Preservation of Space: Is There a Model?

  • Context: Graduate 
  • Thread starter Thread starter -Job-
  • Start date Start date
  • Tags Tags
    Space
Click For Summary

Discussion Overview

The discussion revolves around the concept of whether space can be considered to be preserved in a manner analogous to mass and energy in the universe. Participants explore various models and implications of an expanding universe, the nature of vacuum energy, and the conservation of mass and energy in relation to these ideas.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose a "preservation-of-space" model where the universe expands in some dimensions while collapsing in others.
  • Questions are raised about what exactly is expanding in space and how it can be measured, with references to Einstein's models and speculative ideas about branes.
  • Concerns are expressed regarding the implications of expanding space on vacuum energy and the conservation of mass and energy, with some favoring steady-state cosmology over expanding models.
  • Participants discuss the difficulty of defining measurable properties of vacuum and the challenges in quantifying dark energy as a candidate for vacuum energy.
  • One participant argues that if vacuum is the baseline energy, it raises questions about whether energy can be considered compressed or dense vacuum, and whether matter can be converted to energy or space.
  • Another participant challenges the validity of claims made regarding vacuum energy and its implications for cosmological models, requesting mathematical support for arguments presented.
  • There is a discussion about the relationship between the expansion of the universe and the energy density of the vacuum, with some suggesting that the conservation of mass/energy may be violated due to cosmological expansion.
  • Some participants argue that having more vacuum does not necessarily imply an increase in total energy, suggesting that energy distribution may vary across the universe.
  • Speculation arises about the potential for changing terminology from "expanding" to "creating" in the context of vacuum and energy.

Areas of Agreement / Disagreement

Participants do not reach a consensus, with multiple competing views on the nature of vacuum energy, the implications of an expanding universe, and the conservation of mass and energy. The discussion remains unresolved with ongoing debate and exploration of ideas.

Contextual Notes

Limitations include the difficulty in measuring vacuum properties, the dependence on definitions of energy and mass, and unresolved mathematical implications regarding the relationship between vacuum energy and universal expansion.

-Job-
Science Advisor
Messages
1,152
Reaction score
4
In a universe where mass and energy are preserved why would space not follow the same model? Is there preservation of space? One model of a "preservation-of-space-universe" might be one where the universe, while expanding in a number of dimensions, is collapsing in others.
 
Astronomy news on Phys.org
Hi Job! Welcome to these Forums!

A good question to think through is:"If space is expanding, what exactly is expanding with it and how do you measure it?" Your "preservation-of-space" model could be Einstein's original static cylindrical model modified to have parts expanding and parts collapsing, on the other hand it could be just the sound of 'one brane clapping'!

Garth
 
Another thing that I think about a lot. If space is expanding, there is a whole lot more vacuum nowadays than there used to be. Since the energy of the vacuum is pretty incredible (according to QT) how do we reconcile that with the conservation of mass and energy? I am a whole lot more comfortable with steady-state cosmology than any expanding model, partly because of this conundrum.
 
What measurable property of empty space is there to be conserved? Only mass and energy are known to be conserved in this universe. Defining the properties of the vacuum is more difficult. Dark energy is the only current candidate, and it is difficult to quantify this property.
 
Chronos said:
What measurable property of empty space is there to be conserved? Only mass and energy are known to be conserved in this universe. Defining the properties of the vacuum is more difficult. Dark energy is the only current candidate, and it is difficult to quantify this property.
There is no "empty" space in our universe. The quantum vacuum is the baseline energy level (the ground state) of the universe, so it is very difficult to detect. In order to measure the absolute magnitude of the vacuum, you would need access to a true vacuum with which to compare it, and there does not appear to be any way to produce a true vacuum - one that can somehow exclude quantum effects.

The virtual particles of the vacuum exist, as has been demonstrated by the Lamb shift and various measurements of the Casimir force. If space is expanding, more and more "vacuum" is being produced, and unless you are willing to consider that the quantum vacuum can be rarified, polarized, etc, you must admit that the vacuum in the visible universe today contains twice as much energy (and mass-equivalence) as it did when it was half the present volume.

If you insist that mass and energy be conserved in our universe, you will have a hard time reconciling the concept of vacuum energy with an expanding universe.
 
If vacuum is the baseline energy, then should we say that larger amounts of energy are "compressed", or more "dense", dense vaccum? Similarly, for matter, since matter & energy are interchangeable, do we say that matter is "compressed", or "dense", vaccum?
Can we convert matter to energy to space? Can i compress vacuum to denser energy to matter?
If we were to "compress" all space in the universe, how much matter matter would it produce?
 
Turbo, your model is unfalsifiable. The Lamb Shift and Casimir Force do not prove anything that supports, or falsifies alternative models. I hate to say this buddy, but, show the math. I'm not asking you to do this on your own, just give references to papers that do. I'm no math genius either, but can follow most of it. I do, however, consider you a friend and respect your opinions.
 
Leave my model out of it and consider this only:

1) The vacuum contains energy - from Baez's FAQ the energy density of the vacuum is rho(vacuum) = M4c3/h3 = 1013 [M/proton mass]4 g/cm3.

2) As the universe expands (in the BB model) there is more and more vacuum between the gravitationally-bound bodies, thus more and more vacuum energy.

3) If the universe observes mass/energy conservation, the energy density of the vacuum must decrease exactly in coordination with universal expansion. If not, the more the universe expands, the more energy it contains.

Do you see how this might pose a bit of a problem for the BB theory? You can only have mass/energy conservation if you can supply a mechanism by which the energy density of the vacuum falls off precisely with universal expansion.

Quantum characteristics of the vacuum have cosmological implications, not the least of which is the violation of mass/energy conservation due to cosmological expansion.
__________________________________________________________

I am not (by far!) the only person who is concerned with the behavior of the vacuum and its role in cosmology. You may want to follow a few of the references here:

http://citebase.eprints.org/cgi-bin/citations?id=oai:arXiv.org:hep-th/0012062
 
Last edited by a moderator:
Saying vacuum has a given energy density, and that today we have more vacuum than yesterday may not imply that the universe contains more energy today than yesterday. If we say the universe had an area A yesterday and area B today, and if we know that this extra area B-A is new vacuum created due to the expansion of the universe, then we can only say that today we have the extra (B-A)*rho(vacuum) amount of energy in the universe if we assume that elsewhere the universe has the same energy distribution as yesterday, when in fact it's more likely that today's universe, though containing more vaccum, contains less matter or other forms of energy.
To go out on a limb here, consider the amount of radiation that is never absorved by matter, this energy will make it to the edge of the universe, hence if we observe the same area A of the universe over time we'll see that it must lose energy due to emissions of radiation. We might use the energy lost in this way to account for the energy in the new vaccum.
 
Last edited:
  • #10
-Job- said:
Saying vacuum has a given energy density, and that today we have more vacuum than yesterday may not imply that the universe contains more energy today than yesterday. If we say the universe had an area A yesterday and area B today, and if we know that this extra area B-A is new vacuum created due to the expansion of the universe, then we can only say that today we have the extra (B-A)*rho(vacuum) amount of energy in the universe if we assume that elsewhere the universe has the same energy distribution as yesterday, when in fact it's more likely that today's universe, though containing more vaccum, contains less matter or other forms of energy.
To go out on a limb here, consider the amount of radiation that is never absorved by matter, this energy will make it to the edge of the universe, hence if we observe the same area A of the universe over time we'll see that it must lose energy due to emissions of radiation. We might use the energy lost in this way to account for the energy in the new vaccum.

What if we change the term expanding with creating?
 

Similar threads

High School Dark Energy: Are We All Missing The Obvious?
  • · Replies 4 ·
Replies
4
Views
3K
Undergrad Abundant water from primordial supernovae at cosmic dawn
  • · Replies 1 ·
Replies
1
Views
2K
High School I Need Help on Understanding Some Basic Astrophysics / Sand Clock Universe
  • · Replies 5 ·
Replies
5
Views
4K
Undergrad Energy conservation in Doppler (NOT cosmological) redshifts?
  • · Replies 13 ·
Replies
13
Views
4K
Graduate Did scientists just find that the Universe has finite angular momentum?
  • · Replies 12 ·
Replies
12
Views
4K
Undergrad How Does the Balloon Analogy Explain the Expansion of the Universe?
  • · Replies 5 ·
Replies
5
Views
3K
High School Visible Light Through a Wormhole
  • · Replies 2 ·
Replies
2
Views
2K
High School Questions about relative Space-Time in the Universe
  • · Replies 24 ·
Replies
24
Views
3K
Undergrad Does Spacetime rotate like a vortex?
  • · Replies 6 ·
Replies
6
Views
1K
High School Questions regarding energy in the universe
  • · Replies 3 ·
Replies
3
Views
3K