going on.
I was too cheap to buy the SA article, but it asks the question:
> When light is redshifted by the expansion of the universe, where does its energy go?
Note that there are two sources of redshift. The first is that the
source of light is (usually) moving away from the Earth. This is
observed as red shift. But who says any energy is "lost?" It isn't.
The second source is that redshift occurs in transit directly due to
the expansion. The volume that the energy occupies increases, so the
density decreases while the total amount of energy remains the same.
This is observed as red shift.
micro...@hotmail.com
Aug 14, 2011, 3:53:45 AM8/14/11
to
On Aug 12, 9:53am, Frisbieinstein <patmpow...@gmail.com> wrote:
> On Jul 31, 11:54 pm, Aguirre <sigbangschm...@gmail.com> wrote:
>
> > It is well known and proofed that our universe expands.
>
> > Now my question to you is in what a structure? =A0I say it can only be> On Jul 31, 11:54 pm, Aguirre <sigbangschm...@gmail.com> wrote:
>
> > It is well known and proofed that our universe expands.
>
> > into a no space- time structure. =A0Something where is no structure at
> > all. =A0
>
> I say that it could be anything, or nothing at all. =A0The universe is
> by definition a closed system and anything outside is completely
> unknown.
>
> > Another question is where does the energy to expand comes from?
>
> that no one has much of a clue as to what is going on.
>
> I was too cheap to buy the SA article, but it asks the question:
>
s its energy go?
>
> Note that there are two sources of redshift. =A0The first is that the
> source of light is (usually) moving away from the Earth. =A0This is
> observed as red shift. =A0But who says any energy is "lost?" =A0 It isn't=
>
> The second source is that redshift occurs in transit directly due to
> density decreases while the total amount of energy remains the same.
> This is observed as red shift.
Expansion effects light as it travels billions of light years accross
the universe from the furthest objects. These objects share a common
age from the Big Bang. They are not moving away. Instead space-time is
expanding everywhere inbetween. Space expansion redshifts light by
expanding it. This is equivalent to the motion redshift but is not
motion. It is distance creation as the universe expands.
Rich L.
Aug 15, 2011, 6:10:36 AM8/15/11
to
In General Relativity, energy is relative. There is no absolute energy
for anything that everyone can agree on, especially between things that
are separated in space and time.
for anything that everyone can agree on, especially between things that
are separated in space and time.
Rich L.
Nicolaas Vroom
Aug 28, 2011, 1:11:05 PM8/28/11
to
"Aguirre" <sigbang...@gmail.com> schreef in bericht
news:cbbcbb4b-f96b-4090...@b19g2000yqj.googlegroups.com...
Your question is: is the Universe closed ?
The following document explains that the Universe is cyclic
meaning closed (at short scale):
http://arxiv.org/ftp/arxiv/papers/1011/1011.3706.pdf
See Also:
http://en.wikipedia.org/wiki/Conformal_Cyclic_Cosmology
The current understanding is however that the Universe is an
open expanding system with acceleration.
That means the Cosmological Constant is larger than zero.
The question is how do you prove either one.
The main reason why we assume that the Universe (space)
is expanding is because of redshift (Hubble's Law)
The problem is that only in an Universe where space expansion
is linear Hubble's Law is valid (near the present)
The more this is not true (i.e. acceleration) there is a discrepancy
between the linear relation expressed in Hubble's Law.
For a more detailed explanation of the problems involved See:
http://users.telenet.be/nicvroom/friedmann's equation.htm
Hope this helped.
Nicolaas Vroom
Nicolaas Vroom
Aug 29, 2011, 11:49:40 AM8/29/11
to
"Nicolaas Vroom" <nicolaa...@telenet.be> schreef in bericht
news:3Fu6q.152784$29.3...@newsfe08.ams2...
news:3Fu6q.152784$29.3...@newsfe08.ams2...
>
> For a more detailed explanation of the problems involved See:
> http://users.telenet.be/nicvroom/friedmann's equation.htm
>
Please try this link:
http://users.telenet.be/nicvroom/friedmann's%20equation.htm
raymond
Sep 10, 2011, 2:23:54 AM9/10/11
to
On Jul 31, 10:54=A0am, Aguirre <sigbangschm...@gmail.com> wrote:
> It is well known and proofed that our universe expands.
>
> Now my question to you is in what a structure? =A0I say it can only be
> It is well known and proofed that our universe expands.
>
> into a no space- time structure. =A0Something where is no structure at
> all. =A0Another question is where does the energy to expand comes from?
>
If the universe is a close system, it will expand and also contract.
we are only aware of expansion.
The energy of the expansion comes from the BB.
you can see photons today from the birth of the universe
with a tv on an empty channel set with the image very dark.
r.y
Frisbieinstein
Sep 10, 2011, 11:58:29 AM9/10/11
to
On Sep 10, 2:23�pm, raymond <b...@birdband.net> wrote:
>
>
> The energy of the expansion comes from the BB.
>
>
> The energy of the expansion comes from the BB.
This is not so. It is well-known that the expansion is accelerating.
How can this be?
As far I know, no one knows why the universe expands at all. It
started in a super-dense state. Why wasn't it happy to remain that
way? It has nothing in common with explosions such as we know them on
Earth, since there was no space to expand into. Space itself grew.
Why? How? Beats me. Whatever Penrose may say, I don't see how
entropy has anything to do with it.
raymond
Sep 11, 2011, 3:52:10 AM9/11/11
to
On Sep 10, 10:58am, Frisbieinstein <patmpow...@gmail.com> wrote:
> On Sep 10, 2:23 pm, raymond <b...@birdband.net> wrote:
> > The energy of the expansion comes from the BB.
> This is not so. It is well-known that the expansion is accelerating.
>
yes
> On Sep 10, 2:23 pm, raymond <b...@birdband.net> wrote:
> > The energy of the expansion comes from the BB.
> This is not so. It is well-known that the expansion is accelerating.
>
>
> How can this be?
>
imagine a fabric that its totally folded. every time you
unfold, the size of the space will increase exponentially.
>
> As far I know, no one knows why the universe expands at all.
> It started in a super-dense state. Why wasn't it happy to remain that
> way? It has nothing in common with explosions such as we know them on
> Earth, since there was no space to expand into. Space itself grew.
> Why? How? Beats me. Whatever Penrose may say, I don't see how
> entropy has anything to do with it.
>
this is ordinary knowledge.
r.y
Nicolaas Vroom
Sep 26, 2011, 4:56:44 PM9/26/11
to
"Nicolaas Vroom" <nicolaa...@telenet.be> schreef in bericht
news:3Fu6q.152784$29.3...@newsfe08.ams2...
>
news:3Fu6q.152784$29.3...@newsfe08.ams2...
>
> "Aguirre" <sigbang...@gmail.com> schreef in bericht
> news:cbbcbb4b-f96b-4090...@b19g2000yqj.googlegroups.com...
>> It is well known and proofed that our universe expands.
>>
>> Now my question to you is in what a structure? I say it can only be
>> into a no space- time structure. Something where is no structure at
>> all. Another question is where does the energy to expand comes from?
>>
>>
>
> Your question is: is the Universe closed ?
> news:cbbcbb4b-f96b-4090...@b19g2000yqj.googlegroups.com...
>> It is well known and proofed that our universe expands.
>>
>> Now my question to you is in what a structure? I say it can only be
>> into a no space- time structure. Something where is no structure at
>> all. Another question is where does the energy to expand comes from?
>>
>>
>
> Your question is: is the Universe closed ?
> The current understanding is however that the Universe is an
> open expanding system with acceleration.
> That means the Cosmological Constant is larger than zero.
>
> The question is how do you prove either one.
>
> The main reason why we assume that the Universe (space)
> is expanding is because of redshift (Hubble's Law)
> The problem is that only in an Universe where space expansion
> is linear Hubble's Law is valid (near the present)
> The more this is not true (i.e. acceleration) there is a discrepancy
> between the linear relation expressed in Hubble's Law.
>
> For a more detailed explanation of the problems involved See:
> http://users.telenet.be/nicvroom/friedmann's equation.htm
>
> Hope this helped.
>
>
In order to understand better I have updated the above mentioned
> open expanding system with acceleration.
> That means the Cosmological Constant is larger than zero.
>
> The question is how do you prove either one.
>
> The main reason why we assume that the Universe (space)
> is expanding is because of redshift (Hubble's Law)
> The problem is that only in an Universe where space expansion
> is linear Hubble's Law is valid (near the present)
> The more this is not true (i.e. acceleration) there is a discrepancy
> between the linear relation expressed in Hubble's Law.
>
> For a more detailed explanation of the problems involved See:
> http://users.telenet.be/nicvroom/friedmann's equation.htm
>
> Hope this helped.
>
>
document i.e.
http://users.telenet.be/nicvroom/friedmann's%20equation.htm
This document shows the path of a lightray in the x direction
for different values of the parameters C and Labda of the
Friedmann equation.
I have added a calculation of the parameter z or redshift.
The results shows that the z relation is not linear (as a function
of distance)
What is also interesting that the relation v = c*z is not valid.
(except for small distances when labda = 0)
Any comments ?
Nicolaas Vroom.
Phillip Helbig---undress to reply
Sep 26, 2011, 5:31:41 PM9/26/11
to
In article <GWJfq.286$5W3...@newsfe08.ams2>, "Nicolaas Vroom"
One has to be careful here. The term "closed universe" is used to mean
two things: spatially closed, i.e. finite in size (for the experts:
assume a simple topology for now), and temporarily closed, i.e. it will
collapse in the future. Some of the confusion comes from the fact that
for lambda = 0, one type of closedness implies the other. (For k = 0,
lambda < 0 implies it will recollapse; otherwise it won't, but in both
cases the universe is infinite in size.)
> > The current understanding is however that the Universe is an
> > open expanding system with acceleration.
It is clear that it will expand forever. Whether or not it is spatially
closed is not known (since it is close to the borderline).
> > The problem is that only in an Universe where space expansion
> > is linear Hubble's Law is valid (near the present)
> > The more this is not true (i.e. acceleration) there is a discrepancy
> > between the linear relation expressed in Hubble's Law.
This is true, but well known. It is not a "problem".
> > For a more detailed explanation of the problems involved See:
> > http://users.telenet.be/nicvroom/friedmann's equation.htm
Just a few brief ones. I haven't read it all and haven't checked
everything.
> Friedmann's Equation & The path of a light ray
> Question 1 What is the path of a light ray when the Cosmological
> Constant (Labda) = 0 (Open Universe )
This depends on what you mean by "open" and in general just knowing
lambda is not enough.
> Question 2 What is the path of a light ray when Labda < 0 (Closed
> Universe)
Ditto.
> Question 3 What is the path of a light ray when Labda > 0 (Open
> with acceleration)
Ditto.
> Question 4 For the above three conditions is it possible to
> validate Hubble's Law?
There are two things called "Hubble's Law" in the literature. One is
the observed relation between the luminosity distance and redshift at
low redshift. It is observed; it can't be "validated". The other is
the relation between the proper distance now and its derivative with
respect to time (neither "directly observable") and holds for any
homogeneous and isotropic universe (no physics required).
> In order to simulate space expansion the Friedmann equation is used:
> (See "Introducing Einstein's Relativity" by Ray d'Inverno. Equation 23.1
> (dR/dt)^2= C/R + 1/3 * Labda*R^2 - k
> With flat space (k = 0) we get:
Maybe your 5 questions all assume k = 0. If so, state it out the
outset. This might explain some of the confusion.
One has to be careful here. The term "closed universe" is used to mean
two things: spatially closed, i.e. finite in size (for the experts:
assume a simple topology for now), and temporarily closed, i.e. it will
collapse in the future. Some of the confusion comes from the fact that
for lambda = 0, one type of closedness implies the other. (For k = 0,
lambda < 0 implies it will recollapse; otherwise it won't, but in both
cases the universe is infinite in size.)
> > The current understanding is however that the Universe is an
> > open expanding system with acceleration.
closed is not known (since it is close to the borderline).
> > The problem is that only in an Universe where space expansion
> > is linear Hubble's Law is valid (near the present)
> > The more this is not true (i.e. acceleration) there is a discrepancy
> > between the linear relation expressed in Hubble's Law.
> > For a more detailed explanation of the problems involved See:
> > http://users.telenet.be/nicvroom/friedmann's equation.htm
> In order to understand better I have updated the above mentioned
> document i.e.
> http://users.telenet.be/nicvroom/friedmann's%20equation.htm
> Any comments ?
> document i.e.
> http://users.telenet.be/nicvroom/friedmann's%20equation.htm
Just a few brief ones. I haven't read it all and haven't checked
everything.
> Friedmann's Equation & The path of a light ray
> Question 1 What is the path of a light ray when the Cosmological
> Constant (Labda) = 0 (Open Universe )
This depends on what you mean by "open" and in general just knowing
lambda is not enough.
> Question 2 What is the path of a light ray when Labda < 0 (Closed
> Universe)
Ditto.
> Question 3 What is the path of a light ray when Labda > 0 (Open
> with acceleration)
Ditto.
> Question 4 For the above three conditions is it possible to
> validate Hubble's Law?
There are two things called "Hubble's Law" in the literature. One is
the observed relation between the luminosity distance and redshift at
low redshift. It is observed; it can't be "validated". The other is
the relation between the proper distance now and its derivative with
respect to time (neither "directly observable") and holds for any
homogeneous and isotropic universe (no physics required).
> In order to simulate space expansion the Friedmann equation is used:
> (See "Introducing Einstein's Relativity" by Ray d'Inverno. Equation 23.1
> (dR/dt)^2= C/R + 1/3 * Labda*R^2 - k
> With flat space (k = 0) we get:
Maybe your 5 questions all assume k = 0. If so, state it out the
outset. This might explain some of the confusion.
Nicolaas Vroom
Oct 2, 2011, 2:44:54 PM10/2/11
to
"Phillip Helbig---undress to reply" <hel...@astro.multiCLOTHESvax.de>
schreef in bericht news:j5qpke$5lj$1...@online.de...
What does it mean close to the borderline ?
>> > For a more detailed explanation of the problems involved See:
>> > http://users.telenet.be/nicvroom/friedmann's equation.htm
>
>> In order to understand better I have updated the above mentioned
>> document i.e.
>> http://users.telenet.be/nicvroom/friedmann's%20equation.htm
>
>> Any comments ?
>
> Just a few brief ones. I haven't read it all and haven't checked
> everything.
>
> The other is
> the relation between the proper distance now and its derivative with
> respect to time (neither "directly observable") and holds for any
> homogeneous and isotropic universe (no physics required).
I expect you mean v = H * d. (2)
There is also a relation v = c * z (3)
What I demonstrate in the above mentioned document is that the
relations 1 and 3 are highly nonlinear starting from the bigBang
towards the present using the Friedmann equation assuming Cosmological
Principle for different combinations of the parameters C, Labda and k.
>> In order to simulate space expansion the Friedmann equation is used:
>> (See "Introducing Einstein's Relativity" by Ray d'Inverno. Equation 23.1
>> (dR/dt)^2= C/R + 1/3 * Labda*R^2 - k
>> With flat space (k = 0) we get:
>
> Maybe your 5 questions all assume k = 0. If so, state it out the
> outset. This might explain some of the confusion.
The line "With flat space (k = 0) we get" is almost
at the top of the document.
In the mean time I have improved the document with the results
for k = 1 and k = -1 with Labda = 0 and C= 60
I have also improved the document to show the evolution of z
(redshift) near the Big Bang.
The confusion from my part is how you can use Friedmann's equation
based from observations at present (i.e local) to calculate for example
the age of the Universe not knowing the parameters k, labda and C
Nicolaas Vroom
http://users.pandora.be/nicvroom/
schreef in bericht news:j5qpke$5lj$1...@online.de...
> In article <GWJfq.286$5W3...@newsfe08.ams2>, "Nicolaas Vroom"
> <nicolaa...@telenet.be> writes:
>
>
>> > The current understanding is however that the Universe is an
>> > open expanding system with acceleration.
>
> It is clear that it will expand forever. Whether or not it is spatially
> closed is not known (since it is close to the borderline).
I do not understand what you mean with spatial closed
> <nicolaa...@telenet.be> writes:
>
>
>> > The current understanding is however that the Universe is an
>> > open expanding system with acceleration.
>
> It is clear that it will expand forever. Whether or not it is spatially
> closed is not known (since it is close to the borderline).
What does it mean close to the borderline ?
>> > For a more detailed explanation of the problems involved See:
>> > http://users.telenet.be/nicvroom/friedmann's equation.htm
>
>> In order to understand better I have updated the above mentioned
>> document i.e.
>> http://users.telenet.be/nicvroom/friedmann's%20equation.htm
>
>> Any comments ?
>
> Just a few brief ones. I haven't read it all and haven't checked
> everything.
>
>> Question 4 For the above three conditions is it possible to
>> validate Hubble's Law?
>
> There are two things called "Hubble's Law" in the literature. One is
> the observed relation between the luminosity distance and redshift at
> low redshift. It is observed; it can't be "validated".
I expect you mean: z = H/c * d. (1)
>> validate Hubble's Law?
>
> There are two things called "Hubble's Law" in the literature. One is
> the observed relation between the luminosity distance and redshift at
> low redshift. It is observed; it can't be "validated".
> The other is
> the relation between the proper distance now and its derivative with
> respect to time (neither "directly observable") and holds for any
> homogeneous and isotropic universe (no physics required).
There is also a relation v = c * z (3)
What I demonstrate in the above mentioned document is that the
relations 1 and 3 are highly nonlinear starting from the bigBang
towards the present using the Friedmann equation assuming Cosmological
Principle for different combinations of the parameters C, Labda and k.
>> In order to simulate space expansion the Friedmann equation is used:
>> (See "Introducing Einstein's Relativity" by Ray d'Inverno. Equation 23.1
>> (dR/dt)^2= C/R + 1/3 * Labda*R^2 - k
>> With flat space (k = 0) we get:
>
> Maybe your 5 questions all assume k = 0. If so, state it out the
> outset. This might explain some of the confusion.
at the top of the document.
In the mean time I have improved the document with the results
for k = 1 and k = -1 with Labda = 0 and C= 60
I have also improved the document to show the evolution of z
(redshift) near the Big Bang.
The confusion from my part is how you can use Friedmann's equation
based from observations at present (i.e local) to calculate for example
the age of the Universe not knowing the parameters k, labda and C
Nicolaas Vroom
http://users.pandora.be/nicvroom/
Phillip Helbig---undress to reply
Oct 3, 2011, 4:12:10 AM10/3/11
to
In article <Z1Whq.547$333...@newsfe06.ams2>, "Nicolaas Vroom"
> What does it mean close to the borderline ?
Close to the borderline between a finite universe and an infinite
universe. If Omega + lambda > 1, the universe is finite, otherwise it
is infinite (assuming a simple topology). The measured value of
Omega + lambda is very near 1, but within the errors it could be larger
than 1 or less than 1.
> >> Question 4 For the above three conditions is it possible to
> >> validate Hubble's Law?
> >
> > There are two things called "Hubble's Law" in the literature. One is
> > the observed relation between the luminosity distance and redshift at
> > low redshift. It is observed; it can't be "validated".
> I expect you mean: z = H/c * d. (1)
Yes.
> > The other is
> > the relation between the proper distance now and its derivative with
> > respect to time (neither "directly observable") and holds for any
> > homogeneous and isotropic universe (no physics required).
> I expect you mean v = H * d. (2)
Yes.
> There is also a relation v = c * z (3)
Yes, but valid only at small redshifts.
> The confusion from my part is how you can use Friedmann's equation
> based from observations at present (i.e local) to calculate for example
> the age of the Universe not knowing the parameters k, labda and C
Under the assumption that the Friedmann equations apply, then one can
use local observations to measure the parameters and then calculate
things which depend on them, such as the age of the universe.
<nicolaa...@telenet.be> writes:
> >> > The current understanding is however that the Universe is an
> >> > open expanding system with acceleration.
> >
> > It is clear that it will expand forever. Whether or not it is spatially
> > closed is not known (since it is close to the borderline).
>
> I do not understand what you mean with spatial closed
It means that it has a finite volume.
> >> > The current understanding is however that the Universe is an
> >> > open expanding system with acceleration.
> >
> > It is clear that it will expand forever. Whether or not it is spatially
> > closed is not known (since it is close to the borderline).
>
> I do not understand what you mean with spatial closed
> What does it mean close to the borderline ?
universe. If Omega + lambda > 1, the universe is finite, otherwise it
is infinite (assuming a simple topology). The measured value of
Omega + lambda is very near 1, but within the errors it could be larger
than 1 or less than 1.
> >> Question 4 For the above three conditions is it possible to
> >> validate Hubble's Law?
> >
> > There are two things called "Hubble's Law" in the literature. One is
> > the observed relation between the luminosity distance and redshift at
> > low redshift. It is observed; it can't be "validated".
> I expect you mean: z = H/c * d. (1)
> > The other is
> > the relation between the proper distance now and its derivative with
> > respect to time (neither "directly observable") and holds for any
> > homogeneous and isotropic universe (no physics required).
> I expect you mean v = H * d. (2)
> There is also a relation v = c * z (3)
> The confusion from my part is how you can use Friedmann's equation
> based from observations at present (i.e local) to calculate for example
> the age of the Universe not knowing the parameters k, labda and C
use local observations to measure the parameters and then calculate
things which depend on them, such as the age of the universe.
Nicolaas Vroom
Oct 15, 2011, 9:13:38 AM10/15/11
to
schreef in bericht news:j6ac95$9qk$1...@online.de...
When you go to the document
http://users.telenet.be/nicvroom/friedmann's%20equation.htm
you can read why this is so difficult.
The main reason is : nonlinearity
For example can you use H0 to calculate the age of the Universe
with H0 calculated, based on observations over a distance
100 million years or 33 Mpc ?
I doubt this because relation (2) becomes more complex when
H0 is included.
This becomes something like: v = H0*d* (1 + a*d + b*d*d) etc.
The same problem also exists with the relation (3) above which is
also more complex:
in reality v is a non linear function of z which includes the parameter c.
Relation (3) becomes something like: v = c*z* (1 + q*z + r*z*z) etc.
What I want to say if you want to calculate the parameters C, labda
and k you need at least observations where this non linear
behaviour becomes "visible". (meaning more global)
What makes this extra complex is that the blue line (i.e. the path that a
light ray follows) is indepent of the parameter C. The parameter
C is only important how far back in history we can see. If you want
to observe the Big Bang (assuming you can) than C has to be large.
A second problem is that for certain combinations of labda and k
observations ( z or redshift) are the same making it difficult to
calculate
both.
Nicolaas Vroom
> In article <Z1Whq.547$333...@newsfe06.ams2>, "Nicolaas Vroom"
> <nicolaa...@telenet.be> writes:
>
>> I expect you mean: z = H/c * d. (1)
>
> Yes.
>
> <nicolaa...@telenet.be> writes:
>
>> I expect you mean: z = H/c * d. (1)
>
> Yes.
>
>> I expect you mean v = H * d. (2)
>
> Yes.
>
>> There is also a relation v = c * z (3)
>
> Yes, but valid only at small redshifts.
>
>> The confusion from my part is how you can use Friedmann's equation
>> based from observations at present (i.e local) to calculate for example
>> the age of the Universe not knowing the parameters k, labda and C
>
> Under the assumption that the Friedmann equations apply, then one can
> use local observations to measure the parameters and then calculate
> things which depend on them, such as the age of the universe.
That is correct, but the issue is how do you do that in detail.
>
> Yes.
>
>> There is also a relation v = c * z (3)
>
> Yes, but valid only at small redshifts.
>
>> The confusion from my part is how you can use Friedmann's equation
>> based from observations at present (i.e local) to calculate for example
>> the age of the Universe not knowing the parameters k, labda and C
>
> Under the assumption that the Friedmann equations apply, then one can
> use local observations to measure the parameters and then calculate
> things which depend on them, such as the age of the universe.
When you go to the document
http://users.telenet.be/nicvroom/friedmann's%20equation.htm
you can read why this is so difficult.
The main reason is : nonlinearity
For example can you use H0 to calculate the age of the Universe
with H0 calculated, based on observations over a distance
100 million years or 33 Mpc ?
I doubt this because relation (2) becomes more complex when
H0 is included.
This becomes something like: v = H0*d* (1 + a*d + b*d*d) etc.
The same problem also exists with the relation (3) above which is
also more complex:
in reality v is a non linear function of z which includes the parameter c.
Relation (3) becomes something like: v = c*z* (1 + q*z + r*z*z) etc.
What I want to say if you want to calculate the parameters C, labda
and k you need at least observations where this non linear
behaviour becomes "visible". (meaning more global)
What makes this extra complex is that the blue line (i.e. the path that a
light ray follows) is indepent of the parameter C. The parameter
C is only important how far back in history we can see. If you want
to observe the Big Bang (assuming you can) than C has to be large.
A second problem is that for certain combinations of labda and k
observations ( z or redshift) are the same making it difficult to
calculate
both.
Nicolaas Vroom
Phillip Helbig---undress to reply
Oct 16, 2011, 8:48:10 AM10/16/11
to
In article <TDTlq.435$W56...@newsfe16.ams2>, "Nicolaas Vroom"
case of an empty universe, in which case 1/H0 is the age of the
universe. (Of course, there are combinations of lambda and Omega which
also give 1/H0 for the age of the universe.) For the Einstein-de Sitter
model, the age is 2/3 1/H0. For other combinations of lambda and Omega,
the expression is more complicated (in general an elliptical integral
involving lambda and Omega; H0 is just a scale factor). Another way of
looking at it is that one ALWAYS needs to know lambda and Omega; the
fact that for the emtpy universe (both lambda and Omega = 0) the age is
1/H0 is just a particularly simple special case.
> What I want to say if you want to calculate the parameters C, labda
> and k you need at least observations where this non linear
> behaviour becomes "visible". (meaning more global)
Yes.
I don't know why you are confused. This is all standard stuff which was
worked out, in principle, in the 1920s and 1930s. From the 1960s at
least there are descriptions in more modern notation, and the more
modern they are probably the more familiar the notation will be for you.
Check out Ned Wright's cosmology calculator. Plug in the numbers, get
an answer. This is completely straightforward and there is no ambiguity
here.
MEASURING the cosmological parameters is also straightforward in theory.
In practice, of course, it is more difficult.
> That is correct, but the issue is how do you do that in detail.
> When you go to the document
> http://users.telenet.be/nicvroom/friedmann's%20equation.htm
> you can read why this is so difficult.
> The main reason is : nonlinearity
> For example can you use H0 to calculate the age of the Universe
> with H0 calculated, based on observations over a distance
> 100 million years or 33 Mpc ?
Using ONLY H0 to calculate the age of the universe works only in the
> When you go to the document
> http://users.telenet.be/nicvroom/friedmann's%20equation.htm
> you can read why this is so difficult.
> The main reason is : nonlinearity
> For example can you use H0 to calculate the age of the Universe
> with H0 calculated, based on observations over a distance
> 100 million years or 33 Mpc ?
case of an empty universe, in which case 1/H0 is the age of the
universe. (Of course, there are combinations of lambda and Omega which
also give 1/H0 for the age of the universe.) For the Einstein-de Sitter
model, the age is 2/3 1/H0. For other combinations of lambda and Omega,
the expression is more complicated (in general an elliptical integral
involving lambda and Omega; H0 is just a scale factor). Another way of
looking at it is that one ALWAYS needs to know lambda and Omega; the
fact that for the emtpy universe (both lambda and Omega = 0) the age is
1/H0 is just a particularly simple special case.
> What I want to say if you want to calculate the parameters C, labda
> and k you need at least observations where this non linear
> behaviour becomes "visible". (meaning more global)
I don't know why you are confused. This is all standard stuff which was
worked out, in principle, in the 1920s and 1930s. From the 1960s at
least there are descriptions in more modern notation, and the more
modern they are probably the more familiar the notation will be for you.
Check out Ned Wright's cosmology calculator. Plug in the numbers, get
an answer. This is completely straightforward and there is no ambiguity
here.
MEASURING the cosmological parameters is also straightforward in theory.
In practice, of course, it is more difficult.
Nicolaas Vroom
Oct 25, 2011, 4:56:45 AM10/25/11
to
"Phillip Helbig---undress to reply" <hel...@astro.multiCLOTHESvax.de>
schreef in bericht news:j7e3sr$uqm$3...@online.de...
> In article <TDTlq.435$W56...@newsfe16.ams2>, "Nicolaas Vroom"
> <nicolaa...@telenet.be> writes:
>
>> > Under the assumption that the Friedmann equations apply, then one can
>> > use local observations to measure the parameters and then calculate
>> > things which depend on them, such as the age of the universe.
>>
>> That is correct, but the issue is how do you do that in detail.
>> When you go to the document
>> http://users.telenet.be/nicvroom/friedmann's%20equation.htm
>> you can read why this is so difficult.
>> The main reason is : nonlinearity
>> For example can you use H0 to calculate the age of the Universe
>> with H0 calculated, based on observations over a distance
>> 100 million years or 33 Mpc ?
>
> Using ONLY H0 to calculate the age of the universe works only in the
> case of an empty universe, in which case 1/H0 is the age of the
> universe. (Of course, there are combinations of lambda and Omega which
> also give 1/H0 for the age of the universe.) For the Einstein-de Sitter
> model, the age is 2/3 1/H0.
When you study line one in table 4 in the above mentioned document
> <nicolaa...@telenet.be> writes:
>
>> > Under the assumption that the Friedmann equations apply, then one can
>> > use local observations to measure the parameters and then calculate
>> > things which depend on them, such as the age of the universe.
>>
>> That is correct, but the issue is how do you do that in detail.
>> When you go to the document
>> http://users.telenet.be/nicvroom/friedmann's%20equation.htm
>> you can read why this is so difficult.
>> The main reason is : nonlinearity
>> For example can you use H0 to calculate the age of the Universe
>> with H0 calculated, based on observations over a distance
>> 100 million years or 33 Mpc ?
>
> Using ONLY H0 to calculate the age of the universe works only in the
> case of an empty universe, in which case 1/H0 is the age of the
> universe. (Of course, there are combinations of lambda and Omega which
> also give 1/H0 for the age of the universe.) For the Einstein-de Sitter
> model, the age is 2/3 1/H0.
you can see that my calculations are in agreement.
Line one represents the situation where both labda and k are equal to zero.
>> What I want to say if you want to calculate the parameters C, labda
>> and k you need at least observations where this non linear
>> behaviour becomes "visible". (meaning more global)
>
> Yes.
>
> MEASURING the cosmological parameters is also straightforward in theory.
> In practice, of course, it is more difficult.
I do not know how you can measure the cosmological parameters
> In practice, of course, it is more difficult.
C, Labda and k as expressed in the friedmann equation directly.
What you can measure is magtitude and z and based on those you can
calculate C, Labda and k in theory.
For specific results see:
http://users.telenet.be/nicvroom/friedmann's%20equation.htm#Q6
My first impression is that this is a very difficult issue if you
compare observations with different simulations i.e. for different
combinations of the parameters Labda and k.
Nicolaas Vroom
http://users.telenet.be/nicvroom/
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