Bjarne on: Dark Energy, only an illusion.

[Reality Check]

IThe point with this thread is mainly to ask the question:
Is the gravity effect on space that space stretch, - and hence the exact same property as stretching / expanding space. Yes or no ?

You need to learn some more English in order to make this question make sense.

But...
No. Gravity is not explained by a "stretching / expanding space". It is explained in GR by a curving space-time. Gravity can not be explained by stretching or contracting space-time as pointed out to you last November in another thread (replacing contraction by expansion and drain by source does not change the conclustion):

In flat space the sum of the angles inside a triangle is 180 degrees.
This is no longer true in curved space.
Uniform contraction of space does not produce any curvature of space since it is uniform and preserves shapes. Thus a triangle in flat space which has a sum of 180 degrees still has the same sum after uniform contraction.

Uniform contraction of space does not produce forces when compared to flat space (no GR gravity). This is because straight paths in it remain as straight paths. Newton's laws then show that there is no force.

Nonuniform contraction of space needs sinks and sources of space which has other problems as sol victus has mentioned.

My objection to nonuniform contraction of space is more physical (and perhaps wrong). As I see it a point mass acting as a drain of spacetime will create an infinite curvature at its position. In other words it will be a black hole with all the consequences, e.g. instantly exploding because of Hawking radiation.

It looks like you have it the wrong way around. Gravity is the effect. The curvature of space is the mathematical explanation for the effect.

 

[Farsight]

Bjarne: people rather dismiss Einstein and indeed relativity these days, and don't look at what he actually said in the light of the evidence for the expanding universe. Like you said, he missed that. Why I don't know, because he described a gravitational field in terms of the stress-energy tensor, referring to the energy of a gravitational field, also saying:

"According to this theory the metrical qualities of the continuum of space-time differ in the environment of different points of space-time, and are partly conditioned by the matter existing outside of the territory under consideration. This space-time variability of the reciprocal relations of the standards of space and time, or, perhaps, the recognition of the fact that “empty space” in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitation potentials gμν)"

See his Leyden address for the latter. OK, stress is similar to pressure, they're both measured in Pascals, see http://www.geol.umd.edu/~candela/press.html for more. What Einstein was saying is that space has an innate "pressure", and a gravitational field is a "pressure" gradient. It's an energy-density gradient that constrains mass, and mass is comprised of energy. There's a lot more energy tied up in a planet than in the surrounding space, hence a gravitational field constrains energy.

You know that something under pressure will expand unless it's somehow held in. The universe is space, and if there's nothing beyond it, it's going to expand. However in some regions it can't, because it's gravitationally bound. Hence if some regions expand whilst others don't, the result will be inhomogeneous space. See the quote above and note that this is what a gravitational field is, so the result will be a gravitational anomaly with no causative matter. This is the origin of dark matter. The easiest way to think about dark matter is to think of space. It's dark, it has its vacuum energy. So a region of space with a higher-than-average energy density will have a mass-equivalence, and will be surrounded by a gravitational field, even though there's no dark matter particles to be found.

Dark energy is a property of space itself, essentially vacuum energy. There's a problem called the vacuum catastophe that makes people think it isn't, but they're forgetting about the strong force. Essentially this accounts for the difference between an expanding ball of gas, and an expanding stress ball.

Squeeze a stress ball tight in your fist, and let go. The expansion of the universe is something like that. If some inner portions are constrained, the stress ball expands at a reduced rate, but these do not cause the stress ball to contract. In similar vein gravity didn't stop the expansion of the early universe when it was very dense.

 

[Tubbythin]

The cosmological constant was his biggest mistake he said, but first when he discovered he was wrong.

The CC isn't needed for space to contract or expand. Moreover, his original idea for the CC was that it would STOP space from doing either.

 

[Tubbythin]

This is the origin of dark matter. The easiest way to think about dark matter is to think of space. It's dark, it has its vacuum energy. So a region of space with a higher-than-average energy density will have a mass-equivalence, and will be surrounded by a gravitational field, even though there's no dark matter particles to be found.
.

This is, as far as I can tell, a load of crap. You seem to be claiming that dark matter -which acts to hold things together gravitationally - is made of dark energy - which acts to pull things apart.

 

[Kwalish Kid]

Bjarne: people rather dismiss Einstein and indeed relativity these days, and don't look at what he actually said in the light of the evidence for the expanding universe.

People dismiss the things that Einstein said that were wrong. Like Bjarne here, people dismiss you for making claims about things you do not understand.

What Einstein was saying is that space has an innate "pressure", and a gravitational field is a "pressure" gradient.

That is absolutely not what he was saying. You clearly do not understand what gμν actually means.

It's an energy-density gradient that constrains mass, and mass is comprised of energy.

Again, no. You need to actually learn the math. The stress-energy density tensor describes the presence of mass and energy and through the Einstein Field Equation it in turn constrains the geometry of spacetime.

You know that something under pressure will expand unless it's somehow held in. The universe is space, and if there's nothing beyond it, it's going to expand. However in some regions it can't, because it's gravitationally bound. Hence if some regions expand whilst others don't, the result will be inhomogeneous space.

This is not the general relativistic explanation of space expansion. It's hard to actually point out how wrong it is because it is so bad it is not even wrong. It's not even the same kind of thought. One need only crack open any cosmology textbook to verify this.

See the quote above and note that this is what a gravitational field is, so the result will be a gravitational anomaly with no causative matter. This is the origin of dark matter.

Hunh? There is no origin of dark matter other than some unknown nuclear process. The origin of the evidence for dark matter is purely Newtonian, lying in the difference between how galaxies rotate and how they should rotate. No account of gravity given pure GR changes this evidence. GR does add new ways to produce evidence for dark matter, because it introduced new ways to measure dark matter through gravitational lensing and through large-scale structure measurements.

The easiest way to think about dark matter is to think of space. It's dark, it has its vacuum energy. So a region of space with a higher-than-average energy density will have a mass-equivalence, and will be surrounded by a gravitational field, even though there's no dark matter particles to be found.

Hunh? How does this make any sense? Do you have some calculations to back this up? How does this match the rotation curves of any given galaxy?

Dark energy is a property of space itself, essentially vacuum energy. There's a problem called the vacuum catastophe that makes people think it isn't, but they're forgetting about the strong force. Essentially this accounts for the difference between an expanding ball of gas, and an expanding stress ball.

More sheer nonsense. The strong force plays no role in molecular dynamics.

Squeeze a stress ball tight in your fist, and let go. The expansion of the universe is something like that. If some inner portions are constrained, the stress ball expands at a reduced rate, but these do not cause the stress ball to contract. In similar vein gravity didn't stop the expansion of the early universe when it was very dense.

This is the opposite of what we have learned from cosmological observation. The large densities of the early universe greatly reduced the expansion of the universe!

 

[Floyt]

"E" in JREF! It had never occurred to me that there would be distinct "borders" to regions of Hubble expansion, and that their existence could be easily explained as well.

 

[RussDill]

I say we make a special thread for a battle of the those with "alternative" theories. I've always associated those who call out prominent physicist as crazy as cranks, it never occurred to me that there was a whole 'nother class that refers to them as some sort of appeal to authority. I guess anytime someone seems much more interesting in talking about the scientist, rather than the theory, it should raise red flags.

 

[Bjarne]

We do know what the curvature of space-time really is. It has a strict mathematical definition.

Space is more as math. For exsample: does space have 2 properties:

• Curvature
• Expansive

or are these properties two the same ?.
This is a BIG and important question.
There is more to learn. - Never takes believes, or a limit answer for an answer.

We do know the connection between matter (i.e. energy/stress) and the curvature of space-time.

Only at a very superficial level, - we don't know the cause of how exactly matter bends / curves space.

We do know what the effects of expanding space-time are.

Not exactly
You do not know if you body & surrounding matter + space expands with a unknown rate without you possible know / can measure.

We do know how gravity and expanding space-time affect each other.

GR is only superficially pinprick in the phenomena; gravity.

For example:

1. We know that the sizes of galaxies are proportional to the size of black holes, but not why.
2. We know almost nothing why galaxies have black holes.
3. We know nothing about why galaxies form.
4. Our model of how solar system form is cracking (more and more).
5. Nobody has ever seen dark matter nobody knows what it is. (PLEASE don’t try to convince me that it exists).

The ignorance of the nature of science comes in your naive expectation that science has absolute truths.

I never said that.
But only that I don’t like a completely fragmented and incoherent “picture” of gravity, (and much more) and this is all what we have.

A scientific theory is never set in stone and true for ever and ever.

Sometimes it is.

• The Earth is rotation
• Venus orbit the Sun.
• The earth is not flat.
• Dark Matter do not exist before you have prove it.
• etc...

Your problem is that we know a lot and you show no sign of learning any of this accumulated knowledge.

I have no problem.
But I am just trying to unite fragments to a picture that make sense.
I hate half brained solution and science fiction: such as gravity that disappear in unknown dimension and plenty of such “approved” invention that many times not is necessary.
Rather it is only a question of seeing things in a larger coherent perspective.

No. Gravity is not explained by a "stretching / expanding space".
It is explained in GR by a curving space-time.

This could very well be proven this spring.
What would you then say?
How would you Universe then look like?
How would that affect dark energy, I mean when it is proven that the curvature of space means = gradually stretching space (towards a body) and that this is possible because space have density.

Gravity can not be explained by stretching or contracting space-time as pointed out to you last November in another thread:

Matter contracts space, this is what matter is.
The results is space towards matter gradually stretches more and more.
You know space have "density" hence you also know this is possible.

The universe is space, and if there's nothing beyond it, it's going to expand. However in some regions it can't, because it's gravitationally bound.

I don’t agree.
Lets say that curvature of space = stretching space, then you would be forces to change that opinion right ?

Hence if some regions expand whilst others don't, the result will be inhomogeneous space.

This is the track out of darkness.

I believe its easy to prove mathematically.
Let me ask you the question, why do you think times somewhere runs slower ?
I believe this is only possible because distances are different from place to place. - (Gravity makes the density of the universe inhomogeneous )
We are hence not talking about space-time but rather space-distance-time.
Which mean that times runs slower because distances are stretching? – (This makes sense)
Furthermore now go backwards in time (BigCrunch) what would happen with the meter stick ? - it must shrink. At least the day the Universe only is “1/2” meter in diameter.

Secondly; what about subduction.
We have to take a possible expanding earth more serious.
It’s not more strange than the fact that the universe expands.
(I simply don’t believe there is force enough in inner convection to rise mountains.)

Think about that everything around you also you own body could tomorrow be the double so “big” – BUT you would not be able to measure it. – It could be 100 or 1000 times so big and still you would not discover anything.

Right now and right here the universe could (in theory) expand much faster as we believe, all what we would discover is when something not expands proportional, for example if space between galaxies would expand a little (or much) faster, or if the superficial levels of the Earth would expand faster than the inner area.
These would be the only places where we could see that something is "wrong" with our understanding.
So Neal Adams could in fact be a hero, not a crank.

This would be a consequence if gravity curvature of space = stretching space.

To make it all easy, - someone try to roughly calculate how much faster runs time between 2 distance galaxies compared to here (75.000 LY inside a galaxy).
Let say it is 10%, - this would mean that distances “out there” are relative 10% “shorter”

I think the universe could expand much faster as we believe.
The expansion between galaxies could only be 10% of the real expansion. But these 10% are all what we can see. – simply because we have no other reference points.

NEVER say never.

----------

 

[Farsight]

This is, as far as I can tell, a load of crap. You seem to be claiming that dark matter -which acts to hold things together gravitationally - is made of dark energy - which acts to pull things apart.

Think it through Tubby, step by step. Start with a large region of "empty" space. This space has its vacuum energy, and whilst there are random fluctuations, it's fairly evenly distributed. Now mentally divide the space into cubes, and fill the central cube with matter. Since E=mc² your energy distribution is no longer uniform. Of course, this matter "conditions" the surrounding space, see Einstein's Leyden Address:

"the metrical qualities of the continuum of space-time differ in the environment of different points of space-time, and are partly conditioned by the matter existing outside of the territory under consideration."

This results in a gravitational field in the surrounding cubes. So what then is the energy density of these surrounding cubes? See The Foundation of the General Theory of Relativity and look at page 185 where Einstein says "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". What that means is that there's a higher energy density in those surrounding cubes than in the original empty space. If you could plot energy density from one side to the other, it rises as you approach the centre, then peaks very high where the matter is, then diminishes as you move away.

Look at one of those surrounding cubes, consider it to be a "system", and remember that mass is a measure of a system's energy content. It has a mass-equivalence, and "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". That's your dark matter. It's down to inhomogeneous space, caused by the expanding universe as per the raisins-in-the-cake analogy - a galaxy is surrounded by a halo of inhomogeneous space. That's why CDMS can't find those WIMPs.

Dark energy is the stress-energy itself, and Einstein didn't use that term for nothing. Stress really is akin to pressure, and Einstein even talks about pressure on say pages 185 and 188. Things under pressure expand unless they're constrained. Gravity constrains matter and matter is made of energy, so gravity constrains stress-energy. If it isn't constrained, that stress-energy will make space expand. Yes, the vacuum catastrophe muddies the waters a little, but it isn't rocket science. However some people wave their arms and squeak and squeal and dismiss Einstein, and throw up deliberate diversions like "show us your calculations". But as a skeptic you ought to notice that they don't actually offer a counter-rationale. That's because they can't, and they know it. That's why the kid won't start a thread on dark matter.

 

[Farsight]

..it never occurred to me that there was a whole 'nother class that refers to them as some sort of appeal to authority.

It isn't true Russ. The real cranks are the people who dismiss Einstein along with the obvious evidence and the crushingly simple logic, because they believe that they know better. They don't. Take a look at http://en.wikipedia.org/wiki/Crank_(person) and pay careful attention to this bit:

No argument or evidence can ever be sufficient to make a crank abandon his belief.

Scary, isn't it?

 

[edd]

That's verging on word salad, Farsight. Dark matter is matter. Dark energy is not matter. Matter and different kinds of energy are not completely interchangeable in GR. This particularly shows a misunderstanding:

Things under pressure expand unless they're constrained. Gravity constrains matter and matter is made of energy, so gravity constrains stress-energy. If it isn't constrained, that stress-energy will make space expand.

Dark energy does not induce expansion through pressure in the same way that the air pressure in a balloon drives the expansion of a balloon.

There are reasons people demand calculations and mathematically-based arguments. One of those reasons is that it's way too easy to make a qualitative argument that turns out to be demonstrably wrong when examined quantitatively.

 

[PixyMisa]

Secondly; what about subduction.

What about subduction?

We have to take a possible expanding earth more serious.

The Earth is not expanding.

It’s not more strange than the fact that the universe expands.

The Universe is expanding.

The Earth is not.

Whether you deem either fact strange is irrelevant.

(I simply don’t believe there is force enough in inner convection to rise mountains.)

What you believe is likewise irrelevant.

Continents move. We can measure this. Mountains grow, and we can likewise measure this. The Earth is not expanding. We've measured it too.

Think about that everything around you also you own body could tomorrow be the double so “big” – BUT you would not be able to measure it. – It could be 100 or 1000 times so big and still you would not discover anything.

Completely wrong in every possible way.

Read On Being the Right Size, and then come back and we can talk.

Right now and right here the universe could (in theory) expand much faster as we believe, all what we would discover is when something not expands proportional, for example if space between galaxies would expand a little (or much) faster, or if the superficial levels of the Earth would expand faster than the inner area.

The Earth is not expanding.

These would be the only places where we could see that something is "wrong" with our understanding.

The Earth is not expanding.

So Neal Adams could in fact be a hero, not a crank.

The Earth is not expanding, therefore Neal Adams is a crank.

This would be a consequence if gravity curvature of space = stretching space.

This would be complete nonsense.

NEVER say never.

The Earth is not expanding.

 

[dafydd]

The Earth is not expanding.

 

[Bjarne]

Bjarne
This would be a consequence if gravity curvature of space = stretching space.
Piximisa
Continents move. We can measure this. Mountains grow, and we can likewise measure this. The Earth is not expanding. We've measured it too.

No
We would not be able to measure this when the yardstick expands too.

Bjarne
This would be a consequence if gravity curvature of space = stretching space.
Piximisa
This would be complete nonsense.

It’s irrelevant what you believe
It is possible to prove, this is what counts.

 

[MRC_Hans]

No
We would not be able to measure this when the yardstick expands too.

Ehr, yes we can. If Earth expands, either it gets heavier, or it gets less dense. Even if our meter also expanded, we could still observe this.

Also, you are claiming that space expands at different rates in different places. Such a phenomenon would be extremely easy to observe.

It’s irrelevant what you believe
It is possible to prove, this is what counts.

Perhaps. Then why exactly do you feel it is relevant what YOU believe or don't believe? After all, ALL your arguments so far has been merely beliefs and disbeliefs. So, by your own standard everything you have written up to now is irrelevant.

Hans

 

[PixyMisa]

No
We would not be able to measure this when the yardstick expands too.

WRONG.

Read On Being the Right Size, and then come back and we can talk.

Do not attempt to post anything else before reading that article.

 

[MRC_Hans]

WRONG.

Read On Being the Right Size, and then come back and we can talk.

Do not attempt to post anything else before reading that article.

I don't see that article making many references to cows, so I don't think it will be in Bjarne's range of interest.

Hans

 

[Cosmic Roy]

But off course we must be willing to give up the subduction speculation...

Hi Bjarne.

I can't comment on those parts of the discussion to do with cosmology, but I can say quite definitively that the idea of subduction is not speculation. I can say this with confidence because, not only can tectonic motion itself be observed directly, but subducting slabs can be imaged within the mantle by seismic tomography and earthquake focal mechanism studies. Also remember that, while these lines of evidence support the mechanism of accommodation of plate convergence by subduction, tectonic uplift due to convergence is evidenced by the folded and faulted crust that constitutes the Earth's great mountain chains. Such structures simply could not form on a planet whose crust experiences only tension on a large scale.

 

[Kwalish Kid]

No argument or evidence can ever be sufficient to make a crank abandon his belief.

Scary, isn't it?

So will you change your description of dark matter and dark energy, given how wrong it is?

 

[dafydd]

No
We would not be able to measure this when the yardstick expands too.


It’s irrelevant what you believe
It is possible to prove, this is what counts.

Prove that the earth is expanding.