Does expansion modify the properties of space?

[zapatos]

If I was an outside observer and noticed that two galaxies were farther apart from each other today than they were yesterday, is there some way to determine if they are farther apart due to expansion, motion through space, or some combination of the two? Is it possible to measure the decrease in density of space between galaxies separating due to expansion?

[alpha2cen]

There is Dark energy in the vacuum. It can accelate the expansion of the Universe. Till now we can not measure it. We try to every effort to detect it. Recently a telescope is developed, and installed in the Atacama desert in Chile for searching Dark energy. This area research is about to start now. Everyone who join this research area would be the first researcher in the world. But no data is in there now.

[zapatos]

So is the expectation that over time, as space expands, there will be less dark energy per cubic volume of space?

[lemur]

If EM wave-energy is generated by electrons and gravitational wave-energy by objects with mass, could some other type of energy-waves be generated by protons and/or neutrons? If so, I don't know why such energy wouldn't be readily observable on Earth, since there are plenty of protons and neutrons, but maybe they would only generate waves under very different conditions than on Earth, for example during nuclear reactions within gravitation stronger than that of the sun. After all, electrons and matter only seem to produce photons and gravity-waves because of their relative mobility in the conditions of their motion. If they were "frozen" the way protons and neutrons seem to be by nuclear force most of the time, they probably wouldn't emit or absorb wave-energy, right? Maybe the sun's protons do generate some such waves but only slightly because of the sun's relatively low temp and gravitation. Is this possible?

[alpha2cen]

So is the expectation that over time, as space expands, there will be less dark energy per cubic volume of space?

 

 

We don't know dark matter property well now. And we don't know the vacuum property , either.

Matter is only made of electron, proton, neutron. In the vacuum the otherthings we do not know would be contained.

It,s very difficult to detect them. They have no interation with matter or electromagnetism.

Edited December 25, 2010 by alpha2cen

[lemur]

It,s very difficult to detect them. They have no interation with matter or electromagnetism.

If that's the case, what would you make the instrument out of that you use to detect them with? Something besides matter and electromagnetism?

[alpha2cen]

Resently there are many researchs about Dark matter. But Dark energy area is different. How to detect it? It's not seen directly. This is the frontier thinking area, right or not, add my little thought. If there were very high energy state which can break the vacuum state, the energy + Dark energy would be produced. But we can not imagine the world after that event.

[zapatos]

So why is it thought that dark energy expands space, as opposed to dark energy pushing or pulling objects through space? Is there evidence that this is the case, or is it just that without expansion of space, other theories would have problems? For example, it is determined that galaxy clusters move away from each other at FTL speeds. This means (I guess) that space must be expanding, or that we are wrong about c being the universal speed limit. How do we know expansion is correct and not that we have a problem with c being the speed limit?

[alpha2cen]

So why is it thought that dark energy expands space, as opposed to dark energy pushing or pulling objects through space?

 

Problem is the thing that the expansion is accelerated. Expansion velocity is increased with time. This kind of physical phenomena could not happen without energy.

Where the energy is? It comes from the vacuum. We can not see it in the present.

Edited December 25, 2010 by alpha2cen

[michel123456]

How do we know expansion is correct and not that we have a problem with c being the speed limit?

 

Because throwing the Theory of Relativity to the trash can without any replacement is not an option. It is just like trying to go faster when simultaneously throwing you car away without bying a new one: it drives nowhere.

 

At this moment, Relativity is quite a succesfull Theory. When a discrepancy arises, the easy way is to find a reason for that without having to redo 100 years of physics.

Edited December 25, 2010 by michel123456

[zapatos]

Problem is the thing that the expansion is accelerated. Expansion velocity is increased with time. This kind of physical phenomena could not happen without energy.

Where the energy is? It comes from the vacuum. We can not see it in the present.

So we theorize that the energy is expanding space and not pushing/pulling objects because otherwise it is a major problem for relativity. Does the theory of expansion allow us to predict how expansion happens? Does it give us some ideas on what to test for to see if it is true? In other words, getting back to my original question, does the expansion somehow modify the properties of space in some predicted way?

 

Because throwing the Theory of Relativity to the trash can without any replacement is not an option. It is just like trying to go faster when simultaneously throwing you car away without bying a new one: it drives nowhere.

 

At this moment, Relativity is quite a succesfull Theory. When a discrepancy arises, the easy way is to find a reason for that without having to redo 100 years of physics.

I wasn't trying to suggest that the Theory of Relativity be tossed out, although maybe that is what I was saying without realizing it. I was more wondering if maybe it could be fine tuned for special situations, such as "how massive objects behave at very great distances in the presence of dark energy".

 

I know that it would be easier to find another reason for the recession of galaxies we see, but I'm wondering if we did? Is the idea of expansion testable? Can we look at a portion of space over time and determine if it has been experiencing expansion? Is space going through some predictable and ultimately testable change?

[cypress]

Because throwing the Theory of Relativity to the trash can without any replacement is not an option. It is just like trying to go faster when simultaneously throwing you car away without bying a new one: it drives nowhere.

 

At this moment, Relativity is quite a succesfull Theory. When a discrepancy arises, the easy way is to find a reason for that without having to redo 100 years of physics.

 

True enough but General Relativity does not require that the universe is expanding as a 3 dimensional manifold of some higher dimensional construct. this expansion idea is a mathematical model of the universe constructed to accommodate the presumptions of arbitrary cosmological principles.

 

So no zapatos, there is no major problem with relativity whether or not one assumes expansion. The assumption does provide an mechanism whereby the universe can be considered uniform in all dimensions regardless of ones position and this is the answer to your question. The alternative to the posited expansion is that the earth must be close to the center of the observable universe so that it appears to be uniform in every direction.

[michel123456]

(...)I wasn't trying to suggest that the Theory of Relativity be tossed out, although maybe that is what I was saying without realizing it. I was more wondering if maybe it could be fine tuned for special situations, such as "how massive objects behave at very great distances in the presence of dark energy". (...)

There is a Variable Speed of Light Theory which is outside mainstream physics and others (look here) as the one proposed by Halton Arp. And you may find on the web some articles about alternative explanations of the cosmological redshift but you must be highly cautious about all of these. As much as I know, all alternative theories , except old ones, rely on Relativity.

Edited December 26, 2010 by michel123456

[Sisyphus]

True enough but General Relativity does not require that the universe is expanding as a 3 dimensional manifold of some higher dimensional construct. this expansion idea is a mathematical model of the universe constructed to accommodate the presumptions of arbitrary cosmological principles.

 

So no zapatos, there is no major problem with relativity whether or not one assumes expansion. The assumption does provide an mechanism whereby the universe can be considered uniform in all dimensions regardless of ones position and this is the answer to your question. The alternative to the posited expansion is that the earth must be close to the center of the observable universe so that it appears to be uniform in every direction.

 

Those "arbitrary cosmological principles" are very well experimentally supported. (See http://en.wikipedia.org/wiki/Metric_expansion_of_space#Observational_evidence) The Earth being close to the "center of the universe" does not account for observations, and we currently have no workable (i.e., not contradicted by observation) models that do not involve expansion.

 

Please do not use fringe hypotheses/personal speculation/creation science to respond to questions about mainstream science, especially without identifying it as such.

[cypress]

Those "arbitrary cosmological principles" are very well experimentally supported. (See http://en.wikipedia.org/wiki/Metric_expansion_of_space#Observational_evidence) The Earth being close to the "center of the universe" does not account for observations, and we currently have no workable (i.e., not contradicted by observation) models that do not involve expansion.

 

Please do not use fringe hypotheses/personal speculation/creation science to respond to questions about mainstream science, especially without identifying it as such.

 

My response was to the motivation behind the theory of expansion. Michel indicated that throwing out expansion would overturn the theory of General Relativity which is not correct. What is correct is that the expansion model is an attempt to explain the apparent uniform nature of the universe without having to place our point of observation sufficiently near the center. I made no attempt here to support the expansion theory or the more conventional dimensional model of the universe since this would be a diversion of the primary topic. It is unfortunate that stopping where I did in order to honor the rule of not diverting threads leaves me vulnerable to your unwarranted criticism.

 

The relevance of my previous response to the original question posed is that expansion does modify the properties of space in that it would void a conventional understanding of three dimensional geometry for the universe.

[swansont]

My response was to the motivation behind the theory of expansion. Michel indicated that throwing out expansion would overturn the theory of General Relativity which is not correct. What is correct is that the expansion model is an attempt to explain the apparent uniform nature of the universe without having to place our point of observation sufficiently near the center. I made no attempt here to support the expansion theory or the more conventional dimensional model of the universe since this would be a diversion of the primary topic. It is unfortunate that stopping where I did in order to honor the rule of not diverting threads leaves me vulnerable to your unwarranted criticism.

 

The relevance of my previous response to the original question posed is that expansion does modify the properties of space in that it would void a conventional understanding of three dimensional geometry for the universe.

 

!

Moderator Note

Expansion is part of general relativity; the term is the cosmological constant. (Einstein's "greatest blunder" was to set it to zero). In light of "this expansion idea is a mathematical model of the universe constructed to accommodate the presumptions of arbitrary cosmological principles." it's hard to argue that the criticism was unwarranted. Back on topic, please.

[cypress]

So we theorize that the energy is expanding space and not pushing/pulling objects because otherwise it is a major problem for relativity. Does the theory of expansion allow us to predict how expansion happens? Does it give us some ideas on what to test for to see if it is true? In other words, getting back to my original question, does the expansion somehow modify the properties of space in some predicted way?

 

Again, it is not a major problem for relativity. Einstein's Greatest blunder as he put it was to set the cosmological constant to a non-zero value to fit the popular notion that the universe was static. His blunder was failure to recognize that the volume of the universe was indeed expanding. An expanding volume can be accommodated within GR by postulating a kinetic model initiated by an initial expansive force or by postulating some sort undetected energy throughout the expanse of the universe or through other posits.

 

There does not currently seem to be a mechanism to determine how expansion happens or test to confirm it though there is a fair amount of activity occurring to attempt to do so.

 

I wasn't trying to suggest that the Theory of Relativity be tossed out, although maybe that is what I was saying without realizing it. I was more wondering if maybe it could be fine tuned for special situations, such as "how massive objects behave at very great distances in the presence of dark energy".

 

You did not say it without realizing it. It does not toss out GR. There is still a lot of work occurring around confirming the cosmological constant, though the number seems to be bouncing around a number very close or equal to zero. Here is a link that describes this work to test these ideas.

 

I know that it would be easier to find another reason for the recession of galaxies we see, but I'm wondering if we did? Is the idea of expansion testable? Can we look at a portion of space over time and determine if it has been experiencing expansion? Is space going through some predictable and ultimately testable change?

 

Great questions, I would point you back to the link I provided. There are many more that discuss this issue on the web as well.

Edited December 26, 2010 by cypress

[zapatos]

Thanks to everyone for your contributions!

[Just the Facts]

The universe is NOT expanding. It is plasma and electric currents and magnetic fields moving around all the matter… randomly.

The entire universe is a constant variable of random spontaneity. Very simple to understand once you get on the right track. Gravity has nothing to do with any of what we see happening in the universe. Einstein was wrong. Hawking is wrong. There are NO Black holes... anywhere. The proper equation for how the universe functions is: Plasma + Electric currents + Magnetic fields + Matter = the universe doing what comes naturally. Very simple physics. Just like here on Earth.

 

 

Here is the future of cosmology.

 

Link removed

Edited January 5, 2011 by swansont
Hijack attempt. Repelling boarder.

[swansont]

The universe is NOT expanding.

 

!

Moderator Note

Just the Facts, you have been warned about this already in your short tenure here. Alternative science has only one appropriate place for discussion: its own thread in the Speculations forum.