current status of the horizon problem in cosmology

The horizon problem is the question why different areas on the sky
(think: temperature of the CMB) are similar even though they were not
causally connected (if one calculates the growth of the "sphere of
influence" with time according to classical cosmology). One solution is
inflation (exponential expansion in the very early universe), since in
this picture the regions WERE causally connected but have been moved
apart by inflation.

In the article below, noted cosmologist and famous writer John D. Barrow
claims that there is no horizon problem in cosmology (and hence that at
least this motivation for inflation is not necessary, though of course
that does not prove that inflation didn't happen). Nevertheless, in the
more than 15 years since its publication, the horizon problem is
regularly mentioned.

Has there been a refutation of Barrow's claim in the refereed
literature?

@ARTICLE {JBarrow95a,
AUTHOR = "John D. Barrow",
TITLE = "Why the Universe is not Anisotropic",
JOURNAL = PhysRevD,
YEAR = "1995",
VOLUME = "51",
NUMBER = "6",
PAGES = "3113",
MONTH = "15" # mar # "1995"
}

On May 2, 5:04*am, (Phillip Helbig---
undress to reply) wrote:
The horizon problem is the question why different areas on the sky
(think: temperature of the CMB) are similar even though they were not
causally connected (if one calculates the growth of the "sphere of
influence" with time according to classical cosmology). *One solution is
inflation (exponential expansion in the very early universe), since in
this picture the regions WERE causally connected but have been moved
apart by inflation.

In the article below, noted cosmologist and famous writer John D. Barrow
claims that there is no horizon problem in cosmology (and hence that at
least this motivation for inflation is not necessary, though of course
that does not prove that inflation didn't happen). *Nevertheless, in the
more than 15 years since its publication, the horizon problem is
regularly mentioned.

Has there been a refutation of Barrow's claim in the refereed
literature?

@ARTICLE * * *{JBarrow95a,
* * * * * * * *AUTHOR * * * = "John D. Barrow",
* * * * * * * *TITLE * * * *= "Why the Universe is not Anisotropic",
* * * * * * * *JOURNAL * * *= PhysRevD,
* * * * * * * *YEAR * * * * = "1995",
* * * * * * * * *VOLUME * * * = "51",
* * * * * * * * *NUMBER * * * = "6",
* * * * * * * * *PAGES * * * *= "3113",
* * * * * * * * *MONTH * * * *= "15" # mar # "1995"
* * * * * * * }

If the universe has infinite size and it has redshift due to local
expansion, isotropy is expected. The horizon after 15 billion light
years distance in uniformly unobservable. The expansion may be due to
a spinning universe.

In sci.astro.research Globemaker wrote:
The expansion [[of the universe]] may be due to
a spinning universe.

There are *very* tight observational limits on any overall rotation
of the universe. Notably,
Collins & Hawking
Monthly Notices of the Royal Astronomical Society, Vol. 162, p. 307 (1973)
http://adsabs.harvard.edu/abs/1973MNRAS.162..307C
showed that the universe can't have rotated any more than a few
microarcseconds (i.e., about 1e-11 revolutions) in a Hubble time.

More recently
Bunn, Ferreira, & Silk
Physical Review Letters 77, 2883 (1996)
http://link.aps.org/doi/10.1103/PhysRevLett.77.2883
used a very different analysis to limit the overall rotation
of the universe per Hubble time to no more than around 1e-6
radians, i.e., around 1e-7 revolutions.

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

On May 2, 10:04*am, (Phillip Helbig---
undress to reply) wrote:
The horizon problem is the question why different areas on the sky
(think: temperature of the CMB) are similar even though they were not
causally connected (if one calculates the growth of the "sphere of
influence" with time according to classical cosmology). *One solution is
inflation (exponential expansion in the very early universe), since in
this picture the regions WERE causally connected but have been moved
apart by inflation.

In the article below, noted cosmologist and famous writer John D. Barrow
claims that there is no horizon problem in cosmology (and hence that at
least this motivation for inflation is not necessary, though of course
that does not prove that inflation didn't happen). *Nevertheless, in the
more than 15 years since its publication, the horizon problem is
regularly mentioned.

Has there been a refutation of Barrow's claim in the refereed
literature?


I don't know any refutation of Barrow's claim in the refereed
literature, but I do know that the horizon problem arises from
thinking of the universe within a classical framework, that is to say,
not taking into account an understanding of quantum mechanics. In
quantum theory it is not possible to talk of a distance between
particles unless there is some way to measure, at least in principle,
that distance. I find it obvious that in the early universe, that is
to say early on the timescale of inflation, i.e. ~10^-33 sec no such
measurements are possible, even in principle. It is equally obvious,
from Einstein's argument in the 1905 paper, that the inflation means
that the universe was expanding faster than itself. I.e. that
inflation has always been nonsensical to anyone with a grasp of what
Einstein was actually saying. Oh, I know there are lots of modern
physicists who think they have a better understanding than Einstein,
but quite frankly, they don't, and that is why inflation has found its
way into the text books.

In article
, Oh
No writes:

On May 2, 10:04*am, (Phillip Helbig---
undress to reply) wrote:
The horizon problem is the question why different areas on the sky
(think: temperature of the CMB) are similar even though they were not
causally connected (if one calculates the growth of the "sphere of
influence" with time according to classical cosmology). *One solution is
inflation (exponential expansion in the very early universe), since in
this picture the regions WERE causally connected but have been moved
apart by inflation.

In the article below, noted cosmologist and famous writer John D. Barrow
claims that there is no horizon problem in cosmology (and hence that at
least this motivation for inflation is not necessary, though of course
that does not prove that inflation didn't happen). *Nevertheless, in the
more than 15 years since its publication, the horizon problem is
regularly mentioned.

Has there been a refutation of Barrow's claim in the refereed
literature?


I don't know any refutation of Barrow's claim in the refereed
literature, but I do know that the horizon problem arises from
thinking of the universe within a classical framework, that is to say,
not taking into account an understanding of quantum mechanics.

Right. The general wisdom is that some aspect of quantum mechanics, or
something else in the early universe outside the scope of classical
cosmology, solves the problem. That might be the case. However,
Barrow's point was that such a solution is not NECESSARY. It doesn't
rule out inflation, or anything else outside the scope of classical
cosmology which occurs when classical cosmology is not an appropriate
approximation, but the claim is that the horizon problem actually
doesn't exist in classical cosmology.

"Phillip Helbig---undress to reply"
schreef in bericht ...
The horizon problem is the question why different areas on the sky
(think: temperature of the CMB) are similar even though they were not
causally connected (if one calculates the growth of the "sphere of
influence" with time according to classical cosmology). One solution is
inflation (exponential expansion in the very early universe), since in
this picture the regions WERE causally connected but have been moved
apart by inflation.

In the article below, noted cosmologist and famous writer John D. Barrow
claims that there is no horizon problem in cosmology (and hence that at
least this motivation for inflation is not necessary, though of course
that does not prove that inflation didn't happen). Nevertheless, in the
more than 15 years since its publication, the horizon problem is
regularly mentioned.

Has there been a refutation of Barrow's claim in the refereed
literature?

@ARTICLE {JBarrow95a,
AUTHOR = "John D. Barrow",
TITLE = "Why the Universe is not Anisotropic",
JOURNAL = PhysRevD,
YEAR = "1995",
VOLUME = "51",
NUMBER = "6",
PAGES = "3113",
MONTH = "15" # mar # "1995"
}


For a copy of the article (?) this link:
http://www.gravityresearchfoundation...994/barrow.pdf
For a link to a url discussing the issues involved go he
http://www.astronomynotes.com/cosmolgy/s12.htm

Inflation is the explanation to solve the horizon problem.
In wikipedia we can read:
http://en.wikipedia.org/wiki/Horizon_problem
"Inflation then expanded it rapidly, freezing in these properties
all over the sky; at this point the universe would be forced
to be almost perfectly homogeneous,"
We are speaking here about a time period less than 1 second.
I assume 1 second "my" clock/watch time.
This is extremely short.
I do not understand how you can use this to explain that
the Universe is so homogenous, i.e. that there are roughly
speaking galaxies everywhere.

[[Mod. note -- Is 1 second an "extremely short" time? That depends
on the standard of comparison. For example, 1 second is a very *long*
time compared to processes that operated in a nanosecond. Inflation
is usually understood as taking (*much*) less than a nanosecond.

The following quote from
http://en.wikipedia.org/wiki/Inflation_%28cosmology%29
is a nice brief synopsis of how inflation ensures that the observable
universe is isotropic:
For cosmology in the global point of view, the observable universe
is one causal patch of a much larger unobservable universe; there
are parts of the universe which cannot communicate with us yet.
These parts of the universe are outside our current cosmological
horizon. In the standard hot big bang model, without inflation, the
cosmological horizon moves out, bringing new regions into view. As
we see these regions for the first time, they look no different
from any other region of space we have already seen: they have a
background radiation which is at nearly exactly the same temperature
as the background radiation of other regions, and their space-time
curvature is evolving lock-step with ours. This presents a mystery:
how did these new regions know what temperature and curvature they
were supposed to have? They couldn't have learned it by getting
signals, because they were not in communication with our past light
cone before.[5][6]

Inflation answers this question by postulating that all the regions
come from an earlier era with a big vacuum energy, or cosmological
constant. A space with a cosmological constant is qualitatively
different: instead of moving outward, the cosmological horizon stays
put. For any one observer, the distance to the cosmological horizon
is constant. With exponentially expanding space, two nearby observers
are separated very quickly; so much so, that the distance between
them quickly exceeds the limits of communications. In the global
point of view, the spatial slices are expanding very fast to cover
huge volumes. In the local point of view, things are constantly
moving beyond the cosmological horizon, which is a fixed distance
away, and everything becomes homogeneous very quickly.
-- jt]]

1. IMO the inside of the Sun (Interior of the Earth) is rather
homogeneous. It is a boiling pot. The reason is communication
("lava flows") at very low speeds over very long periods
of time.

[[Mod. note -- The author is mistaken in thinking that the interior
of either the Sun or the Earth is homogeneous. See
http://en.wikipedia.org/wiki/Sun
http://en.wikipedia.org/wiki/Structure_of_the_Earth
for brief introductions to their actual (inhomogeneous) internal
structure.
-- jt]]

2. When you look to pictures of old super novae you see
something that is very inhomogeneous.
http://en.wikipedia.org/wiki/Supernova

This tells me:
1. Slow processes - homogenous results.
2. Fast processes - inhomogenous results.

What is the solution ?

Nicolaas Vroom
http://users.telenet.be/nicvroom/

On May 5, 5:29*pm, (Phillip Helbig---
undress to reply) wrote:
In article
, Oh

No writes:
On May 2, 10:04*am, (Phillip Helbig---
undress to reply) wrote:
The horizon problem is the question why different areas on the sky
(think: temperature of the CMB) are similar even though they were not
causally connected (if one calculates the growth of the "sphere of
influence" with time according to classical cosmology). *One solution is
inflation (exponential expansion in the very early universe), since in
this picture the regions WERE causally connected but have been moved
apart by inflation.

In the article below, noted cosmologist and famous writer John D. Barrow
claims that there is no horizon problem in cosmology (and hence that at
least this motivation for inflation is not necessary, though of course
that does not prove that inflation didn't happen). *Nevertheless, in the
more than 15 years since its publication, the horizon problem is
regularly mentioned.

Has there been a refutation of Barrow's claim in the refereed
literature?

I don't know any refutation of Barrow's claim in the refereed
literature, but I do know that the horizon problem arises from
thinking of the universe within a classical framework, that is to say,
not taking into account an understanding of quantum mechanics.

Right. *The general wisdom is that some aspect of quantum mechanics, or
something else in the early universe outside the scope of classical
cosmology, solves the problem. *That might be the case. *However,
Barrow's point was that such a solution is not NECESSARY. *It doesn't
rule out inflation, or anything else outside the scope of classical
cosmology which occurs when classical cosmology is not an appropriate
approximation, but the claim is that the horizon problem actually
doesn't exist in classical cosmology.

To be honest, the only way I can understand this claim is to think
that Barrow has not understood the problem. The horizon problem
results from a very straightforward argument concerning causality and
the light cone in the early universe. Since it is straightforward I
would think that many people have understood it, and would see
straight away that Barrow's claim does not stand up. It does not
follow that a refutation would have been published, because a) such a
refutation would be fairly trivial and obvious to those who do
understand the problem, and b) it is not necessarily the case that
journals like it when attention is drawn to the publication of claims
which should never have been published in the first place.

"Nicolaas Vroom" schreef in bericht
...

The following quote from
http://en.wikipedia.org/wiki/Inflation_%28cosmology%29
is a nice brief synopsis of how inflation ensures that the observable
universe is isotropic:
For cosmology in the global point of view, the observable universe
is one causal patch of a much larger unobservable universe; there
are parts of the universe which cannot communicate with us yet.
These parts of the universe are outside our current cosmological
horizon. In the standard hot big bang model, without inflation, the
cosmological horizon moves out, bringing new regions into view. As
we see these regions for the first time, they look no different
from any other region of space we have already seen: they have a
background radiation which is at nearly exactly the same temperature
as the background radiation of other regions, and their space-time
curvature is evolving lock-step with ours. This presents a mystery:
how did these new regions know what temperature and curvature they
were supposed to have? They couldn't have learned it by getting
signals, because they were not in communication with our past light
cone before.[5][6]

Inflation answers this question by postulating that all the regions
come from an earlier era with a big vacuum energy, or cosmological
constant. A space with a cosmological constant is qualitatively
different: instead of moving outward, the cosmological horizon stays
put. For any one observer, the distance to the cosmological horizon
is constant. With exponentially expanding space, two nearby observers
are separated very quickly; so much so, that the distance between
them quickly exceeds the limits of communications. In the global
point of view, the spatial slices are expanding very fast to cover
huge volumes. In the local point of view, things are constantly
moving beyond the cosmological horizon, which is a fixed distance
away, and everything becomes homogeneous very quickly.
-- jt]]

IMO there are two issues:
1. Observations - The visible (human / light cone ) issue
2. The physical issue.

The first issue that we see a rather homogenous distribution
of galaxies all around us. This picture represents the past and
only a small (?) part of the total Universe.
Assuming that space expands and using the same telescope with
the same accuracy we will see even less. This is because the
distance you can see which such a telescope is constant.

The second issue is a physical issue: which evolution of physical
processes and events happen to "create" what we see.
Maybe the state of the Universe was always rather homogeneous.
Maybe the state was even more homogeneous in the past
(as observed by the Micro Wave Background Radiation) as in
the present (galaxy Clusters)
IMO you should compare the Big Bang evolution with a Super
Super Nova of a black hole.
IMO you do not need inflation over a very very small timescale.
The problem with inflation (a discontinuous increase and decrease in
speed / a small big bang) is: how did it start and how did it stop.

1. IMO the inside of the Sun (Interior of the Earth) is rather
homogeneous. It is a boiling pot. The reason is communication
("lava flows") at very low speeds over very long periods
of time.

[[Mod. note -- The author is mistaken in thinking that the interior
of either the Sun or the Earth is homogeneous. See
http://en.wikipedia.org/wiki/Sun
http://en.wikipedia.org/wiki/Structure_of_the_Earth
for brief introductions to their actual (inhomogeneous) internal
structure.
-- jt]]
I wrote on purpose "rather" homogeneous.

2. When you look to pictures of old super novae you see
something that is very inhomogeneous.
http://en.wikipedia.org/wiki/Supernova

This tells me:
1. Slow processes - homogenous results.
2. Fast processes - inhomogenous results.

What is the solution ?


Nicolaas Vroom
http://users.telenet.be/nicvroom/

"Nicolaas Vroom" schreef in bericht
...

The following quote from
http://en.wikipedia.org/wiki/Inflation_%28cosmology%29
is a nice brief synopsis of how inflation ensures that the observable
universe is isotropic:
For cosmology in the global point of view, the observable universe
is one causal patch of a much larger unobservable universe; there
are parts of the universe which cannot communicate with us yet.
These parts of the universe are outside our current cosmological
horizon. In the standard hot big bang model, without inflation, the
cosmological horizon moves out, bringing new regions into view. As
we see these regions for the first time, they look no different
from any other region of space we have already seen: they have a
background radiation which is at nearly exactly the same temperature
as the background radiation of other regions, and their space-time
curvature is evolving lock-step with ours. This presents a mystery:
how did these new regions know what temperature and curvature they
were supposed to have? They couldn't have learned it by getting
signals, because they were not in communication with our past light
cone before.[5][6]

Inflation answers this question by postulating that all the regions
come from an earlier era with a big vacuum energy, or cosmological
constant. A space with a cosmological constant is qualitatively
different: instead of moving outward, the cosmological horizon stays
put. For any one observer, the distance to the cosmological horizon
is constant. With exponentially expanding space, two nearby observers
are separated very quickly; so much so, that the distance between
them quickly exceeds the limits of communications. In the global
point of view, the spatial slices are expanding very fast to cover
huge volumes. In the local point of view, things are constantly
moving beyond the cosmological horizon, which is a fixed distance
away, and everything becomes homogeneous very quickly.
-- jt]]

IMO there are two issues:
1. Observations - The visible (human / light cone ) issue
2. The physical issue.

The first issue that we see a rather homogenous distribution
of galaxies all around us. This picture represents the past and
only a small (?) part of the total Universe.
Assuming that space expands and using the same telescope with
the same accuracy we will see even less. This is because the
distance you can see which such a telescope is constant.

The second issue is a physical issue: which evolution of physical
processes and events happen to "create" what we see.
Maybe the state of the Universe was always rather homogeneous.
Maybe the state was even more homogeneous in the past
(as observed by the Micro Wave Background Radiation) as in
the present (galaxy Clusters)
IMO you should compare the Big Bang evolution with a Super
Super Nova of a black hole.
IMO you do not need inflation over a very very small timescale.
The problem with inflation (a discontinuous increase and decrease in
speed / a small big bang) is: how did it start and how did it stop.

1. IMO the inside of the Sun (Interior of the Earth) is rather
homogeneous. It is a boiling pot. The reason is communication
("lava flows") at very low speeds over very long periods
of time.

[[Mod. note -- The author is mistaken in thinking that the interior
of either the Sun or the Earth is homogeneous. See
http://en.wikipedia.org/wiki/Sun
http://en.wikipedia.org/wiki/Structure_of_the_Earth
for brief introductions to their actual (inhomogeneous) internal
structure.
-- jt]]
I wrote on purpose "rather" homogeneous.

2. When you look to pictures of old super novae you see
something that is very inhomogeneous.
http://en.wikipedia.org/wiki/Supernova

This tells me:
1. Slow processes - homogenous results.
2. Fast processes - inhomogenous results.

What is the solution ?


Nicolaas Vroom
http://users.telenet.be/nicvroom/