Hypothetical astrophysics question

"Jeff Root" wrote in message
om...
"CeeBee" replied to Jeff Root:

Yes, of course, but how the heck can you possibly know that
light doesn't go between universes? What theory predicts that
light doesn't go between universes, and what observations is
that theory derived from?

The big bang theory doesn't describe "universes". It just
describes our universe, the development of it, and the phenomenon
in it.

Yes! Exactly!

Since there is no "need" for such hypothesized universes to be
"embedded into something" (are you quoting someone???) that is
able to transmit information, it is therefore impossible for
light to go from one such universe to another? I think that
what you really mean to say is that it *might* be impossible
for light to go from one such universe to another.

The Big Bang theory "predicts" that.

But you just said that the Big Bang theory doesn't say anything
about other universes, only our own! In your next sentence you
contradict that and say that it predicts what can and can't
happen outside our universe! Which is it???

The BB theory applies onlyh to our own universe because
it is the only one that we can possibly have empirical
information about with which to test the theory. There
is no way to know, for example, if the physical constants
for another universe would be the same or different, or
even if another universe was comprised of the same number
of physical and time dimensions.

The BB theory encorporates General Releativity, which
deals with the geometry of space and the propagation of
gravity and light in it. Light travels in space and,
essentially by definition, follows space geodesics; it
cannot leave space if it follows space geodesics, as
space is continuous and boundary-free.


It tells us that space and time were created simultaneously
with the Big Bang,

Actually, the Big Bang theory says nothing about the origin of
space and/or time. It does say that at some time about 13.7
billion years ago everything in the Universe was squished real
close together, was very hot, and was expanding real fast.
It also says that a moment before that, something completely
unknown happened, which no theory is yet able to describe in
any way that makes sense. So, space and time *may* have been
created at that time, or they may not have. There's no way
to say, as yet.

The current BB theory says that space and time were indeed
created at some instant about 13.7 billion years ago. It further
says that they were created in a very dense state; the whole
universe would comfortably fit inside a breadbox for some
tiny fraction of a second from the initiation.


and all matter and energy in it. It predicts how the state
of the universe was, is and will be. If observations are in
accordance with the predictions of the theory, the theory
gains validity.

I fail to see the relevance between universes "embedded" into
something conducting light and me quoting someone, but I might
miss your point.

I asked about your use of the term "embedded" because Greg
used it prominently in a message posted less than two hours
after yours; I don't think the term had been used previously;
and I see no particular reason for its use here.

The idea of universes being embedded in anything sounds goofy.
I agree with you that there is no "need" for such universes to
be "embedded" in anything, so I wonder why you brought it up.
Why did you bring it up?

If I may venture a guess, it is because the model that you
apparently propose has the universe (and perhaps universes)
being created and exploding into a pre-existing, all pervasive
spacetime. In this sense you have our universe embedded
in another. Of course we then need to modify our definition
of the word "universe" to mean a local phenomenon that does
not encompass all of existence, since the pre-existing space
would then seem to be a better candidate for that. We would
have to adjust our sites to theorize about the origin and
geometry of this larger space (and presumably time).

But, returning to current BB theory, our universe is considered
to be a self-contained spacetime entity wherein space and time
are evolving.

[snip]


I haven't seen any theory which predicts observed phenomenae
and also predicts that light can't reach us from a "universe"
other than our own. Or, at least, I haven't seen such a theory
and been made aware that it was such a theory.

That's because you fail to understand the Big Bang theory. It says
that our universe comprises everything.

You have said that it is possible that other universes could
exist. In this post you have said that the Big Bang theory
only describes *our* universe, not others. Now you say the Big
Bang theory asserts that our universe comprises everything.
Contradictions! Which statements should I believe?

The Universe, referring to our universe, comprises everything
that is connected by the spacetime which we inhabit. We
speculate that other universes exist, and we can only
speculate because by definition there can be no causal
connection between separate universes, otherwise they'd be
connected and part of the same universe.


It says you won't meet a boundary with "space outside" because
there isn't such.

There certainly is no indication of any such boundary, and I'm
quite sure that if one exists, neither I nor any other human
will ever "meet" it, because it would be too far away.

There is nothing outside, as there is no outside,

How do you know that? What observations support the idea?
I am not aware of any.

Actually, the recent WMAP data appears to indicate that the
space of our universe is geometrically flat. This means,
from the field equations of General Relativity, that the
universe may be infinite in extent (like a Euclidean plane
is infinite in extent in 2D). Notice that I say "may be".
It could be that the universe is simply so vast that the
portion within our cosmic horizon is empirically
indistinguishible from flat, although the universe as a
whole may have some other geomety.


hence nothing to travel _through_.

One doesn't need to travel "through" anything in order to
travel. One just needs to go from one place to another.

If this were the case, then should expect light, gravity,
and even matter to occasinally leak into unseen dimensions
and disappear from our universe. As far as we can tell
so far (and there are some interesting experiments on-going
testing the very short-range behaviour of gravity in the
search for extra, tiny dimensions -- see the work being
done by Mike Varney), there is no leakage taking place.

If you take a look at Maxwell's theory, you find that light
propagation depends upon space having certain properties,
namely permittivity and permeability. Space also, via
General Relativity and the equivalence principle, is
intimately connected with its contents in that its
geometry is shaped by the mass and energy it contains. I
don't see how anything from inside our universe could be
removed from it and retain its properties (mass, inertia,
charge, etc.).


You can't seem to get yourself unhooked from the idea that
there's _nothing_ outside the universe because there's _no_
outside.

I'd like to know what observations support the assertion that
there is no outside. I can certainly understand that there
*might* not be any outside, but the assertion that there *is*
no outside seems wildly beyond what is known.

See above.


Light can't reach the boundaries of the universe because there
are no boundaries. It can't go outside, it can't go inside. It
can't cross a boundary, because there is no boundary.

Okay, okay. What observations support the assertion that there
is no boundary?

WMAP tentatively points in this direction, as does the recent
observation that the universe seems to be not only expanding,
but accelerating. If it is truly accelerating as we think,
even within our little cosmic horizon, then on the grand
scale the expansion rate must be phenomenal -- space would
be growing at a rate that nothing interernal to the universe
could ever approach a bounday, as that boundary would be
receeding at untold multiples of the speed of light.


You repeatedly suggest that "no theory predicts"; however it's
more "I don't get the theory".

I'm nearly certain that, as you said at the beginning of your
post, the Big Bang theory describes our universe only, and
predicts nothing about other universes or possible relationships
between our universe and other universes.

http://www.astro.ucla.edu/~wright/cosmology_faq.html

I have read a significant chunk of it, and will continue to
work through it as best I can.

http://imagine.gsfc.nasa.gov/docs/as...s/961202c.html

This basically just refers to the balloon model. I used the
balloon model in a talk to my class in 12th grade. I snuck out
of school during lunch hour to buy the balloons, and only had
time to draw galaxies on a white balloon. If I had more time I
would have glued white dots to a black balloon so the galaxies
wouldn't expand along with the balloon.

I think the balloon model is flawed in that the balloon is a
material object which stretches and on which the galaxies are
fixed, whereas there is probably nothing material between the
real galaxies which stretches or expands or holds them in place.
In reality, it is just the distances between galaxies which are
increasing because the matter which comprises the galaxies has
momentum, imparted to it early in the history of the Universe.

This is where your theory departs from standard theory.
Standard theory says that the BB is not a conventional
explosion of matter into a pre-existing space, but an
evolution of space itself.


The balloon model is also flawed in that the surface of the
balloon is strongly curved. The latest observations show the
Universe to be indistinguishable from flat, overall. No
indication of any overall curvature.

Right. The balloon model has significant limitations. Of course,
if you had a REALLY BIG balloon... :-)


BTW the Big Bang theory isn't a religion. There are new idea's
about the creation of our universe, handsomely called the
"ekpyrotic" model: http://www.sciencenews.org/20010922/bob9.asp

Thanks for the link to the Science News article! Ron Cowen
always does an excellent job of explaining complex ideas of
physics and mathematics.

The article contradicts most of your above assertions.
Of course, the main ideas of the article are an alternative
to inflation and a way for the Big Bang to be initiated,
which naturally contradicts those theories in many ways.

I consider inflation, string theory, and brane theory all to
be largely ad hoc and disconnected from observational evidence.
That doesn't mean I reject them, but I doubt them very much.

Inflation seems to be supported by the empirical evidence
so far, or at least it is not contradicted.


I have my own looney speculation which is far less developed
than those theories, but which may be capable of answering
some of the same questions far more simply. It has a serious
failing which is exactly the same as those other theories have:
A shortage of observational evidence. Two observations could
be made to support or refute my speculation.

One is astronomical, involving gravitational lensing. The math
to quantitatively predict the effects of the lensing is beyond
me, but in broad terms I would expect to see very faint radial
lines where light of some distant galaxies or quasars has been
smeared out by lensing galaxies. The opposite of the lensing
actually seen so far, which is concentric and bright.

The other observation is of the response of antihydrogen atoms
to gravity. Experiments at CERN are now getting close to making
this observation. It has the tremendous advantage that a good,
clear result can totally demolish any possibility that my
speculation is correct. It's a real make or break experiment
for my pet notion.

This, of course, is a very good position for any theory to
be in -- an unambiguous test. Keep your fingers crossed!

In message , Joseph Lazio
writes
"GD" == George Dishman writes:

"Joseph Lazio" wrote in message
...
"JG" == John Griffin writes:

JG stuff, with its own origin (big bang or whatever) occupying
JG another part of the infinite space this one is in.

This sounds like Martin Rees' Multiverse concept. He suggests
that multiple universes may in fact exist. In this concept,
though, universes are distinct. One cannot travel from one
universe to another.

GD Joseph, can you say if that is similar to the ideas in this paper
GD by Alan Guth?

GD http://www.arxiv.org/abs/astro-ph/0301199

It is certainly similar in spirit. The difference lies, I think, in
that Guth's idea describes one "connected" Universe while Rees' idea
describes "disconnected" universes. In Guth's idea, as I understand
it, one begins with a single spacetime region. A small chunk of that
inflates to form a "pocket universe." Sometime later, another small
chunk inflates, etc. I think it would be possible, in principle, to
travel from one pocket universe to another. (Though if this idea is
correct, the size of each pocket universe is much larger than the size
of our observable Universe.) Guth doesn't say this explicitly, but it
seems to me that a consequence of this idea is that the same physical
laws would apply everywhere.

I've just bought a copy of Paul Davies' "The Last Three Minutes" which
seems to ascribe this to Andrei Linde. Doesn't Guth's original idea
describe one universe?
--
"Roads in space for rockets to travel....four-dimensional roads, curving with
relativity"
Mail to jsilverlight AT merseia.fsnet.co.uk is welcome.
Or visit Jonathan's Space Site http://www.merseia.fsnet.co.uk

Greg Neill replied to Jeff Root:

Not to mention the fact that if you're seeing it, it's *in* our
universe and not a separate universe.

Under *some* definitions of "universe". Not all.

Clearly, this imaginary thing had no part in our Big Bang, and
existed some time before our Big Bang occurred. I think that
calling it a "universe" is entirely reasonable, and I think
that such other universes could very well exist-- perhaps
infinitely many of them, if space is infinite. Whether we
would be able to see such a distant universe is a question
I'm not sure anyone can answer until we understand the nature
of our own Universe a bit better.

The usual definition applied to our universe is that it
contains everything.

Obviously that definition doesn't apply to the scenario that
John Griffin suggested. "Universe" is a reasonable term to
apply to an entity which resembles our Universe, but which
had a separate and independant origin. Not a new idea.

A separate and independent origin implies no connection.

So, two things which have separate and independant origins
can never have any connection between them? Or what?

Embedded means its part of our universe.

So, if a thumbtack becomes embedded in my foot, the thumbtack
is part of me? Or what? What is your point?

CeeBee used the term "embedded" less than two hours before you
did. Otherwise, I don't think it had been used in this thread.
It seems an odd term to use, and I see no reason to mention it
here, although I do see that you use it below. Did you use it
because CeeBee did?

If the BB scenario is taken to describe it, space itself was
created and began evolving at the moment of the BB. If so,
there is no space for this other universe to pre-exist in,
in our frame of reference.

But in some other frame of reference there *could* be space
for this other universe to exist in? So whether such space
exists or not depends on where you are? And whether the
other universe exists or not depends on where you are?

We can know nothing about something that does not exist
inside our own universe and amenable to measurement.
It must remain pure speculation.

Fine. But irrelevant to the specific scenario we are talking
about. It was hypothesized that light from another universe
had reached us, and was visible and measureable.

Certainly it could not exist in our universe and be a
universe itself.

It depends on what you consider a universe to be. The thing
that John Griffin suggested is clearly something which had no
involvement in the Big Bang which began our Universe. It is
also just as big and as well-populated as our Universe. I'd
say that qualifies it as a separate universe, even if there
is some interaction (perhaps only one way) between the two
universes.

I see no profit in arguing semantics. When I say "universe"
I intend it to mean all that is contained and connected by
space and time in which we are embedded. It would seem that
you are wishing to take the more old-fashioned view of the
early astronomers who first recognized other galaxies for
what they were, and referred to them as "island universes".

The majority of words have multiple meanings. I'm using a
reasonable definition of "universe" that is useful in discussing
the scenario John Griffin suggested. Under my definition, our
Universe encompasses everything that was involved in the Big
Bang, and only that which was involved in the Big Bang. Is your
definition different from that?

I think that your expression, "space and time in which we are
embedded" implies more of a physicality to space and time than
is warranted. It gives a mental image of space and time being
a substance like clay, with stuff embedded in it. Very
misleading. Space and time are only detected and measured
by the behavior of things such as collections of atoms and
beams of light. Whether space and time have any existence
independant of matter is simply unknown.

There can be no connection betwixt or between, so no path
for light to follow.

Why not? What observations support that idea?

By my definition of universe, there can be no connection,
no path between, or else they would be connected by the
same space, thus all the same universe.

Okay, that's using a reasonable definition of "universe".
It just isn't a particularly useful one for the current
discussion. But I'll go along with it. Unless someone comes
up with a better term, how about referring to the object John
Griffin hypothesized as a "monad"?

Everything involved in the Big Bang, then, comprises our monad.
There could be other monads in the Universe, but they might be
impossible to detect, even theoretically. There could be monads
in other universes, but they would definitely be impossible to
detect, even theoretically, so there is no way we can ever have
any idea whether or not they exist or what their properties
might be.

Are those statements satisfactory?

(I see that George Dishman has used terms that are more in line
with what I'm familiar with: "Cosmos" or "macrocosmos" for
"everything" and "Universe" for our part of the Cosmos. Your
definitions appear to conflict with that useage, so I didn't
try to introduce it. I was going to use "subcosmos" instead
of "monad", but the plural "cosmoses" was too grating for me.
George is evidently stronger than I.)

I intend to reply to the rest of your post soon.

-- Jeff, in Minneapolis

..

(John Griffin) wrote in message . com...
(George Buyanovsky) wrote
(Matthew F Funke) wrote
John Griffin wrote:

Two tiny, fuzzy points of light are observed. Observations of
each object indicate that it's a globular galaxy ten billion light
years distant. The first one is exactly that, but the second one
happens to be another entire universe. It's 100,000 times as
far away as the galaxy, and it's emiting ten billion times as
much light. Is there anything that would distinguish these
objects from one another?

Redshift. The universe is expanding, and there is more space in
between us and the object 100,000 times as far away; it would appear to be
more redshifted.

Let me to reformulate it.
Small star - 10 light years.
Huge Quasar ? 10 billion light years.
Huge Quasar moves toward us with exact speed to compensate redshift.
For this arrangement, the redshift is not enough to distinguish them.

I wish I had been more specific in my original question.

In the hypothetical situation, the observations I mentioned were that
radiation from the other universe had the same redshift as radiation
from a galaxy ten billion light years from "here." (The cosmologists
have me wondering if the word "here" is just some kind of strange
idea.) The equal redshift would be purely coincidental, since the
other universe's motion would

It is not by chance I reformulated your question.

The phrase like:

"other universe's motion"

makes no sense at all. Your questions are based on one universe idea.
People here have tried to explain you this. It is not a matter of
complexity it is matter of natural perception of reality, which is,
by the way, has been proven by natural selection ;o)

--George

"George Dishman" wrote in message ...
"John Griffin" wrote in message It turns out that the cosmologists have theories and some experimental
data that say the other universe can't exist.

Not true, at least two of the sources give you links to pages
detailing ways in which other universes might exist

The notion "exist" does not fit to describe validity of multiverse concept.

--George

"Jeff Root" wrote in message
om...
Greg Neill replied to Jeff Root:


A separate and independent origin implies no connection.

So, two things which have separate and independant origins
can never have any connection between them? Or what?

When speaking of universes, then that is so, barring
some form of "collision" by way of motion through a higher
dimension. I don't know if you've happened to read Abbott's
"Flatland", but it is much the same scenario as the 3D
sphere interacting with the 2D plane people.

If two previously separate universes could somehow collide
and happened to estabish an interface (it would be a lucky
thing, them having compatible dimensions and physical
constants), they would for all intents and purposes form
a single, larger universe.


Embedded means its part of our universe.

So, if a thumbtack becomes embedded in my foot, the thumbtack
is part of me? Or what? What is your point?

If a thumbtack becomes embedded in your foot, in a sense it
becomes part of you. Note, however, that the thumbtack was
all along in the same universe with your foot, exchanging
fields and generally interacting.

The point is, if you can see it and it can interact
causally with things in our universe, then it is part
of the universe. It is connected.


CeeBee used the term "embedded" less than two hours before you
did. Otherwise, I don't think it had been used in this thread.
It seems an odd term to use, and I see no reason to mention it
here, although I do see that you use it below. Did you use it
because CeeBee did?

No. I use it because it was an appropriate term.

[snip]


We can know nothing about something that does not exist
inside our own universe and amenable to measurement.
It must remain pure speculation.

Fine. But irrelevant to the specific scenario we are talking
about. It was hypothesized that light from another universe
had reached us, and was visible and measureable.

And I suggest that if light can reach us from the object,
and presumably light from us can reach the object, then
there is a causal connection betwixt and between, and the
object must perforce be part of the same overall universe.


Certainly it could not exist in our universe and be a
universe itself.

It depends on what you consider a universe to be. The thing
that John Griffin suggested is clearly something which had no
involvement in the Big Bang which began our Universe. It is
also just as big and as well-populated as our Universe. I'd
say that qualifies it as a separate universe, even if there
is some interaction (perhaps only one way) between the two
universes.

I see no profit in arguing semantics. When I say "universe"
I intend it to mean all that is contained and connected by
space and time in which we are embedded. It would seem that
you are wishing to take the more old-fashioned view of the
early astronomers who first recognized other galaxies for
what they were, and referred to them as "island universes".

The majority of words have multiple meanings. I'm using a
reasonable definition of "universe" that is useful in discussing
the scenario John Griffin suggested. Under my definition, our
Universe encompasses everything that was involved in the Big
Bang, and only that which was involved in the Big Bang. Is your
definition different from that?

Not essentially. The important difference is that I follow the
standard theory line that space itself was created in the BB,
and that this space is a connected manifold, containing all that
can interact within itself.


I think that your expression, "space and time in which we are
embedded" implies more of a physicality to space and time than
is warranted. It gives a mental image of space and time being
a substance like clay, with stuff embedded in it. Very
misleading. Space and time are only detected and measured
by the behavior of things such as collections of atoms and
beams of light. Whether space and time have any existence
independant of matter is simply unknown.

Sorry, I don't intend to imply a physical, "etherish" version
of space or spacetime. Still, Space has a surprising collection
of properties. For example, it exhibits specific values of
permittivity and permeability (Maxwell's equations). It can
embody stress energy (General Relativity), it can apparently
have an intrinsic geometry modifiable locally and generally by
mass-energy. It supports a background of virtual particles and
energy modes.


There can be no connection betwixt or between, so no path
for light to follow.

Why not? What observations support that idea?

By my definition of universe, there can be no connection,
no path between, or else they would be connected by the
same space, thus all the same universe.

Okay, that's using a reasonable definition of "universe".
It just isn't a particularly useful one for the current
discussion. But I'll go along with it. Unless someone comes
up with a better term, how about referring to the object John
Griffin hypothesized as a "monad"?

Everything involved in the Big Bang, then, comprises our monad.
There could be other monads in the Universe, but they might be
impossible to detect, even theoretically. There could be monads
in other universes, but they would definitely be impossible to
detect, even theoretically, so there is no way we can ever have
any idea whether or not they exist or what their properties
might be.

Are those statements satisfactory?

I suppose, although I might have chosen "universe" and
"multiverse", the latter capable of hosting multiple
universes. Presumably it would involve adding one or
more dimensions to the overall geometry of spacetime.

I think that we still have a difference of detail that
terminology might not be able to overcome. In my version
of the universe and BB, space is created by the BB and
comprises the entirety of the universe. There is no
pre-existing space or framework in which our Bang took
place, and there is no "outside". You seem to favour a
creation of matter and explosion into a pre-existing space
that can host many such bangs. I suspect that the
viewpoints are not satifactorily reconcilable.


(I see that George Dishman has used terms that are more in line
with what I'm familiar with: "Cosmos" or "macrocosmos" for
"everything" and "Universe" for our part of the Cosmos. Your
definitions appear to conflict with that useage, so I didn't
try to introduce it. I was going to use "subcosmos" instead
of "monad", but the plural "cosmoses" was too grating for me.
George is evidently stronger than I.)

I intend to reply to the rest of your post soon.

-- Jeff, in Minneapolis

.

(George Buyanovsky) wrote
(John Griffin) wrote
(George Buyanovsky) wrote
(Matthew F Funke) wrote
John Griffin wrote:

Two tiny, fuzzy points of light are observed. Observations of
each object indicate that it's a globular galaxy ten billion light
years distant. The first one is exactly that, but the second one
happens to be another entire universe. It's 100,000 times as
far away as the galaxy, and it's emiting ten billion times as
much light. Is there anything that would distinguish these
objects from one another?

Redshift. The universe is expanding, and there is more space in
between us and the object 100,000 times as far away; it would appear to be
more redshifted.

Let me to reformulate it.
Small star - 10 light years.
Huge Quasar ? 10 billion light years.
Huge Quasar moves toward us with exact speed to compensate redshift.
For this arrangement, the redshift is not enough to distinguish them.

I wish I had been more specific in my original question.

In the hypothetical situation, the observations I mentioned were that
radiation from the other universe had the same redshift as radiation
from a galaxy ten billion light years from "here." (The cosmologists
have me wondering if the word "here" is just some kind of strange
idea.) The equal redshift would be purely coincidental, since the
other universe's motion would

It is not by chance I reformulated your question.

The phrase like:

"other universe's motion"

makes no sense at all.

That is, it makes no sense if we humans have learned everything.

Your questions are based on one universe idea.

That doesn't make sense. My hypothesis was that there are
other instances of what the cosmologists call a universe.
Since they say no information can be attained from anything
other than our universe, it seems a bit hasty to say anything
at all about a hypothetical "outside."

People here have tried to explain you this. It is not a matter of
complexity it is matter of natural perception of reality, which is,
by the way, has been proven by natural selection ;o)

It isn't "natural" to say that existence itself depends on
the origin of the universe. If it were, there would be lots
more than a few dozen people who can conceptualize it and
formulate theories about it. The big bang was an event, so the
natural thing is to think it had to have some "place" to occur.
It could have occurred somewhere else, and an infinite number
of them could have occurred. Even in the balloon analogy,
someone could stick a pin in the balloon, whether or not a
bug or a weasel walking around on its surface can perceive
anything beyond it.

I wonder what the "creation scientists" think about this.
They created "God" to explain everything, so they probably
agree with the hypothesis of a universe within an infinite
empty space.

By the way, you didn't exactly reformulate my question.
The first guy who observed a quasar thought it was a
star with lots of heavy atoms. Anyway, I don't know
what you mean by "compensate redshift." Moving toward
us, its radiation would be shifted the opposite way.
If it shows no redshift or blueshift, it's at rest
relative to us, isn't it? I guess that could happen
if it's orbiting the center of a galaxy (on the
approaching side) at whatever rate corresponds to
the recession velocity of a galaxy ten billion
light years away...but then when it completes half
a revolution, it would be receding at twice that
velocity...?

"George Buyanovsky" wrote in message om...
"George Dishman" wrote in message ...
"John Griffin" wrote in message
It turns out that the cosmologists have theories and some experimental
data that say the other universe can't exist.

Not true, at least two of the sources give you links to pages
detailing ways in which other universes might exist

The notion "exist" does not fit to describe validity of multiverse concept.

What word would you use instead?

George

"George Dishman" wrote in message ...
"George Buyanovsky" wrote in message om...
"George Dishman" wrote in message ...
"John Griffin" wrote in message
It turns out that the cosmologists have theories and some experimental
data that say the other universe can't exist.

Not true, at least two of the sources give you links to pages
detailing ways in which other universes might exist

The notion "exist" does not fit to describe validity of multiverse concept.

What word would you use instead?

Probably "manifestation" is good to describe the logical consequences
of multiverse construct.

--George

(Jeff Root) wrote in sci.astro:


But you just said that the Big Bang theory doesn't say anything
about other universes, only our own! In your next sentence you
contradict that and say that it predicts what can and can't
happen outside our universe! Which is it???


Note the semicolons. As the Big Bang describes nothing but our own
universe, it can't tell us anything about another universe. If a photon
from another universe would be visible here, it would be subject to the
same laws as a photon from our universe. The Big Bang theory leaves a
photon no room to "leave" our universe.


Actually, the Big Bang theory says nothing about the origin of
space and/or time. It does say that at some time about 13.7
billion years ago everything in the Universe was squished real
close together, was very hot, and was expanding real fast.
It also says that a moment before that, something completely
unknown happened, which no theory is yet able to describe in
any way that makes sense. So, space and time *may* have been
created at that time, or they may not have. There's no way
to say, as yet.



During the Big Bang our current space and time were created. The theory
tells us nothing what happened before, and it's quite interesting, but
not very relevant for the questions raised.



I asked about your use of the term "embedded" because Greg
used it prominently in a message posted less than two hours
after yours; I don't think the term had been used previously;
and I see no particular reason for its use here.


"Embedded" is a perfect description of one medium existing in another
medium. Like "embedded software" in a chip. Or the inside of a house is
a space. It is embedded in the outside space.


The idea of universes being embedded in anything sounds goofy.
I agree with you that there is no "need" for such universes to
be "embedded" in anything, so I wonder why you brought it up.
Why did you bring it up?

In one of your previous posts you suggested that that other universe
could be traveling towards us at high speed. What does it travel through
if there's nothing to travel in?

You also suggested that there is something "outside" our universe that
the light travels through. You told us it was "space".

How does a photon travel from one universe to our universe? What happens
between the moment that photon "leaves" the other universe and "enters"
the other universe?

In a further posting you told us that the light traveled through space:
You brought it up yourself with your idea of a space medium outside the
universe.



You have said that it is possible that other universes could
exist. In this post you have said that the Big Bang theory
only describes *our* universe, not others. Now you say the Big
Bang theory asserts that our universe comprises everything.
Contradictions! Which statements should I believe?


Sorry, but this is playing with words, and it has little to do with your
understanding of the universe.

The Big Bang theory tells us nothing about other universes.
It supposes the universe encompasses all space-time there is, as it
created space-time. It was not created "in" something, it's self-
contained.

There are also new theories about other universes.
They suppose the universe is not all there is. These theories can be
true. They tell nothing about light traveling from one universe to
another universe, or other universes visible from our universe, which
was the starting point.


There certainly is no indication of any such boundary, and I'm
quite sure that if one exists, neither I nor any other human
will ever "meet" it, because it would be too far away.

You don't understand it. The universe has no need for a boundary. It has
nothing to do with "too far away", it has to do with never being able to
reach it. It's like walking the surface of the Earth and never reach the
edge. The edge of the earth is not "too far away", there _is_ no edge.

Before you take it too literally again: traveling the universe and never
reaching a boundary is _not_ the same as walking the surface of the
Earth.
Walking the surface of the Earth is an _example_ of the possibility of
traveling endlessly and never encountering or even observing a boundary.


One doesn't need to travel "through" anything in order to
travel. One just needs to go from one place to another.


Why is that so? How do you do that? How does that happen with a
traveling photon? What mechanics are you referring to? How does that
travel happen? How can you determine that there is travel if there are
no reference points? At what theories about travel are you reffering?

What happens when one goes from one place to another? Is this
spontaneously? Is this sequentially in time? What time is that? Is there
time without space? How does that time exist without space?
How can we separate those places from each other, to determine that the
photon has "traveled"?


I'd like to know what observations support the assertion that
there is no outside. I can certainly understand that there
*might* not be any outside, but the assertion that there *is*
no outside seems wildly beyond what is known.


There are no observations. We weren't talking about observations, we
were talking about theories. If theories predict or describe actual
observations, the theory gains value. If it has gained value, it is used
to describe phenomenon which are not visible.

Black holes are not visible. Yet they were predicted before we even had
a first glimp at a point in space where one might be. Now we know for
sure that they are there. Do they exist or don't they exist?



Your have a notion of inside and outside which is really confined to our
own universe, our own space-time. There's no inside our universe and
outside our universe, there's just universe and no universe: space-time
and no space-time in current theory.
We haven't got a clue if no-space-time is, is something, and if it is
something, what the properties of that something is.

However we do have a notion of what a photon is, and how it propagates,
how it behaves.

Let's assume there is another universe. Let's assume there is an in-
between able to conduct a photon, even if we don't know how to describe
it. Let's forget to ask ourselves how a photon - an element of space-
time - can propagate when there's nothing to propagate in. We can see it
and distinguish it as a photon, so it obeys the same laws as photons in
our universe.
Let's assume the photon can - by some non-space-time magic find its way
to our galaxy.
Let's assume that photon gets to our universe without having a 'space-
time road' to it - however that might happen. It just arrives at our
universe.

Now the problem diminishes, as we know something about the properties of
our universe, our space-time. Where is the outside? Current theory
leaves no room for such an outside. An outside like that presupposes a
boundary, and there's no boundary.

Let's skip that point.
Let's assume that there's an _outside_ without the need of a boundary.
Now the photon hits that outside. It now has contact with our universe,
and has to obey the rules of our universe. That universe has no
boundaries from the _inside_.

How will it _find_ a non-existent inside boundary? How will it _pass_ a
non-existent boundary? What will happen when it passes a non-existent
boundary?
What will happen if you cross two space-times with each other? Will they
mix? Will they merge? How do they exchange information?
What happens to the energy balance in our own universe? Will somewhere
else energy disappear? How or where does that disappear, as at least
nothing in our universe can _leave_ it, given the fact that _outside_
for _our_ energy is non-existent?

As soon as that extra-universal photon interferes with our space, it has
to obey the rules of our space. And our space tells a photon it can not
cross a non-existent boundary.


Okay, okay. What observations support the assertion that there
is no boundary?

There are no observations necessary. You are limited to "I only believe
it when I see it". Theory can predict what will happen, even if it
hasn't happen yet, even if you don't see it - even if you _can't_ see
it.


I think the balloon model is flawed in that the balloon is a
material object which stretches and on which the galaxies are
fixed, whereas there is probably nothing material between the
real galaxies which stretches or expands or holds them in place.
In reality, it is just the distances between galaxies which are
increasing because the matter which comprises the galaxies has
momentum, imparted to it early in the history of the Universe.


No. Space between galaxies expand. The fabric of space itself expands.



The balloon model is also flawed in that the surface of the
balloon is strongly curved. The latest observations show the
Universe to be indistinguishable from flat, overall. No
indication of any overall curvature.


A _flat_ universe has nothing to do with it's actual 3D-form: it means
that the rules of Euclidian geometry apply to it. It means it has the
_geometry_ of a flat surface, not that it _is_ a flat surface.

The balloon model is a way to grasp the notion that a surface can be
limited, yet without boundaries. It can help you visualize why you never
will fall off the Earth. It can help you with understanding that this
might be apllicable to higher dimensions too. It doesn't tell us
anything about the actual form of the universe.



The article contradicts most of your above assertions.
Of course, the main ideas of the article are an alternative
to inflation and a way for the Big Bang to be initiated,
which naturally contradicts those theories in many ways.


It tries to solve some serious problems in the current theories.
It builds on them. There are very few scientists who claim to have the
ultimate theory.


--
CeeBee


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