| Topic: |
Science > Physics |
| User: |
"Tony M" |
| Date: |
13 Apr 2006 03:28:17 PM |
| Object: |
Big Bang and Dimensionality |
Hi All,
Was wondering if someone could answer the following which I've read (or
seen
on TV) many times:
1) The expansion of the universe is often referred to as being like the
surface of a balloon being blown up. The continuing separation of the
galaxies is described as the continual expansion of the surface of the
Balloon.
2) The Universe has no centre.
In the first instance, the surface of a balloon is two dimensional
(excepting time) so does this mean that we are all two dimensional
cardboard
cutouts with no depth?
If the universe has no centre, what's at the centre of the balloon (or
in
any case across the radius of the ''balloon')?
If matter curves space-time then if there is no matter is space linear
or
does 'space' not exist?
If the universe has no centre then what is the universe expanding from
(i.e.
what is at the centre of the expansion if all galaxies are drifting
apart)?
If there is no centre then the galaxies cannot be separating (i.e. the
separation 'area' does not contain 'space')?
Some thoughts for Easter.
Regards,
.
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| User: "Jim Black" |
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| Title: Re: Big Bang and Dimensionality |
14 Apr 2006 01:31:31 AM |
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"Tony M" <polsolsa@yahoo.com> wrote in message
news:1144960097.709910.21090@v46g2000cwv.googlegroups.com...
Hi All,
Was wondering if someone could answer the following which I've read (or
seen
on TV) many times:
1) The expansion of the universe is often referred to as being like the
surface of a balloon being blown up. The continuing separation of the
galaxies is described as the continual expansion of the surface of the
Balloon.
2) The Universe has no centre.
In the first instance, the surface of a balloon is two dimensional
(excepting time) so does this mean that we are all two dimensional
cardboard
cutouts with no depth?
If the universe has no centre, what's at the centre of the balloon (or
in
any case across the radius of the ''balloon')?
As others have said, it's only an analogy. Real space-time has four
dimensions: Length, width, depth, and time. If you wished, you could think
of space-time as a four-dimensional surface in a higher-dimensional space,
but the higher-dimensional space would have to have at least 15 dimensions.
Thus, most physicists prefer to stick with four dimensions, and instead
change the rules of geometry. For example, in curved space-time, the angles
of a triangle do not need to add up to 180 degrees. In the end, science is
based on experiments, and unless an experiment was able to measure something
outside our four-dimensional surface, the question of which viewpoint is
correct cannot be answered by science.
That said, for the purposes of studying cosmology, we often use the
approximation that the universe is perfectly homogenous (the same in all
places) and isotropic (the same in all directions). Obviously, the universe
is not exactly the same in all places; for example, the center of the sun is
a lot different from deep space. But whether the matter is concentrated in
stars and galaxies or spread out uniformly has very little effect on the
large-scale behavior of the universe. So as long as the total mass in any
two large regions of the same volume is about the same, cosmology as we know
it is okay. To the point: If we make this approximation, we can get away
with using only 5 dimensions for the higher-dimensional space, instead of
15, at least for the case of a positively or negatively curved universe. I
don't know how to do it for the flat case. It's a good way to understand
the universe, but like any model, one mustn't take it any more seriously
than it was intended.
If matter curves space-time then if there is no matter is space linear
or
does 'space' not exist?
The word "flat" is preferred to "linear" because "linear" has a special
meaning in physics: An equation is linear if adding any two solutions
together, or multiplying one by a constant, results in a solution that also
satisfies the equation. The theory of general relativity can cope with a
universe without matter. According to general relativity, an empty universe
could either be flat or curved by gravitational waves.
On the other hand, quantum mechanics says that there is a minimum possible
amount of energy that space must contain. This energy is called the
zero-point energy because it is subtracted out of many calculations, but
according to current theory it is infinite. At the moment, it's still a
mystery how to combine quantum mechanics and general relativity into a
single consistent theory of everything, so it may not be possible to answer
your question yet.
If the universe has no centre then what is the universe expanding from
(i.e.
what is at the centre of the expansion if all galaxies are drifting
apart)?
From the perspective our galaxy, the other galaxies are moving away from us.
But an observer on a different galaxy, in relative motion to us, would see
the motions of the galaxies differently. He would see that all of the
galaxies were moving away from him. Since both observers' perspectives are
equally valid, neither galaxy can be said to be the center.
If there is no centre then the galaxies cannot be separating (i.e. the
separation 'area' does not contain 'space')?
In the balloon model, the distances between the galaxies are represented by
the distances you would measure along the surface of the balloon using a
flexible ruler.
.
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| User: "Old Man" |
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| Title: Re: Big Bang and Dimensionality |
13 Apr 2006 04:59:20 PM |
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"Tony M" <polsolsa@yahoo.com> wrote in message
news:1144960097.709910.21090@v46g2000cwv.googlegroups.com...
Hi All,
Was wondering if someone could answer the following which I've read (or
seen
on TV) many times:
1) The expansion of the universe is often referred to as being like the
surface of a balloon being blown up. The continuing separation of the
galaxies is described as the continual expansion of the surface of the
Balloon.
2) The Universe has no centre.
In the first instance, the surface of a balloon is two dimensional
(excepting time) so does this mean that we are all two dimensional
cardboard
cutouts with no depth?
If the universe has no centre, what's at the centre of the balloon (or
in
any case across the radius of the ''balloon')?
The sphere has 4 dimensions. The surface then has 3.
It's naught but an ingenious analogy that works quite
well. The sphere's three dimensional surface has no
center. Quit trying to get more out of it than is given
or is intended.
[Old Man]
.
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| User: "Traveler" |
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| Title: Re: Big Bang and Dimensionality |
13 Apr 2006 05:46:06 PM |
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On Thu, 13 Apr 2006 16:59:20 -0500, "Old Man" <nomail@nomail.net>
wrote:
The sphere has 4 dimensions. The surface then has 3.
It's naught but an ingenious analogy that works quite
well. The sphere's three dimensional surface has no
center. Quit trying to get more out of it than is given
or is intended.
None of this crap will ever make any sense because it is based on the
existence of continuous structures. As any highschool kid should know
by now, continuity (infinite divisibility) leads to an infinite
regress by definition. It's crap. Only a crackpot member of the
geriatric physics community would still be discussing a continuous
universe and crap like expanding space in this day and age. There is
no fucking space, goddamnit!
Nasty Little Truth About Space:
http://www.rebelscience.org/Crackpots/nasty.htm#Space
Now wake the ***** up, old fart, and inject yourself with a shot of HGH
and viagra mixed with oatmeal. The universe is discrete. There are no
spheres, no circles, no lines, no space, no time dimension, no
dimensions curled up into little fucking balls. None of that twentieth
century crackpottery should be discussed in this century. Real physics
is only about particles, their properties and their interactions.
Nothing else. All of that other crap is either abstract or voodoo.
ahahaha...
Louis Savain
Why Software Is Bad and What We Can Do to Fix It:
http://www.rebelscience.org/Cosas/Reliability.htm
.
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| User: "Ben Turpin" |
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| Title: Re: Big Bang and Dimensionality |
13 Apr 2006 06:27:14 PM |
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On Thu, 13 Apr 2006 18:46:06 -0400, Traveler wrote:
On Thu, 13 Apr 2006 16:59:20 -0500, "Old Man" <nomail@nomail.net> wrote:
The sphere has 4 dimensions. The surface then has 3. It's naught but an
ingenious analogy that works quite well. The sphere's three dimensional
surface has no center. Quit trying to get more out of it than is given
or is intended.
None of this crap will ever make any sense because it is based on the
existence of continuous structures. As any highschool kid should know by
now, continuity (infinite divisibility) leads to an infinite regress by
definition. It's crap. Only a crackpot member of the geriatric physics
community would still be discussing a continuous universe and crap like
expanding space in this day and age. There is no fucking space, goddamnit!
Nasty Little Truth About Space:
http://www.rebelscience.org/Crackpots/nasty.htm#Space
Now wake the ***** up, old fart, and inject yourself with a shot of HGH and
viagra mixed with oatmeal. The universe is discrete. There are no spheres,
no circles, no lines, no space, no time dimension, no dimensions curled up
into little fucking balls. None of that twentieth century crackpottery
should be discussed in this century. Real physics is only about particles,
What distinguishes one particle from another? How can you go from looking
at one particle to looking at another without going through some kind of
transition where particle 1 is fading away into particle 2? If 1 isn't
fading into 2, where does 1 end and 2 begin?
their properties and their interactions. Nothing else. All of that other
crap is either abstract or voodoo. ahahaha...
Louis Savain
Why Software Is Bad and What We Can Do to Fix It:
http://www.rebelscience.org/Cosas/Reliability.htm
.
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| User: "Traveler" |
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| Title: Re: Big Bang and Dimensionality |
13 Apr 2006 08:37:01 PM |
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On 13 Apr 2006 23:27:14 -0000, Ben Turpin <eyesopen@ipkall.com> wrote:
On Thu, 13 Apr 2006 18:46:06 -0400, Traveler wrote:
On Thu, 13 Apr 2006 16:59:20 -0500, "Old Man" <nomail@nomail.net> wrote:
The sphere has 4 dimensions. The surface then has 3. It's naught but an
ingenious analogy that works quite well. The sphere's three dimensional
surface has no center. Quit trying to get more out of it than is given
or is intended.
None of this crap will ever make any sense because it is based on the
existence of continuous structures. As any highschool kid should know by
now, continuity (infinite divisibility) leads to an infinite regress by
definition. It's crap. Only a crackpot member of the geriatric physics
community would still be discussing a continuous universe and crap like
expanding space in this day and age. There is no fucking space, goddamnit!
Nasty Little Truth About Space:
http://www.rebelscience.org/Crackpots/nasty.htm#Space
Now wake the ***** up, old fart, and inject yourself with a shot of HGH and
viagra mixed with oatmeal. The universe is discrete. There are no spheres,
no circles, no lines, no space, no time dimension, no dimensions curled up
into little fucking balls. None of that twentieth century crackpottery
should be discussed in this century. Real physics is only about particles,
What distinguishes one particle from another?
Their properties. Even a particle's position (its coordinates) is its
own intrinsic property. Particles may interact only if they have equal
positions.
How can you go from looking
at one particle to looking at another without going through some kind of
transition where particle 1 is fading away into particle 2? If 1 isn't
fading into 2, where does 1 end and 2 begin?
It's all in the particles' properties and nature's conservation
principles. Nothing else is needed.
Louis Savain
Why Software Is Bad and What We Can Do to Fix It:
http://www.rebelscience.org/Cosas/Reliability.htm
.
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| User: "T Wake" |
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| Title: Re: Big Bang and Dimensionality |
13 Apr 2006 03:38:29 PM |
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"Tony M" <polsolsa@yahoo.com> wrote in message
news:1144960097.709910.21090@v46g2000cwv.googlegroups.com...
Hi All,
Was wondering if someone could answer the following which I've read (or
seen
on TV) many times:
1) The expansion of the universe is often referred to as being like the
surface of a balloon being blown up. The continuing separation of the
galaxies is described as the continual expansion of the surface of the
Balloon.
2) The Universe has no centre.
In the first instance, the surface of a balloon is two dimensional
(excepting time) so does this mean that we are all two dimensional
cardboard cutouts with no depth?
This is an analogy. It is used to help people visualise the reality, it is
not meant to be an accurate model of reality.
The surface of the balloon in the analogy is showing two of the three
spatial dimensions. In reality, the universe has three spatial dimensions,
you could try to imagine this as the surface of the balloon repeated in all
directions.
If you can come up with a better visualisation for an object which is
expanding equally in all directions and has no centre then please do so, as
the balloon analogy has been the source of much crackpottery. (Ignore
anything Spaceman posts in this thread).
If the universe has no centre, what's at the centre of the balloon (or
in any case across the radius of the ''balloon')?
The centre of the balloon is the centre of the ballon. For the purposes of
the analogy, you only look at the surface of the balloon. It is two
dimensional (as you said yourself).
If matter curves space-time then if there is no matter is space linear
or does 'space' not exist?
Well, hard to see how this can be answered scientifically as it falls beyond
the realms of the scientific method.
Could be either.
As a side line, "mass curves space-time" is a better way of saying it.
"Matter" does not have to have mass. (cf. Photons)
If the universe has no centre then what is the universe expanding from
(i.e. what is at the centre of the expansion if all galaxies are drifting
apart)?
There is no centre of expansion. The expansion is taking place between large
scale structures (galactic clusters) and all are moving away from each
other, in all three dimensions.
The fact everything moves away from everything else identifies there is no
centre.
If there is no centre then the galaxies cannot be separating (i.e. the
separation 'area' does not contain 'space')?
I dont get your reasoning here. Why can they not be separating? The distance
between large scale structures has been measured to be increasing - it is
where H_0 comes in.
.
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| User: "Dave Lister" |
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| Title: Re: Big Bang and Dimensionality |
13 Apr 2006 04:55:10 PM |
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"T Wake" <Usenet.es7AT@gishpuppy.com> wrote in
news:p5-dnZ9DostQK6PZRVny1g@pipex.net:
The fact everything moves away from everything else identifies there
is no centre.
The balloon has a center - in a dimension not on the surface of a balloon.
The universe might have a center, but not in the three spatial
dimensions...
--
Elect a Crook - Vote Republican
.
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| User: "T Wake" |
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| Title: Re: Big Bang and Dimensionality |
13 Apr 2006 05:52:21 PM |
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"Dave Lister" <retsildivad33@hotmail.com> wrote in message
news:Xns97A497CA8D996retsildivad33hotmail@70.169.32.36...
"T Wake" <Usenet.es7AT@gishpuppy.com> wrote in
news:p5-dnZ9DostQK6PZRVny1g@pipex.net:
The fact everything moves away from everything else identifies there
is no centre.
The balloon has a center - in a dimension not on the surface of a balloon.
The universe might have a center, but not in the three spatial
dimensions...
Ok, fair point. It is unlikely though, that there are more than three
spatial dimensions as the effects on gravity, strong force, light etc all
diminish in a manner commensurate with three spatial dimensions.
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| User: "Jim Black" |
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| Title: Re: Big Bang and Dimensionality |
14 Apr 2006 12:02:14 AM |
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"T Wake" <Usenet.es7AT@gishpuppy.com> wrote in message
news:p5-dnZ9DostQK6PZRVny1g@pipex.net...
As a side line, "mass curves space-time" is a better way of saying it.
"Matter" does not have to have mass. (cf. Photons)
Since light does curve space-time, it would be better to say that energy,
momentum, and stress all curve space-time.
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| User: "T Wake" |
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| Title: Re: Big Bang and Dimensionality |
14 Apr 2006 05:34:54 AM |
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"Jim Black" <tramspap@yahoo.com> wrote in message
news:e1nabi$tso$1@emma.aioe.org...
"T Wake" <Usenet.es7AT@gishpuppy.com> wrote in message
news:p5-dnZ9DostQK6PZRVny1g@pipex.net...
As a side line, "mass curves space-time" is a better way of saying it.
"Matter" does not have to have mass. (cf. Photons)
Since light does curve space-time, it would be better to say that energy,
momentum, and stress all curve space-time.
Does light curve space time on it's own? Wouldn't that imply the light had
its own gravitational field, which in turn gives it mass - the incidence of
the curvature (if detectable) would be a determining factor for the mass of
photons. Or I am missing something?
As an example: from http://people.cornell.edu/pages/jag8/lightfield.html
"And the fact that light is "bent" by a gravitational field does not mean it
produces a gravitational field. Light follows the geodesic paths of
spacetime, and is a co-mover with spacetime, like every other form of energy
which spacetime carries. But light does not "warp" spacetime nor produce a
gravitational field" (John A. Gowan, Feb., 2006)
(although I admit, this is a badly written website, it was the first I found
:-))
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| User: "Jim Black" |
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| Title: Re: Big Bang and Dimensionality |
14 Apr 2006 06:31:18 AM |
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"T Wake" <Usenet.es7AT@gishpuppy.com> wrote in message
news:-9adnbcSU4ZK56LZRVnyjQ@pipex.net...
"Jim Black" <tramspap@yahoo.com> wrote in message
news:e1nabi$tso$1@emma.aioe.org...
"T Wake" <Usenet.es7AT@gishpuppy.com> wrote in message
news:p5-dnZ9DostQK6PZRVny1g@pipex.net...
As a side line, "mass curves space-time" is a better way of saying
it. "Matter" does not have to have mass. (cf. Photons)
Since light does curve space-time, it would be better to say that
energy, momentum, and stress all curve space-time.
Does light curve space time on it's own? Wouldn't that imply the
light had its own gravitational field, which in turn gives it mass -
the incidence of the curvature (if detectable) would be a
determining factor for the mass of photons. Or I am missing
something?
Not mass, just energy, pressure, or momentum, and light has all three.
In fact, in the early universe, light was the primary cause of
space-time curvature:
-> The volume of the box scales as R^3, so we expect the matter
-> density to behave as:
->
-> rho_m ~ R^-3
->
-> The energy density of radiation falls more quickly than this,
-> because although the number of photons is preserved, each photon
-> expands with the universe and hence loses energy because its
-> frequency is falling. Running the universe back in time, the
-> radiation energy density increases faster than the matter density
-> and eventually overtakes it. However, this happens so close to the
-> beginning of time (when R was about a thousandth of its present
-> value) that we can ignore this short period and leave radiation out
-> of the calculations.
http://www.jb.man.ac.uk/~jpl/cosmo/friedman.html
As an example: from
http://people.cornell.edu/pages/jag8/lightfield.html "And the fact
that light is "bent" by a gravitational field does not mean it
produces a gravitational field. Light follows the geodesic paths of
spacetime, and is a co-mover with spacetime, like every other form
of energy which spacetime carries. But light does not "warp"
spacetime nor produce a gravitational field" (John A. Gowan, Feb.,
2006)
(although I admit, this is a badly written website, it was the first
I found :-))
Worse, it appears to be a crank website:
-> The fact that the scientific "establishment" believes that freely
-> moving light in vacuum (space) produces a gravitational field
-> continues to be a major conceptual roadblock in their ongoing
-> effort to unify gravitation with the other forces. This is a major
-> (and crucial) point of difference between my theory and
-> "established" physics.
According to his biography
(http://people.cornell.edu/pages/jag8/author.html),
his connection to Cornell was that he studied agriculture there, and
subsequently "worked for the departments of Entomology, Ecology and
Systematics, and Floriculture, all at Cornell, as a research
technician."
And yes, the fact that light is bent by gravitation does mean it has
to
produce a gravitational field of its own; otherwise you'd have a
blaring
violation of the conservation of momentum.
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| User: "T Wake" |
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| Title: Re: Big Bang and Dimensionality |
14 Apr 2006 06:40:17 AM |
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"Jim Black" <tramspap@yahoo.com> wrote in message
news:e1o150$pth$1@emma.aioe.org...
Not mass, just energy, pressure, or momentum, and light has all three.
In fact, in the early universe, light was the primary cause of
space-time curvature:
-> The volume of the box scales as R^3, so we expect the matter
-> density to behave as:
->
-> rho_m ~ R^-3
->
-> The energy density of radiation falls more quickly than this,
-> because although the number of photons is preserved, each photon
-> expands with the universe and hence loses energy because its
-> frequency is falling. Running the universe back in time, the
-> radiation energy density increases faster than the matter density
-> and eventually overtakes it. However, this happens so close to the
-> beginning of time (when R was about a thousandth of its present
-> value) that we can ignore this short period and leave radiation out
-> of the calculations.
http://www.jb.man.ac.uk/~jpl/cosmo/friedman.html
Thanks for the link - after I had sent the last post, I read more on that
website and (like you) came to the conclusion it was, after all, written by
a madman. Sorry.
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| User: "Sam Wormley" |
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| Title: Re: Big Bang and Dimensionality |
13 Apr 2006 04:19:50 PM |
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Tony M wrote:
If there is no centre then the galaxies cannot be separating (i.e. the
separation 'area' does not contain 'space')?
No Center
http://www.astro.ucla.edu/~wright/nocenter.html
Also see Ned Wright's Cosmology Tutorial
http://www.astro.ucla.edu/~wright/cosmolog.htm
http://www.astro.ucla.edu/~wright/cosmology_faq.html
WMAP: Foundations of the Big Bang theory
http://map.gsfc.nasa.gov/m_uni.html
WMAP: Tests of Big Bang Cosmology
http://map.gsfc.nasa.gov/m_uni/uni_101bbtest.html
.
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