Darren New <dne### [at] sanrrcom> wrote:
> Now, if space expanded and gravity pulled everything back together, that 
> makes sense. But that still doesn't answer the question of whether (for 
> example) a brick floating in intergalactic space would be 10% bigger if 
> given enough time.

  I don't think the brick would expand because forces which are much
stronger than gravity are keeping it together.

-- 
                                                          - Warp

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Warp <war### [at] tagpovrayorg> wrote:
>   This is also the reason why galaxies can recede from us faster than c.

  Btw, there's an interesting paper on the subject here:

http://arxiv.org/pdf/astro-ph/0310808

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                                                          - Warp

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Darren New nous apporta ses lumieres en ce 2008/01/02 21:48:
> Warp wrote:
>>   Galaxies do not expand because their gravity keeps them in shape. In
>> other words, gravity inside (and near) galaxies is strong enough to
>> "resist" the expansion. Consequently nothing inside galaxies expands.
> 
> Hmmmm.... I'll take this idea with a grain of salt. :-)
> 
>>   Another slightly difficult thing to grasp is that a constant expansion
>> of the universe actually means that galaxies recede from us at an 
>> exponential
>> rate. At each certain unit of time space distances double, which means 
>> that
>> the distance between two galaxies grows exponentially with time. 
> 
> Yet, funny enough, the number of galaxies we see in an area is constant 
> for a given volume, or close to it. This implies that perhaps the 
> galaxies aren't receding at all, and space isn't growing at all.
It is NOT constant! There are several regions in space that don't have any 
galaxies for 100's of millions of light-years in any direction, and some where 
galaxies are clustered toggether with average distances around a few 10000's 
light-years. Our galaxy is around 27000 light years across.
You have galaxies clusters, then super clusters and mega clusters. You have 
galaxies "filaments", literaly very long strings of galaxies and galaxies 
clusters stretching for billions of light-years.
> 
> I saw an interesting paper that postulated that what we observe would 
> also be correct if further galaxies simply had a time axis pointing away 
> from us. I.e., plot the universe on the surface of a sphere, and have 
> time running perpendicular to the surface. The further apart two points 
> are, the more red-shifted they will see each other, even if the sphere 
> isn't expanding. It explains why we see a constant number of galaxies in 
> a given space, and a number of other problems as well (like the "dark 
> energy" expansion effect). It also explains the background radiation, 
> the fact that it's flat everywhere, and that
Once again, the background radiation is realy not constant at all. It contains 
both small scale and large scale "textures" with intensity variations of around 
1 to 100.
> 
> I'm eager to hear about it coming out in a peer-reviewed journal.
> 
>>   Dark energy has been postulated as an explanation for this. It somehow
>> causes an inflationary effect on the universe, making it to expand in an
>> accelerated way.
> 
> Sounds ad hoc to me. :-)  Fortunately, none of this affects my life in 
> even the most trivial way, until some scientist actually *does* 
> understand it well enough to make predictions and hence technology. :-)
> 
>>   (All this is not based on professional literature, so don't take it
>> for granted. It's just how I have understood it with me extremely limited
>> understanding.)
> 
> Understood. Thanks for the lay interpretation.
> 
It should be noted that some far galaxies are not receding fast enough and that 
others, closer ones, are receding to fast.

-- 
Alain
-------------------------------------------------
Stay out of my head, its a bad neighborhood.

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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> Now, if space expanded and gravity pulled everything back together, that 
>> makes sense. But that still doesn't answer the question of whether (for 
>> example) a brick floating in intergalactic space would be 10% bigger if 
>> given enough time.
> 
>   I don't think the brick would expand because forces which are much
> stronger than gravity are keeping it together.

In other words, space expands, but then the brick collapses again? Sure, 
it's possible. It still doesn't explain why space expands but the matter 
in it doesn't. It's like saying "time slows down, but the spring in the 
clock keeps it running the same speed". :-)

I don't think this works for celestial objects. If you added space 
between the sun and the earth without slowing the orbit of the earth (in 
absolute velocity terms), you'd make an unstable system where the earth 
would tend to move even farther from the sun.

-- 
   Darren New / San Diego, CA, USA (PST)
     It's not feature creep if you put it
     at the end and adjust the release date.

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Darren New <dne### [at] sanrrcom> wrote:
> >   I don't think the brick would expand because forces which are much
> > stronger than gravity are keeping it together.

> In other words, space expands, but then the brick collapses again? Sure, 
> it's possible.

  No. Space expands, the brick doesn't.

> It still doesn't explain why space expands but the matter 
> in it doesn't. It's like saying "time slows down, but the spring in the 
> clock keeps it running the same speed". :-)

  Hey, I'm just repeating what they are saying. Don't blame me.

  Things like expansion of the universe still make a lot of sense when
compared to the wackiness of quantum mechanics, which has all kinds of
things akin go magic. (For example particles being in two places at the
same time. This includes the possibility of a particle being inside and
outside the event horizon of a black hole at the same time. Go figure.)

> I don't think this works for celestial objects. If you added space 
> between the sun and the earth without slowing the orbit of the earth (in 
> absolute velocity terms), you'd make an unstable system where the earth 
> would tend to move even farther from the sun.

  AFAIK space doesn't expand inside galaxies.

-- 
                                                          - Warp

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In article <477d216a@news.povray.org>, war### [at] tagpovrayorg says...
> Darren New <dne### [at] sanrrcom> wrote:
> > >   I don't think the brick would expand because forces which are much
> > > stronger than gravity are keeping it together.
> 
> > In other words, space expands, but then the brick collapses again? Sure
, 
> > it's possible.
> 
>   No. Space expands, the brick doesn't.
> 
> > It still doesn't explain why space expands but the matter 
> > in it doesn't. It's like saying "time slows down, but the spring in the
 
> > clock keeps it running the same speed". :-)
> 
>   Hey, I'm just repeating what they are saying. Don't blame me.
> 
>   Things like expansion of the universe still make a lot of sense when
> compared to the wackiness of quantum mechanics, which has all kinds of
> things akin go magic. (For example particles being in two places at the
> same time. This includes the possibility of a particle being inside and
> outside the event horizon of a black hole at the same time. Go figure.)
> 
> > I don't think this works for celestial objects. If you added space 
> > between the sun and the earth without slowing the orbit of the earth (i
n 
> > absolute velocity terms), you'd make an unstable system where the earth
 
> > would tend to move even farther from the sun.
> 
>   AFAIK space doesn't expand inside galaxies.
> 
You keep repeating this, but other theories imply that, yes it does, its 
just that the force that makes the universe expand is *huge*, but weak. 
I.e., its like 10 billion hand fans waving at a sail. That amount of 
force *might* have the effect of making the boat move, but its effects 
on a fly passing in front of any given fan isn't going to do much. By 
the same token, gravity is sufficient, for now, to prevent any obvious 
expansion of places where it dominates, but we are talking about an 
expansion rate, where it dominates, of like 1 gazillionth of a 
millimeter per billion years, or some absurdly small change. Small 
enough that its not going to be detectable, using any known instrument, 
until like 10,000 times to time its going to take for the sun to burn 
out.

It rather depends on "which" of the current theories you look at, and 
who is discussing them. There are a lot of attempts to fit the math 
together to work, and none of them have a clear picture, so all we have 
is approximate guesses. Some of what you say fits, some of it doesn't, 
so its is possible that the universe will die heat death, by *very 
slowly* being ripped apart, including atoms, but at a rate that will 
leave 99.9% of all suns dead by the time it starts to happen anyway, 
but, at this point, slightly less possible, according to some people in 
the field, that matter will remain intact, but the universe will just 
keep expanding at an accelerating rate.

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void main () {

    if version = "Vista" {
      call slow_by_half();
      call DRM_everything();
    }
    call functional_code();
  }
  else
    call crash_windows();
}

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In article <477d1268$1@news.povray.org>, ele### [at] netscapenet 
says...
> Darren New nous apporta ses lumieres en ce 2008/01/02 21:48:
> > Warp wrote:
> >>   Galaxies do not expand because their gravity keeps them in shape. In
> >> other words, gravity inside (and near) galaxies is strong enough to
> >> "resist" the expansion. Consequently nothing inside galaxies expands.
> > 
> > Hmmmm.... I'll take this idea with a grain of salt. :-)
> > 
> >>   Another slightly difficult thing to grasp is that a constant expansi
on
> >> of the universe actually means that galaxies recede from us at an 
> >> exponential
> >> rate. At each certain unit of time space distances double, which means
 
> >> that
> >> the distance between two galaxies grows exponentially with time. 
> > 
> > Yet, funny enough, the number of galaxies we see in an area is constant
 
> > for a given volume, or close to it. This implies that perhaps the 
> > galaxies aren't receding at all, and space isn't growing at all.
> It is NOT constant! There are several regions in space that don't have an
y 
> galaxies for 100's of millions of light-years in any direction, and some 
where 
> galaxies are clustered toggether with average distances around a few 1000
0's 
> light-years. Our galaxy is around 27000 light years across.
> You have galaxies clusters, then super clusters and mega clusters. You ha
ve 
> galaxies "filaments", literaly very long strings of galaxies and galaxies
 
> clusters stretching for billions of light-years.
> > 
And at least one recently discovered region that is completely "black" 
in the sense that there are no stars, gases, etc. in it, but where light 
seems to instead "slow down" as it passes through, rather than speeding 
up, via gravitational shifts. So, yeah, hardly "constant". lol

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void main () {

    if version = "Vista" {
      call slow_by_half();
      call DRM_everything();
    }
    call functional_code();
  }
  else
    call crash_windows();
}

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Darren New wrote:
> stbenge wrote:
>> nemesis wrote:
>>>
>>> perhaps our own Universe is nothing but a side-effect of something 
>>> bigger...
>>
>> Some of the new theories point an explanation regarding this. 
>> According to the theories, only certain particles can pass between 
>> dimensions, or branes. Two of these particles are tachyons and 
>> gravitons (not sure if the latter have been identified yet though).
> 
> And Dust!
> 

Or grains of salt, depending on how much stock you put into these new 
theories ;)

Sam

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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>>>   I don't think the brick would expand because forces which are much
>>> stronger than gravity are keeping it together.
> 
>> In other words, space expands, but then the brick collapses again? Sure, 
>> it's possible.
> 
>   No. Space expands, the brick doesn't.

That doesn't really make sense.  "Everything gets longer, except your 
rulers."  It would seem to be changing fundamental physical constants.

>   Hey, I'm just repeating what they are saying. Don't blame me.

Fair enough. :-)

>   AFAIK space doesn't expand inside galaxies.

OK. More weirdness. Have you heard any postulates on why that would be 
the case? Space only expands where the gravity is sufficiently low? 
Sounds like "Fire Upon the Deep" to me, where the speed of light gets 
faster the farther away from galaxies you get. :)

-- 
   Darren New / San Diego, CA, USA (PST)
     It's not feature creep if you put it
     at the end and adjust the release date.

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Darren New <dne### [at] sanrrcom> wrote:
> >   No. Space expands, the brick doesn't.

> That doesn't really make sense.

  It makes sense when there's a force opposing the expansion.

  Think about it this way: The distance between atoms in a molecule is
determined by the bounding forces between atoms. These are proportional
to the charge of the electrons, or whatever. It's a constant. It doesn't
change. If you tried to separate the atoms of a molecule, this force would
resist it.

  I suppose it's not too much different than the cause why you don't
drop to the center of the Earth due to gravity: Because there's a force
stopping you from doing so.

>  "Everything gets longer, except your 
> rulers."  It would seem to be changing fundamental physical constants.

  Not everything gets longer. Only intergalactic space, far away from
the galaxies, gets longer.

> >   AFAIK space doesn't expand inside galaxies.

> OK. More weirdness. Have you heard any postulates on why that would be 
> the case? Space only expands where the gravity is sufficiently low? 

http://en.wikipedia.org/wiki/Hubble%27s_law

"In using Hubble's law to determine distances, only the velocity due
to the expansion of the universe can be used. Since gravitationally
interacting galaxies move relative to each other independent of the
expansion of the universe, these relative velocities, called peculiar
velocities, need to be accounted for in the application of Hubble's
law. The Finger of God effect is one result of this phenomenon
discovered in 1938 by Benjamin Kenneally. In systems that are
gravitationally bound, such as galaxies or our planetary system, the
expansion of space is (more than) annihilated by the attractive force
of gravity."

-- 
                                                          - Warp

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