The Observed Universe, Our Universe, Our Big Bang.

On Saturday, July 12, 2014 5:16:21 AM UTC-4, Phillip Helbig---undress to reply wrote:
As I mentioned before what is sense of defining a physical concept
(ie Our Universe) centered around our point of view.

It's just a word. Whether you call it the universe, the observable
universe, or George doesn't matter.

Quite obviously, if one wants to communicate ideas
clearly and have discussions where all parties
understand what each is saying, then words and
definitions most certainly do matter.

This is especially true in science, where using
the correct technical terms is required for
clarity and accuracy.

Op zaterdag 12 juli 2014 11:16:21 UTC+2 schreef Phillip Helbig:
In article , Nicolaas Vroom
writes:

Right. The observable universe obviously depends on our position:

As I mentioned before what is sense of defining a physical concept
(ie Our Universe) centered around our point of view.

It's just a word. Whether you call it the universe, the observable
universe, or George doesn't matter.

It is a concept. Accordingly to Tegmark page 120 it means a spherical
region with Earth at the center.
At page 121 we also read:
As we saw in Chapter 3, this is more than 14 b lightyears because light
gets helped along by the expansion of space.

The question is: are "Our observable Universe" and "all what is
created as a result of the Big Bang" identical concepts

Accordingly to Tegmark at page 121:
As we saw inflation predits that there is even more.
Inflation predicts that there are doppelganger universes. (free interpretation)
This is the simplest example of parallel universes

To calculate the proper distance Now of the CMB radiation you have to
use the Friedmann equation. (Now approximate 35 b light years)

Right.

The Friedmann equation describes all what created as a result of
the Big Bang. IMO the two are identical ?

Right. If you like, the Friedmann equation describes what we call the
universe and Tegmark calls the Level I multiverse.
Tegmark at page 121 writes:
All the level I parallel universes together form the Level I multiverse.

"To me the most impressive piece of evidence for inflation is the flatness
problem - the closeness of the mass density of the early universe to the
critical value."
IMO that means that Lambda and omega(Lambda) are zero.

No; it means that the sum is 1.
You are right. The sum of omega(M) and omega(lambda) are 1.
omega(M) = 1 when mass density = critical density


Which is in conflict which the currently accepted value that omega(Lambda)
is 0,73 and omega(M) = 0.27 using Lambda=0,01155

When I do a simulation using the above values then omega(M) is equal in
increments of 1 b light years: (age 13,74)
0,991 0,97 0,93 0,87 0,81 0,74 0,67 0,6 0,53 0,47 0,4 0,35 0,3 0,27

what the simulation shows that in general in the early universe the
density is always close to the critical density and that this is no
prove that inflation theory is correct.

Where did you get the idea that flatness implies that lambda and Omega
are zero?

Alan Guth in his book at page 25 writes (See Figure 2.4) that at 1 Second
Omega(M) is between 0.9999999999999995 and 1.0000000000000005 with omega(M)
at present between 0 and 2.
This means with omega(M) at present = 0,27 then
omaga(M) at 1 second = 0.9999999999999997

Inflation fairly robustly predicts an almost flat universe.
i.e. that k=0 ?

How likely
such a universe is without inflation is not clear. It is difficult to
talk about probability in the context of the universe.

IMO the most important issue to discuss is the influence of inflation
on the Friedmann equation and the total size of of Our Universe now.
This is what Alan Guth describes in his book at page 185.
When you study study figure 10.6 my interpretation is, that with inflation
the size is the same but the age is a fraction of a second younger.

Inflation is over very, very, very early. After that, traditional
cosmology explains what we need. The effect of inflation is to make the
sum of lambda and Omega very close to 1 or, in other words, the radius
of curvature much larger than the Hubble radius.

I expect that when you study the CMB radiation and type 1 SN that both
demonstrate that k = 0.
The real thing to explain how inflation causes this and that that is the only
physical explanation.
Alan Guth at page 24 writes:
"As can be seen from the graph the mass density at one second must have been
equal to the critical density to an accuracy of better than one part
in 10^15"
It is true that the graph demonstrates this, but how do you know that
the graph is correct and is a correct image at what happened at that moment ?

Nicolaas Vroom

Op vrijdag 11 juli 2014 22:23:47 UTC+2 schreef Phillip Helbig:
In article , Nicolaas Vroom
writes:

7 b years after the BB the radius was roughly 5 b lightyears.
At present the radius is again very small.

It doesn't shrink in an expanding universe, neither in co-moving nor in
proper distance. What you are thinking of is that there is a maximum
distance AT THE TIME OF EMISSION.
Exactly that is what I'am thinking of.

Yes, that's true. Don't confuse this with the proper distance NOW.

We can only observe a tiny
bit of Our universe (All what is created after the BB) at present.

It depends on what you mean by "at present".
is identical as Now.

The
CURRENT radius of the observable universe is measured in dozens of
light-years (more than the 13.7 which is the age of the universe---that
is the light-travel time, but expansion increases the distance NOW,
though of course we cannot observe EVENTS, only OBJECTS, which are NOW
at that distance).
I fully agree with one comment,
What we observe now are events (SN) which happened 1 or 5 b years ago
of objects which are NOW at that distance.

If the radius of curvature of the universe is much
larger than the Hubble radius (as seems to be the case), then it is
indeed the case that the universe is much larger (perhaps infinitely
larger) than the observable universe.

That is why the concept of observable Universe does not make sense.
When the Universe is much larger as the observable Universe than it is
the larger Universe we should try to study. IMO it does not make sense
to study only a small part of all what is "created" by the BB.
IMO we should study the evolution of the Universe completely independent
of any human point of view.
Of course all our observations should "match" what "we" observe.
I assume it is this larger Universe which is described by the Friedmann
equation.

The problem is that Tekmark also assumes that the Universe is larger
than our observed Universe. He also assumes that this larger part are
parallel universes and are predicted by the inflation theory.

Nicolaas Vroom

On 7/14/2014 10:40 AM, Nicolaas Vroom wrote:

The problem is that Tekmark also assumes that the Universe is larger
than our observed Universe.

Don't you assume that the surface of the earth is bigger
than your observed surface of the earth? If yes, than I
think your attitude is a bigger problem than Tegmark's.

(Although in terms of scale it is smaller of course, but
I'm sure you know what I mean!)

He also assumes that this larger part are parallel
universes and are predicted by the inflation theory.

No, you confuse it with another step. The larger part
beyound the observable part is his first assumption (and
a reasonable one I believe). The parallel universes
predicted by inflation theory are an addition to this!
(And their creation is predicted *only* under assumption
of the existence of certain fields with certain properties
which can be tested in principle by high-energy physics.)

--
Jos


Nicolaas Vroom

In article , Nicolaas Vroom
writes:

It is a concept. Accordingly to Tegmark page 120 it means a spherical
region with Earth at the center.

Right.

At page 121 we also read:
As we saw in Chapter 3, this is more than 14 b lightyears because light
gets helped along by the expansion of space.

Right. This explains how the proper radius of the observable universe
NOW can be more light years than the number of years since the big bang.

The question is: are "Our observable Universe" and "all what is
created as a result of the Big Bang" identical concepts

No. The former is the observable universe and the latter the universe.
Or, in Tegmark's terminology, the former is the universe and the latter
is the Level I multiverse.

Some people in the British Isles mean "the Continent" when they say
"Europe". :-)

Accordingly to Tegmark at page 121:
As we saw inflation predits that there is even more.
Inflation predicts that there are doppelganger universes. (free
interpretation)
This is the simplest example of parallel universes

By this he means that inflation predicts that the universe is much
larger than the observable universe, perhaps infinitely larger. By
"simplest example" he means what he calls the Level I multiverse.

When I do a simulation using the above values then omega(M) is equal in
increments of 1 b light years: (age 13,74)
0,991 0,97 0,93 0,87 0,81 0,74 0,67 0,6 0,53 0,47 0,4 0,35 0,3 0,27

what the simulation shows that in general in the early universe the
density is always close to the critical density and that this is no
prove that inflation theory is correct.

This is a generic feature of non-empty big-bang models. You can just
look at how Omega, lambda and K depend on the scale factor. As R
approaches 0, the latter two terms become arbitrarily small, so only the
Omega term remains, which implies that Omega is 1.

This does not prove that inflation is correct. Historically, it has
been seen as a problem which inflation could solve, so it could be seen
as some type of circumstantial evidence for inflation. The usual
argument goes that it is somehow strange that Omega was so close to 1
early on, so there must be some reason for it. This is discussed in
some detail in a paper I wrote

http://www.astro.multivax.de:8000/he.../flatness.html

See also the references in the paper, particularly Lake. My impression
is that the importance of the flatness problem has been exaggerated.
There are other problems which a) seem like real problems and b) don't
seem to have an explanation other than inflation (which doesn't mean
that another explanation is impossible), such as the isotropy problem
(though I think Sean Carroll has a recent paper on the question whether
the universe is fine-tuned which claims that there is some other
solution; it's on my list of things to read but frankly my motivation
has dropped somewhat since Carroll doesn't seem to respond to questions,
comments and criticism---maybe he's spending too much time on
television). In contrast to most authors, Tegmark doesn't mention the
flatness problem first when discussing conundrums of classical
cosmology, and actually refers indirectly to my paper in a footnote in
this part of the book, so perhaps I've manage to convince him somewhat.

Where did you get the idea that flatness implies that lambda and Omega
are zero?

Alan Guth in his book at page 25 writes (See Figure 2.4) that at 1 Second
Omega(M) is between 0.9999999999999995 and 1.0000000000000005 with omega(M)
at present between 0 and 2.

Right. But that doesn't imply that lambda and Omega are zero.

This means with omega(M) at present = 0,27 then
omaga(M) at 1 second = 0.9999999999999997

I'll take your word for it. :-)

Inflation fairly robustly predicts an almost flat universe.
i.e. that k=0 ?

Yes, or very close to it.

How likely
such a universe is without inflation is not clear. It is difficult to
talk about probability in the context of the universe.

IMO the most important issue to discuss is the influence of inflation
on the Friedmann equation and the total size of of Our Universe now.

It essentially has no influence on the Friedmann equation. If the
universe is almost flat, then the observable universe is only a small
part, whether or not inflation happened. (Although inflation implies a
flat universe, a flat universe does not need inflation. No-one claims
that it does. Some claim that it is improbable without inflation, but I
think that Lake has a good argument against this.)

This is what Alan Guth describes in his book at page 185.
When you study study figure 10.6 my interpretation is, that with inflation
the size is the same but the age is a fraction of a second younger.

I don't follow you here. If we go back in time, using the Friedmann
equation, we see Omega approach 1 and lambda approach 0 and k approach
0, whatever their values are today. This implies that, at some very
early time, the universe was vastly larger than the Hubble radius at
that time. This is what one expects from inflation. It could also
happen without inflation; the question is how likely that is.

I expect that when you study the CMB radiation and type 1 SN that both
demonstrate that k = 0.

Not really. The CMB is rather sensitive to Omega+lambda, so in a sense
measures k "directly". At the current redshifts used, the SNIa m-z
diagram is sensitive to roughly Omega-lambda. Combining these
constraints gives values of lambda and Omega which are consistent with
other tests.

"As can be seen from the graph the mass density at one second must have been
equal to the critical density to an accuracy of better than one part
in 10^15"
It is true that the graph demonstrates this, but how do you know that
the graph is correct and is a correct image at what happened at that moment ?

If you evolve the Friedmann equation into the past, this is what you
get.

In article , Nicolaas Vroom
writes:

If the radius of curvature of the universe is much
larger than the Hubble radius (as seems to be the case), then it is
indeed the case that the universe is much larger (perhaps infinitely
larger) than the observable universe.

That is why the concept of observable Universe does not make sense.
When the Universe is much larger as the observable Universe than it is
the larger Universe we should try to study.

How? At best, we can infer theoretically what it should be like, based
on other theories. This is what Tegmark means when he says that
multiverses are predictions of other theories. They can't be directly
observed, but we should take them seriously in the same way that we
believe what GR says about the interior of black holes, even though we
can observe nothing there either.

IMO it does not make sense
to study only a small part of all what is "created" by the BB.
IMO we should study the evolution of the Universe completely independent
of any human point of view.
Of course all our observations should "match" what "we" observe.
I assume it is this larger Universe which is described by the Friedmann
equation.

Righ.

The problem is that Tekmark also assumes that the Universe is larger
than our observed Universe.

This is not an assumption. Calculate, for the concordance model, the
size of the universe and the size of the observable universe.

He also assumes that this larger part are
parallel universes

That is just what he CALLS the Level I multiverse. His Level I
multiverse is completely mainstream---1920s cosmology; he just has a
rather unorthodox term for it.

and are predicted by the inflation theory.

Inflation DOES predict this, but that is not to say that it could not
exist without inflation.

In article , Jos Bergervoet
writes:

The problem is that Tekmark also assumes that the Universe is larger
than our observed Universe.

Don't you assume that the surface of the earth is bigger
than your observed surface of the earth?

No assumption needed. One can measure the size of what one can see on
Earth, and calculate the size of the Earth.

He also assumes that this larger part are parallel
universes and are predicted by the inflation theory.

No, you confuse it with another step. The larger part
beyound the observable part is his first assumption (and
a reasonable one I believe).

This is what he calls the Level I multiverse. In some sense inflation
predicts it, since inflation predicts a (nearly) flat universe, in which
generically the observable universe is much smaller (perhaps infinitely
smaller) than the entire universe.

The parallel universes
predicted by inflation theory are an addition to this!
(And their creation is predicted *only* under assumption
of the existence of certain fields with certain properties
which can be tested in principle by high-energy physics.)

This is Tegmark's Level II multiverse. It, too could exist without
inflation.

Op zondag 13 juli 2014 14:19:07 UTC+2 schreef Robert L. Oldershaw:

Quite obviously, if one wants to communicate ideas
clearly and have discussions where all parties
understand what each is saying, then words and
definitions most certainly do matter.

This is especially true in science, where using
the correct technical terms is required for
clarity and accuracy.

I fully agree with you. It is especially true in astronomy
specific when you study the evolution of the Universe ie the Big Bang.
Regarding the evolution it very important to describe this evolution
completely indepent from the human point of view.
In a certain sense you should describe this evolution with your
eyes closed.
Phillip Helbig in his posting at 11 July writes:

The observable universe obviously depends on our position: we
are at the centre of it. It is like the horizon on Earth: the average
person can see about 11 km if there are no obstructions.

The distance you can observe (assuming a flat service) depents
about your height. With this distance you can calculate the radius
of the earth.
The point is you should not study what is directly observed
(the smaller circle) but the larger part (in this case the earth)
of which this circle is a part.

The same with the Universe. You should not start with what is observed
(even in principle because than you have to define what that means).
In stead you should start with all what is created after the big bang.
and specify what is assumed and what you know based on observations.
Mark Tegmark in his book also mentions that the (Our) Universe is larger
than what is observed. If this is true than you should start from
the largest part (as created by the (our) Big Bang)

Along the same line (but a complete different issue) it is wrong
to call the state of the dice inside a box and before you look
inside the box in a superposition state. This is clearly a definition
based on a human observation and has nothing to do with the
actual state which does not change when you make the observation.

When the state is up to claim that the state is down in a parallel
universe does not makes much sense specific if you agree with the
law of action reaction.
Generally speaking this law claims that all what is happening at present
in our universe is a result of a reaction on a previous action.
All those actions can be traced down to previous reactions/actions etc etc
all the way down to the (Our) Big Bang.
The claim that me throwing a dice also causes a change in a parallel
universe is in conflict with this law because their is no physical
connection. (What about the reverse?)
Anyway before you make such a proposition you much first clearly
define what a parallel universe physical is.
Specific you have to clarify if this parallel universe is part of our
Big Bang or a different one (see above).

Astronomy (physics) is about observations, experiments and finding the
descriptions of the processes involved. When you are lucky these
descriptions can be captured in mathematical laws.
It is not necessary that all these laws in all their detail
and in all their grandeur have to be observed by humans. The whole
point is that they should be clear and not in conflict which each other.

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

Op maandag 14 juli 2014 22:18:36 UTC+2 schreef Jos Bergervoet:
On 7/14/2014 10:40 AM, Nicolaas Vroom wrote:

The problem is that Tekmark also assumes that the Universe is larger
than our observed Universe.

Don't you assume that the surface of the earth is bigger
than your observed surface of the earth? If yes, than I
think your attitude is a bigger problem than Tegmark's.

Please read my reply in the latest posting of Robert Oldershaw

(Although in terms of scale it is smaller of course, but
I'm sure you know what I mean!)

Science is about Science.

He also assumes that this larger part are parallel
universes and are predicted by the inflation theory.

No, you confuse it with another step. The larger part
beyound the observable part is his first assumption (and
a reasonable one I believe).

IMO you should study primarily this larger part and
use the information collected based on the smaller part.
The first question to answer: is this larger part created
as a result of Our Big Bang.
The second question is: does the Friedmann equation apply.
The third question is: Is the size of influenced
by the concept of inflation.

The parallel universes
predicted by inflation theory are an addition to this!

Let us first come to an agreement about all what is created
as a result of Our Big Bang.

Nicolaas Vroom.

In article , Nicolaas Vroom
writes:

IMO you should study primarily this larger part and
use the information collected based on the smaller part.

By definition, we can observe only the observable universe. We cannot
study what lies behind the limit of the observable universe (the
particle horizon). At best, we can infer something about it, by
assuming that the universe will not suddenly change at the boundary of
the observable universe (which would imply that we are in a special
place; why should the universe change at a certain distance from US?)
and/or by extrapolating from theories which have been shown to be useful
in our observable universe.

The first question to answer: is this larger part created
as a result of Our Big Bang.

Yes.

The second question is: does the Friedmann equation apply.

Yes.

The third question is: Is the size of influenced
by the concept of inflation.

Not really. Except for rather special combinations of the cosmological
parameters lambda and Omega, the size of the observable universe is of
the same order of magnitude as the Hubble radius. What is the size of
the universe? The radius of curvature is given by
1/SQRT(|Omega+lambda-1|) multiplied by the Hubble radius. So, if the
universe is exactly flat, the radius of curvature is infinite and the
size of the universe is infinite: an infinite 3-dimensional Euclidean
space. If Omega+lambda1, then we have negative spatial curvature and
also an infinite universe. We know from observations that Omega+lambda
is very close to 1, so we know that the universe is very much bigger
than the observable universe, perhaps infinitely so. (Note for experts:
I am assuming a trivial topology here.)

This is purely classical cosmology and has nothing to do with inflation.
Inflation comes into the picture via two routes. One, there is some
evidence for inflation, such as the spectral index of primordial
perturbations, which was a robust prediction of inflation and has since
been confirmed. Second, inflation naturally leads to Omega+lambda very
close to 1, so one could see (near) flatness as indicating that
something like inflation must have happened. How likely such a universe
is without inflation is a matter of debate (see my paper on this topic
mentioned earlier in this thread).

Inflation essentially increases the size of the universe from around the
Planck length to the size of a basketball during the first 10^{-35} of a
second or whatever early on. The Hubble length is still approximately
the Planck length, though. After that, the Friedmann equation applies.

Let us first come to an agreement about all what is created
as a result of Our Big Bang.

There is agreement: it is that which is described by the Friedmann
equation, what many people call the universe (and what Tegmark calls the
Level I multiverse, since he refers to what many call the observable
universe as the universe).