A thought about dark energy

[xelasnave]

IF dark energy can be seen as a pushing force, and that seems to be the general view, and capable of holding galaxies in place by an external force where does this pushing force cease??? somewhere outside the solar system?..somewhere just above our heads?..I ask exactly where does the push of dark energy stop and the supposed force of gravity attraction take over? I find it hard to see how a force that can hold galaxies in place externally stops somewhere outside our world..why would such a force be stopped by anything? Of course my point is simply I can not see that it would stop.. leaving the inescapable conclusion that gravity pushes through out the Universe.. I know its a thing with me but surely such an observation must suggest our current beliefs that gravity attracts must be reviewed.. The word "attraction" should be used to describe "boy girl things" not a force that manifests itself with a clear demonstration of pushing... If dark energy runs out of puff to allow "ättraction" to take over could someone who knows more please point out to me what I have wrong.. Needless to say I think attraction is an unsupported opinion I put down to human experience without consideration to what is being observed by cosmologists.. Is there one experiment that clearly demonstrates gravity attracts? Or is attraction just something we included without observations such as those of Abel 2029 (or Abell 2029).
When does the push of dark energy stop? and why does it stop where you may suggest such that the human experience can be entertained?.
alex

[xelasnave]

Further I think space time suggests neither a pull or a push ..any views on this thought?
alex

[Kal (Andrew)]

I think that there is no extent to which it ceases to stop pushing.

Maybe it's because I'm a libran, but I like balance in everything. I think it is possible that two objects with mass can both attract one another through gravity, and repel each other through "dark energy" at the same time. Both forces can exist at the same time.

[xelasnave]

Kal thank you for your input. I dont know much about space time but as I understand it it suggests neither pushing or pulling..I see it as the geometric representation of the situation. When one talkes about a bend in space time it is visualised by a bent line on a grid. The grid line is bent toward a Mass formuleas determine the bend or the gravitation I suppose.
My contention is simply that gravity pushes as evidenced by observations as to galaxies "holding" together.. I personally doubt if the pushing effect of dark energy being as powerful as it appears stops short of us.. we think attraction when in point of fact there is no reason to do so..has there been an experiument proving what we see as gravitation is in fact a force of attraction I dont thionk there is..so I think reliance on an observation and the conclusion draw from say Abel 2029 that the "force" pushes is a reasonable one to subscibe to..
I like your even handed approach to give attraction some hope of survival but one must ask at what point "above" us does dark energy give over to attraction..As I have said I doubt that it does..
I think your coment re space time not having a view is indeed correct...I can live with that at least the other side does not get a leg up
alex

[Doug]

Given that 'dark energy' is only a twinkle in the eye of some cosmologists,
any such exchange of influence would logically occur when gravity's attractive force exceeds dark energy's push. Dark energy is not however a necessary thing, only a mathematical fudge factor. Consider the integral of 2x. Is it not x squared + k where k is merely the constant of integration?
Yet had our 2x merely been the first derivative of x squared to begin with, then k would have to have the value of zero. In the same way dark energy is simply 'k' a constant that might have some influence if needed in the future. In other words it simply balances an equation; nothing more.

Alex I can't check any of this with the professor as he is on a lecture tour at present, but I think there is a danger of interpreting images without having strong observational evidence.
Consider this simple scenario; I crack an egg and place its contents into a bowl. Then I spill the egg onto the floor and throw the shell into the middle of the mess. Some time later you come along and seeing the mess, assume that I must have dropped the egg onto the floor, breaking it. That is what it looks like however you would be wrong. Later information might show that the shell was empty when it hit the floor, but for now you can only assume.
Abel 2029? accidental or natural?
Gravity....push or pull? (dinner break)

[Doug]

As for Gravity being a push instead of an attraction, how might that account for the mass dependency factor? If a push, then it is external to the masses involved and as such would not be larger or lesser with various masses. We do see gravity being larger with larger masses, which strongly suggests that gravity is intimately involved with mass.

All very confusing really,

Doug

[ispom]

I was a child I got stated a conception of the world, to which I feel again and again drawn:
The universe is infinite in space and time.
After long erring it is solidified again in such a way,
only that for "universe” now is placed “multiverse”
because our universe is a transient thing:

for the first time my originally sanctified conception of the world disturbed,
when I had learned in the school:
all energy transforms into warmth, the universe must die a heat death.
Then I read in a book concerning the escape of the galaxies with the consequence: the universe will expand all the time,
as consequence is the cooling death inevitably.
Then the "cyclic universe" dominated the popular-scientific literature:
it comes sometime to a "big crunch", thus again to a heat death!

Now the dark energy is up to date, it drives apart the Univerum, is proportionally the volume,
the more largely the universe will be the faster, exponentially.
The area between the galaxies expand with greater then light velocity,
we soon will see no more galaxies in the sky,
the energy dilutes itself over an inconceivably large universe
and the large cooling death is our inevitable fate!

Fortunately for my soul is the fact that the string- theoreticians discovered the Multiversum.
everything at our universe changed,
suffer the heat or cooling death
but in the Multiversum is applyed the cosmological principle from eternity to eternity

amen, sagt Ispom

[Kal (Andrew)]

How does matter/antimatter come into the picture I wonder? I ask this because (please correct me if I am wrong) Hawking radiation as theorised by Stephen Hawking is made when matter and antimatter seperating out of nothing with one of them being drawn into the black hole and the other escaping as radiation. Now if matter and antimatter can appear out of nothing at all, and then (usually) recombine almost as fast as it appears, then isn't a vacuum filled with the energy of this matter/antimatter?

[xelasnave]

Doug....
"Given that 'dark energy' is only a twinkle in the eye of some cosmologists,
any such exchange of influence would logically occur when gravity's attractive force exceeds dark energy's push. Dark energy is not however a necessary thing, only a mathematical fudge factor. Consider the integral of 2x. Is it not x squared + k where k is merely the constant of integration?
Yet had our 2x merely been the first derivative of x squared to begin with, then k would have to have the value of zero. In the same way dark energy is simply 'k' a constant that might have some influence if needed in the future. In other words it simply balances an equation; nothing more.

alex's thought...Yes I can see why you could say that, given generally how those who engage these issues will approach them, maybe I am grabbing at merely a fudge factor generated by a necessity to round off the big bang equations... well I will be happy to jump on any band wagon I came.I have grabbed space time for my purposes.. but ceratinly if it(dark energy) is merely an expression for the sake of foomulae to "them" to me I still see the "gravity rain thing" maybe it has to be stronger than the sums attribute to dark energy ...but I have not relied at all upon any sums ...the gravity rain is an idea not a theory so it can run around undressed as it were . Still I see dark energy as a real force and it probably is the gravity rain I have sort for some time now. Morosophia can be blamed no doubt. But the gravity rain thread elsewhere has just gone over 10,000 reading robots no doubt but how strange that search engines are so hungry.
Doug....
"Alex I can't check any of this with the professor as he is on a lecture tour at present, but I think there is a danger of interpreting images without having strong observational evidence.
Consider this simple scenario; I crack an egg and place its contents into a bowl. Then I spill the egg onto the floor and throw the shell into the middle of the mess. Some time later you come along and seeing the mess, assume that I must have dropped the egg onto the floor, breaking it. That is what it looks like however you would be wrong. Later information might show that the shell was empty when it hit the floor, but for now you can only assume.
Abel 2029? accidental or natural?"

alex's thought...Indeed but I do no worse than many others out there really it is my humble opinion that many projects have figured how the egg go to be on the floor and the project will back up that notion..I see the usefulness of dark energy as it can be mt gravity rain.. think of all the work I can rely upon thats been already done on dark energy..errrr gravity rain..whatever.. I blame the hopeless condition of morosophia I am aflictted with such that I can only see everything as evidence for my proposition... convenient excuse but without the condition I would have given up on my idea and if nothing else its drives my hunt for knowledge...and I have learnt that if you look on the net you can get as much evidence as you want to support anything you can think of... I think Abel 2029 says what I think it says to me..yes we could work out every set of conditions for the broken egg on the floor and actually list every possible reason for the arrangement before us...and yet such observation cant be brought to bear on something like Abel 2029 and ...then with absolute belief feel you are right on what you come up with..I am strong to state my case but have been around to know one can be fooled easiest by ones self.. I therefore trust myself little... but Abel 2029 could not hold up using an internal force ..and this is the case with pretty well all spirals .
Abel 2029 accidental or natural mmmm me thinks nothing is accidental even a broken egg on the floor.
Dough
"Gravity....push or pull?"
alex's thought....
The words on 10,000 robots lips but I am here to say I am 100% in the push camp... just in case there were any doubts as I tend to keep my thoughts on gravity to myself

Anyways there are a lot of people looking for dark energy that may find if it works my way they wont need any dark matter.. thats what I see and look at the egg on the floor and used my efforts to explain how it broke.
Give my fond regards to the professor.
alex

[xelasnave]

Sorry that looks like Doug is saying most of that I have stuffed up the quote thing.. please give me time to fix it
alex

[xelasnave]

Originally Posted by Doug

As for Gravity being a push instead of an attraction, how might that account for the mass dependency factor? If a push, then it is external to the masses involved and as such would not be larger or lesser with various masses. We do see gravity being larger with larger masses, which strongly suggests that gravity is intimately involved with mass.

All very confusing really,

Doug

In the gravity attracts Universe mass is said to attract, this I say is an assumption not supported by the space time approach and explaination of gravity ..which says merely that space bends in relation to mass with no comment as to attraction or indeed pushing ..to be even sided
However in the gravity rain Universe mass relates to ther mass as "shields" against the pressure of the gravity rain..the dark energy perhaps. Larger mass provides a greater shield translating to greater gravitation.
alex

[xelasnave]

Originally Posted by ispom

I was a child I got stated a conception of the world, to which I feel again and again drawn:
The universe is infinite in space and time.
After long erring it is solidified again in such a way,
only that for "universe” now is placed “multiverse”
because our universe is a transient thing:

for the first time my originally sanctified conception of the world disturbed,
when I had learned in the school:
all energy transforms into warmth, the universe must die a heat death.
Then I read in a book concerning the escape of the galaxies with the consequence: the universe will expand all the time,
as consequence is the cooling death inevitably.
Then the "cyclic universe" dominated the popular-scientific literature:
it comes sometime to a "big crunch", thus again to a heat death!

Now the dark energy is up to date, it drives apart the Univerum, is proportionally the volume,
the more largely the universe will be the faster, exponentially.
The area between the galaxies expand with greater then light velocity,
we soon will see no more galaxies in the sky,
the energy dilutes itself over an inconceivably large universe
and the large cooling death is our inevitable fate!

Fortunately for my soul is the fact that the string- theoreticians discovered the Multiversum.
everything at our universe changed,
suffer the heat or cooling death
but in the Multiversum is applyed the cosmological principle from eternity to eternity

amen, sagt Ispom

I know that the Big Bang theory is favoured at the moment but imagine that perhaps the Universe could be ageless...no start no end ..and infinite ..no top , no bottom , no sides... no unhappy endings.. maybe data is being interpreted incorrectly and we are not expanding even... but you know the good thing one can have a long term opinion on the fate of the Universe and probably not be around to be proved wrong.
alex

[xelasnave]

Originally Posted by Kal

How does matter/antimatter come into the picture I wonder? I ask this because (please correct me if I am wrong) Hawking radiation as theorised by Stephen Hawking is made when matter and antimatter seperating out of nothing with one of them being drawn into the black hole and the other escaping as radiation. Now if matter and antimatter can appear out of nothing at all, and then (usually) recombine almost as fast as it appears, then isn't a vacuum filled with the energy of this matter/antimatter?

I personally dont like to work with things that pop into and out of exsistence and tolerate a situation where when when out of exsistence a Universe filled with these could be technically called empty. Now indeed it was "empty" before the big bang it is presumed but I guess it wasnot because of the anti matter... I simply dont buy the anti matter approach and with respect to Mr S Hawking he should not call his idea a theory. Because he is a great mind he is given some freedom of demands to back up some of his ideas but many of them are respectfully ideas only... mind you some ideas are better than others but science requires proof
So Kal thanks for that but I really think anti matter needs a long hard look sorry that I could not answer your question... I just think there is energy from every object that is in effect causing a pressure which I see as how gravity really works.. its a see it ot you dont thing and unfortunately I think I am the only person who sees it this way...so there is a problem..You know what yoy think it is...mmmm me.. I however see it differently. Thanks again
alex

[glenc (Glen)]

A Force from Empty Space: The Casimir Effect
Credit & Copyright: Umar Mohideen (U. California at Riverside) Explanation: This tiny ball provides evidence that the universe will expand forever. Measuring slightly over one tenth of a millimeter, the ball moves toward a smooth plate in response to energy fluctuations in the vacuum of empty space. The attraction is known as the Casimir Effect, named for its discoverer, who, 50 years ago, was trying to understand why fluids like mayonnaise move so slowly. Today, evidence is accumulating that most of the energy density in the universe is in an unknown form dubbed dark energy. The form and genesis of dark energy is almost completely unknown, but postulated as related to vacuum fluctuations similar to the Casimir Effect but generated somehow by space itself. This vast and mysterious dark energy appears to gravitationally repel all matter and hence will likely cause the universe to expand forever. Understanding vacuum fluctuations is on the forefront of research not only to better understand our universe but also for stopping micro-mechanical machine parts from sticking together.

[AGarvin]

How does matter/antimatter come into the picture I wonder? I ask this because (please correct me if I am wrong) Hawking radiation as theorised by Stephen Hawking is made when matter and antimatter seperating out of nothing with one of them being drawn into the black hole and the other escaping as radiation. Now if matter and antimatter can appear out of nothing at all, and then (usually) recombine almost as fast as it appears, then isn't a vacuum filled with the energy of this matter/antimatter?

The vacuum energy your refering to here is the cosmological constant, called Lambda, and is one of the proposals to explain dark energy.. In General Relativity, it's basically shifting Einstiens original constant that he added to create a static universe to the stress-energy tensor on the other side of the equation. It has the property of producing negative pressure. Problem is, vacuum energy is a quantum effect and when you calculate its value, the result is something like 120 orders of magnitude to large.

[xelasnave]

Hi Glen, I will have a look at all that. When I started my gravity rain rant in another forum they directed me to Casimir energy as it pushes.. at least thats the way I recall it.. I will have a look but (as all things) I saw it as supportive in so far as "nature" demonstrated, as I read it, a pushing force.
It is only revealed at a microscopic level aas I recall..anyways thanks and I will look at all this and what I have looked at before.
alex

[xelasnave]

Strike that I was thinking about "Crompton Effect" which I will re read.
alex

[dcnicholls]

We're in hairy country here, and it's very easy to speculate using terminology that has a specific physics meaning, without understanding the underlying implications. We need to tread carefully. That said, some thoughts.

Until String Theory (or Brane theory) comes of age, it's nearly impossible to try to connect Quantum Mechanics (the wonderfully successful theory of the physics of the subatomic realm) and General Relativity (the wonderfully successful theory of the Universe on the large scale) in the same thought train, but both have useful insights. Right now, they don't easily connect, and it's a very active area of research.

There have been numerous experiments to measure the attractive force of gravity. It has most certainly been shown that one mass attracts another through gravity. That's how Newton's Gravitational Constant has been measured. (General Relativity simplifies nicely to Newton's theory of gravity on the human scale.)

So after the Big Bang (see below) the sudden immense expansion of the Universe gradally slowed due to the "drag" of the gravitational attraction of all masses in the Universe on all other masses.

Brian Schmidt (Mt Stromlo) and his colleagues have pretty good observational evidence that some billions of years ago, the gradual slowing of the expansion of the Universe after the Bing Bang started to go into reverse.

Incidentally, the Big Bang theory is almost universally (sorry, pun) accepted by cosmologists as the right description of what has been happening over the past 12 or so billion years.

Anyway the reverse discoverd by Schmidt and others has been attributed to the mysterious quantity called "Dark Energy". This fits easily into the equations for General Relativity, under the (rather too convenient) parameter Lambda in the equations for General Relativity. This was originally seen by Einstein as a fudge factor to keep the Universe stationary (which of course was a mistake).

What Dark Energy is remains obscure. Vacuum Energy (as in the Casimir Effect) seems to be related.

On the microscopic scale, Quantum Mechanics provides some interesting insights, too. In the Standard Model (widely accepted and very relaible as a predictor of the behaviour of matter and energy at the quantum level), the several forces evident in nature are associated with "elementary particles". The particles are said the "mediate" the forces. For example, the particle associated with the Electromagnetic Force is the photon.

Not all the associated paticles have been found. The force of Gravity has an associated (hypothetical) elementary particle called the Graviton. This particle has not yet been created in any of the Particle Accelerators (CERN etc).

One of the more elegant ideas about the expansion Schmidt and others have found from their supernova work is that the Graviton might have some mass. It is conventionally assumed that the Graviton has no mass, like the photon.

However, if it does have some mass, this implies (through complex maths) that the force of gravity starts to "let go" beyond a certain distance, and this fits - albeit qualitatively - quite nicely with the observed "Dark Energy" expansion.

We have a very long way to go before understanding what is going on out there (or in there), and it's a very exciting time to be a High Energy Physicist or a Cosmologist. And very confusing for the rest of us

Good sources of further information are the regular articles on these subjects in New Scientist magazine. Wikipedia is another excellent place to look. See for example the info on the Graviton at http://en.wikipedia.org/wiki/Graviton

DN

[xelasnave]

Hi DN thanks for your very well thought thru input.
Do you know how a graviton interacts with mass to produce gravity?
The difficulty of admitting a particle can have mass seems to be tied to the requirement that mass can not reach C I personaly believe that dark energy will be a particle ,generated somehow within the electromagnetic system ..if such a particle is generated within the ënergy"output of an object ..star or brown dwalf.. but every object within the Universe I see the result a form of pressure..or the way dark energy may interact.. thats why anything I can learn about particle interaction is very interesting..the graviton for example as you mentioned.. but I cant see how it interacts with mass.. it must somehow.
Thanks again for sharing your thoughts.
alex

[dcnicholls]

Gravitons are at best hypothetical particles. Their existence is presumed from the other (known) elementary particles that "mediate" the other forces. Nobody has seen one and it's probable nobody will because of the huge energies likely required to make one appear. It's not clear to me how "mediating" relates to interacting. I don't think it's a matter of swarms of gravitons hooning about doing the work of gravity on any mass they come in contact with. We run slap bang into the usual wave/particle duality problem.

Re having mass, AFAIK the mass that may be associated with a graviton is extremely small.

Similar to a neutrino. Originally these beasts were supposed to have no mass, but it turns out they probably do have a very small mass, which allows them to flip between the three different types of neutrino. This explains why the neutrinos apparently coming from the core of the Sun were not the type expected from the nuclear physics going on there. It appears they've transformed themselves into another type by the time they get to Earth. See for example, http://www.ps.uci.edu/~superk/oscillation.html

DN