Uniform expansion of the spacetime metric?

[DStahl]

On another BB several members opined that if the Universe were expanding uniformly everywhere (atoms, planets, galaxies all getting bigger) then we would not be able to detect the expansion. I don't get it. It seems to me that if you make an electron's atomic orbit larger then the forces between it and the nucleus must be adjusted, and if you expand a ruler then the electrostatic forces between the molecules in the ruler must be adjusted...or else eventually the ruler would start behaving as a gas. Same with gravity and the other forces--everything has to smoothly adjust to the increasing metric. It seems an incredible kludge.

Am I all wet, as usual? Or is there some sort of logical way that such a uniform expansion of the spacetime metric would result in a Universe in which nuclear fusion and chemical reactions and all behaved the same way 8 billion years ago as they do today?

[GrapesOfWrath]

Well, I can't speak for those others, but if you simply make everything bigger then presumably the resultant forces will be bigger also--or that seems to be their point, that if you scale up everything, then no one inside the frame can tell that it occurred.

Obviously, that gets a little tricky, if you're going to do it right. But if you assume that it is done right, then of course it would be undetectable, right?

My guess [HERE] will continue to be
that where earthlings are really "hay wired"
in there thinking, [yeah even computers] are
in the constructs of time. ESPECIALLY
that long term iteration interval commonly
refered to as eturnity {best check spelling}
my guess that the concept of long intervals
{um many lines of text} distorts in some way
the tempral concept somehow? for now i'll
just say :| rings of Saturn |" and 4get it.

[DStahl]

GrapesOfWrath: "Well, I can't speak for those others, but if you simply make everything bigger then presumably the resultant forces will be bigger also--or that seems to be their point, that if you scale up everything, then no one inside the frame can tell that it occurred."

Well, yes, but-but-but! That would mean that the charge and mass of electrons, for example, would have to increase--where's the mechanism for that? That is, can the expansion of spacetime create charge and mass ex nihilo? Well, maybe it can, since the expansion creates more spacetime, but it still smells fishy to me. Paging Dr. Rosen!

I think I agree, HUb', and
I wonder if string theory
(or another such super-unification)
will give us a new view of time.
As far as our work-a-day
instinctive understanding of
ourselves as creatures inside
a time-flow goes, I'll bet an
internet cookie we'll be stuck
with that as long as we rely
on meat computers for brains!

--Don

[GrapesOfWrath]

On 2001-12-23 15:54, DStahl wrote:
As far as our work-a-day
instinctive understanding of
ourselves as creatures inside
a time-flow goes, I'll bet an
internet cookie we'll be stuck
with that as long as we rely
on meat computers for brains!

You're on. I'd say we're going to see a breakthrough in that within ten years--long before we've exhausted the potential of our "meat computers."

[DStahl]

Just to clarify, Grapes, I was betting that our instinctive time-sense will stick around. Kind of like we instinctively gauge the trajectory of a ball rebounding from a backboard but to gauge the chances of an electron either rebounding or tunneling through a barrier we have to resort to the somewhat counterintuitive formalism of QED. I'll bet superstrings or another theory (probably within 10 years) will give us a similar formalism for time. But I will also bet that the theory will run counter to our instinctive time sense.

Sheesh. Just wind up my spring and watch the words come flying out...I'll shut up now.

--Don

<font size=-1>[ This Message was edited by: DStahl on 2001-12-23 19:43 ]</font>

[GrapesOfWrath]

Hehehehe

Let me get this straight. You're betting our instinctive time-sense will still be with us, as long as we use meat computers. By "instinctive," you mean, calculated by our meat computers?

I'm saying that our concept of time will change, just as radically as it did in 1905.

On 2001-12-23 15:54, DStahl wrote: To: 1-12-24 8:24 A.M.
GrapesOfWrath: "Well, I can't speak for those others, but if you simply make everything bigger then presumably the resultant forces will be bigger also--or that seems to be their point, that if you scale up everything, then no one inside the frame can tell that it occurred."|1| Interesting? just this morning
|2| while the IBM 5150 (clasic)
Well, yes, but-but-but! That would mean that the charge and mass of electrons, for example, would have to increase--where's the mechanism for that? That is, can the expansion of spacetime create charge and mass ex nihilo? Well, maybe it can, since the expansion creates more spacetime, but it still smells fishy to me. Paging Dr. Rosen!|3|
|4| was attempting to get the data required
I think I agree, HUb', and..........|5| for me to control
I wonder if string theory ..........|6| the charts & graphs
(or another such super-unification).|7| of the price
will give us a new view of time.....|8| of electrons
As far as our work-a-day ...........|9| being sent about
instinctive understanding of........|A| in the solar system
ourselves as creatures inside.......|B| in a coo
a time-flow goes, I'll bet an.......|C| it left me a message
internet cookie we'll be stuck......|D| in effect that I
with that as long as we rely........|E| simply was "NOT"
on meat computers for brains!.......|F| listening
|g| well I `poise there was some truth to that
--Don
8:31 A.M. HUb' and if i find the lines

I will upCHuck som of it. L8R

[DStahl]

Grapes: "By "instinctive," you mean, calculated by our meat computers?"

Almost...I mean as intuited by our meat computers. I'll bet we'll be able to use those fantastic devices to calculate a unified quantum spacetime metric, but it may run counter to what our intuition tells us about time. Just like the idea of a photon passing through two slits at once runs against our intuitive understanding of how 'things' behave.

You know, I've read somewhere that since our brains functions through processes that are sensitive to the arrow of time (electrochemical for the most part, right?) then the arrow of time is unavoidably built in at the lowest possible level. On the other hand, the human mind is capable of rather incredible abstractions; perhaps someday we will be able to deal with non-linear (or whatever) spacetime as intuitively as we now deal with the idea of getting out of bed at time T and going back to bed at time T + x. But I bet the intuitive ability will lag far, far behind the ability to calculate 'realistic time!'

-->coming back to astronomy: When we get a solid theory of 'realistic time' I hope it can tell us exactly how time came into being at the Big Bang.

--Don

[Chip]

On 2001-12-22 20:35, DStahl wrote:
On another BB several members opined that if the Universe were expanding uniformly everywhere (atoms, planets, galaxies all getting bigger) then we would not be able to detect the expansion. I don't get it. It seems to me that if you make an electron's atomic orbit larger then the forces between it and the nucleus must be adjusted, and if you expand a ruler then the electrostatic forces between the molecules in the ruler must be adjusted...or else eventually the ruler would start behaving as a gas. Same with gravity and the other forces--everything has to smoothly adjust to the increasing metric. It seems an incredible kludge.

Am I all wet, as usual? Or is there some sort of logical way that such a uniform expansion of the spacetime metric would result in a Universe in which nuclear fusion and chemical reactions and all behaved the same way 8 billion years ago as they do today?

I may be all wet too, but I think the basic concept is that on the largest scale, the fabric of space itself is expanding and not the matter, be it on the galactic or atomic scale. The matter is moving along with the expansion.

Another question involving uniform expansion could be: since there is evidence that the universe is accelerating, then isn't it's expansion not "uniform" over time in terms of velocity relative to the past?

Also, since the expansion has no center (as in a conventional explosion,) then does it necessarily follow that it has to expand uniformly throughout the visible universe? Again, not uniformly over time?

Chip

[DStahl]

Chip, I agree with you on all counts. The alternate viewpoint, as far as I can see, is that all space expands uniformly, even the space between the point particles making up an atom--the electrons and quarks. One of the fellows on the other site (physicsforums.com) agrees with me that the idea is not realistic. The others haven't checked in.

--Don S.

[Argos]

If the universe is scaling up uniformly, so that we don't realize, I think we are before a static universe.

I rank with those who favor the expansion of the space-time fabric, not matter.

[DStahl]

Hmm! I think you mean that if everything, including, say, the mass and charge of electrons and protons, is scaling together then there would be no difference between an expanding, contracting, or static universe. I agree. Or maybe the only differences would be metaphysical?

--Don

[Argos]

On 2002-01-06 20:00, DStahl wrote:
Hmm! I think you mean that if everything, including, say, the mass and charge of electrons and protons, is scaling together then there would be no difference between an expanding, contracting, or static universe. I agree. Or maybe the only differences would be metaphysical?

--Don

Sure. I believe only metaphysics can handle the distinction properly in such conditions. Or maybe a "higher order" physics.

[Howard]

Pertaining to this topic, I read in the Inflationary Universe by Alan Guth, that
space itself is expanding, but the strong, weak and electromagnetic forces
between particles remains the same. So an atom, star, etc. would remain the
same size. If these forces weakened, then the atoms would expand, and you
would not detect a difference.

[czeslaw]

The space may expanse but according to the relation of Mass/Radius. The Planck length is 10-^35 m close to small Black Hole and 10-^15 in an empty Universe.

I can’t find a link for it now but this expansion is not freely.
It would be violation of the energy conservation law. An increase of the distance between heavy galaxies cost a lot of energy.

[heusdens]

Can anyone explain the logic that photons would redshift because a change in the space metric, and other matter (protons, electrons) are not affected by this effect?

And since GR is based on the idea that there isn't an aether, what is actually the meaning of space expansion? How can changing of metrics have any physical effect whatsoever?

And, since this is equivalent, we could also say, the metrics of space stay the same, but all atoms, protons, electrons and neutrons and things consisting of such particles shrink.

Or maybe we should get rid of the idea that there is any change in the metrics of space?

For an alternative physics explenation, see:
http://www.spaceandmotion.com

[Bob Angstrom]

Can anyone explain the logic that photons would redshift because a change in the space metric, and other matter (protons, electrons) are not affected by this effect?

And since GR is based on the idea that there isn't an aether, what is actually the meaning of space expansion? How can changing of metrics have any physical effect whatsoever?

And, since this is equivalent, we could also say, the metrics of space stay the same, but all atoms, protons, electrons and neutrons and things consisting of such particles shrink.

Or maybe we should get rid of the idea that there is any change in the metrics of space?

For an alternative physics explenation, see:
http://www.spaceandmotion.com

It is important to remember that space and time can not be separated. Any change in the metric of space must involve a proportional change in the metric of time. In GR, whenever space expands, time accelerates and the only metric that does not change is the speed of light. If space and matter are both expanding we would not be able to detect expansion but, whenever space expands, time accelerates and this produces a disconnect between the scale of space and the scale of matter. In the model you noted by Hasellhurst, matter consists of waves. The expansion of space causes material waves to grow larger while the acceleration of time causes material waves to grow smaller. The net effect is that matter, like the speed of light, remains the same while space expands so, relative to the static scale of the material world, we observe space as expanding.

[czeslaw]

If a space expands alone it should has an energy - it must be something like aether.

If the distances grows in an empty space the energy must be put in from outside.

There is no other possibility, I think.

[john hunter]

Dear Dstahl,

Your original thread was about the expansion of objects as well as the distance between objects. I agree that the expansion predicted by Einsteins equations, should be interpreted to apply to objects too - in such a way that the expansion is almost undetectable.

The way this could occur, is for every physical constant to 'rescale' depending on the number of length dimensions in it. For example Plancks constant has metres squared for its length dimension, so h changes as
hexp(2Ht), H is the Hubble constant. However G must change as Gexp(3Ht), because G has length cubed as its length dimension. This would rescale the sizes of atoms and forces in such a way that no change is detectable.

This is described in www.gravity.uk.com/cosmological_model.html , the beauty of what you described, with this approach, is that both gravitation and the redshift of light arise naturally from the conservation of energy.

The redshift occurs, due to the variation of Plancks constant with time (and E= hf).

The rescaling 'causes' gravity, and there is a very natural solution of the flatness problem , because the strength of gravity depends on the proximity of surrounding matter. This is discussed in another thread ...Conjecture:does G decrease for dense matter.

Your, and other members, interpretation of the expansion, together with this approach may give a real alternative to traditional 'big bang'.

All the best,

John Hunter.

[Bob Angstrom]

The redshift occurs, due to the variation of Plancks constant with time (and E= hf).

The rescaling 'causes' gravity, and there is a very natural solution of the flatness problem , because the strength of gravity depends on the proximity of surrounding matter. This is discussed in another thread ...Conjecture:does G decrease for dense matter.
John Hunter.

I agree that, if time is a constant while space expands, the result would be a rescaling of our constants including Planck’s h, Newton’s G, and even Einstein’s c. Astronomers generally agree that distant redshifts are due to the expansion of space and that we should not think of the Big Bang as some kind of explosion scattering ejecta into pre-existing space but, when distant redshifts are evaluated, this good advise is forgotten and redshifts are interpreted as explosion type recessional velocities. I think we will eventually discover that the Hubble constant is directly related to the expansion of space and this expansion is not the same as a recessional velocity. I suspect the relationship will look a lot like Ashmore’s paradox where the Hubble constant is equal to Planck’s constant times the radius of an electron divided by the mass of the electron. H=hr/m

[john hunter]

Dear Mr Angstrom,

It seems that the units (dimensions) don't match each other on the formula you just gave.

Does Anyone have any comments on a 'rescaling' universe in which the expansion applies to the size of objects as well as space...for which the physical constants should rescale , the variation of each depending on their length dimensions (as described above)?

John Hunter.

[czeslaw]

If length and constants would be rescaled proportionally we have detect no change, I think. The Redshift is because a relative difference of the distance and constants but this needs an energy.

Why do we speak - the Universe starts from point singularity ?
May be the energy not supplied from outside ?
It would be much easier to explain Redshift and acceleration of the expanssion too.

[john hunter]

Dear Czeslaw,

Who were you replying to, I'm not sure what you mean.

However you mentioned the accelerating expansion, this may be explained by a reinterpretation of Einsteins equations, in the section where a rescaling universe is described in, www.gravity.uk.com/cosmological_model.html

John Hunter.

[czeslaw]

I wrote, we have just a problem if we start a Universe and space from a point singularity. A rescaling universe seems difficult to detect as the space recession as well.

If we reject a point singularity is it much easier then.
If we acccept an energy supply from outside Background there would be no violation of conservation law.

[RussT]

czeslaw
Senior Member
wrote;
[If a space expands alone it should has an energy - it must be something like aether.

If the distances grows in an empty space the energy must be put in from outside.

There is no other possibility, I think.]

[If a space expands alone it should has an energy]Why???

I believe this 'assumption' clouds the whole issue. The name it is given "Dark Energy" assumes this.

The term "The Expansion of Space" is also misleading because it 'assumes' that "somehow" space is "MAKING" more space at the rate of the Hubble constant.

Then you have to add the "Repulsive Force" to account for the even faster expansion!

So, everyone 'assumes' these are 'Energy' and 'Gravity' related. They are not!

The "STUFF" of empty space cannot be thought of in these ways to understand the Hubble Constant original Expansion and then the "Repulsive Forces" extra expansion!

Gravities part is only as it is being added to the universe (one galaxy at a time), it begins to slow the Hubble Expansion, brings it to a halt, or maybe even begins to contract it, until the 'Repulsive Force' becomes strong enough to counteract the Gravity, and the universe begins to 'Expand' even faster, because more and more of the "Repulsive Force" is being made!

[If the distances grows in an empty space the energy must be put in from outside.]

And this is not necessary...all the energy in our universe comes from the "inside" of our universe...it comes from the galaxies being created.

And all of this of course depends on wheather the universe "IS" expanding!!!

RussT
S=G

[czeslaw]

Good problem.
If you want to overcome a gravity you have to have an other force. This repulsive force x increase of the distance = Energy. Doesn't matter , this is in a real space or space recesses alone a work have to be done. Dark Energy, Quintessence, Zero Point Energy, Vacuum Energy, Kasimir Force Effect, Space Recession, Space Inflation all of them did work - a galaxies have now higher gravitationally potential towards each other then before (distances grows). This potential is taken from something, not from nothing.

According to WMAP observations a geometry of our Universe is flat. A light and dark matter gives ~ 30 % a mass (energy) of the Observable Universe. The 70 % is the unknown energy.

In my opinion is it a rest of the previous energy (Photons, Neutrinos) moving around our Observable Universe supplied this energy to us and pulled us gravitationally towards its bottom.

This problem of Dark Energy will be solved if we know exactly how the Black Hole works.

[Bob Angstrom]

Dear Mr Angstrom,

It seems that the units (dimensions) don't match each other on the formula you just gave.

Does Anyone have any comments on a 'rescaling' universe in which the expansion applies to the size of objects as well as space...for which the physical constants should rescale , the variation of each depending on their length dimensions (as described above)?

John Hunter.

John Hunter,

H=hr/m is an odd pairing but it works.
The Hubble constant ‘H’ is 64km/s per Mpc which converts to 2.06 x10^-18 m^3 s^-1.
Planck’s ‘h’ is 6.626 x 10^-34Js.
The radius of the electron ‘r’ is the classical radius of 2.82x 10^15m. The classical radius of the electron is defined as the effective radius of the electron when it is interacting with other particles or photons.
The ‘m’ is the electron’s rest mass of 9.1x10^-31 kg.
The value of hr/m works out to be 2.05x10^-18 m^3 s^-1.
This is in the same ball park as the observed Hubble constant of 2.06 x 10^-18 m^3 s^-1 so H is set equal to hr/m. This is not a derived formula but H and hr/m are equated because the values are nearly the same and they appear too close to just be a coincidence. The formula suggests that the Hubble constant is the slope of hr/m rather than a series of recessional velocities.
The electron is important to our measurement of the universe because changes in the length of the light waves emitted by electrons are our only measurable gage of expansion and this may be the connection to H.

As for the rest of your question, we can best model the universe by using any one of three main constants: space, time, or the speed of light. Changing from one constant to another should not change any of the physics involved since there is no such thing as a preferred reference frame.

Model A: If time is a constant, then space is an expanding variable and there is a rescaling of Einstein’s c and the other “constants”. Such a universe would begin hot and crowded and be gradually cooled by expansion. This model is the same as the Big Bang except that a rescaling of the constants makes it impossible to interpret distant redshifts as straight forward recessional velocities.

Model B: If we use the speed of light as a constant, then there is no rescaling of constants but space should expand while time accelerates. This model is midway between the two because it involves a simultaneous expansion of space and a contraction of matter. The acceleration of time causes the wave-like nature of matter to contract. It is most clear from this model that space can expand with no influx of energy because the energy for expansion comes from the contraction of matter.

Model C: If we use space as a constant, then there is a rescaling of the speed of light and other “constants” because time is an accelerating variable. The universe of this model begins vast and cold and grows warmer with time. Space is not expanding because length is by definition a constant. The universe appears to be expanding but the expansion is an illusion because all material objects are growing smaller and the contraction of the material world also causes objects to grow warmer. The acceleration of time causes light from modern sources to be blueshifted relative to light from ancient sources.

John, am I correct in presuming that your model is similar to what I describe as Model A?
The Model C is the model that most closely resembles the universe as we observe it. For example, the most ancient part of the universe that we can visualize (the CMBR) is also the largest (it completely surrounds the visible universe) it is the coldest (2.73K) and it is the least blueshifted.

[heusdens]

It is important to remember that space and time can not be separated. Any change in the metric of space must involve a proportional change in the metric of time. In GR, whenever space expands, time accelerates and the only metric that does not change is the speed of light. If space and matter are both expanding we would not be able to detect expansion but, whenever space expands, time accelerates and this produces a disconnect between the scale of space and the scale of matter. In the model you noted by Hasellhurst, matter consists of waves. The expansion of space causes material waves to grow larger while the acceleration of time causes material waves to grow smaller. The net effect is that matter, like the speed of light, remains the same while space expands so, relative to the static scale of the material world, we observe space as expanding.

But this (expansion of space-time metrics) is what comes out of the mathematics of GR, and is not observed directly. Indirectly it is only observed in the form of redshift-distance relationship (Hubble law).
There are other viable explenations for that relationship.
WSM theory for example proposes that this is caused by the fact that distance 'matter' can less interact with our 'matter', because there is less of a common universe sphere (each point in space has it's own 'universe bubble' the size of a Hubble radius), which is seen as redshift-distance relationship.
(see: http://www.spaceandmotion.com).

[john hunter]

Dear Mr Anstrom,

Yes model A is the closest, but the recaling of all dimensions, including the objects, would leave the universe appearing unchanged, so any 'expansion'. or cooling must be an extra 'on top' of the rescaling. In the model I proposed, this second type of expansion, would be due to explosions caused by a reduction of 'G' for regions of high mass/radius ratio.

All the best,

J. Hunter.

P.S You seem to be using units for H of m^3 s^-1, but shouldn't they just be s^-1.