Expanding space or contracting matter?

  • #1
16
0

Main Question or Discussion Point

Expanding universe or contracting matter?

this may look very weird question, but what if instead of that the universe is expanding, all matter is contracting as a function of its (proper) time?

[itex] Δs' = Δs_0 /F(t) [/itex]

The contraction of matter would effect on the lenght unit what we use.

I am posting this as thought experiment and i am just interested to know where does this kind of thinking crash down and hit the wall of reality.

If it is assumed that any structure in cosmological lenght scale do not contract when the matter in small length scales is contracting, we would measure that cosmological distances would appear to grow as a function of time.

We would get the usual Robertson-Walker metric:

[itex] ds^2 = dt^2 - a(t) dr^2 [/itex]

as in expanding space, but the underlying reason for this metric would now be not the expansion of space,
but contraction of the unit length we use.

This kind of weird possibility has to explain all cosmological observations to be a valid explanation. In addition to produce robertson-Walker metric, It should be able to explain The following two basic observations:

(i) Cosmological time dilation
(ii) Cosmological redshift and energy loss of the photon

and yes, contracting matter does not support these observations. So, is it worth of a throwing to rubbish bin?



-maybe not yet, there is still one thing what might make it look at least somewhat sensible.


(i) First, It should be able to explain cosmological time dilation - that is, that distant objects appears to have time dilation.

Cosmological time dilation is explained by expanding universe by the expansion of the photons that travel through expanding space.

If it is thought that there is no expanding universe, but that there is contracting matter, there would not be observation of cosmological time dilation.

I think the only sensible solution for this problem is that if the matter were contracting, the time unit of the matter should be contracting also. Otherwise it just does not make sense. :

[itex] Δt' = Δt0 /F(t) [/itex]

where F(t) is some function.

So The change of the length unit and time unit would be together:

[itex] Δt'= Δt_0 /F(t) [/itex]
[itex] Δs'= Δs_0 /F(t) [/itex]

and the formula for scale factor a(t) in the metric equation has to be linear relative to the time unit the observer uses:

[itex] a(t') = 1 + H t'[/itex]

[itex] a(t) = F(t) [/itex]

assuming that all matter in the universe share exactly same proper time.

(ii) Secondly, this kind of hypothesis should also explain cosmological redshift and cosmological energy loss of the photon.

Again the only sensible solution for this would be that as the matter contracts, and observers own unit length and unit time contracts, it has to be that the observers measurement of the energy and momenta, must change such that:

[itex] ΔE'_{measured in photon}= ΔE_0 / F(t) [/itex]
[itex] dp'_{measured in photon} = dp_0 / F(t) [/itex]

The changes in the units of which the observer uses would be the opposite.

To put these four equations together, the changes of the time, lengt, energy and momentum are :

[itex] Δt' = Δt_0 / F(t) [/itex]
[itex] Δs' = Δs_0 / F(t) [/itex]
[itex] ΔE' = ΔE_0 * F(t) [/itex]
[itex] Δp' = Δp_0 * F(t) [/itex]

There is a theoretical fact In physics that it is possible to determine any kind of unit system by defining only three different kind of units - length unit, time unit and energy or momentum unit. All other units can be then derived from these 3 units by dimensional analysis.

Here i am not talking about just unit conversion of length, time and energy /momentum, but real, actual changes. But similarly as in unit conversion, from three equations, it is possible to derive the contraction or expansion equations for all physical measurables from these three or four equations.

Example : a mass

[itex] p'/p = m'/m , v'/v = 1 ⇒ m' = m0 * F(t) [/itex]

example : A local force

[itex] F' / F = m'/m a'/a = m'/m (1/dt'/dt) = F(t)^2 [/itex]

example: A local charge

[itex] q'/q = F'/F * (s'/s)^2 ⇒ q' = q_0 * F(t) [/itex]

example: Coulomb's constant

[itex] k'/k = F'/F * (s'/s)^2 * (1/ e'/e)^2 = 1/ F(t)^2 [/itex]



Key problem: What happens to energy conservation principle?

So the mass of the matter would be increasing according to these equations.

Due to the mass-energy equivalence, E = mc^2, it seems that increase of the mass would mean that the energy content of the matter should increase.

But If we look for example contraction of hydrogen atom, if we do not care of the mass-energy content, the change of the energy in this system is negative, because the matter-wavelength of the electron decreases. (The change in coulomb constant is cancelled by the changes in electrons and protons charges if the distance r stays constant during the change. you can do this by evaluating by dimensional analysis how k and e changes and end up that k'/k (e'/e)^2 = 1) And for the same reason the electron should emit the energy difference in the form of radiation when it goes more near to nucleus.

Similarly, by similar deduction, all bounded Quantum mechanical systems should lose their system energy.



Another key problem: weird predictions:

IF the contraction of matter depends on the proper time, the hypothesis that the matter is contracting would make different prediction than expanding space.

1) The assumption that all matter share common proper time cannot be true in the following cases:

-in Compact objects like neutron stars and Black Holes
-In relativistic jets like in quasar jets
-In ultrarelativistic cosmic rays

If the contraction of the matter is dependent to the proper time of the matter, then this kind of idea would predict that in relativistic phenomenom that extends to cosmological time scales, there should exist differently contracted matter. But this kind of thing has never been observed in nature.

example: ultrarelativistic jet appear to have redshift and cross section expansion as a function of its distance from the source.

2) for same reason, if the contraction of matter depends on its proper time, the black hole event horizon shouldn't be contracting. This would give prediction that the radius of black holes should appear to increase at the same rate than the space appears to be expanding. And this would mean that Black holes appear to gain mass from nowhere.
 
Last edited:

Answers and Replies

  • #2
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2
the observation is the expansion, so if this is no sf, what then? beyond the main stream? anyway IMHO the wrong forum
 
  • #3
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the observation is the expansion, so if this is no sf, what then? beyond the main stream? anyway IMHO the wrong forum
i think it is a simple theoretical question, thats why i ask it here. if that would not be the case i would post a different kind of thread and post it in science fiction forum.
 
  • #5
16
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OK, which simple question should I answer?
the question is -

whether the observed Robertson-Walker-Friedmann-Lemaitre metric of the spacetime


ds^2 = dt^2 - a(t) dr^2

together with all cosmological observations such as

-expansion of distances
-cosmological redshift and time dilation
-Tolman test (surface brighness is proportional to (1+z)^4 )
and other observations
-observed scale factor a(t) evolution history (that fits to so called benchmark model)

...can be alternatively explained if instead of the empty space is expanding, all matter in the universe is contracting as a function of proper time?


i make here two points i think are important to see:

(1) In order to be able to explain correctly the following observations

-expansion of distances in cosmological scales
-cosmological redshift (1+z) = 1 + H0t (linear approximation) = ?
-cosmological time dilation - redshift relation: dt'/dt0 = (1+z)
-small angular diameter - redshift relation d'/d = (1+z)
-correct surface-brightness- redshift relation: F'/F0 = (1+z)^4
(where the power 4 is sum of photon energy loss, photon number decrease and the increase of cross section of thin light ray)

not only the length unit of the matter, but also the time unit and energy unit, should change like

s'/s0 = A(t)
t'/t0 = A(t)
E'/E0 = 1/ A(t)

where A(t0) = 1 and A(t) is some decreasing function of proper time

,otherwise it is not possible to have correct cosmological observations mentioned above by assuming only that the length unit of the matter in the universe is contracting. So i think it would be pointless to speak about contraction of the length only.That is why i write about that.

2) one point i is Also that, with only contraction of length, that would change the properties of the matter over time, this would result for example different kind of star evolution.

But if these 3 changes happen simultaneosly in all matter in all stars, and in all matter, it may be possible that local observer wouldnt be able to measure any changes.

it may be possible that there would be only two visible changes in the point of view of the observer:

a)Distant stars or objects appear to have time dilation in past similarly as if they were moving away from us
B)distances between stars appear to grow as a function of time, and all things were close together in the past.This is simply because the distant object that are weakly bound to each other do not contract close together when all matter in them contracts.[/QUOTE]
 
  • #6
16
0
the question is -

whether the observed Robertson-Walker-Friedmann-Lemaitre metric of the spacetime


ds^2 = dt^2 - a(t) dr^2

together with all cosmological observations such as

-expansion of distances
-cosmological redshift and time dilation
-Tolman test (surface brighness is proportional to (1+z)^4 )
and other observations
-observed scale factor a(t) evolution history (that fits to so called benchmark model)

...can be alternatively explained if instead of the empty space is expanding, all matter in the universe is contracting as a function of proper time?


i make here two points i think are important to see:

(1) In order to be able to explain correctly the following observations

-expansion of distances in cosmological scales
-cosmological redshift (1+z) = 1 + H0t (linear approximation) = ?
-cosmological time dilation - redshift relation: dt'/dt0 = (1+z)
-small angular diameter - redshift relation d'/d = (1+z)
-correct surface-brightness- redshift relation: F'/F0 = (1+z)^4
(where the power 4 is sum of photon energy loss, photon number decrease and the increase of cross section of thin light ray)

not only the length unit of the matter, but also the time unit and energy unit, should change like

s'/s0 = A(t)
t'/t0 = A(t)
E'/E0 = 1/ A(t)

where A(t0) = 1 and A(t) is some decreasing function of proper time

,otherwise it is not possible to have correct cosmological observations mentioned above by assuming only that the length unit of the matter in the universe is contracting. So i think it would be pointless to speak about contraction of the length only.That is why i write about that.

2) one point i is Also that, with only contraction of length, that would change the properties of the matter over time, this would result for example different kind of star evolution.

But if these 3 changes happen simultaneosly in all matter in all stars, and in all matter, it may be possible that local observer wouldnt be able to measure any changes.

it may be possible that there would be two main visible changes in the point of view of the observer:

a)Distant stars or objects appear to have time dilation in past similarly as if they were moving away from us
B)distances between stars appear to grow as a function of time, and all things were close together in the past.This is simply because the distant object that are weakly bound to each other do not contract close together when all matter in them contracts.

which looks similar as if the space were just expanding
 
  • #7
bcrowell
Staff Emeritus
Science Advisor
Insights Author
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Take a look at this paper: Dicke, "Mach's principle and invariance under transformation of units," Phys Rev 125 (1962) 2163, http://journals.aps.org/pr/abstract/10.1103/PhysRev.125.2163. Dicke shows in appendix 1 that GR can be represented as a theory of flat spacetime in which the units of measurement vary. This is equivalent to hypothesizing that matter changes its properties from point to point in such a way that clocks and measuring rods change their properties. Because the theory is isomorphic to GR, no special, exciting phenomena occur.
 
  • #8
PeterDonis
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The OP proposal here is personal speculation. The Dicke paper is the best available mainstream response. Thread closed.
 

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