Big Bang and The Edge of The Universe?

[Jeff Root]

Yeah, sorry Jeff - as far as I can see all you are doing is
presenting the same assertions.

Obviously. There isn't much to what I have to say. All I
could do was try to clarify what was unclear. Same this time.

Your first paragraph is an absolutely perfect example of it.

Here it is again:

Any mechanism which causes things to be the same in
different locations causally connects them.

That is an interesting definition of causally connected.
One I would not subscribe to at the moment as it dives
deeply into areas not covered by current theory, as of yet.

It is completely straightforward. It can't be any other way.
You and I have similar DNA because we are causally
connected by our common ancestors. Without those
common ancestors it would be extremely unlikely that
we would be anything alike.

It can be many other ways.

What I referred to is causality. I gave a single, very simple
example of causality. The example of two things (you and I)
connected by our common ancestors, causing us to have similar
phenotypes.

Everything involved in the Big Bang is causally connected in
the same way as the example. It is what the term "causality"
means. It is what causality is.

Causality is not as simple as you make out ...

I didn't think I said enough about causality to give any
impression of either simplicity or complexity. I barely
mentioned the subject, and gave only a single example.
Of course there are all kinds of complexities. If you think
it is necessary to go into some of them, say what they are,
and what makes them necessary.

... and is being investigated as a fundamental aspect of the
space time it is linked to. Theories other than String theory
seem to be probing deeply into what is meant by causality
and how it can be used to 'build' spacetime. So if they turn
out to be better than Strings then we would have the situation
where any universe with causality would end up with the same
spacetime structure as our own. So by your logic that would
mean everything with causality would be causally connected.

Okay, maybe I agree with that. If the Universe (in the large)
is governed by natural laws which inevitably result in all
parts of the Universe having the same spacetime structure,
then all parts of the Universe are causally connected via
the spacetime structure and the natural laws which govern
that structure.

Is that in any way a problem?

Does it in any way conflict with what I've said?

-- Jeff, in Minneapolis

[astromark]

In a adjacent thread I have asked some of the concepts of ..'Concepts of reality.'

There is a obvious overlap as this subject begins to explore all the possible ramifications of 'Different' rules.

We only have a knowledge of one.. this one.

To assert any different set of standards a other would need to be found

and studied. We have NO knowledge of other do we ?

There is always going to be questions un answered.

We know a great deal.. and still more questions arise..

[WayneFrancis]

And there is no reason why it should have similar properties.

If there were some reason, that reason would indicate a causal
connection.

No a causal connections means a change in one can be felt by the other.

2 object that have similar properties but are not causally connected is a different issue.

Unfortunately for our ability to discuss this, we don't (and can't)
have any actual examples of causally-disconnected things to
examine and consider. That would be tremendously helpful.

It is unprovable yes but doesn't mean we can't talk about the theory behind it.

I wouldn't say exactly that. I would say that there is no reason
to assume that such a spot would have a gravitational constant.

And this is my issue with your claim. That "there is no reason to assume that such a spot would have a gravitational constant"

Why wouldn't it? We look out through the visible universe and see no indication that the gravitational constant changes. Why would we make an assumption that it would? I'm not saying it can't. It could be the fact that the gravitational constant, in this thought experiment, does change but it is at a rate that is smaller then we could detect over our visible universe.

Essentially you are saying that point A has a gravitational constant of 6.67300×10[sup]-11[sup]m³kg^-1s^-2 We detect measure B as having a gravitation constant of 6.67300×10[sup]-11[sup]m³kg^-1s^-2 but point C since it is not causally connected to us that we can't assume that it even has one. I say yes we can because we have no reason to think otherwise and it is more likely that there isn't some drastic change just beyond our cosmic horizon. So things 48 billion light years away seem to follow the same physics that we follow. Why should you expect anything but the same at 49 billion light years away?

I say that everything which has ever participated in the cosmic
expansion of the Big Bang is causally connected. Anything
which has never participated in the cosmic expansion or Big
Bang may be causally disconnected from us, and may not have
any of the properties of spacetime, matter, and energy that we
are familiar with. Or it may. But there is no reason to assume
that it would.

The more similar things are, the more likely that the similarity
is due to a causal connection. That is not a hard and fast rule
of course, but I think it is a very good rule of thumb.

If two spots have the same gravitational constant, I'd guess
that it is because they are causally connected.


If A and B are similar *because* they are causally connected,
and B and C are simllar because they are causally connected,
then A and C are similar because they are causally connected.


On the other hand, if A and B are similar because they are
causally connected, but B and C are similar just by chance,
even though they are causally connected, then A and C are
similar just by chance, and we don't have enough info to say
whether A and C are causally connected or not.

A, B, and C are toymakers. A and B know each other, and B
and C know each other. But A and C know nothing of each
other's existence.

Toymaker B makes xylophones that he invented. Toymaker A
makes xylophones that he copied from toymaker B. Toymaker
C makes xylophones that he copied from toymaker B. So the
xylophones of toymakers A and C are causally connected.

No A & C are not causally connected in the way most people use it.
If A makes a change in their design C can not and will not ever know about it.
Just because A & C can be effected by the same event doesn't mean A can ever effect C

You are stretching the definition of "causally connected" as we talk about stuff outside of our Hubble volume and this is the problem.

In the second scenario, Toymaker B again makes xylophones
that he invented, and toymaker A again makes xylophones that
he copied from toymaker B. But toymaker C makes zylophones
that he invented, and which just happen to be identical to the
xylophones made by A and B. So the xylophones of toymaker
A are not causally connected to the zylophones of toymaker C,
even though they are identical, and even though toymakers A
and C happen to be causally connected via toymaker B.

None of the above implies that A ever affects C, or that C ever
affects A. Toymaker B may have died before toymakers A and
C were born.

So you agree that A can't effect C or vice versa but yet you try to claim they are causally connected when they are clearly not.
Its a non sequitur in same way as saying

John shoots Bill, John shoots Jane. Bill dies because Jane Dies.

No Bill and Jane die because of John not because of anything that happened to the other one.

[

I haven't complained that there is a conflict between the observed
flatness and a toroidal geometry. To do that I would have to study
the details of how toroidal curvature might affect observations,
which I haven't done. What I have complained is that I don't see
how or whether a toroidal topology can exist without a toroidal
geometry, and that a toroidal geometry seems utterly unlikely.

-- Jeff, in Minneapolis[/QUOTE]

So you agree that A can't effect C or vice versa but yet you try to claim they are causally connected when they can no longer effect each other.

So the only way I agree with you is that they have the same origins and I don't see where that is against mainstream science. The universe, not just the visible universe, could be infinite in expanse but still have originated from the same cause which just seems to suggest to me you don't like infinities but I've never seen anything that shows that the universe could not be infinite in expanse just that if it is that it was never finite in volume and note that a volume of zero transitioning to infinity does not have the problems of a finite size transitioning to infinity.

I think half of it is we are talking semantics here and the other half is your belief that you can't have a transition from zero to infinity and me saying that there is no problem as long as that transition doesn't go through a finite stage.

[WayneFrancis]

Jeff;

What happens to a very early hydrogen cloud, when it moves beyond our Cosmic Horizon ?

Does it suddenly loose its physical properties just because it is no longer causally connected to our observable universe? Do the photons it once produced, cease to exist? With your rationale, what happens if it enters the domain of a realm having different adopted physical properties ? What happens during its approach to this realm ?

Whilst I agree that there is no reason to assume the same values of the fundamental 'constants' we measure, there are still abstracted parameters, which we can infer might be applicable, regardless of the precise conditions of their origins. (Eg: the concept of Inflaton Fields, comes to mind). If this principle is accepted, then there would seem to be 'causality' everywhere throughout the universe, with the Big Bang as one possible evidence-based, universally common phenomenon, possibly capable of producing different outcomes.

This also does not exclude other origin events either, but inferences can be drawn from what we have observed, in order to encroach upon the boundaries of the presently causally disconnected.

Regards

Much better wording then what I said.

[Strange]

I think I may have just understood one reason why I could never understand some of Jeff's arguments!

Jeff, can I just test my new-found understanding:

If the laws of physics are the same everywhere in an infinite universe would you describe everywhere as being "causally connected" because of that?

[astromark]

Causally connected and having since evolved a different aspect might be entirely possible, mightn't it ?

[Jeff Root]

Wayne,

I've practically finished a reply to you, but need to work on a
detail before I post it.


Strange,

If the laws of physics are *caused* to be the same everywhere,
then everywhere is causally connected.

If the laws of physics are the same in different regions of the
Universe just by pure coincidence, with no causal connection
between those regions, then -- obviously -- the regions aren't
causally connected.

All I'm claiming is a dumb tautology: If things are causally
connected they're causally connected. If they're not, they're
unlikely to be very similar.

The laws of physics are complex enough that if they are the
same everywhere in the Universe, then everywhere in the
Universe is almost certainly causally connected. It is very
unlikely that they'd be the same everywhere by chance.


Mark,

That happens constantly, all around us. And it is a practical
problem in many ways.

-- Jeff, in Minneapolis

[WayneFrancis]

I think the difference is Jeff uses "causally connected" in a manner which that can be confusing to ... well at least me.

Jeff is right that there can be 2 spot that have future light cones that never intersect but who may have a common origin. That common origin means they, in the technical sense, where causally connected in that both spots where formed from the same event.

The issue I have is those 2 spots may not and need not have intersecting light cones and it is easy to think that they needed to have, at least, intersecting light cones in the past.

I for one most often think about future light cones when discussing "causal connections" but by definition that is not a requirement. But given that neither is the requirement for the 2 spots to have any intersecting light cones, past or future. If space is infinite and has not always been around then it is a makes more sense that it when from zero volume to infinite volume instantly. Now the 2 points in space now because of expansion may never have intersecting future light cones and that is true for the instant after the transition from zero volume to infinite volume. Thus the 2 points in space never communicated but since they share the same origin are "casually connected".

How you go from that and say that the universe can't be infinite is still beyond me.

Those 2 spots may or may not have all the same constants we have but if we see no change in the constants in our visible universe and we assume that both points originated from the same event and thus there is a chain of points in space that link the two, even though no information can ever pass between them in the future, then it isn't unreasonable to assume that the constants remain the same and for all intensive purposes it doesn't matter because we can never prove or disprove it.

[WayneFrancis]

Wayne,

I've practically finished a reply to you, but need to work on a
detail before I post it.


Strange,

If the laws of physics are *caused* to be the same everywhere,
then everywhere is causally connected.

If the laws of physics are the same in different regions of the
Universe just by pure coincidence, with no causal connection
between those regions, then -- obviously -- the regions aren't
causally connected.

All I'm claiming is a dumb tautology: If things are causally
connected they're causally connected. If they're not, they're
unlikely to be very similar.

The laws of physics are complex enough that if they are the
same everywhere in the Universe, then everywhere in the
Universe is almost certainly causally connected. It is very
unlikely that they'd be the same everywhere by chance.


Mark,

That happens constantly, all around us. And it is a practical
problem in many ways.

-- Jeff, in Minneapolis

'

And I think many people here would say

If the laws of physics are *caused* to be the same everywhere, then everywhere is causally connected.

is better said

If the laws of physics are *caused* to be the same everywhere, then everywhere was causally connected at one time.

"is" really makes the brain think that it is a current situation and not a situation from the origin.

[Shaula]

So basically this is another "If I redefine the term to be different from its strict technical sense and more in line with what I want it to mean then I am right" line of argument.

[Selfsim]

I've found this thread to be really interesting until around post #144. I'd like to pass on a personal 'Thank you' to all who have contributed so much.

Ned Wright's page explaining the expansion of the observable universe, starting from a finite origin, within a homogenic, isotropic infinite expanse, serves a useful purpose, provided one is prepared to 'take on' the standard model's inflationary mechanism acting everywhere.

If one explores the theory and goes further, and 'takes on' eternal inflation and/or bubble nucleation mechanisms, then there is a lot more to be considered and explored from topological and geometrical perspectives. The inflation concept adopted in the modern day, (ie: post 1994 textbooks), Standard Cosmological Model, has a very firm place within the physical Laws so far deduced from observations of our own part of what might as well be, an overall infinite 'megaverse' or 'multiverse'.

If inflation, (caused by random quantum fluctuations within a primordial inflaton field, acting in accordance with known quantum mechanical and thermodynamic principles), can happen once in an infinite isotropic, homogeneous megaverse, then it can happen again over and over, with each 'pocket (observable) universe' being bounded by their own cosmological causality horizons.

Whilst eternal inflation within our own pocket (observable) universe, has problems as far as nuclear synthesis observational evidence is concerned, there is no reason I can see, to rule it out beyond our own pocket universe, for modelling purposes.

There is no particular reason to assume that other pocket universes beyond our own, have an identical solution to the 'fundamental equations of nature' as those which fit our own pocket universe observations, which result in our local Laws (like those involved in our own nucleosynthesis). The 'constants' we see in our own pocket, might be measurable and calculable by us, because these values also gave rise to us, starting with primordial nucleosynthesis. So far, the overall 'fundamental equations of nature' might not be completely known to us in detail, but we have hints from mathematical theory, that the diversity of solutions to the ones we know about, is absolutely mind-blowing.

Diversity is the clue as far as I'm concerned. It is frequently overlooked because it is difficult to explain, but it is the key to opening one's mind to the likelihood that 'something else is afoot' in place we find ourselves in. Exploring the theory is our only chance of making some inroads, when we already know our observations are limited by our Cosmological Horizons. Theoretical exploration is what allows us to make sense of our surroundings. Empirical observations serve to provide the comfort of assurance about theory.

Regards

[Jeff Root]

Wayne,

Your two most recent posts make much of what I say here even
more redundant than it already was, but I'll post it anyway.
Starting with comments at the end of your post #183:

I think half of it is we are talking semantics here and the
other half is your belief that you can't have a transition from
zero to infinity and me saying that there is no problem as
long as that transition doesn't go through a finite stage.

Yes. That is the problem exactly.

I have been arguing against what you said, not what you meant,
and you have been aguing against what I said, not what I meant.

The issue of 2 causally disconnected points having similar
properties I don't see as a problem. I don't see why some
other point in the universe that isn't causally connected to
us shouldn't have similar properties.

And there is no reason why it should have similar properties.

If there were some reason, that reason would indicate a
causal connection.

No a causal connection means a change in one can be felt
by the other.

That is indeed a causal connection. What I described is also
a causal connection.

2 object that have similar properties but are not causally
connected is a different issue.

Yes, it is. Two things having similar properties which are
not due to a causal connection is a case of coincidence.
Coincidence is a different issue from causal connectedness.

Unfortunately for our ability to discuss this, we don't (and can't)
have any actual examples of causally-disconnected things to
examine and consider. That would be tremendously helpful.

It is unprovable yes but doesn't mean we can't talk about the
theory behind it.

Of course.

I thought you might present some examples to counter my
assertion. Whether it is true that we don't and can't have
any actual examples of causally-disconnected things depends
on the specific causes and effects you are concerned with.
For more mundane possible connections, it is easy to find
counter-examples.

Tomatoes were not used in European foods in the 1400's,
because the tomato was unknown there. Its existence in the
western hemisphere was causally disconnected from European
cuisine of the time. Tomatoes in America could not affect
pizzas in Italy.

On the other hand, Italians in the 1400's were arguably in the
future light cone of existing tomatoes. There could have been
a causal connection according to modern theoretical physics,
but there wasn't, because no tomatoes had been transported
from America to Italy.

For example take the gravitational constant. Why should a spot
that isn't causally connected to us have a different value for the
gravitational constant besides your say so?

I wouldn't say exactly that. I would say that there is no reason
to assume that such a spot would have a gravitational constant.

And this is my issue with your claim. That "there is no reason
to assume that such a spot would have a gravitational constant"

Why wouldn't it?

Why would it?

I didn't say it wouldn't have a gravitational constant. I didn't
say it couldn't have the same gravitational constant we have.
I just say that there is no reason to assume that a spot that has
no causal connection with our location would have properties
similar to ours, such as a gravitational constant.

We look out through the visible universe and see no indication
that the gravitational constant changes.

Agreed.

Why would we make an assumption that it would?

You are asking about a spot which has no causal connection
with the visible Universe. So the properties of the visible
Universe can't serve as a guide to the properties at that spot.
Why should I assume that its properties would coincidentally
be the same as the properties here?

Essentially you are saying that point A has a gravitational
constant of 6.67300×10[sup]-11[sup]m³kg^-1s^-2
We detect measure B as having a gravitation constant of
6.67300×10[sup]-11[sup]m³kg^-1s^-2
but point C since it is not causally connected to us that we
can't assume that it even has one.

That is not what I said.

If points A and B have the same gravitational constant because
they are causally connected, and points B and C have the same
gravitational constant because they are causally connected,
then points A and C will have the same gravitational constant
because they are both causally connected with point B.

Point A might never be able to have any effect on point C.
Point C might never be able to have any effect on pont A.
But if point B can affect both points A and C, then points
A and C are not unlikely to have properties in common.

I say yes we can because we have no reason to think otherwise
and it is more likely that there isn't some drastic change just
beyond our cosmic horizon. So things 48 billion light years
away seem to follow the same physics that we follow. Why
should you expect anything but the same at 49 billion light
years away?

I don't. I expect that what is 49 billion light-years away is
causally connected to the Big Bang, as we are, so conditions
there could be very much the same as they are here.

I say that everything which has ever participated in the cosmic
expansion of the Big Bang is causally connected. Anything
which has never participated in the cosmic expansion or Big
Bang may be causally disconnected from us, and may not have
any of the properties of spacetime, matter, and energy that we
are familiar with. Or it may. But there is no reason to assume
that it would.

The more similar things are, the more likely that the similarity
is due to a causal connection. That is not a hard and fast rule
of course, but I think it is a very good rule of thumb.

If two spots have the same gravitational constant, I'd guess
that it is because they are causally connected.
. . .

If A and B are similar *because* they are causally connected,
and B and C are simllar because they are causally connected,
then A and C are similar because they are causally connected.

On the other hand, if A and B are similar because they are
causally connected, but B and C are similar just by chance,
even though they are causally connected, then A and C are
similar just by chance, and we don't have enough info to say
whether A and C are causally connected or not.

A, B, and C are toymakers. A and B know each other, and B
and C know each other. But A and C know nothing of each
other's existence.

Toymaker B makes xylophones that he invented. Toymaker A
makes xylophones that he copied from toymaker B. Toymaker
C makes xylophones that he copied from toymaker B. So the
xylophones of toymakers A and C are causally connected.

No A & C are not causally connected in the way most
people use it.

I say that they are.

If they are not causally connected, then how *are* they
connected?

If A makes a change in their design C can not and will not
ever know about it.

Correct.

Just because A & C can be affected by the same event
doesn't mean A can ever affect C

Correct.

You are stretching the definition of "causally connected"
as we talk about stuff outside of our Hubble volume ...

I don't think so.

... and this is the problem.

I agree.

So you agree that A can't affect C or vice versa but yet
you try to claim they are causally connected when they
are clearly not.

Clearly, they *are* connected. Toymakers A and C would
almost certainly not be making identical xylophones if
there were no causal connection between them.

Its a non sequitur in same way as saying

John shoots Bill, John shoots Jane. Bill dies because
Jane Dies.

No, Bill and Jane die because of John, not because of
anything that happened to the other one.

According what I've said over and over, Bill and Jane die
similarly because their deaths are causally connected by
John's shooting them similarly.

The statement that "Bill dies because Jane dies" came
from nowhere. It isn't implied by anything I've said.

(Your next quotes were garbled. Some removed.)

So you agree that A can't affect C or vice versa but yet
you try to claim they are causally connected when they can
no longer affect each other.

Yes. The same causes affected both of them, so they are
causally connected.

So the only way I agree with you is that they have the same
origins and I don't see where that is against mainstream
science. The universe, not just the visible universe, could
be infinite in expanse but still have originated from the same
cause which just seems to suggest to me you don't like
infinities ...

I have no problem with infinities at all. In fact, my
expectation is and has always been that the Universe is
infinite in extent.

... but I've never seen anything that shows that the universe
could not be infinite in expanse, just that if it is, it was
never finite in volume. And note that a volume of zero
transitioning to infinity does not have the problems of a
finite size transitioning to infinity.

There appear to be three things we disagree on:

1) What to call the relationship between events which are
connected by a common cause, but cannot affect each other.


2) Whether zero is finite.

My algebra textbook doesn't say whether zero is finite or not,
but it does say:

A set that contains no members is called the empty set or
null set. It is denoted by the symbol Ø and is considered
a finite set.

One physics professor I asked this morning said the statement
that zero is not finite doesn't have any meaning to him, and
the other said that he would think zero is finite.

Since zero obviously isn't infinite, I'd say it is finite.


3) Whether "transitioning" from small or zero volume to
infinite volume makes any physical sense.

As a mathematical transformation I have no problem with it.
As physics it breaks practically every rule in the book!
Things never behave anything like that in nature. Patterns
of light and shadow can appear instantaneously on a surface,
but such patterns are not physical things. The light which
forms the patterns cannot reach the surface instantaneously.

-- Jeff, in Minneapolis

[Selfsim]

3) Whether "transitioning" from small or zero volume to
infinite volume makes any physical sense.

As a mathematical transformation I have no problem with it.
As physics it breaks practically every rule in the book!
Things never behave anything like that in nature.

Well, then you need a new rule book ... not because that book says that transitioning from small volumes to an infinite volumes in a finite time, doesn't make sense, but because its definition of theoretical physics, leaves a LOT to be desired.

Jeff, this conversation needs to be about the inflationary component of the Standard Model, (or its equivalents), if you want it to progress in a rational, balanced way.

Mainstream theoretical physics recognises the inflationary mechanism as being capable of increasing the volume of the early universe by a scale factor of at least 10⁷⁸. And what's more, it has been shown to have been capable of doing this over a period from 10⁻³⁶ seconds after the Big Bang, to somewhere between 10⁻³³ and 10⁻³² seconds.

'In nature', things can behave like that !

Regards

[Jeff Root]

3) Whether "transitioning" from small or zero volume to
infinite volume makes any physical sense.

Mainstream theoretical physics recognises the inflationary
mechanism as being capable of increasing the volume of
the early universe by a scale factor of at least 10⁷⁸.

What mechanism are you talking about?

And what's more, it has been shown to have been
capable of doing this over a period from 10⁻³⁶ seconds
after the Big Bang, to somewhere between 10⁻³³ and
10⁻³² seconds.

How has it been shown?

'In nature', things can behave like that !

What things?

Notice that ALL of my remarks have been about the Big Bang
resulting in an INFINITE Universe. The specific remarks that
you quoted were about an INFINITE Universe appearing
INSTANTANEOUSLY, without EVER having a finite size.

Your reply is about Inflation, which increases a volume of the
early Universe by a tremendously large factor, tremendously
rapidly. Instead of a scale factor of 10⁷⁸, try 10^78000000000.
That's still way, way, way, way less than infinite, of course.

-- Jeff, in Minneapolis

[Selfsim]

What mechanism are you talking about?
...
How has it been shown?
...
What things?

Jeff;

Based on your comments over several past threads, it seems that you have some kind of conceptual roadblock in understanding the physical mechanism of Cosmic Inflation, and the extent to which it can be physically taken. (That's Ok, we all reach those points at sometime or other in Astrophysical areas, (myself included), and this one relies on many other unintuitive concepts).

Inflation is what distinguishes the 'explosion' you believe in, (which doesn't explain observational evidence), from what is observed.

The observed Laws of Physics underwrite the inflation mechanism. The existence of states of matter that have a high energy density that cannot be rapidly lowered, (one of which is called a false vacuum), is the key to understanding inflation. The false vacuum state arises naturally in any theory containing scalar fields. Pressure differences can arise, which are then able to do work on eachother. Pressures arising from energy density differences in GR, create gravitational fields: positive for attractive gravitation, negative for repulsive. The negative pressure mechanism is what ultimately drives inflation and the expansion of the early universe. Note that there is no upper limit to the amount of expansion. The expansion goes on, whilst the false vacuum maintains nearly a constant energy density, which means the total energy increases with the cube of the linear expansion factor. If the early universe started out at a size of ~10^-24 cms, (note: a finite volume), then this takes the expansion to a factor of ~10⁷⁸.

Conservation of energy places no limit on how much the universe can inflate, as there is no limit to the amount of negative energy that can be stored in a gravitational field.

What does this have to do with spatial geometry ?
The spatial geometry of the universe is described by: ω + λ / 3H². The 'ω' (omega) term (discussed by speedfreek in post #180) is defined by ω = ρ /ρ_c, (where ρ is the actual mass density and ρ_c is the critical mass density), and thus relates the spatial geometry to energy densities and the curvature/flatness issue.

Inflation explains the observed flatness, whilst also explaining other observed characteristics. (See below).

For omega to be anywhere in the range it is today, one second after the BB, it must have been equal to a precision of one in the last digit of a 15^th decimal place value of omega. If this level of precision wasn't achieved, then our universe would not match what we see today. There is no reason to assume that such precision will commonly occur elsewhere, (or is even 'average' amongst multiple, similar-in-principle 'creation' events elsewhere). Thus via the same mechanism, there is no reason to think that 'universes' created elsewhere, would resemble ours, in even the slightest detail, including flatness, or finiteness.

Can you please describe a known 'explosion', which can be generalised as being capable of achieving this precision, or characteristics ?
I assert that the idea of the BB as a 'normal' explosion, simply does not explain today's observational physical evidence, leading to spatial 'flatness', large-scale isotropy, homogeneity and CMBR temperature even-ness. Propagation of this physically unsupportable lurking belief, should thus not continue, unless you can demonstrate it.

Regards

[Spoons]

Firstly, please forgive me if this ground has been covered and clarified, as the thought occurred to me while reading the second page and I needed to get it down before it scurried off to a dark and damp corner of my mind. As such I still need to go back and continue reviewing the whole thread.

It seems to me that in these sort of discussions a bit of the confusion comes from people bending the definition of Universe to fit whatever counter argument they are making at the time.

The discussion starts off that the "Universe" was "kicked off" (i'm trying to avoid the word created, as it wasn't necessarily, nor does the theory try to suggest it was) in the Big Bang, and then we generally go on to discuss this "Universe" in terms as the ongoing existence of the contents of that big bang. When people start to ask what is outside of this "Universe" they are told they are talking nonsense because the "Universe" is all there is, ever was and ever will be.

Hang on - but that seems to possibly be twisting the defined term "Universe" for the discussion. It seems that peoples interpretations of the definition of Universe is somewhat rubbery, since some talk of a Multiverse, whereby the old, traditional view of a Universe as everything there is then becomes a bubble containing our local set of physical laws, and the greater expanse may possibly then share some of the laws, possibly with different variables, possibly all the same but in a shifted higher dimension, etc. If you say anything outside that bubble is also part of the Universe (which seems to be a move to try to eradicate the Multiverse that some people seem to dislike) then the Universe did not all feel the effects of the Big Bang, only a local portion thereof.

This seems to be a symantics game that comes up regularly in these discussions. I can't help but think people generally do understand what each other are talking about when they use their locally defined term "Universe" but let this little symantics game get in the way of the greater discussion.

For the purposes of the question of the edge of the "Universe" (that being the contents of the big bang and our set of "Universal laws)" could we not assume that our "Universe" is a bubble within a greater body of existence, and if so is it unreasonable to ask about the edge of that subset body of existence? (I am sure there are ways in which it could be argued you couldn't observe that body, or the laws of that great body might be such that they twist everything to look like a club sandwich, confetti or your mum's pool cue, but I am curious what the response to that might be.)

[Spoons]

On reflection, I suppose what I am wondering about is more a matter of whether in the idea of multiverses the various universes are separated withing another 4 dimensional forum, or whether they are separated by other dimensions, in which case the concept and the visualisation of one universe and it's interaction with another probably rather loses any kind of sense.

Never mind, carry on, pip pip and all that. *tips hat to the smart folk*

I really should give these things more than a passing thought in between my work duties before I pipe up in a thread.

[Selfsim]

Hi Spoons;

I agree that there's a lot of word confusion recently come into play in this thread. We should use the terms 'observable (obs) universe' and 'multiverse' in order to more clearly distinguish the bits we're talking about (??).

There's also different 'add-ons' (or extensions) to the Standard Model we're talking about here. Making definite statements coming from the vanilla flavoured Standard Model, (without inflation/expansion, for instance), results in a perception that Inflationary models, (for eg), are somehow 'ruled out', (from Physics), which may not necessarily be the intention of the speaker (??).

Not discussing those extensions, also leaves a perception that what theory has to say, doesn't count, which may also not be the intention (??).

I also have issues with String/M-Theory/Inflationary models, but none which result in my asserting their exclusion from behaving in accordance with the known Physical Laws (from our own obs universe). I'm pretty sure that I, for one, don't know enough to do that. There are many critics of the Inflationary Models, and what they have to say also seems perfectly reasonable to me, and contributes to the overall understanding).

In M-Theory, the branes seem to be separated by domains of string, (or particle), adherence properties, and the properties of the branes/strings themselves … although interchanges of certain strings with 'the bulk', seems to be allowed in some models, but not in others (it gets complex).

Hope that helps.

Regards

[noncryptic]

Mainstream theoretical physics recognises the inflationary mechanism as being capable of increasing the volume of the early universe by a scale factor of at least 10⁷⁸. And what's more, it has been shown to have been capable of doing this over a period from 10⁻³⁶ seconds after the Big Bang, to somewhere between 10⁻³³ and 10⁻³² seconds.

'In nature', things can behave like that !

By "that" does Jef not mean 'going from zero to anything in any amount if time'? Which Jeff says is not possible, and you say is possible -

but the example that you provide as argument contains neither zero not infinite. How does that show it is possible to go from zero to anything in any amount if time?

The most that it shows is that you can go from small to infinite if allowing for an infinite amount of time. No argument there, but an infinite amount of time has not yet passed, so the the result of the BB that we know is not (yet) infinite.

[Shaula]

the the result of the BB that we know is not (yet) infinite.

Nobody is saying it is as far as I can tell. What has been said is that the observable universe evolved from a hot dense state. That does not rule out the idea that the rest of the universe is infinite. Just means it evolved from an area outside the small dense area of spacetime we know our surroundings came from. Jeff is extrapolating back and saying that the whole of the bang event was finite, spatially, so produced a finite universe. There is no evidence for that.

[noncryptic]

In hindsight, i did not clearly say there what meant to say.

What i meant to say is not about "the result that we know", but about "the BB that we know":

The BB that we know (which may or may not be the only one) had a result (part of which we know and part of which we don't know).
That result can not be infinite in expanse if the hot dense state from which it originates was not of infinite density. The only way i see to accomodate an infinite amount of stuff with finite density is if the hot dense state took up an infinite amount of space to begin with.

[Shaula]

is if the hot dense state took up an infinite amount of space to begin with.

Indeed and that was my point. We know that a hot, dense volume evolved into our observable universe. We know how big that volume was. We do not know that, for example, the entire infinite expanse of the universe was not created by some event which occured outside our space time (by definition as it created it) that led to the entire infinite expanse being filled with hot dense material, one small volume of which became what we see.

The whole point I was trying to make is that we know about the evolution of the volume into our observable universe. We do not know what was happening outside it, whether it was all of the bang or just a tiny bit of it. Arguing that the entire infinite universe (if it is infinite) came from a finite volume on the grounds that our observable universe came from a finite volume is not what people are saying. The argument that the universe cannot be infinite because it came from this finite volume is likewise completely flawed as it makes the underlying assumption that the small volume we know about was all of the bang, or that the bang was finite in volume. Neither of which arerequired.

[WayneFrancis]

Wayne,

Your two most recent posts make much of what I say here even
more redundant than it already was, but I'll post it anyway.
Starting with comments at the end of your post #183:

...

There appear to be three things we disagree on:

1) What to call the relationship between events which are
connected by a common cause, but cannot affect each other.

And I think I didn't make this clear before. I agree that the definition you use when you say 'causally connected' is correct. I just point out that some people, at least I, think of that phrase meaning more about what happens "now" then the root cause. So maybe for people like me you can stress the difference between having a common origin and currently not able to communicate any information.

2) Whether zero is finite.

My algebra textbook doesn't say whether zero is finite or not,
but it does say:

A set that contains no members is called the empty set or
null set. It is denoted by the symbol Ø and is considered
a finite set.

One physics professor I asked this morning said the statement
that zero is not finite doesn't have any meaning to him, and
the other said that he would think zero is finite.

Since zero obviously isn't infinite, I'd say it is finite.

Wish I had my son here.

Zero is a very special think and has different meanings in different context.

I'd say as far as sets go you can say there are null volumes, finite volumes and infinite volumes.
a null volume isn't a finite volume ... it is a null volume.

You can transition from a null volume to a finite volume or a null volume to an infinite volume but not a finite volume to an infinite volume.

Ask the professors the question in context. IE can a manifold transition from zero volume to a infinite volume just as it could transition from a zero volume to a finite volume.

The requirement is that in this universe the energy expended for a finite volume would be finite and the energy expended for a infinite volume would be infinite. If you have a problem
with "infinite" energy then I'd say you'd have to think that the universe is some type of cyclic universe because expansion can't go on for ever because even in a finite universe that would be an infinite amount of energy.

Regardless there is no logical reason to say there can't be infinite energy at the start of the universe even if you can't get your head around it or it doesn't feel right in your gut.

3) Whether "transitioning" from small or zero volume to
infinite volume makes any physical sense.

As a mathematical transformation I have no problem with it.
As physics it breaks practically every rule in the book!
Things never behave anything like that in nature. Patterns
of light and shadow can appear instantaneously on a surface,
but such patterns are not physical things. The light which
forms the patterns cannot reach the surface instantaneously.

-- Jeff, in Minneapolis

You know all the rules of physics?

Energy conservation is only a local "rule" and many people have problems when applying it at the large scale because it isn't applicable at those scales. As it has been pointed out before what you see "in nature" has very little resemblance to the universe at the very large or small scale. Quantum physics never behaves like anything in nature we see either but it damn sure seems to be spot on and like wise things at the very large scale probably work very differently to how our brains evolved to understand.

Its like the complaint about the universe can't be a torus because planets aren't in the shape of a torus and spheres are very prevalent in the universe. That reasoning is cherry picking data and can be very misleading if you don't understand the big picture.

You seem to think the universe is a 3 sphere and it could be nothing but a 3 sphere. The experts seem to put forth a whole host of manifolds that the universe could be in and on paper the 3 sphere, from my understanding, doesn't hold any more weight then many of the others so while you like it and it gives you warm fuzzies to think that the universe is that way there is more or less evidence for it then a 3 torus and stretching "Planets are 2 spheres and stretching that and claiming the universe is more likely a 3 sphere then a 3 torus" is just that ... a stretch.

[WayneFrancis]

What mechanism are you talking about?


How has it been shown?


What things?

Notice that ALL of my remarks have been about the Big Bang
resulting in an INFINITE Universe. The specific remarks that
you quoted were about an INFINITE Universe appearing
INSTANTANEOUSLY, without EVER having a finite size.

Your reply is about Inflation, which increases a volume of the
early Universe by a tremendously large factor, tremendously
rapidly. Instead of a scale factor of 10⁷⁸, try 10^78000000000.
That's still way, way, way, way less than infinite, of course.

-- Jeff, in Minneapolis

Scale factor doesn't say anything about what it is working on. Multiply 2 * 2 and get 4 and you can multiply ∞ * 2 and get ∞. The scale factor is the same for both.

Tell me why this would be allowed Øx = 10 and this Øx = ∞ is not?

[Cougar]

It seems that peoples interpretations of the definition of Universe is somewhat rubbery, since some talk of a Multiverse, whereby the old, traditional view of a Universe as everything there is then becomes a bubble containing our local set of physical laws, and the greater expanse may possibly then share some of the laws, possibly with different variables, possibly all the same but in a shifted higher dimension, etc.

In fact, Brian Greene recently came out with a new book that is like a literature review of a half dozen or more versions of multiverses and parallel universes. Appropriately titled The Hidden Reality. My personal feeling is, this is very speculative stuff. If it interests kids in science, that's obviously a good thing.

For the purposes of the question of the edge of the "Universe" (that being the contents of the big bang and our set of "Universal laws)" could we not assume that our "Universe" is a bubble within a greater body of existence...

Well, you could "assume" it, but I don't think there is any justification for choosing that assumption over the opposite assumption that there is no greater body of existence. We don't know either way, and it's hard to imagine how we'd ever be able to know.

[WayneFrancis]

In hindsight, i did not clearly say there what meant to say.

What i meant to say is not about "the result that we know", but about "the BB that we know":

The BB that we know (which may or may not be the only one) had a result (part of which we know and part of which we don't know).
That result can not be infinite in expanse if the hot dense state from which it originates was not of infinite density. The only way i see to accomodate an infinite amount of stuff with finite density is if the hot dense state took up an infinite amount of space to begin with.

I go one step further then that. Ie

If the universe had a zero volume at one point in time and that volume had some amount of energy then while the energy density was infinite the amount of energy was not.
If the energy was finite then I'd say the universe could be and probably is finite. But if the actual energy was also infinite then the universe is probably infinite.

I recognise that this is speculation of "before" the big bang. And I recognise that the inflationary event we call the big bang may be finite in volume but I'm not sure if it is required to be even though what we can see and can ever see is always finite in nature.

[WayneFrancis]

Indeed and that was my point. We know that a hot, dense volume evolved into our observable universe. We know how big that volume was. We do not know that, for example, the entire infinite expanse of the universe was not created by some event which occured outside our space time (by definition as it created it) that led to the entire infinite expanse being filled with hot dense material, one small volume of which became what we see.

The whole point I was trying to make is that we know about the evolution of the volume into our observable universe. We do not know what was happening outside it, whether it was all of the bang or just a tiny bit of it. Arguing that the entire infinite universe (if it is infinite) came from a finite volume on the grounds that our observable universe came from a finite volume is not what people are saying. The argument that the universe cannot be infinite because it came from this finite volume is likewise completely flawed as it makes the underlying assumption that the small volume we know about was all of the bang, or that the bang was finite in volume. Neither of which arerequired.

well said

[Aethelwulf]

For there to be a boundary, it needs to be a boundary ''between something and something else''.

If there is no outside to the universe, which GR indicates, then the universe cannot have a boundary. There are some string theories which entertain an outside to the universe. In these models, our universe is a brane floating about in a multidimensional pool. In these theories, the universe most definately would have a boundary. However, there are some exotic theories of the universe, such as the Black Hole Universe theory, which states that we are living in a Black Hole... I believe Sean Carrol has been travelling about advocating this model. If we are in a black hole, then the universe as we know it would also have a boundary.

[Cougar]

However, there are some exotic theories of the universe, such as the Black Hole Universe theory, which states that we are living in a Black Hole... I believe Sean Carrol has been travelling about advocating this model.

No. Actually, Sean Carroll says exactly the opposite. "You may have noticed that the universe is actually expanding, rather than contracting as you might expect the interior of a black hole to be."

[Aethelwulf]

No. Actually, Sean Carroll says exactly the opposite. "You may have noticed that the universe is actually expanding, rather than contracting as you might expect the interior of a black hole to be."

Sorry.

I was going on secondary information. I hadn't read any of this work concerning his speculations. A string theorist told me he was peddling this theory and I just took it as gospal.

Thanks.